Agrin is expressed by MSCs and stimulates in vitro hematopoiesis. (A-B) Confocal images of primary mMSCs isolated from the endosteum (A) or in vitro cultured mMSCs (B) stained for agrin (green) and nuclear DNA (blue). Right panel shows the isotype control. Scale bars, 40 μm. The images are representative of ∼ 95% of the plated mMSCs. (C) Confocal images of osteogenically differentiated mMSCs stained for osteopontin (green). Scale bar, 20 μm. (D) Confocal images of adipogenically differentiated mMSCs stained for FABP4. Scale bar, 50 μm (green). (E) Sorted Lin⁻ c-Kit⁺ BM cells (45.1) were cultured either directly or separated by transwell assay on MSC monolayers from control (ctrl) and Musk-L;Agrn^−/− mice. Hematopoietic proliferation of CD45.1⁺ cells was measured 5 days later. Data are shown as mean ± SEM; n = 4; **P < .01