Fig. 4.

Developmental Osr1⁺ cells are a source for adult FAPs. a Osr1 is expressed in PDGFRα⁺ interstitial mesenchymal progenitors at birth (postnatal day P0). b Osr1 cell lineage tracing in adult (P84/12 week) Osr1 ^GCE/+;R26R ^LacZ/+ animals after Tamoxifen induction at P0. Osr1⁺ cell progeny is marked by immunolabelling for beta-Galactosidase (bGal). Perinatal Osr1⁺ cells give rise to interstitial PDGFRα⁺ FAPs. c Osr1 cell lineage tracing in adult (12 week) Osr1 ^GCE/+;R26 ^mTmG/+ animals after Tamoxifen induction at P0; Osr1 ^+/+;R26 ^mTmG/+ animals used as controls are shown left. FAPs (Sca1⁺, CD34⁺), satellite cells (SAT) and double-negaitve cells (DN) were FACS-isolated and analysed for mGFP expression. Only FAPs contained a clearly detectable mGFP⁺ population (n = 3). d mGFP⁺ and mGFP⁻ FAPs isolated as in c were cytospun and analysed for PDGFRα and Tcf4 expression. Quantification is shown below (n = 3). e The contribution of p0 Osr1⁺ cells to muscle interstitial PDGFRα⁺ and Tcf4⁺ cells was quantified on sections of Osr1 ^GCE/+;R26 ^mTmG/+ animals in the indicated muscles. Quantification is shown below (n = 4). Values represent mean ± s.e.m. N-numbers indicate biological replicates, i.e. samples from different specimen