A novel in vitro model for xenorejection and immune mechanisms using bioengineered living skin equivalents

We hypothesized that an in vitro bioengineered skin (LSE) could be used for the study of xenogeneic inflammatory or immunosuppressive mechanisms. Murine fibroblasts (10(4)/mL) were mixed with type 1 rat-tail collagen to form a matrix (approximately 5 days) on which human keratinocytes (NHEK, 10(5)/75 microL) were seeded. The xeno-LSE was used as a rejection target organ in vitro. Rejection was achieved by the addition of human lymphocytes (10(6)/75 microL). At various intervals of growth, control LSEs without lymphocytes (CON) and rejecting LSEs with immunocytes (REJ) were analyzed. Slides were stained with hematoxylin & eosin and examined under light microscopy. REJ xenocomposite LSEs showed classic histologic signs of rejection. There was separation of the D-E junction with the presence of dyskeratotic and necrotic cells with a concomitant inflammatory infiltrate. The CON LSEs showed essentially normal dermis (collagen fibroblast matrix) and keratinocytes. A significant finding was the separation of the D-E junction in the absence of an inflammatory infiltrate. Previous studies have shown that human keratinocytes can be grown with human fibroblasts that are histologically similar to natural human skin. This discohesive nature of the murine fibroblasts and human keratinocytes may represent an important intercellular interaction associated with xeno-cellular interactions and is worthy of further study. Furthermore, the ability to grow xeno-composite tissues has profound implications in the face of organ donor shortages. They may represent an eventual in vitro replacement of skin and even solid organs.