**Author details**

as a skin barrier [40]. Other advantages to the use of 3D skin cell cultures include longer cell culture use between 10 and 30 days [40]. More recent human skin equivalent (HSE) cultures can even be used for up to 20 weeks [41]. Skin substitutes that are derived from only the epidermal layer and primarily keratinocytes are limited in their use for testing of products related to particular types of skin conditions that involve the immune system, including testing of products for wound healing [47]. Full thickness models consisting of both the epidermal and dermal layers are thus beneficial [8]. 3D bioprinting of skin constructs are also advantageous as they provide a greater accuracy in placement of cells and extracellular matrices as well as having the potential of imbedding vasculature in the skin construct as bioprinting of vasculature is also possible [54]. Skin constructs made through bioprinting are also considered to have high plasticity [54]. Skin bioprinting may also be used for developing 3D models for drug testing, such as diseased skin models, and are considered to provide more uniform models vs. manually developed skin models [55]. The primary disadvantage to the use of 3D skin cell cultures, however, is the cost associated with developing these cultures [40, 54]. See

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

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.

**Table 1** for a summary of the information presented in this section.

**8. Conclusion**

14 Cell Culture

interactions were developed [7].

manually developed skin models [55].

**Conflict of interest**

No conflicts of interest.

Arezou Teimouri, Pollen Yeung and Remigius Agu\*

\*Address all correspondence to: remigius.agu@dal.ca

Dalhousie University, Halifax, Canada
