| Popis: |
Skin is the largest organ of the human body (8-10 kg, 1.5-2.0 m2, 10(11) cells of epidermal, mesenchymal and neural origin). Although endowed with remarkable regeneration ability, the recovery after major injuries viz. burns requires appropriate surgical treatment, temporary coverage of defects and supportive measures. Large defects are covered with viable transplants of autologous or allogeneic skin, frozen or lyophilized human and animal skin, bioartificial tissues made of synthetic or biodegradable materials, sheets of keratinocytes cultured in vitro. The use of autotransplants is limited by the size of preserved skin areas as well as by general condition of the patient. Allotransplants collected from cadavers or volunteers are rejected after 1 or 2 weeks and thus afford only temporary coverage. Grafts of human or animal skin devitalized by lyophilization or freezing in glycerol accommodate connective tissue and blood vessels ingrowing from the graft bed but eventually dissolve. Artificial skin consists of collagen, chondroitin or similar fiber network (substituting the dermis) covered by semipermeable silicon foil (substituting the epidermis). After healing in, the silicon foil is peeled off and replaced by skin autotransplants or autologous keratinocytes grown and expanded in vitro. The technique for massive production of human keratinocytes, invented some twenty years ago, has been applied for clinical purposes by several specialized centers. During the culture period of approximately three weeks the keratinocyte population may enlarge five to ten thousandfold. Keratinocytes obtained from a 1.5 cm2 piece of skin (half of a postal stamp) may thus yield progeny sufficient for the coverage of 1.5 m2, which is almost the total body surface. The period required for culturing autologous keratinocytes is bridged by temporary transplants and vigorous supportive treatment of the patient. Cultured keratinocytes display all essential features of keratinocytes in situ. They divide and differentiate, express membrane structures required for intercellular communication and reception of signals regulating cell division and differentiation, secrete cytokines. In addition to clinical application, the culture of human keratinocytes is a convenient and useful model for studies of cellular biology. This review is illustrated by first examples of keratinocyte cultures grown in our laboratory. |
