Provided herein are methods for increasing the number of hematopoietic stem and progenitor cells (HSPCs) in vivo or in vitro. The methods can include the steps of selecting a subject in need of an increased number of HSPCs and administering to the subject an effective amount of an inhibitor of VEGF to increase the number of HSPCs in the subject. Optionally, the methods include the steps of contacting a population of HSPCs and supporting cells with an inhibitor of VEGF, and contacting the population of HSPCs and supporting cells with a parathyroid hormone (PTH) receptor agonist. Also provided is a method for increasing the number of hematopoietic stem and progenitor cells (HSPCs) in a subject including the steps of administering to the subject an inhibitor of VEGF, and administering to the subject a parathyroid hormone (PTH) receptor agonist. The method is optionally used in a subject or for a with decreased osteogenesis, including, for example, when the subject has a bone fracture or has osteoporosis. Compositions and kits for increasing the number of HSPCs comprising (i) one or more doses of an inhibitor of VEGF and (ii) one or more doses of a PTH receptor agonist are also provided.
