Fig. 6: Analysis of local mesenchymal stromal cell subtypes at the site of injury 3 days post-surgery revealed significant differences in subtype distribution and priming.

Mesenchymal stromal cells (MSCs) were analyzed via flow cytometry in the untreated bone marrow and at the fracture site in the immunoaged and aged groups. a Flow cytometric analysis of bone marrow from the untreated bone versus the fracture hematoma three days post-surgery. Osteotomy increased the availability of MSCs (CD45-CD34-CD31-(Lin)Sca-1+) at the fracture site. The mobilization and recruitment of MSCs was significantly increased in the aged group. The immunoaged group, however, showed less proliferation and migration. b The heterogeneity of MSC subtypes also differed between groups with different immunological experience levels. Specialized MSCs were present at different frequencies, as a higher percentage of MSCs in the aged mice were PαS cells (Sca-1+ CD140a+), whereas a higher percentage were murine skeletal stem cells (mSSC, Sca-1+ CD51+) in the immunoaged mice. N = 4 per group; box-and-whisker plot with a line at the median; Welch’s t-test; black * = between immunological experience groups, gray * = between untreated and osteotomized groups.