MATHEMATICAL MODELS OF CALCIUM AND TIGHT JUNCTIONS IN NORMAL AND RECONSTRUCTED EPIDERMIS
Bulletin of the Australian Mathematical Society
The epidermis is the uppermost layer of the skin. It possesses a distinct stratified structure consisting of four sublayers and a characteristic calcium profile which is strongly implicated in regulating this structure. The calcium concentration rises from low concentrations in the lowest sublayers (stratum basale and stratum spinosum) to a peak in the overlying sublayer (stratum granulosum) and then drops to negligible levels in the most superficial sublayer (stratum corneum). The factors that
... ). The factors that regulate the formation of the epidermal calcium profile are currently a source of debate. These factors definitely include (1) passive regulation by the primary barrier function of the stratum corneum, but may also include (2) active regulation due to calcium exchanges between cells and the surrounding extracellular fluid (ECF) and (3) extracellular transport limitation in the stratum granulosum due to the secondary barrier formed by tight junctions there. The relative importance of the latter two factors to the formation of the epidermal calcium profile has yet to be resolved. Epidermal cells (keratinocytes) can also be cultured in vitro to form a multilayered structure ('reconstructed epidermis') that strongly resembles its in vivo counterpart ('normal epidermis'). However, reconstructed epidermis typically lasts less than a month, following a well-defined but unexplained growth and deterioration pattern. This is a serious clinical issue that affects its ability to be stored as a readily available skin replacement for patients requiring emergency treatment. Because the calcium distribution regulates epidermal structure, it is quite possible that its altered dynamics in vitro could be responsible for the deterioration of reconstructed epidermis, although this has not yet been investigated.