Proliferation of human keratinocytes and cocultured human keratinocytes and fibroblasts in three-dimensional fibrin constructs.

Over the last several years, our in vitro and in vivo studies have focused on optimizing the use of fibrin to deliver cells. We have shown that some three-dimensional (3D) fibrin constructs with specific fibrinogen and thrombin concentration support robust proliferation of normal human dermal fibroblasts, whereas different fibrinogen and thrombin concentrations support high mesenchymal stem cell proliferation in 3D fibrin constructs. In this article, we found that normal human epithelial keratinocytes proliferate well in 3D fibrin constructs consist of fibrinogen concentration ranging from 17 to 33 mg/mL and thrombin concentration of 1 U/mL. Further, using a new proliferation assay, we studied the proliferation of fibroblasts and keratinocytes cocultured in various 3D fibrin constructs of different fibrinogen and thrombin concentrations. We found that 3D fibrin constructs with a range of fibrinogen concentration (5-34 mg/mL) and a thrombin concentration of 1 U/mL produce an optimal cell proliferation for both cell types when cocultured. This profile of proliferation is different from that seen when keratinocytes or fibroblasts are incorporated separately in 3D fibrin constructs. In conclusion, we found that one needs to choose the fibrinogen and thrombin concentration carefully depending on the cell type to deliver; that is, different fibrin constructs with different fibrinogen and thrombin concentration are required to deliver fibroblasts or keratinocytes alone or to codeliver both cell types. Moreover, there seems to be a cross-talk between keratinocytes and fibroblasts when they are cointroduced in 3D fibrin constructs. This feedback could be due to the effects of growth factors produced by the two cell types in the 3D fibrin constructs.