TNFSF11 and Osteopenia: M-CSF activates mTOR/PI3K/Akt pathway, and it has been shown that rapamycin blocks M-CSF and RANKL-induced osteoclastogenesis.28 Our study offers novel insights pointing to inhibition of frequency of osteoclast progenitor pool by rapamycin in Sf mice leading to amelioration of osteopenia.