**8. Conclusion**

Testing the efficacy and safety of dermatological products and medications using *in vitro* methods such as cell cultures can be considered as a replacement to animal testing. Cell cultures currently exist in both 2D and 3D forms. The very first cell cultures developed were of human skin which allowed for a better understanding of the physiological functions of the skin [5]. *In vitro* skin cell cultures developed initially were primarily 2D with keratinocytes as the primary cell types used [8, 9]. However, it became evident that an *in vitro* model consisting of both keratinocytes and fibroblasts is required to better mimic the physiological functions of the human skin, especially with relation to the wound healing properties of the skin [5]. For this reason, 3D cell cultures that allowed greater cell-to-cell and cell-to-extracellular matrix interactions were developed [7].

It is evident from the information presented in this chapter that 3D skin cell cultures can more closely mimic *in vivo* processes vs. 2D skin cell cultures for both wound healing and psoriasis. In addition, full thickness 3D skin equivalents that consist of both an epidermal and dermal layer are a better representation of the human skin [8]. Microfabricated cell systems, however, provide arguably an even better model for mimicking *in vivo* skin processes including vasculature and thus allowing for the testing of absorption of pharmaceutical products [50–52]. Additionally, 3D bioprinting provides greater accuracy in placement of cells and extracellular matrices along with the potential of imbedding vasculature in the skin construct as well as having great plasticity [54]. 3D bioprinted skin models also provide more uniform models vs. manually developed skin models [55].
