Sirolimus stimulates HSPC expansion in B6 mice carrying c-Kit mutation. Heterozygous B6-Wv mice carrying c-Kit mutation were untreated (CON, N = 7) or were injected with 2 mg/kg/d of sirolimus (SIR, N = 8) for 13 days. Mice were bled and analyzed at day 14. A, Peripheral blood RBC, WBC, and platelet counts and total BM cells in B6-Wv mice treated with or without sirolimus. B, Proportions and total numbers of KSL and KSLS HSPCs in the BM of B6-Wv mice treated with or without sirolimus. C, Proportions and total numbers of c-Kit-expressing Lin⁻ and total BM cells in sirolimus-treated B6-Wv mice. *P < .05; ***P < .001; ****P < .0001. BM, bone marrow; HSPCs, hematopoietic stem and progenitor cells; KSLS, KSLCD150⁺