Inhibition of PFKFB3 suppresses osteoclastogenesis and prevents ovariectomy-induced bone loss.

Osteoclasts are multinucleated cells derived from the monocyte/macrophage cell lineage under the regulation of receptor activator of nuclear factor-κB ligand (RANKL). In previous studies, stimulation by RANKL during osteoclastogenesis was shown to induce a metabolic switch to enhanced glycolytic metabolism. Thus, we hypothesized that blockage of glycolysis might serve as a novel strategy to treat osteoclast-related diseases. In the present study, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), an essential regulator of glycolysis, was up-regulated during osteoclast differentiation. Genetic and pharmacological inhibition of PFKFB3 in bone marrow-derived macrophages suppressed the differentiation and function of osteoclasts. Moreover, intraperitoneal administration of the PFKFB3 inhibitor PFK15 prevented ovariectomy-induced bone loss. In addition, glycolytic activity characterized by lactate accumulation and glucose consumption in growth medium was reduced by PFKFB3 inhibition. Further investigation indicated that the administration of L-lactate partially reversed the repression of osteoclastogenesis caused by PFKFB3 inhibition and abrogated the inhibitory effect of PFK15 on the activation of NF-κB and MAPK pathways. In conclusion, the results of this study suggest that blockage of glycolysis by targeting PFKFB3 represents a potential therapeutic strategy for osteoclast-related disorders.

Alginate hydrogel cross-linked by Ca2+ to promote spinal cord neural stem/progenitor cell differentiation and functional recovery after a spinal cord injuryhh.

Alginate capillary hydrogels seeded with differentiated cells can fill the lesion cavity and promote axonal regeneration after grafting into the injured spinal cord. Neural stem/progenitor cells (NSPCs) can potentially repair the spinal cord; however, effects of alginate hydrogels (AHs) on NSPCs remain unknown. In this study, we fabricated AHs cross-linked by Ca2+ and seeded hydrogels with rat embryonic day 14 NSPCs. Immunocytochemistry and electron microscopy show that NSPCs survive, proliferate and differentiate into neurons in vitro within the capillaries. After transplantation into an acute T8 complete spinal cord transection site in adult rats, approximately one-third (38.3%) of grafted cells survive and differentiate into neurons (40.7%), astrocytes (26.6%) and oligodendrocytes (28.4%) at 8 weeks post-grafting. NSPCs promote the growth of host axons within the capillaries in a time-dependent manner. Host axons make synapse-like contacts with NSPC-derived neurons within the hydrogel channels, and graft-derived axons extend into the host white and gray matter making putative synapses. This is paralleled by improved electrophysiological conductivity across the lesion and partial hindlimb locomotor recovery.

Urolithin A Inhibits the Catabolic Effect of TNFα on Nucleus Pulposus Cell and Alleviates Intervertebral Disc Degeneration in vivo.

Low back pain (LBP) is a common worldwide disease that causes an enormous social economic burden. Intervertebral disc degeneration (IDD) is considered as a major cause of LBP. The process of IDD is complicated and involves both inflammation and senescence. The production of pro-inflammatory cytokines, including tumor necrosis factor (TNF)α and interleukin (IL)-1ß, is increased in the degenerating intervertebral disc, inducing extracellular matrix degradation. Urolithin A (UA) is a metabolite compound resulting from the degradation of ellagitannins by gut bacteria. UA has been reported to be useful for the treatment of diseases associated with inflammation, senescence, and oxidative damage. Therefore, we hypothesized that UA may be an effective treatment for IDD. This study examined the effects of UA on IDD in vitro and in vivo and explored their underlying mechanisms. Our findings indicated that UA could attenuate cellular senescence induced by hydrogen peroxide in nucleus pulposus cells. UA treatment decreased TNFα-induced matrix metalloproteinase production and the loss of collagen II. At the molecular level, UA considerably blocked the phosphorylation of the extracellular signal-regulated kinase, c-JUN N-terminal kinase, and Akt pathways. In vivo study illustrated that UA treatment could ameliorate IDD in a needle-punctured rat tail model, which was evaluated by X-ray imaging, magnetic resonance imaging, and histological analysis. Thus, the results of our study revealed that UA may be a useful therapeutic agent for the treatment of IDD.

Inhibition of PRMT5 suppresses osteoclast differentiation and partially protects against ovariectomy-induced bone loss through downregulation of CXCL10 and RSAD2.

Protein arginine methyltransferase 5 (PRMT5) is an arginine methylation methyltransferase that regulates various physiological processes. Abnormal PRMT5 activity has been reported in inflammation and various types of cancers. Because osteoclast differentiation is characterized by the activation of inflammation-related pathways, we speculated that PRMT5 may play a role in this process. In the present study, we found that PRMT5 was upregulated during osteoclast differentiation. Knockdown of PRMT5 with siRNA in bone marrow mononuclear cells (BMMs) resulted in inhibition of receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation. Consistent with the PRMT5 knockdown results, the PRMT5 inhibitor EPZ015666 (EPZ) suppressed osteoclast differentiation and bone resorption. Intraperitoneal administration of EPZ prevented ovariectomy-induced bone loss. Moreover, RANKL-induced NF-κB and MAPK activation was inhibited by EPZ. Expression microarrays showed that the expression of several osteoclast formation-related genes was altered by EPZ treatment, including chemokine C-X-C motif ligand 10 (CXCL10). Administration of recombinant CXCL10 partially reversed the osteoclastogenesis inhibition effect of the PRMT5 inhibitor. Intriguingly, RSAD2, which is a reported antiviral protein, was apparently suppressed when PRMT5 was inhibited. Knockdown of RSAD2 with siRNA in BMMs led to inhibition of osteoclast differentiation. Subsequent ChIP-qPCR identified that both PRMT5 inhibition and knockdown resulted in decreased H3R8 or/and H4R3 methylation at CXCL10 and RSAD2 promotors. In conclusion, our study found that PRMT5 is an activator of osteoclast differentiation and inhibition of PRMT5 partially suppressed osteoclastogenesis through downregulation of CXCL10 and RSAD2.