Rajan, A. M. | Search bioRxiv

bioRxiv2023

Single-cell analysis reveals distinct fibroblast plasticity during tenocyte regeneration in zebrafish

Despite their importance in tissue maintenance and repair, fibroblast diversity and plasticity remain poorly understood. Using single-cell RNA sequencing, we uncover distinct sclerotome-derived fibroblast populations in zebrafish, including progenitor-like perivascular/interstitial fibroblasts, and specialized fibroblasts such as tenocytes. To determine fibroblast plasticity in vivo, we develop a laser-induced tendon ablation and regeneration model. Lineage tracing reveals that laser-ablated tenocytes are quickly regenerated by preexisting fibroblasts. By combining single-cell clonal analysis and live imaging, we demonstrate that perivascular/interstitial fibroblasts actively migrate to the injury site, where they proliferate and give rise to new tenocytes. By contrast, perivascular fibroblast-derived pericytes or specialized fibroblasts, including tenocytes, exhibit no regenerative plasticity. Interestingly, active Hedgehog (Hh) signaling is required for the proliferation of activated fibroblasts to ensure efficient tenocyte regeneration. Together, our work highlights the functional diversity of fibroblasts and establishes perivascular/interstitial fibroblasts as tenocyte progenitors that promote tendon regeneration in a Hh signaling-dependent manner. TEASERPerivascular/interstitial fibroblasts function as plastic progenitors during tenocyte regeneration.

developmental biology↗

bioRxiv2020

Dual function of perivascular fibroblasts in vascular stabilization in zebrafish

Blood vessels are vital to sustain life in all vertebrates. While it is known that mural cells (pericytes and smooth muscle cells) regulate vascular integrity, the contribution of other cell types to vascular stabilization has been largely unexplored. Using zebrafish, we identified sclerotome-derived perivascular fibroblasts as a novel population of blood vessel associated cells. In contrast to pericytes, perivascular fibroblasts emerge early during development, express the extracellular matrix (ECM) genes col1a2 and col5a1, and display distinct morphology and distribution. Time-lapse imaging reveals that perivascular fibroblasts serve as pericyte precursors. Genetic ablation of perivascular fibroblasts results in dysmorphic blood vessels with variable diameters. Strikingly, col5a1 mutants show spontaneous hemorrhage, and the penetrance of the phenotype is strongly enhanced by the additional loss of col1a2. Together, our work reveals dual roles of perivascular fibroblasts in vascular stabilization where they establish the ECM around nascent vessels and function as pericyte progenitors. AUTHOR SUMMARYBlood vessels are essential to sustain life in humans. Defects in blood vessels can lead to serious diseases, such as hemorrhage, tissue ischemia, and stroke. However, how blood vessel stability is maintained by surrounding support cells is still poorly understood. Using the zebrafish model, we identify a new population of blood vessel associated cells termed perivascular fibroblasts, which originate from the sclerotome, an embryonic structure that is previously known to generate the skeleton of the animal. Perivascular fibroblasts are distinct from pericytes, a known population of blood vessel support cells. They become associated with blood vessels much earlier than pericytes and express several collagen genes, encoding main components of the extracellular matrix. Loss of perivascular fibroblasts or mutations in collagen genes result in fragile blood vessels prone to damage. Using cell tracing in live animals, we find that a subset of perivascular fibroblasts can differentiate into pericytes. Together, our work shows that perivascular fibroblasts play two important roles in maintaining blood vessel integrity. Perivascular fibroblasts secrete collagens to stabilize newly formed blood vessels and a sub-population of these cells also functions as precursors to generate pericytes to provide additional vascular support.

developmental biology↗