CD206+ M2-like macrophages protect against intervertebral disc degeneration partially by targeting R-spondin-2.

OBJECTIVE: This study aimed to explore the specific function of M2 macrophages in intervertebral disc degeneration (IDD). METHODS: Intervertebral disc (IVD) samples from normal (n = 4) and IDD (n = 6) patients were collected, and the expression of M2-polarized macrophage marker, CD206, was investigated using immunohistochemical staining. Nucleus pulposus cells (NPCs) in a TNF-α environment were obtained, and a mouse caudal IVD puncture model was established. Mice with Rheb deletions, specifically in the myeloid lineage, were generated and subjected to surgery-induced IDD. IDD-induced damage and cell apoptosis were measured using histological scoring, X-ray imaging, immunohistochemical staining, and TdT-mediated dUTP nick end labeling (TUNEL) assay. Finally, mice and NPCs were treated with R-spondin-2 (Rspo2) or anti-Rspo2 to investigate the role of Rspo2 in IDD. RESULTS: Accumulation of CD206 in human and mouse IDD tissues was detected. Rheb deletion in the myeloid lineage (RheBcKO) increased the number of CD206+ M2-like macrophages (mean difference 18.6% [15.7-21.6%], P < 0.001), decreased cell apoptosis (mean difference -15.6% [-8.9 to 22.2%], P = 0.001) and attenuated the IDD process in the mouse IDD model. NPCs treated with Rspo2 displayed increased extracellular matrix catabolism and apoptosis; co-culture with a conditioned medium derived from RheBcKO mice inhibited these changes. Anti-Rspo2 treatment in the mouse caudal IVD puncture model exerted protective effects against IDD. CONCLUSIONS: Promoting CD206+ M2-like macrophages could reduce Rspo2 secretion, thereby alleviating experimental IDD. Rheb deletion may help M2-polarized macrophages accumulate and attenuate experimental IDD partially by inhibiting Rspo2 production. Hence, M2-polarized macrophages and Rspo2 may serve as therapeutic targets for IDD.

Growing trend of China's contribution to the field of spine: a 10-year survey of the literature.

PURPOSE: China, as a rapidly developing country with the largest population including over 50,000 orthopaedic surgeons, has an increasing importance in the field of spine. However, the quantity and quality of research production in the field of spine in the major regions of China-Mainland China, Taiwan, and Hong Kong is unclear. This study aimed to investigate the contribution of China to the field of spine. METHODS: Articles published in the 5 major spine journals originating from Mainland China, Taiwan and Hong Kong in 2004-2013 were retrieved from the database of Web of Science. The number of articles, impact factors, citations, article type, city, institution, funding source and conflict of interest were analyzed. RESULTS: There were 1006 publications in the 5 spine journals between 2004 and 2013 from China, including 706 from Mainland China, 210 from Taiwan, and 90 from Hong Kong. The time trend of the number of articles from these three regions showed a significant increase of 8.74-fold (from 23 to 201) between 2004 and 2013 (p = 0.000). From 2006, the number of publications from Mainland China exceeded Taiwan and Hong Kong. Mainland China had the highest total impact factors (1686.54) and total citations (4214), followed by Taiwan (498.93; 2009) and Hong Kong (222.89; 1311). Hong Kong had the highest mean impact factor (2.48) and mean citations (14.46), followed by Mainland China (2.40; 10.26) and Taiwan (2.38; 10.14). The journal Spine published the largest number of articles (470), followed by European Spine Journal (268). CONCLUSIONS: Chinese contributions to the field of spine have a significant increase during the past 10 years, particularly from Mainland China. Hong Kong had the highest quality research output in terms of mean impact factor and mean citation per article.

Effects of HGF and KGF gene silencing on vascular endothelial growth factor and its receptors in rat ultraviolet radiation­induced corneal neovascularization.

Hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF), two paracrine growth factors, modulate corneal epithelial cell metabolism, apoptosis and survival. Vascular endothelial growth factor (VEGF) serves as a proangiogenic factor in corneal neovascularization (CNV), which is a major cause of vision impairment and corneal blindness. The aim of the present study was to evaluate the ability of HGF and KGF to influence VEGF and its receptor, kinase insert domain receptor (Flk­1) in corneal injury and CNV in rats induced by ultraviolet radiation (UVR). An UVR­induced corneal injury rat model was successfully established to characterize the expression patterns of KGF, HGF, VEGF and Flk­1 in corneal tissues. Corneal epithelial cells were extracted and treated with small interfering RNAs (siRNAs) targeting KGF, HGF or both (si­KGF, si­HGF or si­HGF/KGF). The effects of HGF and KGF were examined through detection of the expression of KGF, HGF, VEGF and Flk­1, and the evaluation of cell proliferation, cell cycle and cell apoptosis. The expression levels of KGF, HGF, VEGF and Flk­1 in corneal tissues were increased in the rat model. In the cell experiments, the transfection of si­HGF/KGF resulted in reductions in VEGF, Flk­1, KGF and HGF. In addition, decreased cell proliferation and elevated cell apoptosis were found in the corneal epithelial cells from the rat model following KGF and HGF gene silencing. Taken together, these findings suggest that HGF and KGF gene silencing inhibits UVR­induced corneal epithelial proliferation and CNV and may function as novel targets for corneal wound healing.

NGF-induced axon growth is mediated by localized inactivation of GSK-3beta and functions of the microtubule plus end binding protein APC.

Little is known about how nerve growth factor (NGF) signaling controls the regulated assembly of microtubules that underlies axon growth. Here we demonstrate that a tightly regulated and localized activation of phosphatidylinositol 3-kinase (PI3K) at the growth cone is essential for rapid axon growth induced by NGF. This spatially activated PI3K signaling is conveyed downstream through a localized inactivation of glycogen synthase kinase 3beta (GSK-3beta). These two spatially coupled kinases control axon growth via regulation of a microtubule plus end binding protein, adenomatous polyposis coli (APC). Our results demonstrate that NGF signals are transduced to the axon cytoskeleton via activation of a conserved cell polarity signaling pathway.

BMP7-Based Functionalized Self-Assembling Peptides Protect Nucleus Pulposus-Derived Stem Cells From Apoptosis In Vitro.

Tissue engineering has shown great success in the treatment of intervertebral disk degeneration (IVDD) in the past decade. However, the adverse and harsh microenvironment associated in the intervertebral disks remains a great obstacle for the survival of transplanted cells. Although increasing numbers of new materials have been created or modified to overcome this hurdle, a new effective strategy of biological therapy is still required. In this study, bone morphogenic protein 7 (BMP7)-based functionalized self-assembling peptides were developed by conjugating a bioactive motif from BMP-7 (RKPS) onto the C-terminal of the peptide RADARADARADARADA (RADA16-I) at a ratio of 1:1 to form a new RADARKPS peptide. Human nucleus pulposus-derived stem cells (NPDCs) were cultured in the presence of RADA-RKPS or RADA16-I in an apoptosis-promoting environment that was induced by tumor necrosis factor-alpha, and cells were cultured with RADA16-I in normal medium that served as the control group. After 48 h of apoptosis induction, the viability, proliferation, apoptosis rate, and expression of apoptosis-related genes of NPDCs in the different groups were evaluated, and the differentiation of NPDCs toward nucleus pulposus-like cells was tested. The results showed that the RADA-RKPS peptide could significantly protect the survival and proliferation of NPDCs. In addition, the application of RADA-RKPS decreased the rate of cell apoptosis, as detected by TUNEL-positive staining. Furthermore, our in vitro study confirmed the apoptosis-protecting effects of RADA-RKPS peptides, which significantly reduced the BAX/BCL-2 ratio of NPDCs and upregulated the gene expression of collagen II a1, aggrecan, and Sox-9 after 48 h of apoptosis induction. Collectively, these lines of evidence suggest that RADA-RKPS peptides confer a protective effect to NPDCs in an apoptosis environment, suggesting their potential application in the development of new biological treatment strategies for IVDD.

Neurotrophins support regenerative axon assembly over CSPGs by an ECM-integrin-independent mechanism.

Chondroitin sulfate proteoglycans (CSPGs) and myelin-based inhibitors are the most studied inhibitory molecules in the adult central nervous system. Unlike myelin-based inhibitors, few studies have reported ways to overcome the inhibitory effect of CSPGs. Here, by using regenerating adult dorsal root ganglion (DRG) neurons, we show that chondroitin sulfate proteoglycans inhibit axon assembly by a different mechanism from myelin-based inhibitors. Furthermore, we show that neither Rho inhibition nor cAMP elevation rescues extracellular factor-induced axon assembly inhibited by CSPGs. Instead, our data suggest that CSPGs block axon assembly by interfering with integrin signaling. Surprisingly, we find that nerve growth factor (NGF) promotes robust axon growth of regenerating DRG neurons over CSPGs. We have found that, unlike naive neurons that require simultaneous activation of neurotrophin and integrin pathways for axon assembly, either neurotrophin or integrin signaling alone is sufficient to induce axon assembly of regenerating neurons. Thus, our results suggest that the ability of NGF to overcome CSPG inhibition in regenerating neurons is probably due to the ability of regenerating neurons to assemble axons using an integrin-independent pathway. Finally, our data show that the GSK-3beta-APC pathway, previously shown to mediate developing axon growth, is also necessary for axon regeneration.