Figure 4.

Agent-based modeling of homeostasis in bone and skin. (A) Agent-based models such as the hybrid cellular automaton (HCA) can describe complex homeostasis like the one in the bone, orchestrated by several cell types and involving a number of signaling molecules (Araujo et al. 2014). (B) An HCA model of prostate cancer with homeostasis of the epithelial cells. Although not always the case, in some simulations, homeostasis can be restored even after cancer initiation. (C) An HCA model of melanoma initiation showing a homeostatic layer of skin growing over the course of a year via interactions between three cell populations (melanocytes, keratinocytes, and fibroblasts) modulated by growth factors (transforming growth factor β [TGF-β], epidermal growth factor [EGF], and basic fibroblast growth factor [bFGF]). (D) (1) Cell population dynamics highlight homeostatic fractions; (2) an emergent property of the homeostatic skin structure is its ability to heal in response to (3) wounding events of differing depths.