IGF-1 administration significantly elevates the platelet levels in vivo and thereby promotes platelet recovery in irradiated mice. (A-B) Peripheral platelet levels (A) and CD41⁺ cells in BM (B) in C57BL/6 mice injected with saline or rhIGF-1 for 7 days. (C-D) H&E staining for MK quantification in the BM from C57BL/6 mice after rhIGF-1 injection. Ten high-power fields per sample were counted. (E) Peripheral platelet counts in C57BL/6 mice irradiated with 6.0Gy total-body irradiation following saline or rhIGF-1 treatment. (F-G) Days that is essential for 50% (F) or 100% (G) recovery of platelet loss from the nadir in irradiated mice with saline or rhIGF-1 injection. (H) Peripheral platelet counts in mice that received BM transplantation (BMT) following a 10.0Gy of irradiation (I-J) Days needed for 50% (I) or 100% (J) recovery of platelet loss from the nadir in grafted mice after rhIGF-1 administration. *P < .05, **P < .01.