Dermal Microvascular Responses of Human Induced Pluripotent Stem Cell-Derived Skin Organoids to Inflammation and Injury.

Cutaneous dermal microvascular responses are critical to common inflammatory skin conditions and effective wound healing. However, few laboratory models effectively recreate the spatially intact microenvironment essential for genesis and function of the human dermal microcirculation. Recently, stem cell-derived skin organoids (SKOs) have been developed that possess many microanatomic and cellular features of native human skin, including hair-forming epidermis and an underlying dermal layer containing endothelial-lined channels. Here, temporal dynamics of human SKO vasculogenesis are profiled and organoid responses to inflammatory and traumatic stimuli are interrogated. SKOs generated from induced pluripotent stem cells expressing endothelial-specific green fluorescent protein develop vasculogenic foci by post-differentiation day 6 that evolved into extensive microvascular networks that persisted beyond 4 months in culture. Multiplex antibody arrays provided mechanistic insight into secreted effectors supporting early events in SKO vasculogenesis. Over time, SKO microvasculature became ensheathed by mural cells producing collagen IV-rich basement membranes, whereas endothelium retained signatures of proliferative activity/immaturity. Functionally, SKOs treated with proinflammatory cytokines expressed markers of endothelial and perivascular vascular activation, with concomitant release of endogenous inflammatory mediators. Finally, wounding of SKOs via sharp dissection provided the first demonstration of angiogenic healing responses that were further augmented by exogenous vascular endothelial growth factor. Overall, this advanced human culture system represents a highly relevant model for understanding biological responses by the dermal microvasculature.