Provided are methods for isolating subpopulations of stem cells. In some embodiments, the presently disclosed methods include selecting subsets of cells that are positive for CD34 or Sca-1, are further positive for one or more of FSHR, LHCGR, PRLR, AR, ESRα, ESRβ, and PGR; and are negative for each of CD45R/B220, Gr-1, TCRαβ, TCRγδ, CD11b, and Ter-119. In some embodiments, the subpopulations are further fractioning into CD45− and CD45+ fractions. Also provided are populations of stem cells isolated by the presently disclosed methods, compositions that include the presently disclosed subpopulations in pharmaceutically acceptable carriers, methods for expanding stem cells, methods for stimulating proliferation of MSCs, methods for treating subjects suffering from exposure to radiation, and methods for producing gametes in vitro.