**4.** *In vitro* **models for assessing wound healing activity**

*In vitro* models are generally simple, rapid and involve minimal ethical consideration compared to whole animal work and allow insight into the biochemical and physiological processes induced by the test agent. Many pharmacological agents at different concentrations can be evaluated concurrently without intrinsic heterogenecity associated with *in vivo* models [14]. As regenerative skin is characterized by connective as well as epithelial tissues, both cell types, dermal fibroblasts as well as human fibroblasts (either primary cells or cell lines), should be used for complete assessment of wound healing activity. *In vitro* models are relevant in study of cell-cell and cell-matrix interaction to mimic cell migration during wound healing. *In vitro* models can employ single cell systems, three dimensional systems, multicellular systems or organ cultures in assessing the wound healing properties of wound healing agents or compounds [14, 15].
