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Sonic hedgehog (Shh) determines cerebellar granule cell (GC) progenitor proliferation and medulloblastoma pathogenesis. However, the pathways regulating GC progenitors during embryogenesis before Shh production by Purkinje neurons and their roles in tumorigenesis remain unclear. The cilium-localized G-protein-coupled receptor Gpr161 suppresses Shh-mediated signaling in the neural tube. Here, by deleting Gpr161 in mouse neural stem cells or GC progenitors, we establish Gpr161 as a tumor suppressor in Shh subtype medulloblastoma. Irrespective of Shh production in the cerebellum, Gpr161 deletion increased downstream activity of the Shh pathway by restricting Gli3-mediated repression, causing more extensive generation and proliferation of GC progenitors. Moreover, earlier deletion of Gpr161 during embryogenesis increased tumor incidence and severity. GC progenitor overproduction during embryogenesis from Gpr161 deletion was cilium dependent, unlike normal development. Low GPR161 expression correlated with poor survival of SHH subtype medulloblastoma patients. Gpr161 restricts GC progenitor production by preventing premature and Shh-dependent pathway activity, highlighting the importance of basal pathway suppression in tumorigenesis., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)

Skeletal stem cells (SSCs) that are the major source of osteoblasts and adipocytes in adult bone marrow express leptin receptor (LepR). To test whether LepR regulates SSC function, we conditionally deleted Lepr from limb bone marrow stromal cells, but not from the axial skeleton or hypothalamic neurons, using Prx1-Cre. Prx1-Cre;Lepr(fl/fl) mice exhibited normal body mass and normal hematopoiesis. However, limb bones from Prx1-Cre;Lepr(fl/fl) mice exhibited increased osteogenesis, decreased adipogenesis, and accelerated fracture healing. Leptin increased adipogenesis and reduced osteogenesis by activating Jak2/Stat3 signaling in bone marrow stromal cells. A high-fat diet increased adipogenesis and reduced osteogenesis in limb bones from wild-type mice, but not from Prx1-Cre;Lepr(fl/fl) mice. This reflected local effects of LepR on osteogenesis and adipogenesis by bone marrow stromal cells and systemic effects on bone resorption. Leptin/LepR signaling regulates adipogenesis and osteogenesis by mesenchymal stromal cells in the bone marrow in response to diet and adiposity., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The reparative properties of bone marrow stromal cells (BMSCs) have been attributed in part to the paracrine action of secreted factors. We isolated typical human BMSCs by plastic adherence and compared them with BMSC sub-populations isolated by magnetic-activated cell sorting against CD133 (CD133-derived BMSCs, CD133BMSCs) or CD271 [p75 low-affinity nerve growth factor receptor (p75LNGFR), p75BMSCs]. Microarray assays of expressed genes, and enzyme-linked immunosorbent assays (ELISAs) of selected growth factors and cytokines secreted under normoxic and hypoxic conditions demonstrated that the three transit-amplifying progenitor cell populations were distinct from one another. CD133BMSC-conditioned medium (CdM) was superior to p75BMSC CdM in protecting neural progenitor cells against cell death during growth factor/nutrient withdrawal. Intracardiac (arterial) administration of concentrated CD133BMSC CdM provided neuroprotection and significantly reduced cortical infarct volumes in mice following cerebral ischemia. In support of the paracrine hypothesis for BMSC action, intra-arterial infusion of CD133BMSC CdM provided significantly greater protection against stroke compared with the effects of CD133BMSC (cell) administration. CdM from CD133BMSCs also provided superior protection against stroke compared with that conferred by CdM from p75BMSCs or typically isolated BMSCs. CD133 identifies a sub-population of nonhematopoietic stem/progenitor cells from adult human bone marrow, and CD133BMSC CdM may provide neuroprotection for patients with stroke.