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Grafting
Artificial
Skin
Obtained
from
Cultured
Cells
After
Severe
Burns - Skin is prehaps the only organ that can be artificially made from cell culture and used for grafting, when skin is severely damaged due to severe burns. Of the few cell types that can be cultured are keratinocytes, which make 90% of the epidemis of skin.
They are responsible for giving rise to corneocytes (dead cells) making the external cornified layers of skin, and their proliferation is facilitated by the products of fibroblasts found in the dermis layer of the skin.
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Since fibroblasts are useful for culturing keratinocytes, fibroblast cells called 3T3 cells were used (after irradiating with lethal dose to prevent their own growth) to cover the bottom of vessel, before adding epidermal cells for culturing them. Other substances added in culture medium included epidermal growth factors, cholera toxin and a mixture of other growth factors.
Only '1-10%' epidermal cells proliferate, others having already started the process of differentiation. These cells form colonies, are separated again and transferred to fresh culture to allow better growth. The process of separating cells from colonies and reculturing them is continued to discourage stratification of cell layers and allow the cell colonies to become confluent forming a sheet of pure epithelium.
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The cells of this sheet of epithelium are linked by desmosomes. This cultured epithelium can be detached from the vessel using the enzyme dispase, washed free of extraneous protein, attached to a backing of gauze and brought to the hospital to be used for grafting on the patients having severe burns.
A meticulous preparation of wounds is required, since they are often contaminated, and complete elimination of micro-organisms is essential.It is important that cultured kerationcytes used to generate epidermis must come from the unburned portion of the skin of the patient himself; otherwise these will be soon rejected.
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Starting from 3 cm2 skin of the patient, it can be expanded 5,000 fold in 3-4 weeks to supply 1. 7m2 of skin needed for an adult human. The entire body may need 350 grafts, each of 25cm2 to cover only the front or back surface.
Before the cultured epithelium became available, split thickness grafts were used which involved transfer of 0.3mm thick skin (epidermis + part of dermis) from one part of body to the other. Such grafting leads to quick recovery and normalization of skin.
However, in grafting of cultured skin, if samples of regenerated skin are taken over a period of five years , the different elements of normal skin return at different rates, but eventually normal skin, with all essential components, is regeneraled.
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A variety of diseases have also been treated using cultured keratinocytes. Following are some examples:
(i) Scars on skin can be removed using cultured skin.
(ii) Cultured oral keratinocytes have been used to regenerate epitheluim of mouth.
(iii) Cultured urethral keratinocytes have been used to repair congenital penile defects.
(iv) For some middle ear diseases with troublesome discharge also, cultured epidermal keratinocytes are used.
(v) Chronic skin ulcers have also been treated with cultured grafts; even allografts (skin from another individual) are successful in these ulcers.
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More than 500 patients throughout the world have already received cultured keratinocytes for treatment of burms, ulcers or other conditions. However, this is a very small number in comparison with the number of patients, who need this help. In future, other cell types may also be successfully cultured and used for following applications:
(i) use of cultured endothelial cells for lining of vascular prostheses (artificial limbs, etc.);
(ii) use of cultured urothelial cells to repair urinary tracts;
(iii) use of pancreatic islet cells to treat diabetes;
(iv) use of cultured liver cells to provide for hepatic function;
(v) use of cultured myoblasts to treat muscle diseases. A more detailed account of the subject is available in Scientific Americal (Nov., 1991).
Fertility control Efforts have also been made in the past for developing safe, efficacious, cost effective, long lasting and reversible contraceptives. In this connection, following examples demonstrate the success of Indian scientists in this area.
Once a weak oral pill. For the last 20 years, scientists at the Central Drug Research Institute (CDRI), Lucknow, have been working for the development of an oral, once a week, non-hormonal contraceptive pill.
This effort resulted in developing a pill called centchroman sold in the commercial name 'Saheli', which was sent to the market in June, 1991. This pill has proved to be free from any side effect and is now in great demand all over the world, being the only non-hormonal contraceptive pill.
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