Collagen Vascular Diseases
Collagen Vascular Diseases
What are Collagen Vascular Diseases?
What Happens When People Have Collagen Vascular Diseases?
Living with Collagen Vascular Diseases
Collagen vascular diseases are a diverse group of diseases in which the body reacts against its own tissues, often causing joint pain and inflammation, fever, rash, fatigue, and difficulty swallowing.
KEYWORDS
for searching the Internet and other reference sources
Autoimmunity
Dermatomyositis
Inflammation
Lupus
Polyarteritis nodosa
Polymyositis
Rheumatology
Scleroderma
Sjögren’s syndrome
Collagen vascular diseases have been recognized for a long time. Rheumatoid arthritis is a chronic inflammatory* disease that causes stiffness in the joints (places where bones meet), and can lead to disfigurement. It is an ancient disease; bone changes showing this condition have been identified in skeletons thousands of years old. Systemic lupus erythematosus (er-i-thee-ma-TO-sis), which affects multiple organs and tissues throughout the body, was first described in 1828.
- * inflammation
- is the body’s reaction to irritation, infection, or injury that often involves swelling, pain, redness, and warmth.
What are Collagen Vascular Diseases?
Collagen vascular diseases, sometimes called connective tissue diseases (CTDs) or autoimmune diseases, cover a wide array of disorders in which the body’s natural immune or self-protection system fails to recognize its own tissues and goes on attack against itself. Some of these diseases limit their damage to a single organ, and others spread problems throughout the body.
Immune responses to foreign bodies
In a healthy immune system, antigens (foreign bodies such as viruses and bacteria) are recognized as different from regular body tissues. When an antigen enters the bloodstream, it triggers the production of antibodies, substances that attack the alien substance. Lymphocytes (LIM-fo-sites) and leukocytes (LOO-ko-sites) are the special white blood cells responsible for creating these antibodies.
Lymphocytes include two subtypes (T cells and B cells), which have the unique ability to recognize the invading alien and alert the immune system to destroy it. The process is highly specialized: different lymphocytes recognize specific antigens and produce antibodies against only that particular antigen.
Autoimmune responses
In collagen vascular diseases, this immune system malfunctions. Rather than responding to foreign antigens, the body produces antibodies (autoantibodies) against its own antigens and normal proteins. Researchers do not understand what gets this autoimmune process started, but they have a fairly good idea of how it proceeds once it begins.
Systemic lupus erythematosus (SLE)
People with lupus develop antibodies to their own nucleic (noo-KLAY-ic) acids* and cell structures,
including those in the heart, kidneys, and joints. As a result of a faulty interaction between lymphocyte B and T cells, the cells fail to identify a protein as normal, mistake it for a foreign antigen, and then move on to produce autoantibodies called antinuclear antibodies. These antinuclear antibodies attack the nucleus and DNA (genetic material) in healthy cells. Immune complexes are the result of this mistaken battle. When they accumulate in the kidney, blood vessels, joints, and other sites, they cause inflammation and tissue damage.
- * nucleic acids
- are the cell structures that transfer genetic information: DNA (deoxyribonucleic acid) transfers information to RNA (ribonucleic acid), which leads to the production of body proteins.
Rheumatoid arthritis
In rheumatoid arthritis, the autoimmune process begins in connective tissue and the cushiony membranes that surround joints and the ends of bones. Collagen (KOL-a-jen) is the tough glue-like protein that gives joints their support and flexibility, and it represents 30 percent of the body’s protein. Rheumatoid arthritis is thought to begin when T cells mistake the body’s own collagen cells for foreign antigens and alert B cells to produce antibodies to fight the invader. The leukocytes rush in and produce cytokines (SY-to-kines), small proteins that are essential in healing the body but that cause serious damage in large doses. The inflammation and joint damage that result can lead to joint deformities and can spread throughout the body, wherever there is connective tissue.
Causes
Researchers are studying the causes of autoimmune diseases. Some autoimmune diseases have strong genetic components and may be passed down from parents to children. Environmental factors may act to trigger these diseases in some way. Fatigue, stress, and higher levels of certain antibodies also may lead to these diseases. Even ultraviolet rays of sunlight have been suggested as possible contributing causes. Collagen vascular diseases are not contagious; people cannot catch these diseases from one another.
What Happens When People Have Collagen Vascular Diseases?
Symptoms Symptoms differ depending on the illness, but they often include joint pain, fever, rash, recurrent infections, fatigue, mouth ulcers, dry mouth and dry eyes, hair loss, difficulty swallowing, swollen glands, or fingers and toes that get overly cold when exposed to cooler temperatures. In addition to systemic lupus erythematosus and rheumatoid arthritis, collagen vascular diseases include:
- Scleroderma: This progressive and systemic sclerosis (skle-RO-sis) causes skin to thicken and tough fibrous tissue to form in the internal organs of the digestive tract, kidneys, heart, and lungs.
- Sjögren’s syndrome: This causes dry mouth, dry eyes, and other symptoms.
- Polymyositis and dermatomyositis: These are inflammatory muscle disorders that may also affect the skin, the heart, and the lungs.
- Mixed connective tissue diseases: These combine features of lupus, scleroderma, and polymyositis.
- Polyarteritis nodosa: This disorder can damage small and medium-sized arteries of almost any organ, including the kidneys, heart, and intestines.
Diagnosis A complete medical history and a physical examination are the basis for the diagnosis of autoimmune disease. A number of laboratory tests can be used to help diagnose collagen vascular diseases. Blood tests can check levels of autoantibodies. Other tests include rheumatoid factor tests, urinalysis, blood counts, liver and kidney tests, and a sedimentation rate, which will give a nonspecific indicator of inflammation. A chest x-ray and other tests of specific lung function also may be done, since collagen vascular disorders occasionally produce breathing difficulties.
Treatment At present, there are no cures for autoimmune diseases, although some may go into remission as symptoms disappear for periods of time. Treatment depends on the extent of the disease. Doctors may prescribe steroid creams or anti-inflammatory medications to ease discomfort. In advanced cases, immunosuppressant drugs may help lessen the immune system’s over-reaction.
Living with Collagen Vascular Diseases
These serious diseases often require adjustments in activities of daily living. People with rheumatoid arthritis often have early morning stiffness that lasts for about an hour, after which they can go on about their day. Avoiding certain foods, and reducing physical and emotional stresses, also seem to reduce symptoms for some people.
See also
Arthritis
Fever
Infection
Lupus
Resources
American Autoimmune Related Diseases Association, 15475 Gratiot Avenue, Detroit, MI 48205
Telephone 313-371-8600
http://www.aarda.org
Lupus Foundation of America, 1300 Piccard Drive, Suite 200,
Rockville, MD 20850-4303
Telephone 301-670-9292
http://www.lupus.org
Sjögren’s Syndrome Foundation, 333 North Broadway,
Jericho, NY 11753
Telephone 800-4-SJOGRENS
http://sjogrens.com
Scleroderma Foundation, 89 Newbury Street, Suite 201,
Danvers, MA 01923
Telephone 800-722-HOPE
http://www.scleroderma.org
Collagen Periurethral Injection
Collagen Periurethral Injection
Definition
Purpose
Description
Aftercare
Risks
Normal results
Alternatives
Definition
Collagen periurethral injection is a procedure in which collagen is injected around the urethra and bladder neck as a treatment for stress incontinence in women.
Purpose
The bladder and urethra are supported by muscles, ligaments, and connective tissues around the base of the bladder. This support prevents the leakage of urine, along with the watertight seal provided by the urethra.
KEY TERMS
Anesthetic— A drug that causes unconsciousness or a loss of general sensation.
Bladder— A membranous sac that serves as a reservoir for urine. Contraction of the bladder results in urination.
Catheterization— The placement of a catheter in a specific anatomic area most commonly for the purpose of treatment or diagnosis.
Collagen— The protein substance of the white fibers (collagenous fibers) of skin, tendon, bone, cartilage, and all other connective tissue.
Cystoscope— An instrument that allows the doctor to see inside the bladder and remove tissue samples.
Epidural— Located within the spinal canal, on or outside the dura mater, the tough membrane surrounding the spinal cord.
Incontinence— The inability to control excretory functions, as defecation (fecal incontinence) or urination (urinary incontinence).
Periurethral— Surrounding the urethra.
Stress incontinence— Involuntary loss of urine that occurs during physical activity such as coughing, sneezing, laughing, or exercise.
Urethra— The tube that passes urine from the bladder to the outside.
As a result of pregnancy, childbirth, and aging, or damage by scarring from surgery or radiotherapy, these structures may become damaged or weakened, thus causing stress incontinence, meaning an involuntary loss of urine that occurs during physical activity such as coughing, sneezing, laughing, or exercise.
The injection of bulking agents, such as collagen, around the urethra aims to improve the lost support of the bladder and urethra. The substance most commonly used for injection is collagen; other bulking agents are being developed; for example, a silicon base suspended in a viscous gel called Macroplastique. Teflon paste, introduced in the 1970s, initially gave good results, but was discontinued after reported problems with excessive scarring and with the migration of Teflon particles to other tissues in the body. The collagen used in the procedure comes from the cartilage of cattle and has been extensively sterilized to produce a viscous paste for injection. There is no risk
WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?
Collagen periurethral injection is a procedure that is performed in a hospital or clinic on an outpatient basis by a surgeon.
of bovine spongiform encephalopathy (BSE) transmission because the processing of the paste destroys any bacterial or viral particles.
Description
The collagen periurethral injection procedure is quick, and usually over within 15-20 minutes. No incisions are made, meaning that it can be carried out using a local anesthetic or a regional anesthetic such as an epidural. The surgeon uses a fine fiber-optic cystoscope to examine the inside of the urethra and bladder, and then inserts a fine needle to inject the collagen. Usually three injections are made around the urethra. The exact amount of collagen used depends on how much closure the urethra requires.
Aftercare
Since the procedure is very short and there is little discomfort afterwards, it is performed on an outpatient basis, and women can go home the same day. Recovery from the operation is very quick.
Risks
Periurethral injection is not associated with major complications. Urinary tract infection is common in up to a fifth of the women having undergone the procedure, but is usually quickly and easily treated with antibiotics. Some women experience difficulty urinating immediately after the procedure, but this is not unexpected following an operation involving the bladder and urethra that may easily lead to swelling and bruising of the tissues. It is an uncommon problem after periurethral injection. The condition usually settles quickly, but may require catheterization. Long-term problems are very rare.
Normal results
Since periurethral injection is so quick and easy with very few complications, it would appear to be an ideal treatment for stress incontinence; however, there is a problem with the longer-term results. Within three
QUESTIONS TO ASK THE DOCTOR
- How is a collagen periurethral injection performed?
- Why is the collagen injection required?
- What are the risks of the procedure?
- Is the injection procedure painful?
- Are there alternatives?
- How long will it take for me to recover?
- What are the after-effects of the injection?
- How many collagen periurethral injections do you perform each year?
months after injection, good results are reported with at least 80% of women cured or improved. After two years, less than half of these women will still be cured. Longer-term studies are still being performed, but it is likely that positive results will continue to diminish. This is due to the injected collagen dispersing away from the urethra over time. Injections can be repeated and some women do require more than one injection before they are cured. Ongoing research into new injection substances may improve these results. The results in younger, physically active women are also less successful, usually lasting for a shorter time. Repeated injections are not a simple solution because collagen is very expensive and the long-term effects of repeated injections are unknown. Physicians prefer one of the alternative operations if long-term cure of stress incontinence is the aim.
Alternatives
Other treatments are available to treat incontinence. They include:
- Physiotherapy—this treatment aims to increase the strength and support provided by the pelvic floor muscles.
- Surgical procedures—operations such as colposuspension, sling procedures, needle-suspensions, and vaginal repair operations are all based on lifting and re-supporting the bladder and urethra.
Resources
BOOKS
American Medical Association. American Medical Association Family Medical Guide, 4th ed. Hoboken, NJ: Wiley & Sons, 2004.
Burgio, K. L., L. Pearce, A. J. Lucco, and K. F. Jeter. Staying Dry: A Practical Guide to Bladder Control. Baltimore: Johns Hopkins University Press, 1990.
Kaschak Newman, D. Managing and Treating Urinary Incontinence. Baltimore: Health Professions Press, 2002.
PERIODICALS
Block, C. A., C. S. Cooper, and C. E. Hawtrey. “Long-term Efficacy of Periurethral Collagen Injection for the Treatment of Urinary Incontinence Secondary to Myelomeningocele.” Journal of Urology 169 (January 2003): 327–329.
Culligan, P. J., et al. “The Safety of Reusing Injectable Collagen: A Multicenter Microbiological Study.” International Urogynecological Journal of Pelvic Floor Dysfunction 13 (2002): 232–234.
Dmochowski, R. R., and R. A. Appell. “Injectable Agents in the Treatment of Stress Urinary Incontinence in Women: Where Are We Now?” Urology 56 (December 2000): 32–40.
Kassouf, W., G. Capolicchio, G. Berardinucci, and J. Cor-cos. “Collagen Injection for Treatment of Urinary Incontinence in Children.” Journal of Urology 165 (May 2001): 1666–1668.
OTHER
National Women’s Health Information Center.http://www.womenshealth.gov/.
Rackley, Raymond. “Periurethral Injection Therapy for Incontinence.” eMedicine. June 29, 2006. www.emedicine.com/med/topic3049.htm.
“Stress Incontinence.” Medline Encyclopedia. May 15, 2006. www.nlm.nih.gov/medlineplus/ency/article/000891.htm.
ORGANIZATIONS
Office of Women’s Health, U.S. Food and Drug Administration, 5600 Fishers Lane, Rockville, MD, 20857, (301) 827-0350, http://www.fda.gov/womens/default.htm.
Monique Laberge, Ph.D.
Laura Jean Cataldo, R.N., Ed.D.
Colon anastomosis seeIleoanal anastomosis
Collagen Periurethral Injection
Collagen periurethral injection
Definition
Collagen periurethral injection is a procedure in which collagen is injected around the urethra and bladder neck as a treatment for stress incontinence in women.
Purpose
The bladder and urethra are supported by muscles, ligaments, and connective tissues around the base of the bladder. This support prevents the leakage of urine, along with the watertight seal provided by the urethra. As a result of pregnancy, childbirth, and aging, or damage by scarring from surgery or radiotherapy, these structures may become damaged or weakened, thus causing stress incontinence, meaning an involuntary loss of urine that occurs during physical activity such as coughing, sneezing, laughing, or exercise .
The injection of bulking agents such as collagen around the urethra aims to improve the lost support of the bladder and urethra. The substance most commonly used for injection is collagen; other bulking agents are being developed, for example, a silicon base suspended in a viscous gel called Macroplastique. Teflon paste, introduced in the 1970s, initially gave good results, but was discontinued after reported problems with excessive scarring and with the migration of Teflon particles to other tissues in the body. The collagen used in the procedure comes from the cartilage of cattle and has been extensively sterilized to produce a viscous paste for injection. There is no risk of bovine spongiform encephalopathy (BSE) transmission because the processing of the paste destroys any bacterial or viral particles.
Description
The collagen periurethral injection procedure is quick, and usually over within 15–20 minutes. No incisions are made, meaning that it can be carried out using a local anesthetic or a regional anesthetic such as an epidural. The surgeon uses a fine fiber-optic cystoscope to examine the inside of the urethra and bladder, and then inserts a fine needle to inject the collagen. Usually three injections are made around the urethra. The exact amount of collagen used depends on how much closure the urethra requires.
Aftercare
Since the procedure is very short and there is little discomfort afterwards, it is performed on an outpatient basis, and women can go home the same day. Recovery from the operation is very quick.
Risks
Periurethral injection is not associated with major complications. Urinary tract infection is common in up to a fifth of the women having undergone the procedure, but is usually quickly and easily treated with antibiotics . Some women experience difficulty urinating immediately after the procedure, but this is not unexpected following an operation involving the bladder and urethra that may easily lead to swelling and bruising of the tissues. It is a relatively uncommon problem after periurethral injection, but may occur. The condition usually settles quickly, but may require catheterization. Long-term problems are very rare.
Normal results
Since periurethral injection is so quick and easy with very few complications, it would appear to be an ideal treatment for stress incontinence. However, there is a problem with the longer-term results. Within three months after injection, good results are reported with at least 80% of women cured or improved. However, after two years, less than half of these women will still be cured. Longer-term studies are still being performed, but it is likely that the results will keep becoming poorer as time goes by. This is due to the injected collagen dispersing away from the urethra over time. Injections can be repeated and some women do require more than one injection before they are cured. Ongoing research into newer injection substances may improve these results. The results in younger, physically active women are also less successful, usually lasting for a shorter time. Repeated injections are not the simple solution they may seem, because collagen is very expensive and the long-term effects of repeated injections are unknown. Physicians thus tend to prefer one of the alternative operations if long-term cure of stress incontinence is the aim.
Alternatives
Other treatments are available to treat incontinence. They include:
- Physiotherapy. This treatment aims to increase the strength and support provided by the pelvic floor muscles.
- Surgical procedures. Operations such as colposuspension, sling procedures, needle-suspensions, and vaginal repair operations are all based on lifting and re-supporting the bladder and urethra.
Resources
books
Burgio, K. L., L. Pearce, A. J. Lucco, and K. F. Jeter. Staying Dry: A Practical Guide to Bladder Control. Baltimore: Johns Hopkins University Press, 1990.
Kaschak Newman, D. Managing and Treating Urinary Incontinence. Baltimore: Health Professions Press, 2002.
periodicals
Block, C. A., C. S. Cooper, and C. E. Hawtrey. "Long-term Efficacy of Periurethral Collagen Injection for the Treatment of Urinary Incontinence Secondary to Myelomeningocele." Journal of Urology 169 (January 2003): 327–329.
Culligan, P. J., et al. "The Safety of Reusing Injectable Collagen: A Multicenter Microbiological Study." International Urogynecological Journal of Pelvic Floor Dysfunction 13 (2002): 232–234.
Dmochowski, R. R., and R. A. Appell. "Injectable Agents in the Treatment of Stress Urinary Incontinence in Women: Where Are We Now?" Urology 56 (December 2000): 32–40.
Kassouf. W., G. Capolicchio, G. Berardinucci, and J. Corcos. "Collagen Injection for Treatment of Urinary Incontinence in Children." Journal of Urology 165 (May 2001): 1666–1668.
organizations
National Association for Women's Health. 300 W. Adams Street, Suite 328, Chicago, IL 60606-5101. (312) 786-1468. <http://www.nawh.org/>.
other
National Women's Health Information Center. <www.4woman,org/>.
"Periurethral Injection Therapy for Incontinence." eMedicine. <www.emedicine.com/med/topic3049.htm>.
"Stress Incontinence." MEDLINE Encyclopedia. <www.nlm.nih.gov/medlineplus/ency/article/000891.htm>.
Monique Laberge, Ph.D.
WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?
Collagen periurethral injection is a procedure that is performed in a hospital or clinic on an outpatient basis by a surgeon.
QUESTIONS TO ASK THE DOCTOR
- How is a collagen periurethral injection performed?
- Why is the collagen injection required?
- What are the risks of the procedure?
- Is the injection procedure painful?
- Are there alternatives?
- How long will it take to recover?
- What are the after-effects of the injection?
- How many collagen periurethral injection do you perform each year?
Collagen
Collagen
Collagen is a protein found abundantly throughout the bodies of animals including humans. In humans, collagen makes up about one-third of the total body weight. Collagen is an important component of the body’s connective tissues, which perform a variety of functions in the body. These tissues provide the framework, or internal scaffolding, for various organs such as the kidneys and lymph nodes. Connective tissues also impart great support and strength to structures such as the bones and tendons. Blood, an important type of connective tissue, transports oxygen and nutrients throughout the body.
Connective tissue is composed of a nonliving, gellike material called a matrix, in which living cells are embedded. The matrix is composed of different kinds of protein fibers, the most common of which is collagen.
Collagen is a fibrous protein; that is, it is composed of many fibers. Each fiber consists of three microscopic ropes of protein wrapped around each other. The fibers in collagen are arranged parallel to each other, and are often grouped together in bundles. The bundling of collagen fibers gives the fibers greater strength than if they occurred individually. Collagen fibers are extremely tough and can resist a pulling force, but because they are not taut, they allow some flexibility.
Collagen is a primary component of the connective tissue located in the dermis, the tough inner layer of the skin. This kind of connective tissue is also found in mucous membranes, nerves, blood vessels, and organs. Collagen in these structures imparts strength, support, and a certain amount of elasticity. As the skin ages, it loses some of its elasticity, resulting in wrinkles. Recently, injections of animal collagen given under the surface of the skin have been used to “plump up” the skin and remove wrinkles. However, this treatment is controversial. Many people develop allergic reactions to the collagen, and the procedure must be performed by a qualified physician.
Collagen is also a component of a kind of connective tissue that surrounds organs. This connective tissue encases and protects delicate organs like the kidneys and spleen.
Other locations where collagen fibers are prominent are in the tendons and ligaments. Tendons are straps of tough tissue that attach muscles to bones, allowing for movement. Ligaments are structures that hold the many bones of a joint, such as the knee joint,
KEY TERMS
Cartilage— A connective tissue found in the knees, tip of the nose, and outside of the ears; it provides flexibility and resilience to these structures.
Ligaments— Structures that hold the bones of joints in the proper position.
Matrix— The nonliving, gellike component of connective tissue.
Tendon— A strap of tissue that connects muscle to bone, providing for movement.
in proper position. Tendons and ligaments differ slightly in structure. In ligaments, the collagen fibers are less tightly packed than in tendons; in some ligaments, the fibers are not parallel.
Collagen adds strength to tendons and ligaments, and it imparts some stretch to these structures by allowing for some flexibility. However, collagen is not extremely elastic. If tendons and ligaments are stretched too far, these structures will tear, which may lead to problems in movement and bone position. Many athletes tear tendons and ligaments. When tearing occurs, the joint or bone in which the structures occur must be immobilized to allow for proper healing.
Cartilage is a connective tissue found in various places throughout the body, including the tip of the nose, the outside of the ears, the knees, and parts of the larynx and trachea. Cartilage consists of collagen fibers and cartilage cells. At these locations, collagen provides flexibility, support, and movement. Cartilage soaks up water like a sponge and is therefore somewhat springy and flexible. For example, if the tip of the nose is pushed in and let go, it springs immediately back into place.
In vertebrates, which include all animals with a backbone, connective tissues are highly organized and developed. In invertebrates, which include the animals without backbones, connective tissues are not as well organized. However, in nematodes, also known as roundworms (an invertebrate animal), collagen plays a role in movement. The outer covering of the nematode, called the cuticle, consists primarily of collagen. The collagen helps the nematode move and also imparts some longitudinal elasticity. Because the collagen fibers crisscross each other and are not parallel in the nematode cuticle, nematodes are limited in side-to-side movement.
See also Muscular system.
Resources
BOOKS
Brandt, Frederic. AgeLess: The Definitive Guide to Botox, Collagen, Lasers, Peels, and Other Solutions for Flawless Skin. New York: Willima Morrow, 2002.
Brinckmann, Jurgen, Holger Notbohm, and P.K. Muller, eds. Collagen: Primer in Structure, Processing and Assembly. New York: Springer, 2005.
Kane, Michael A.C. The Botox Book. London: Piatkus Books, 2002.
Kathleen Scogna
collagen
Collagen is one of the ‘structural proteins’ (the other widespread one is elastin), which provide support to the tissues. By crude analogy with string, the principal mechanical property of collagen is its ability to resist distending force (tensile strength), which is vastly greater than its ability to resist compression or twisting (compression and torsion strengths). The tensile strength of collagen is so high as to be comparable, weight for weight, with that of steel. Elastin, by contrast, has a low tensile strength but the important mechanical properties of distensibility and resilience: the capability for relatively long range stretching under load and for returning to the original dimensions when the distending force is removed. Collagen can stretch only by about 2% without damage.
Collagen and elastin fibres often co-exist, notably in tissues which regularly undergo considerable changes in shape, such as skin, lungs, and blood vessels. The essentially inextensible, high tensile strength collagen is able to exist and function alongside the elastic fibres simply by having considerable slack. This can easily be illustrated if you pinch up the skin on the back of the hand: it returns to its original shape on release by virtue of the elastic fibres (a property progressively impaired in old age due to degeneration of the elastic fibres, with consequent increase in skin wrinkling). Now with the fingertips push the same skin on the back of the hand sideways and note that it slides quite freely until displacement comes to a distinct halt (when the collagen has used its slack and the tough fibres are pulled into alignment, resisting the distending force).
Collagen is synthesized by fibroblasts, the living cells present in all connective tissue, so named because they generate fibres — of collagen. There are in fact several types, with minor variations of molecular structure. Like all proteins, collagens are constructed from amino acid units; they are all glycoproteins, meaning that glucose and other simple sugars are attached to the amino acid chains. Each long, thin molecule consists of three chains of over 1000 units; each chain is helical, and the three in turn form a triple helix. A molecule is about 300 nm long — over 3000 end-to-end would measure 1 mm — but in fully-formed collagen they overlap lengthwise, and are also linked side to side, providing longer, wider, and very tough fibres. Again like all proteins in the body, collagen has a finite life span after which it is degraded to the constituent amino acids and replaced by new fibres. The synthesis within the fibroblasts is a complex process; the three chains are separately assembled, and then wound into the triple helix, which is extruded. Once outside the cell, the molecules aggregate and forge links as described.
The complexity of collagen synthesis involves multiple enzymes, so that a congenital deficiency of any of these can lead to some disorder of its formation. This accounts for there being a wide variety of clinical syndromes associated with such disorders: there can be fragile bones, with fractures from minimal trauma; fragile blood vessels with widespread bruising; dental defects; readily dislocating joints; a bent or twisted spine; thin, hyperelastic skin; and poor wound healing. Apart from these inborn defects, deprivation of ascorbic acid (vitamin C) at any time of life interferes with a step in collagen synthesis; the resulting bleeding, bruising, and poor healing are part of the picture of scurvy.
With ageing, habitually exposed areas of skin in white-skinned people show broken and disordered collagen fibres, related to the effects of UV light. Deficient replacement of collagen also contributes to thinning and wrinkling of the skin, and, together with mineral loss, to osteoporosis — decreasing bone mass.
These changes suggest that the continuous production of new fibroblasts, and by them of new collagen, progressively declines. Fibroblasts in culture outside the body divide again and again, but do not continue to replicate indefinitely. When such cultures from different animal species are compared, it is found that the number of cell divisions is related to the lifespan of each species, and is also related inversely to the age of the donor from any one species: a finding of considerable interest in the study of the ageing process.
Hugh Elder, and Sheila Jennett
See also ageing; connective tissue.
Collagen
Collagen
Collagen is a protein found abundantly throughout the bodies of animals, including humans. In fact, collagen makes up about one-third of the total body weight. Collagen is an important component of the body's connective tissues, which perform a variety of functions in the body. These tissues provide the framework, or internal scaffolding, for various organs such as the kidneys and lymph nodes. Connective tissues also impart great support and strength to structures such as the bones and tendons. Blood , an important type of connective tissue , transports oxygen and nutrients throughout the body.
Connective tissue is composed of a nonliving, gel-like material called a matrix, in which living cells are embedded. The matrix is composed of different kinds of protein fibers, the most common of which is collagen.
Structure of collagen
Collagen is a fibrous protein; that is, it is composed of many fibers. Each fiber consists of three microscopic ropes of protein wrapped around each other. The fibers in collagen are arranged parallel to each other, and are often grouped together in bundles. The bundling of collagen fibers gives the fibers greater strength than if they occurred individually. Collagen fibers are extremely tough and can resist a pulling force , but because they are not taut, they allow some flexibility.
Locations and functions of collagen
Collagen is a primary component of the connective tissue located in the dermis, the tough inner layer of the skin. This kind of connective tissue is also found in mucous membranes, nerves, blood vessels, and organs. Collagen in these structures imparts strength, support, and a certain amount of elasticity . As the skin ages, it loses some of its elasticity, resulting in wrinkles. Recently, injections of animal collagen given under the surface of the skin have been used to "plump up" the skin and remove wrinkles. However, this treatment is controversial. Many people develop allergic reactions to the collagen, and the procedure must be performed by a qualified physician.
Collagen is also a component of a kind of connective tissue that surrounds organs. This connective tissue encases and protects delicate organs like the kidneys and spleen.
Other locations where collagen fibers are prominent are in the tendons and ligaments. Tendons are straps of tough tissue that attach muscles to bones, allowing for movement. Ligaments are structures that hold the many bones of a joint, such as the knee joint, in proper position. Tendons and ligaments differ slightly in structure. In ligaments, the collagen fibers are less tightly packed than in tendons; in some ligaments, the fibers are not parallel.
Collagen adds strength to tendons and ligaments, and it imparts some stretch to these structures by allowing for some flexibility. However, collagen is not extremely elastic. If tendons and ligaments are stretched too far, these structures will tear, which may lead to problems in movement and bone position. Many athletes tear tendons and ligaments. When tearing occurs, the joint or bone in which the structures occur must be immobilized to allow for proper healing.
Cartilage is a connective tissue found in various places throughout the body, including the tip of the nose, the outside of the ears, the knees, and parts of the larynx and trachea. Cartilage consists of collagen fibers and cartilage cells. At these locations, collagen provides flexibility, support, and movement. Cartilage soaks up water like a sponge and is therefore somewhat "springy" and flexible. If the tip of the nose is pushed in and let go, it springs immediately back into place.
Examples of collagen in the animal kingdom
In vertebrates , which include all animals with a backbone, connective tissues are highly organized and developed. In invertebrates , which include the animals without backbones, connective tissues are not as well organized. However, in nematodes, also known as roundworms (an invertebrate animal), collagen plays a role in movement. The outer covering of the nematode, called the cuticle, consists primarily of collagen. The collagen helps the nematode move and also imparts some longitudinal elasticity. Because the collagen fibers crisscross each other and are not parallel in the nematode cuticle, nematodes are limited in side-to-side movement.
See also Muscular system.
Resources
books
Ayad, Shirley, et al. The Extracellular Matrix Factsbook. San Diego: Academic Press, 1994.
Hay, Elizabeth D., ed. The Cell Biology of Extracellular Matrix. New York: Plenum Press, 1991.
Kucharz, Eugene. The Collagens: Biochemistry and Pathophysiology. New York: Springer-Verlag, 1992.
periodicals
Fackelmann, Kathy A. "Chicken Collagen Soothes Aching Joints." Science News 144 (September 25, 1993): 198.
Johnstone, Iain L. "The Cuticle of the Nematode Caenorhabditis elegans " BioEssays 16 (March 1993): 171.
Young, Crain M., et al. "Smart Collagen in Sea Lilies." Nature 366 (December 9, 1993): 519.
Kathleen Scogna
KEY TERMS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- Cartilage
—A connective tissue found in the knees, tip of the nose, and outside of the ears; it provides flexibility and resilience to these structures.
- Ligaments
—Structures that hold the bones of joints in the proper position.
- Matrix
—The nonliving, gel-like component of connective tissue.
- Tendon
—A strap of tissue that connects muscle to bone, providing for movement.
Collagen
Collagen
OVERVIEW
Collagen (KO-lah-jen) is the most abundant protein in the animal kingdom. Approximately one third of the protein in a mammal's body is collagen. It makes up a major portion of the connective tissue found in skin, joints, ligaments, muscles, tendons, and bones. Different types of collagen occur in different species. That is, the collagen found in humans is somewhat different from that found in cows, and both human and cow collagen differ from the collagen found in other animals, such as dogs and ats. Nonetheless, all forms of collagen have a common molecular structure that consists of three rope-like strands intertwined with each other. Each strand (called tropocollagen) is a polymer consisting of amino acids, the most common of which are glycine, proline, and hydroxyproline. Collagens differ from each other in regard to the relative amounts of each amino acid present.
KEY FACTS
OTHER NAMES:
Not applicable
FORMULA:
Not applicable
ELEMENTS:
Carbon, hydrogen, oxygen, nitrogen
COMPOUND TYPE:
Organic
STATE:
Solid
MOLECULAR WEIGHT:
100,000 to 150,000 g/mol
MELTING POINT:
Not applicable
BOILING POINT:
Not applicable
SOLUBILITY:
Not applicable
HOW IT IS MADE
Collagen is synthesized in the bodies of all higher vertebrates in a complex series of reactions that begin with the linking of amino acids with each other. Amino acids are organic compounds that contain both the carboxyl group (-COOH) and the amino group (-NH2). The amino acids are joined to each other in very long chains known as polypeptides (a word meaning "many amino acids"). After assembly, polypeptide chains intertwine with each other in groups of three to make large molecules called procollagen ("early collagen"), which is then cut into smaller pieces by enzymes designed especially for that purpose. The three strands that make up each collagen group are held together by the action of vitamin C molecules.
COMMON USES AND POTENTIAL HAZARDS
All of the connective tissue in the body contains collagen. This collagen is flexible but not stretchy and will tear if pulled to strongly. Collagen is also a primary component of cartilage, the material that fills the gaps between bones and fills out structures that are firm but somewhat soft, such as the end of the nose and ears. There are at least a dozen types of collagen in the body, each one with a slightly different physical and chemical structure.
Type I is the most abundant kind of collagen. It forms long strands that criss-cross the spaces between cells and is found throughout the body, particularly in tendons, bones, and scars. Type II collagen is found in cartilage, and Type III collagen in granulation tissue that forms when wounds heal. Type IV collagen comprises the basal lumina, the membrane that supports skin and internal surfaces. The eight other types of collagen all have their specific functions in the body.
Plastic surgeons use collagen to fill wrinkles and lines in their patients' faces and bodies. As people age, the tissue that fills out their faces and makes the skin look smooth and tight breaks down, leaving lines and wrinkles. Injecting collagen into wrinkles fills the area under the skin with tissue that puffs out the skin, making it firm and smooth again. Doctors also use collagen to fill in scars. In most cases, collagen treatments are not permanent. The collagen breaks down or is absorbed and additional treatments are necessary to remove wrinkles.
Interesting Facts
- When collagen is treated with boiling water, it is converted to gelatin, a widely used household product. Popular desserts such as Jell-O® are made from collagen taken from the hooves, bones, and connective tissue of cows and pigs.
- In the cooking method known as "braising", meats are heated for a long time over low heat. During braising, collagen molecules "melt" (break apart) producing a tender meaty product in a rich broth that turns to gelatin as it cools. By contrast, cooking meat over high heat causes proteins to shrink and become tougher.
Words to Know
- POLYMER
- A compound consisting of very large molecules made of one or two small repeated units called monomers.
- POLYPEPTIDE
- A molecule composed of many amino acids in a chain.
Several health disorders result from inadequate or abnormal collagen in the body. Scurvy, caused by a deficiency of vitamin C, is the best known of these. When adequate amounts of vitamin C are not present in the body, collagen molecules break apart and muscles and joints are damaged. Ehlers-Danlos syndrome is a disorder that occurs when collagen molecules are weakened, causing bruising of the skin, rupture of arteries or intestines, overly flexible joints, skin and bone deformities, and hip dislocations. Osteogenesis imperfecta results in poorly formed bones and causes the sclera (the white part of the eye) to turn blue.
FOR FURTHER INFORMATION
"Collagenase and Collagen: What Is Collagen?" BioSpecifics Technologies Corporation. http://www.biospecifics.com/collagendefined.html (accessed on December 6, 2005).
"Collagens." Kimball's Biology Pages. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Collagens.html (accessed on December 6, 2005).
Goodsell, David S. "Collagen: Your Most Plentiful Protein." Protein Data Bank. http://www.rcsb.org/pdb/molecules/pdb4_1.html (accessed on December 6, 2005).
Collagen
Collagen
Collagen is a family of proteins; in animals these proteins play critical roles in tissue architecture, tissue strength, and cell to cell relationships. The major component of all connective tissue matrixes, collagen is found in tissues such as skin, blood vessels, bone, tendon, and ligament, and is characterized by tremendous strength.
The word "collagen" derives from the Greek word for "glue"; this derivation is based on the observation that insoluble collagen, when heated in water, becomes soluble, gummy gelatin that can be used in the manufacture of glues or as a thickener in foods. There are ten known forms of collagen that, because of differences in functional requirements and chemical environments, differ in some details of composition. All forms of collagen share the same basic structure: three polypeptide chains coiled together to form a triple helix . (These triple coils, in turn, become coiled together.) Collagen polypeptide chains generally contain around 1,000 amino acids.
An individual collagen polypeptide chain has a large number of repeating amino acid sequences, most often glycine–X–Y, where X is often proline and Y is often hydroxyproline. Lysine, in its pure form or modified to hydroxylysine, is also found in collagen. Both hydroxyproline and hydroxylysine are formed via the enzyme-catalyzed oxidations of the proline and lysine amino acid side chains, which occur after the collagen polypeptide has been synthesized. These enzymatic reactions require ascorbic acid (vitamin C) as a cofactor .
Individual collagen polypeptides form an extended, left-handed triple helix, which is longer and less compact than the α -helixes often seen in proteins. Three of these helixes then form a molecule of tropocollagen , the basic building block of collagen, by coiling around a central axis in a right-handed, triple-helical arrangement. The side chain of every third amino acid is very close to the central axis of this superhelix . Glycine, with the smallest side chain of any amino acid, is more easily accommodated in these arrangements than the larger, bulkier amino acids.
Tropocollagen molecules associate in a staggered fashion to form collagen fibrils , which are stronger than steel wire of similar size. Collagen fibrils are strengthened and stabilized mainly by covalent cross-links, existing both within and between individual tropocollagen molecules. These crosslinks represent the enzyme-catalyzed formation of covalent bonds involving lysine and hydroxylysine side chains. The extent of cross-linking depends on the specific function of the collagen molecule involved and the age of the animal; older animals have more highly cross-linked and therefore more rigid collagen.
There are a number of collagen-related disorders that have been identified. Many of these are the result of derangements in the biosynthesis of collagen. Scurvy, characterized by bleeding gums, loose teeth, skin lesions, and weakened blood vessels, results from severe vitamin C deficiency, which makes it almost impossible for afflicted individuals to form hydroxyproline and hydroxylysine. The conditions, known collectively as the Ehlers–Danlo syndromes, result from defects in the processing of collagen polypeptides.
In addition to its importance in the production of animal glue, collagen is the basis for gelatin, which forms when collagen fibers are denatured as a result of heating and then get tangled up with each other. Collagen is also used for various biomedical applications.
see also Denaturation; Peptide Bond; Proteins.
Matthew A. Fisher
Bibliography
Branden, Carl, and Tooze, John (1999). Introduction to Protein Structure, 2nd edition. New York: Garland Publishing.
Meyers, Robert A., ed. (1995). Molecular Biology and Biotechnology: A Comprehensive Desk Reference. New York: VCH.