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Epithelial-Mesenchymal Interactions Between Hair Follicles and Dermal Adipose Tissue

2022; Springer Nature; Linguagem: Inglês

10.1007/978-3-030-98331-4_6

2196-8993

Raúl Ramos, Maksim V. Plikus,

Skin and Cellular Biology Research

The skin forms the outer layer of the body and provides animals with an array of functions vital for their survival and adaptation to external environment. Hair follicles and dermal adipose tissue (dWAT) are two major components of mammalian skin, each with its distinct anatomy and cellular lineage. Yet, in late embryogenesis they come in direct contact and become physiologically coupled in adulthood into a remodelling cycle. Indeed, in species, such as Mus musculus, dWAT prominently and reversibly expands in volume when adjacent hair follicles transition from resting to active growth phase. Recent studies reveal that such coupling is supported by direct epithelial-mesenchymal interactions between hair follicle and dWAT cells via several paracrine signaling pathways. Here, we review classic and emerging literature regarding epithelial-mesenchymal interactions between hair follicles and dWAT and its implications for mammalian skin physiology under thermoregulatory, immuno-protective, and regenerative contexts. We conclude that reciprocal molecular interactions between hair follicles and dWAT are essential for normal physiology of mammalian skin. Paracrine signals between closely associated hair follicles and dWAT profoundly affect each other’s cyclic behavior and tissue volume. Upon excisional skin wounding, newly regenerated hair follicles in the center of the scar secrete signaling factors that induce reprograming of the cellular fate of wound fibroblasts into new adipocytes. Further, upon bacterial infection, both dermal adipocytes and, likely, hair follicles install a rapid innate immune response to combat pathogenic invasion. In summary, cyclic epithelial-mesenchymal interactions between hair follicles and dWAT are essential for optimizing their joint thermoregulatory, immune-protective and regenerative functions. Further study of their communications will not only provide answers to standing questions in basic skin biology, but can also inform new solutions to unmet clinical needs, including therapies for alopecia, lipodystrophy and skin scarring.