The differentiation factor NEL-like molecule-1 (NELL-1) has been reported as osteoinductive in multiple in vivo preclinical models. Bone morphogenetic protein (BMP)-2 is used clinically for skeletal repair, but in vivo administration can induce abnormal, adipose-filled, poorquality bone. We demonstrate that NELL-1 combined with BMP2 significantly optimizes osteogenesis in a rodent femoral segmental defect model by minimizing the formation of BMP2-induced adipose-filled cystlike bone. In vitro studies using the mouse bone marrow stromal cell line M2-10B4 and human primary bone marrow stromal cells have confirmed that NELL-1 enhances BMP2-induced osteogenesis and inhibits BMP2-induced adipogenesis. Importantly, the ability of NELL-1 to direct BMP2-treated cells toward osteogenesis and away from adipogenesis requires intact canonical Wnt signaling. Overall, these studies establish the feasibility of combining NELL-1 with BMP2 to improve clinical bone regeneration and provide mechanistic insight into canonical Wnt pathway activity during NELL-1 and BMP2 osteogenesis. The novel abilities of NELL-1 to stimulate Wnt signaling and to repress adipogenesis may highlight new treatment approaches for bone loss in osteoporosis. NEL-like molecule-1 (NELL-1) is an osteoinductive growth factor first identified through its overexpression in pathologically fusing suture specimens from patients with craniosynostosis. 1,2 Transgenic Nell1-overexpressing mice recapitulate craniosynostosis-like phenotypes, exhibiting gross calvarial bone overgrowth and increased osteoblast differentiation. 3 Conversely, Nell1 deficiency severely disrupts bone growth, as mice with nonsense mutations in Nell1 die perinatally with major skeletal anomalies in the craniofacial complex, spine, and long bones. 4e6 Highlighting the central role of NELL-1 in skeletal development, NELL-1 mediates key downstream effects of the master osteogenic regulator runt-related transcription factor 2 (RUNX2) 7 and can partially rescue RUNX2 loss of function. 8 NELL-1 can also transiently activate mitogen-activated protein kinase signaling to induce RUNX2 phosphorylation and osteogenic differentiation. 9 Recently, we

Bone-morphogenetic protein 2 (BMP2) is currently the only Food and Drug Administration-approved osteoinductive growth factor used in clinical settings for bone regeneration and repair. However, the use of BMP2 is encumbered by numerous clinical complications, including postoperative inflammation and life-threatening cervical swelling. Thus, methods to prevent BMP2-induced inflammation would have far-reaching clinical implications toward improving current BMP2-based methods for bone regeneration. For the first time, we investigate the potential role of the growth factor Nel-like molecule-1 (NELL-1) in inhibiting BMP2-induced inflammation. Adult rats underwent a femoral bone onlay procedure, treated with either BMP2 protein (4 mg/mL), NELL-1 protein (4 mg/mL), or both proteins combined. Animals were evaluated at 3, 7, and 14 days postoperatively by histology, histomorphometry, immunohistochemistry, and real-time PCR for markers of inflammation (TNFa, IL6). The relative levels of TNFa and IL6 in serum were also detected by ELISA. The mechanism for NELL-1's antiinflammatory effect was further assessed through examining inflammatory markers and generation of reactive oxygen species (ROS) in the mouse embryonic fibroblast NIH3T3 cells. BMP2 significantly induced local inflammation, including an early and pronounced polymorphonuclear cell infiltration accompanied by increased expression of TNFa and IL6. Treatment with NELL-1 alone elicited no significant inflammatory response. However, NELL-1 significantly attenuated BMP2-induced inflammation by all markers and at all timepoints. These local findings were also confirmed using systemic serum inflammatory biomarkers (TNFa, IL6). In each case, NELL-1 fully reversed BMP2-induced systemic inflammation. Lastly, our findings were recapitulated in vitro, where NELL-1 suppressed BMP2 induced expression of inflammatory markers, as well as NF-kB transcriptional activity and generation of ROS. BMP2-induced inflammation is a serious public health concern with potentially life-threatening complications. In the present study, we observed that the growth factor, NELL-1, significantly attenuates or completely reverses BMP2-induced inflammation. The mechanisms of NELL-1's anti-inflammatory effect are only partially elucidated, and may include reduction of NF-kB transcriptional activity or ROS generation.

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Bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor-β family, plays critical roles in cell differentiation, modeling and regeneration processes in several tissues. BMP-2 is also closely associated with various malignant tumors. microRNAs negatively and posttranscriptionally regulate gene expression and function as oncogenes or tumor suppressors. Herein, we report that miR-656 expression was significantly downregulated in glioma cell lines and tissues. We identified and confirmed that BMP receptor, type 1A (BMPR1A) is a direct target of miR-656. The expression of BMPR1A was negatively correlated with that of miR-656 in human glioma tissues. We further demonstrated that miR-656 suppressed glioma cell proliferation, neurosphere formation, migration and invasion with or without exogenous BMP-2. Engineered knockdown of BMPR1A diminished the antiproliferation effect of miR-656 in vitro. Moreover, the canonical BMP/Smad and non-canonical BMP/mitogen-activated protein kinase (MAPK) pathways were inhibited by miR-656 overexpression. Several cancer-related signaling molecules, including cyclin B, cyclin D1, matrix metalloproteinase-9, p21 and p27, were also involved in miR-656 function in glioma cells. The tumor-suppressing function of miR-656 was validated using an in vivo intracranial xenograft mouse model. Notably, ectopic expression of miR-656 markedly reduced tumor size and prolonged the survival of mice treated with or without BMP-2. These results elucidate the function of miR-656 in glioma progression and suggest a promising application for glioma treatment.

Introduction: Skeletal aging is associated not only with alterations in osteoblast (OB) and osteoclast (OC) number and activity within the basic metabolic unit, but also with increased marrow adiposity. Peroxisome proliferatoractivated receptor gamma (PPARg) is commonly considered the master transcriptional regulator of adipogenesis, however, it has known roles in osteoblast and osteoclast function as well. Here, we designed a lentiviral delivery system for PPARg shRNA, and examined its effects in vitro on bone marrow stromal cells (BMSC) and in a mouse intramedullary injection model. Methods: PPARg shRNA was delivered by a replication-deficient lentiviral vector, after in vitro testing to confirm purity, concentration, and efficacy for Pparg transcript reduction. Next, control green fluorescent protein lentivirus or PPARg shRNA expressing lentivirus were delivered by intramedullary injection into the femoral bone marrow of male SCID mice. Analyses included daily monitoring of animal health, and postmortem analysis at 4 weeks. Postmortem analyses included high resolution microcomputed tomography (microCT) reconstructions and analysis, routine histology and histomorphometric analysis, quantitative real time polymerase chain reaction analysis of Pparg transcript levels, and immunohistochemical analysis for markers of adipocytes (PPARg, fatty acid binding protein 4 [FABP4]), osteoblasts (alkaline phosphatase [ALP], osteocalcin [OCN]), and osteoclasts (tartrateresistant acid phosphatase [TRAP], Cathepsin K).Results: In vitro, PPARg shRNA delivery significantly reduced Pparg expression in mouse BMSC, accompanied by a significant reduction in lipid droplet accumulation. In vivo, a near total reduction in mature marrow adipocytes was observed at 4 weeks postinjection. This was accompanied by significant reductions in adipocytespecific markers. Parameters of trabecular bone were significantly increased by both microCT and histomorphometric analysis. By immunohistochemical staining and semi-quantification, a significant increase in OCN + osteoblasts and decrease in TRAP + multinucleated osteoclasts was observed with PPARg shRNA treatment. Discussion: These findings suggest that acute loss of PPARg in the bone marrow compartment has a significant role beyond anti-adipose effects. Specifically, we found pro-osteoblastogenic, anti-osteoclastic effects after PPARg shRNA treatment, resulting in improved trabecular bone architecture. Future studies will examine the isolated and direct effects of PPARg shRNA on OB and OC cell types, and it may help determine whether PPARg antagonists are potential therapeutic agents for osteoporotic bone loss.