Transforming growth factor beta 1 (TGFβ1) 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 TGFβ1 signaling in macrophages, and not mesenchymal stem/progenitor cells (MPCs), is critical in HO formation. In-depth single cell transcriptomic and epigenomic analyses in combination with immunostaining of cells from the injury site demonstrate increased TGFβ1 signaling in early infiltrating macrophages, with open chromatin regions in TGFβ1 stimulated genes at binding sites specific for transcription factors of activated TGFβ1 (SMAD2/3). Genetic deletion of TGFβ1 receptor type 1, (Tgfbr1;Alk5) in macrophages, results 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 TGFβ1/3 ligand trap TGFβRII-Fc, which results in decreased HO formation and a delay macrophage infiltration to the injury site. Overall, our data support the role of the TGFβ1/ALK5 signaling pathway in HO.
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, Joseph A. Greenstein, Reagan Nelson, Husain A. Rasheed, Nicholas Livingston, Kaetlin Vasquez, Amanda K. Huber, Benjamin Levi