A murine model of large-scale bone regeneration reveals a selective requirement for Sonic Hedgehog

Maxwell A. Serowoky, Stephanie T. Kuwahara, Shuwan Liu, Venus Vakhshori, Jay R. Lieberman, Francesca V. Mariani

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6 Scopus citations

Abstract

Building and maintaining skeletal tissue requires the activity of skeletal stem and progenitor cells (SSPCs). Following injury, local pools of these SSPCs become active and coordinate to build new cartilage and bone tissues. While recent studies have identified specific markers for these SSPCs, how they become activated in different injury contexts is not well-understood. Here, using a model of large-scale rib bone regeneration in mice, we demonstrate that the growth factor, Sonic Hedgehog (SHH), is an early and essential driver of large-scale bone healing. Shh expression is broadly upregulated in the first few days following rib bone resection, and conditional knockout of Shh at early but not late post-injury stages severely inhibits cartilage callus formation and later bone regeneration. Whereas Smoothened (Smo), a key transmembrane component of the Hh pathway, is required in Sox9+ lineage cells for rib regeneration, we find that Shh is required in a Prrx1-expressing, Sox9-negative mesenchymal population. Intriguingly, upregulation of Shh expression and requirements for Shh and Smo may be unique to large-scale injuries, as they are dispensable for both complete rib and femur fracture repair. In addition, single-cell RNA sequencing of callus tissue from animals with deficient Hedgehog signaling reveals a depletion of Cxcl12-expressing cells, which may indicate failed recruitment of Cxcl12-expressing SSPCs during the regenerative response. These results reveal a mechanism by which Shh expression in the local injury environment unleashes large-scale regenerative abilities in the murine rib.

Original languageEnglish (US)
Article number30
Journalnpj Regenerative Medicine
Volume7
Issue number1
DOIs
StatePublished - Dec 2022
Externally publishedYes

Bibliographical note

Funding Information:
We would like to thank Divya Patel, Shifa Hossein, Abigail Leyva, David Wen, and Sophia Bougioukli for their technical assistance. We would additionally like to thank Gage Crump, D’Juan Farmer, and Claire Arata for their thoughtful feedback on the manuscript. We also thank Andy McMahon and Haruhiku Akiyama for sharing Ihh:LacZ and Sox9:CreER mouse lines. This work was supported with funding from the Roy E. Thomas Graduate Fellowship (M.A.S.), the National Institutes of Health (T32 HD060549 to M.A.S., S.T.K., and S.L.; R01 AR069700 to F.V.M.; R01 AR057076 to J.R.L.), and a University of Southern California Regenerative Medicine Initiative Award (F.V.M., J.R.L.).

Publisher Copyright:
© 2022, The Author(s).

PubMed: MeSH publication types

  • Journal Article

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