PDGF receptor expression on BM MSCs, in relation to systemic changes, by flow cytometry. A) Positive correlation between BM MSCs quantified by CFU-Fs assay and by flow cytometry for the CD45-CD271+ phenotype. B) Average proportions of PDGFRα(CD140a)- and PDGFRβ(CD140b)-positive subpopulations within BM MSCs (empty bars) and control HLCs (dark bars), showing the abundance of both PDGF receptors on MSCs compared to HLCs. Error bars represent SDs, n =10. C) CD140a (left panel) and CD140b (right panel) expression on CD45-CD271+ MSCs from 10 individual patients at two time-points; adjacent bars represent Day 0 Baseline and the second time point. D) Correlations between changes in proportion CD140a and CD140b receptor positive MSCs with changes in platelet levels in the same patient (<1 decline, >1 increase). BM, bone marrow; CFU-F, colony-forming unit-fibroblast; HLCs, haematopoietic lineage cells; MSCs, mesenchymal stem cells; PDGR, platelet-derived growth factor; SD, standard deviation.