Une nouvelle méthode de culture cellulaire pour le remplacement permanent du revêtement cutané endommagé

Abstract

Les fonctions de la peau sont multip����es et vitales, si bien qu'aucun être humain ou animal ne peut s'en passer. Malheureusement, cet organe essentiel s'avère fragile et est sujet à de nombreuses agressions provenant du milieu extérieur. Les traumatismes graves comme les brûlures nécessitent impérativement le remplacement de la peau endommagée. Plusieurs méthodes ont été développées pour tenter de régénérer le revêtement cutané détruit, chacune présentant ses avantages et ses inconvénients. Ainsi, la solution idéale n'existe-t-elle toujours pas, justifiant de nouvelles recherches et de nouvelles approches. L'une d'entre elles, la culture et la greffe de feuillets épidermiques chimères, apparaît aujourd'hui très prometteuse.

Skin is the main interface between the organism and the environment. This organ is only a few millimetres thick, but still constitutes the body's largest organ. It is particularly vulnerable to environment-induced traumas. Extensive skin loss such as in burns causes serious complications and may lead to death if not prevented by early wound closure. In extensively burned patients, donor site availability for meshed skin autografting remains the limiting factor for wound coverage and skin replacement. The concept of using allogeneic skin for burn treatment remains an interesting one. However, full engraftment does not occur since these grafts remain immunogenic. Recently, cultured epithelial sheets have been used as an adjunct therapy. Human epidermal cells have been grown in vitro and successfully used for grafting onto skin defects and extensive burn wounds. However, this new therapeutic approach has the disadvantage of requiring delays of up to 4 to 5 weeks to allow epithelial cells to grow in vitro. Some research groups have tried to overcome this drawback by grafting allogeneic epidermal sheets devoid of Langerhans cells. However, strong arguments based on immunological mechanisms have prompted doubts about the permanent survival of these cultured epidermal allografts. Since cultured epithelium allografting proved impossible, as well as the fact that the cutaneous tissues of extensively burned patients have to be replaced quickly and permanently, using an experimental model, we devised, a new culture technology using allogeneic and syngeneic epithelial cells for chimeric graftable sheet production. Indeed, 14 days postgrafting, chimeric implants (50 %Balb/c-50 %3CH/HeN, 25 %Balb/c-75 %C3H/HeN grafted onto Balb/c adult mice) showed the same percentages of implantation success (> 80%) as for isografts. Histological studies revealed a well-organized cutaneous tissue containing basal and suprabasal cell layers. These histological observations were confirmed by results showing the presence of basement membrane proteins (laminin, and type IV collagen). The chimeric results were comparable to those obtained with isografts, meanwhile allografts showed complete degradation, indicating implant rejection. Thirty days postgrafting, immunohistological studies revealed that chimeric implants allowed epidemis regeneration, and that these chimeric epithelial sheets showed no sign of rejection over time, while their allogeneic keratinocytes seemed to be passively 'removed' from the implants. Clinically, the use of this chimeric culture method (mixture of allogeneic and autologous keratinocyte populations) for large burn wound treatment could be a significant therapeutic advance. It may reduce by at least 50% the previously described delay for epidermal culture, and significantly lower the cost of burn management during patient hospitalization. Also, since the ultimate aim in allogeneic transplantation is to achieve immunological tolerance between donors and recipients, this chimeric culture approach may provide ways to study tolerance phenomena in cutaneous tissues. [References: 39]