TYPES OF COLLAGEN
Nearly 28 types of collagen have been identified so far which is composedof 46 distinct polypeptide chains. All of them have a characteristic triple helix but the length of the helix and the size and nature of non-helical portion varies from one to another type (Miller, 1984). Among these the 5 most common ones are:
Collagen I: Skin, bone ,teeth, tendon, ligament, vascular ligature, organs (main constituent of the organic part of bone)
Collagen II: Eyes and cartilage (main constituent of cartilage).
Collagen III: Reticulate (main constituent of reticular fibers), skin, muscle, blood vessels.
Collagen IV: Forms the epithelium-secreted layer of the basement membrane and the basal lamina.
CHARACTERISTICS OF COLLAGEN
Supports most of the tissues in the form of extracellular matrix and gives structure to the cells. It has great tensile strength exhibited by its presence in tendons, bones, cartilage, fascia, etc. It provides elasticity and strength to the skin and helps in tissue and organ development. Collagen provides protection to skin by inhibiting the absorption of toxins and pathogens (Fratzl, 2008). It has role in biological functions of a cell (cell survival, proliferation and differentiation), helps in healing of damaged bones or blood vessels and maintains structural integrity (Buehler, 2006).
It makes use of the skin and bone of cow. It is one of the major industrial sources of collagen. Due to the outbreak of diseases such as BSE, TSE,FMD especially mad cow disease,which pose a threat to the humans, researchers are in search for an alternative safer source of collagen. One of the major disadvantages of bovine collagen is that nearly 3% of the population is allergic to it causing a hindrance in its usage. Bovine Achilles tendon is used industrially to obtain type I collagen. Type IV is obtained from the placental villi and type II from nasal or articular cartilage. Bovine is made use of in different development stages such as fet al bovine dermis used for tendon reinforcement, skin and wound healing (in the form of collagen matrix); neonata bovine dermis is used for hernia repair, plastic and reconstructive surgery; adult bovine pericardium for hernia repair and muscleflap reinforcement (Parenteau-Bareil et al., 2010; Ahuja et al.,2012).
The skin and bones of pigs are utilized. This source iswidely used for obtaining collagen for industrial purpose. Since porcine collagen is almost similar to human collagen it does not cause much allergic response when used. But just like the bovine source the setback of zoonosis poses a risk of contamination and pigs are forbidden due to religious constrains. Adult porcine dermis and small intestinal mucosa is used for tendon reinforcement, hernia repair, skin and wound healing, plastic and reconstructive surgery (Cortial et al., 2006).
Marine source is found to be the safest source for obtaining collagen presently. Another reason for approving this source is due to the belief that “life originated from marine”. Collagen extraction from animal source is complex, time consuming and expensive. The yield obtained is also lower when compared to other sources (approximately 12 g of collagen per 1 kg of the raw material used). Due to the concern over adverse inflammatory and immunologic response and prevalence of various diseases among land animals which causes health complications, marine sources have started to be researched (Addad et al., 2011; Perumal, 2013; Exposito et al., 1999, 2002;). Marine source has got ample advantages over the land animal sources such as:
- Free of zoonosis such as BSE, TSE and FMD
- High content of collagen
- Environment friendly
- Has lower body temperature than animals thereby aids in greater absorption
- Greater absorption due to low molecular weight.
- Less significant religious and ethical constrains
- Minor regulatory and quality control problems
- Presence of biological contaminants and toxins almost negligible
- Low inflammatory response
- Less immunogenic
- Metabolically compatible
This source includes the use of marine invertebrates and vertebrates such as fishes, star fish, jellyfish, sponges, sea urchin,octopus, squid, cuttlefish, sea anemone and prawn (Krishnan & Subramanian & Lin, 2008; Sugiura et al., 2009; Song et al., 2006; Strawich et al., 1971).
The bones, skin, fins, scales of fresh or salt water fishes are mainly used for this purpose. This in turn helps to reduce environmental pollution as these are the considered a waste during fish processing. Study of collagen from marine origin comprises of marine vertebrates and invertebrates. Vertebrates include mainly the fishes (Liang et al., 2010; Tzaphlidou and Berillis, 2002).
Collagen mainly type I was obtained from the skin of
- Gadus morhua
- silver carp Hypophthal michthysmolitrix
- Japanese sea-bass,
- chub mackerel bullhead shark,
- Sole fish;
- Thunnus obesus
- skipjack tuna,
- Japanese sea-bass,
- yellow sea bream,
- horse mackerel; fin of
- Japanese sea-bass scales of
- Pagrus major
- Oreochromis niloticas
OTHER ANIMAL SOURCES
It includes chicken, kangaroo tail, rat tail tendon, duck feet, equine tendon (horse),alligators bone and skin, birds feet, sheep skin (ovine source),frog skin and sometimes even from humans (Johnson et al., 1999; Wood et al., 2008). Recombinant human collagen is used which lower immunogenicity has compared to other sources. Adult equine pericardium is used for tendon reinforcement, skin and wound healing and hernia repair. Type I and II collagen is isolated from equine skin, articular cartilage and flexor tendon (Cortial et al., 2006). Collagen type I,II,III and V were obtained from chicken neck among which type I was predominant. Chicken feet are an abundant source of collagen. Type IX is also found in the chicken embryo sternal cartilage and type I and III from its skin, type IV from its muscular tissues (Hutmacher, 2000; Quereshi, 2010; Mayne et al., 1980). Type I collagen was also obtained from the fallopian tube of bull frog (Wang et al., 2011). From invertebrates tissue of Archaeogastropod, Neritacrepidularia, gastropod collagen was characterized (Palpandi et al., 2010).
Collagen is the most abundant protein found in the animal kingdom. Different types of collagen have already been identified and many more are yet to be found out. The role the collagen plays in our body is chiefly due to its characteristic triple helix. Each type of collagen exhibits different distinctiveness based on their structural features. Collagen is obtained from numerous sources primarily from land animals and birds. Due to the outbreak of diseases such as BSE, TSE, and FMDetc among the land animals, search for an alternative source of collagen became indispensible. Marine sources have started to be explored as a reliable and economic source of collagen. It includes marine fishes, starfish, sponges, jelly fish, squid, etc. The various studies performed till date proves it to be a promising source. Collagen has widespread applications in numerous fields such as pharmaceutical, medical, biomedical, food industry, cosmetics, etc. A wide range of applications of collagen have by now been recognized and many more are waiting be revealed in future. Research is still on its way to identify the various unexplored sources of collagen.
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