Reorganizing Niche Architecture Still Preserves Organ Function in the Hair Follicle

Stem cells ability to build and replenish tissues depends on support from their niche. While niche architecture varies across different organs, the functional importance of niche architecture is unclear. During hair follicle growth, multipotent epithelial progenitors build hair via crosstalk with their remodeling fibroblast niche, the dermal papilla, providing a powerful model to functionally interrogate different niche architectures. Through intravital imaging, we show that dermal papilla fibroblasts remodel both individually and collectively to form a polarized, structurally robust niche. Polarized TGF{beta} signaling precedes structural niche polarity, and loss of TGF{beta} signaling in dermal papilla fibroblasts leads them to progressively lose their stereotypic architecture and instead surround the epithelium. The reorganized niche relocates multipotent progenitors, but nevertheless supports their proliferation and differentiation. However, progenitor differentiation is completed prematurely, resulting in compromised hair production. Overall, our results reveal that niche architecture optimizes organ efficiency, but is not absolutely essential for organ function.