Hematopoiesis recovery is augmented after FSH treatment. a, b Cell surface expression of FSHR (green) on both small VSELs (top panel) and slightly bigger HSCs (bottom panel) which survive 5-FU treatment in mouse BM on D4. c Co-expression of SCA-1 (red) and FSHR (green) on the same cells. The nuclei are counterstained with DAPI. Scale bar = 20 μm. d, e H & E sections on D4 showed increased BM cellularity after FSH treatment on D4 (d) compared with FSH minus control. e In 5-FU + FSH-treated sections, the endogenous bone marrow regeneration was almost complete by D7 after 5-FU treatment compared with untreated controls. f Flow cytometry data showed an increase in number of VSELs and HSCs on FSH treatment. g BrdU uptake also increased on FSH treatment slightly in the primitive Lin–/CD45– (enriched in VSELs) while a significant increase (p < 0.001) was seen in Lin–/CD45+ (HSC-enriched) cells. h Upregulation of transcripts specific for pluripotent, primordial germ cells, and proliferation markers on FSH treatment compared with untreated controls. Significant increase in Oct-4 and Stella transcripts was observed. Please note that Oct-4 transcripts (which reflect HSCs) were more than Oct-4A (which reflects VSELs). Bars in f, g represent average ± SD and in h average ± SEM. Representative of five experiments in f, g and in h data obtained from three experiments. *p ≤ 0.05. ***p ≤ 0.001. D4-5-FU, D7-5-FU days post 5-FU treatment, FSH follicle-stimulating hormone, BM bone marrow, 5-FU 5-fluorouracil, H & E hematoxylin and eosin, VSEL very small embryonic-like stem cell, FSHR follicle stimulating hormone receptor, SCA-1 stem cell antigen-1, HSC hematopoietic stem cell, OCT-4 octamer binding transforming factor-4, BrdU bromodeoxyuridine (Color figure online)