Abstract
Transforming growth factor–β1 (TGF-β1) plays a central role in normal and aberrant wound healing, but the precise mechanism in the local environment remains elusive. Here, using a mouse model of aberrant wound healing resulting in heterotopic ossification (HO) after traumatic injury, we find autocrine TGF-β1 signaling in macrophages, and not mesenchymal stem/progenitor cells, is critical in HO formation. In-depth single-cell transcriptomic and epigenomic analyses in combination with immunostaining of cells from the injury site demonstrated increased TGF-β1 signaling in early infiltrating macrophages, with open chromatin regions in TGF-β1–stimulated genes at binding sites specific for transcription factors of activated TGF-β1 (SMAD2/3). Genetic deletion of TGF-β1 receptor type 1 (Tgfbr1; Alk5), in macrophages, resulted in increased HO, with a trend toward decreased tendinous HO. To bypass the effect seen by altering the receptor, we administered a systemic treatment with TGF-β1/3 ligand trap TGF-βRII-Fc, which resulted in decreased HO formation and a delay in macrophage infiltration to the injury site. Overall, our data support the role of the TGF-β1/ALK5 signaling pathway in HO.
Authors
Nicole K. Patel, Johanna H. Nunez, Michael Sorkin, Simone Marini, Chase A. Pagani, Amy L. Strong, Charles D. Hwang, Shuli Li, Karthik R. Padmanabhan, Ravi Kumar, Alec C. Bancroft, Joey A. Greenstein, Reagan Nelson, Husain A. Rasheed, Nicholas Livingston, Kaetlin Vasquez, Amanda K. Huber, Benjamin Levi
Figure 1
Canonical TGF-β signaling in the mouse distal hind limb where HO forms.
