Although some markers for the epidermal stem cell compartment have been proposed, their role in specifically identifying keratinocyte stem cells is still controversial.
Therefore, the identification of surface epithelial stem cells relies on either the evaluation of their proliferative capacity or on the identification of slow cycling, [3H]TdR- and BrdU-retaining cells, the latter being feasible only on laboratory animals. The proliferative capacity of human lining epithelial stem cells can be evaluated in vitro by means of clonal analysis. Indeed, three types of keratinocytes with different capacities for multiplication have been identified and isolated in human epidermis, hair follicle, limbal-corneal and conjunctival epithelia, i.e. holoclones, meroclones and paraclones. The authors have recently demonstrated
that cultured autografts bearing holoclones can indeed rapidly and permanently cover a large body surface. Preparation of the wound bed and maintenance
of epidermal stem cells in culture are found to be crucial to the clinical success of the technology. The implications and clincial results of permanent coverage of massive full-thickness burns, treatment of "stable" vitiligo with cultured epidermal autografts and permanent coverage of damaged ocular surfaces after complete loss of the corneal-limbal epithelium as well as ex vivo gene therapy of junctional epidermolysis bullosa are reported in this study and literature review. Basic "quality controls" of the culture system may eliminate one important hitherto uncontrolled variable in the evaluation of cultured autograft clinical performance and should represent a starting point for improving epithelial cultivation, in order to achieve satisfactory and reproducible clinical result
