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学术报告

12:30-13:30, Monday, September 11


Speaker: Ya-Chieh Hsu, Ph.D.

Professor

Harvard Department of Stem Cell and Regenerative Biology

Topic: transit-amplifying cells: The real GOVERNOR OF Tissue REGENERATION

Host: Ting Chen, Ph.D.

Abstract

Most of the regenerative tissues employ transit-amplifying cells (TACs) that are positioned in between stem cells and differentiated progeny. In a classical hierarchical model, stem cells undergo limited divisions to produce TACs, which then proliferate rapidly to expand the system and produce diverse differentiated cell types. Although TACs are indispensible for generating tissues, they have been viewed largely as a transit point between stem cells and downstream lineages.

Our studies in the hair follicles however, have unleashed some fascinating biology and unanticipated functions of TACs. Ongoing works from my lab suggest that hair follicles’ transit amplifying cells (HF-TACs, also known as the matrix) orchestrate concurrent changes of the niche, including several different populations in the dermis. Together, these changes allow the skin to accommodate and support the rapidly downgrowing hair follicles and heal wounds faster in anagen. One example is HF-TACs’ function in promoting dermal adipogenesis: We discover that Sonic Hedgehog (SHH) secreted by the HF-TACs acts on dermal adipocyte precursors to promote dermal adipogenesis. This finding provides a mechanism by which hair follicle regeneration and dermal adipogenesis can be coupled tightly. In addition, this finding also uncovers a critical role for TACs in orchestrating the generation of both their own progeny (differentiated cells of the hair) and a neighboring lineage (adipocytes) to achieve concomitant tissue production across lineages.

Together with my previous published work, HF-TACs have emerged as key players in tissue regeneration through coordinating tissue production, governing stem cell behaviors, and instructing niche remodeling.