Semaphorin 3A promotes osteogenic differentiation of BMSC from type 2 diabetes mellitus rats

Semaphorins and the bone marrow microenvironment: New candidates that influence the hematopoietic system

The bone marrow is a haven for hematopoietic and non-hematopoietic cells, creating complex micro-anatomical regions called niches. These distinct niches all participate in an intricate orchestra of cellular interactions that regulates the hematopoietic stem cell and its progenies. In this review, we provide a detailed description of the three most well-known bone marrow niches and their participation in hematopoiesis. We use pre-clinical data, including different in vitro and in vivo studies to discuss how a group of proteins called Semaphorins could potentially modulate both hematopoietic and non-hematopoietic cells, establishing links between the niches, semaphorins, and hematopoietic regulation. Thus, here we provide a deep dive into the inner functioning of the bone marrow and discuss the overarching implications that semaphorins might have on blood formation.

SiJunZi decoction ameliorates bone quality and redox homeostasis and regulates advanced glycation end products/receptor for advanced glycation end products and WNT/β-catenin signaling pathways in diabetic mice

ETHNOPHARMACOLOGICAL RELEVANCE

SiJunZi decoction (SJZD), one of the traditional Chinese medicine formulas, has been clinically and traditionally used to improve glucose and lipid metabolism and promote bone remodeling.

AIM OF THE STUDY

To study the actions and mechanisms of SJZD on bone remodeling in a type 2 diabetes mouse model.

MATERIALS AND METHODS

Diabetic mice generated with a high-fat diet (HFD) and streptozotocin (STZ) were subjected to SJZD treatment for 8 weeks. Blood glucose and lipid profile, redox status and bone metabolism were determined by ELISA or biochemical assays. Bone quality was evaluated by micro-CT, three-point bending assay and Fourier transform infrared spectrum (FTIR). Bone histomorphometry alterations were evaluated by Hematoxylin-Eosin (H&E), tartrate resistant acid phosphatase (TRAP) staining and Safranin O-fast green staining. The expressions of superoxide dismutase 1 (SOD1), advanced glycation end products (AGEs), receptor for advanced glycosylation end products (RAGE), phosphorylated nuclear factor kappa-B (p-NF-κB), NF-κB, cathepsin K, semaphorin 3A (Sema3A), insulin-like growth factor 1 (IGF1), p-GSK-3β, (p)-β-catenin, Runt-related transcription factor 2 (Runx2) and Cyclin D1 in the femurs and/or tibias were examined by Western blot or immunohistochemical staining. The main constituents in the SJZD aqueous extract were characterized by a HPLC/MS.

RESULTS

SJZD intervention improved glucose and lipid metabolism and preserved bone quality in the diabetic mice, in particular glucose tolerance, lipid profile, bone microarchitecture, strength and material composition. SJZD administration to diabetic mice preserved redox homeostasis in serum and bone marrow, and prevented an increase in AGEs, RAGE, p-NF-κB/NF-κB, cathepsin K, p-GSK-3β, p-β-catenin expressions and a decrease in Sema3A, IGF1, β-catenin, Runx2 and Cyclin D1 expressions in tibias and/or femurs. Thirteen compounds were identified in SJZD aqueous extract, including astilbin, liquiritin apioside, ononin, ginsenoside Re, Rg1, Rb1, Rb2, Ro, Rb3, Rd, notoginsenoside R2, glycyrrhizic acid, and licoricesaponin B2.

CONCLUSIONS

SJZD ameliorates bone quality in diabetic mice possibly via maintaining redox homeostasis. The mechanism governing these alterations are possibly related to effects on the AGEs/RAGE and Wnt/β-catenin signaling pathways. SJZD may offer a novel source of drug candidates for the prevention and treatment of type 2 diabetes and osteoporosis.

Sema3A Modified PDLSCs Exhibited Enhanced Osteogenic Capabilities and Stimulated Differentiation of Pre-Osteoblasts

Genetically engineered stem cells, not only acting as vector delivering growth factors or cytokines but also exhibiting improved cell properties, are promising cells for periodontal tissue regeneration. Sema3A is a power secretory osteoprotective factor. In this study, we aimed to construct Sema3A modified periodontal ligament stem cells (PDLSCs) and evaluated their osteogenic capability and crosstalk with pre-osteoblasts MC3T3-E1. First, Sema3A modified PDLSCs was constructed using lentivirus infection system carrying Sema3A gene and the transduction efficiency was analyzed. The osteogenic differentiation and proliferation of Sema3A-PDLSCs was evaluated. Then, MC3T3-E1 was directly co-cultured with Sema3A-PDLSCs or cultured in condition medium of Sema3A-PDLSCs and the osteogenic ability of MC3T3-E1 was assessed. The results showed that Sema3A-PDLSCs expressed and secreted upregulated Sema3A protein, which confirmed successful construction of Sema3A modified PDLSCs. After osteogenic induction, Sema3A-PDLSCs expressed upregulated ALP, OCN, RUNX2, and SP7 mRNA, expressed higher ALP activity, and produced more mineralization nodes, compared with Vector-PDLSCs. Whereas, there was no obvious differences in proliferation between Sema3A-PDLSCs and Vector-PDLSCs. MC3T3-E1 expressed upregulated mRNA of ALP, OCN, RUNX2, and SP7 when directly co-cultured with Sema3A-PDLSCs than Vector-PDLSCs. MC3T3-E1 also expressed upregulated osteogenic markers, showed higher ALP activity, and produced more mineralization nodes when cultured using condition medium of Sema3A-PDLSCs instead of Vector-PDLSCs. In conclusion, our results indicated that Sema3A modified PDLSCs showed enhanced osteogenic capability, and also facilitated differentiation of pre-osteoblasts.

Semaphorin 3A delivered by a rapidly polymerizing click hydrogel overcomes impaired implant osseointegration in a rat type 2 diabetes model

Semaphorin 3A (sema3A) is an osteoprotective factor that enhances bone formation while inhibiting osteoclast bone resorption. It is produced by rat calvarial osteoblasts cultured on grit-blasted/acid-etched microtextured (SLA) titanium surfaces at higher levels than on tissue culture polystyrene, suggesting that it may improve performance of titanium implants in vivo, particularly in conditions characterized by compromised bone quality. To test this, we established a clinically relevant type 2 diabetes mellitus (T2DM) rat model and used a non-toxic click hydrogel that rapidly polymerizes in situ (GEL) to provide localized controlled delivery of sema3A. In vitro studies confirmed that sema3A released from GEL was biologically active, increasing osteoblast differentiation of a pre-osteoblast cell-line. Whereas increased sema3A production was not observed in T2DM calvarial osteoblasts cultured on SLA, exogenous sema3A enhanced surface-induced osteoblast differentiation, indicating that it would be a viable candidate for in vivo use. Delivery of sema3A either by GEL or by local injection to bone defects enhanced osseointegration of SLA implants in the T2DM rats. Trabecular bone mass and bone-to-implant contact were decreased in T2DM rats compared to normal rats; sema3A delivered locally improved both parameters. These findings suggest that reduced trabecular bone contributes to poor osseointegration in T2DM patients and support GEL as a promising treatment option for sustained release of therapeutic doses of sema3A. Moreover, using this clinically translatable T2DM model and developing a biocompatible, Cu-free click chemistry hydrogel platform for the non-invasive delivery of therapeutics has major implications for regenerative medicine as a whole. STATEMENT OF SIGNIFICANCE: Osseointegration is compromised in patients with poor bone quality due to conditions like type 2 diabetes mellitus (T2DM). Previously, we showed that semaphorin 3A (sema3A) production is increased when human bone marrow stromal cells are cultured on titanium substrates that support osseointegration in vivo, suggesting it may enhance peri-implant osteogenesis in diabetes. Here we established a spontaneously developing T2DM rat model with clinical translatability and used it to assess sema3A effectiveness. Sema3A was delivered to the implant site via a novel copper-free click hydrogel, which has minimal swelling behavior and superior rheological properties. Osseointegration was successfully restored, and enhanced compared to burst release through injections. This study provides scientific evidence for using sema3A to treat impaired osseointegration in T2DM patients.

LncRNA TCF7 contributes to high glucose-induced damage in human podocytes by up-regulating SEMA3A via sponging miR-16-5p

AIMS/INTRODUCTION

Long non-coding RNAs (lncRNAs) exert essential functions in the pathogenesis of diabetic nephropathy (DN). LncRNA T-cell factor 7 (TCF7) and semaphorin-3A (SEMA3A) have been found to be involved in the progression of diabetic nephropathy. However, whether the effect of TCF7 on the pathogenesis of diabetic nephropathy is mediated by SEMA3A remains unclear.

MATERIALS AND METHODS

TCF7, miR-16-5p, and SEMA3A were quantified by a qRT-PCR or immunoblotting method. A CCK-8 assay gauged the cell viability. Measurement of cell apoptosis was done using flow cytometry. RNA immunoprecipitation (RIP), dual-luciferase reporter, and RNA pull-down assays were utilized to assay the targeted interactions among the variables.

RESULTS

The TCF7 and SEMA3A levels were elevated in serum from patients with diabetic nephropathy. TCF7 silencing or SEMA3A depletion ameliorated high glucose (HG)-induced podocyte injury. Moreover, TCF7 silencing protected against HG-induced podocyte injury by down-regulating SEMA3A. TCF7 targeted miR-16-5p, and miR-16-5p targeted SEMA3A. Furthermore, TCF7 affected the expression of SEMA3A by competing specifically for shared miR-16-5p.

CONCLUSIONS

These findings suggested that TCF7 silencing attenuated high glucose-induced podocyte damage partially through the miR-16-5p/SEMA3A regulation cascade.

Metformin enhances the osteogenic activity of rat bone marrow mesenchymal stem cells by inhibiting oxidative stress induced by diabetes mellitus: an in vitro and in vivo study

PURPOSE

The purpose of this study was to determine whether metformin (MF) could alleviate the expresssion of reactive oxygen species (ROS) and improve the osteogenic ability of bone marrow mesenchymal stem cells derived from diabetic rats (drBMSCs) in vitro, and to evaluate the effect of MF on the ectopic osteogenesis of drBMSCs in a nude mouse model in vivo.

METHODS

BMSCs were extracted from normal and diabetic rats. In vitro, a cell viability assay (Cell Counting Kit-8), tests of alkaline phosphatase (ALP) activity, and western blot analysis were first used to determine the cell proliferation and osteogenic differentiation of drBMSCs that were subjected to treatment with different concentrations of MF (0, 50, 100, 200, 500 μM). The cells were then divided into 5 groups: (1) normal rat BMSCs (the BMSCs derived from normal rats group), (2) the drBMSCs group, (3) the drBMSCs + Mito-TEMPO (10 μM, ROS scavenger) group, (4) the drBMSCs + MF (200 μM) group, and (5) the drBMSCs + MF (200 μM) + H₂O₂ (50 μM, ROS activator) group. Intracellular ROS detection, a senescence-associated β-galactosidase assay, ALP staining, alizarin red staining, western blotting, and immunofluorescence assays were performed to determine the effects of MF on oxidative stress and osteogenic differentiation in drBMSCs. In vivo, the effect of MF on the ectopic osteogenesis of drBMSCs was evaluated in a nude mouse model.

RESULTS

MF effectively reduced ROS levels in drBMSCs. The cell proliferation, ALP activity, mineral deposition, and osteogenic-related protein expression of drBMSCs were demonstrably higher in the MF-treated group than in the non-MF-treated group. H₂O₂ inhibited the effects of MF. In addition, ectopic osteogenesis was significantly increased in drBMSCs treated with MF.

CONCLUSIONS

MF promoted the proliferation and osteogenic differentiation of drBMSCs by inhibiting the oxidative stress induced by diabetes and enhenced the ectopic bone formation of drBMSCs in nude mice.

Axon guidance molecules in immunometabolic diseases

The global prevalence of metabolic diseases, such as obesity, diabetes, and atherosclerosis, is rapidly increasing and has now reached epidemic proportions. Chronic tissue inflammation is a characteristic of these metabolic diseases, indicating that immune responses are closely involved in the pathogenesis of metabolic disorders. However, the regulatory mechanisms underlying immunometabolic crosstalk in these diseases are not completely understood. Recent studies have revealed the multifaceted functions of semaphorins, originally identified as axon guidance molecules, in regulating tissue inflammation and metabolic disorders, thereby highlighting the functional coupling between semaphorin signaling and immunometabolism. In this review, we explore how semaphorin signaling transcends beyond merely guiding axons to controlling immune responses and metabolic diseases.

Silicified collagen scaffold induces semaphorin 3A secretion by sensory nerves to improve in-situ bone regeneration

Sensory nerves promote osteogenesis through the release of neuropeptides. However, the potential application and mechanism in which sensory nerves promote healing of bone defects in the presence of biomaterials remain elusive. The present study identified that new bone formation was more abundantly produced after implantation of silicified collagen scaffolds into defects created in the distal femur of rats. The wound sites were accompanied by extensive nerve innervation and angiogenesis. Sensory nerve dysfunction by capsaicin injection resulted in significant inhibition of silicon-induced osteogenesis in the aforementioned rodent model. Application of extracellular silicon in vitro induced axon outgrowth and increased expression of semaphorin 3 A (Sema3A) and semaphorin 4D (Sema4D) in the dorsal root ganglion (DRG), as detected by the upregulation of signaling molecules. Culture medium derived from silicon-stimulated DRG cells promoted proliferation and differentiation of bone marrow mesenchymal stem cells and endothelial progenitor cells. These effects were inhibited by the use of Sema3A neutralizing antibodies but not by Sema4D neutralizing antibodies. Knockdown of Sema3A in DRG blocked silicon-induced osteogenesis and angiogenesis almost completely in a femoral defect rat model, whereas overexpression of Sema3A promoted the silicon-induced phenomena. Activation of “mechanistic target of rapamycin” (mTOR) pathway and increase of Sema3A production were identified in the DRG of rats that were implanted with silicified collagen scaffolds. These findings support the role of silicon in inducing Sema3A production by sensory nerves, which, in turn, stimulates osteogenesis and angiogenesis. Taken together, silicon has therapeutic potential in orthopedic rehabilitation.

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Nerve innervation, vascularization and tissue mineralization integrated into a single scaffold.

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Silicified collagen scaffolds has therapeutic potential in orthopedic rehabilitation.

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Silicified collagen scaffolds promote in-situ bone regeneration via sensory nerve innervation and semaphorin 3A production.

Bioinformatics Analysis Identified miR-584-5p and Key miRNA-mRNA Networks Involved in the Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Human periodontal ligament cells (PDLCs) play an important role in periodontal tissue stabilization and function. In the process of osteogenic differentiation of PDLSCs, the regulation of molecular signal pathways are complicated. In this study, the sequencing results of three datasets on GEO were used to comprehensively analyze the miRNA-mRNA network during the osteogenic differentiation of PDLSCs. Using the GSE99958 and GSE159507, a total of 114 common differentially expressed genes (DEGs) were identified, including 62 up-regulated genes and 52 down-regulated genes. GO enrichment analysis was performed. The up-regulated 10 hub genes and down-regulated 10 hub genes were screened out by protein-protein interaction network (PPI) analysis and STRING in Cytoscape. Similarly, differentially expressed miRNAs (DEMs) were selected by limma package from GSE159508. Then, using the miRwalk website, we further selected 11 miRNAs from 16 DEMs that may have a negative regulatory relationship with hub genes. In vitro RT-PCR verification revealed that nine DEMs and 18 hub genes showed the same trend as the RNA-seq results during the osteogenic differentiation of PDLSCs. Finally, using miR-584-5p inhibitor and mimics, it was found that miR-584-5p negatively regulates the osteogenic differentiation of PDLSCs in vitro. In summary, the present results found several potential osteogenic-related genes and identified candidate miRNA-mRNA networks for the further study of osteogenic differentiation of PDLSCs.

miR-140-3p regulates the osteogenic differentiation ability of bone marrow mesenchymal stem cells by targeting spred2-mediated autophagy

Understanding the function and regulatory mechanism of miR-140-3p on the osteogenic differentiation of bone mesenchymal stem cells (BMSCs). Alizarin Red staining, Alkaline phosphatase (ALP) staining, and ALP activity were used to detect the ability osteogenic differentiation. miR-140-3p or Spred2 overexpression into BMSCs using lentiviral vectors and the result were analyzed by Reverse transcription quantitative polymerase chain reaction (RT-qPCR). The relation between miR-140-3p and Spred2 was examined by luciferase reporter assay. CCK8 assay was used to detect the proliferation of BMSCs. RT-qPCR and Western blot analysis were both used to detect altered gene and protein in osteogenic differentiation of BMSCs, respectively. The BMSCs which were induced for 21 days were analyzed by Alizarin Red staining, (ALP) staining and ALP activity. RT-qPCR analysis showed that overexpressed miR-140-3p promotes osteogenic differentiation. Western blots results indicated that the overexpression of Spred2 suppressed miR-140-3p. Luciferase reporter assay indicated that Spred2 can integrate with miR-140-3p directly. Meanwhile, the protein level of ALP, OCN, and Runx2, the markers of chondrogenesis, was increased when miR-140-3p increased or Spred2 overexpressed in the osteoinductive medium applied to the BMSCs. Our study demonstrated the association between miR-140-3p and Spred2 in osteogenic differentiation of BMSCs for the first time. Furthermore, our detections also revealed that Spred2-induced autophagic signaling accelerates the progress of osteogenic differentiation ability of BMSCs.

Exploring the Mechanism of Total Flavonoids of Drynariae Rhizoma to Improve Large Bone Defects by Network Pharmacology and Experimental Assessment

Drynariae Rhizoma (DR) has been demonstrated to be effective in promoting fracture healing in clinical use. In the study, we tried to predicate potential signaling pathways and active ingredients of DR via network pharmacology, uncover its regulation mechanism to improve large bone defects by in vivo and in vitro experiment. We total discovered 18 potential active ingredients such as flavonoids and 81 corresponding targets, in which mitogen-activated protein kinase (MAPK) signaling pathway has the highest correlation with bone defects in pathway and functional enrichment analysis. Therefore, we hypothesized that flavonoids in DR improve large bone defects by activating MAPK signaling pathway. Animal experiments were carried out and all rats randomly divided into TFDR low, medium, and high dosage group, model group and control group. 12 weeks after treatment, according to X-ray and Micro-CT, TFDR medium dosage group significantly promote new bone mineralization compared with other groups. The results of HE and Masson staining and in vitro ALP level of BMSC also demonstrated the formation of bone matrix and mineralization in the TFDR groups. Also, angiographic imaging suggested that flavonoids in DR promoting angiogenesis in the defect area. Consistently, TFDR significantly enhanced the expression of BMP-2, RUNX-2, VEGF, HIF-1 in large bone defect rats based on ELISA and Real-Time PCR. Overall, we not only discover the active ingredients of DR in this study, but also explained how flavonoids in DR regulating MAPK signaling pathway to improve large bone defects.

A Dual Peptide Sustained-Release System Based on Nanohydroxyapatite/Polyamide 66 Scaffold for Synergistic-Enhancing Diabetic Rats' Fracture Healing in Osteogenesis and Angiogenesis

Diabetes mellitus impairs fracture healing and function of stem cells related to bone regeneration; thus, effective bone tissue engineering therapies can intervene with those dysfunctions. Nanohydroxyapatite/polyamide 66 (n-HA/PA66) scaffold has been used in fracture healing, whereas the low bioactivity limits its further application. Herein, we developed a novel bone morphogenetic protein-2- (BMP-2) and vascular endothelial growth factor- (VEGF) derived peptides-decorated n-HA/PA66 (BVHP66) scaffold for diabetic fracture. The n-HA/PA66 scaffold was functionalized by covalent grafting of BMP-2 and VEGF peptides to construct a dual peptide sustained-release system. The structural characteristics and peptide release profiles of BVHP66 scaffold were tested by scanning electron microscopy, Fourier transform infrared spectroscopy, and fluorescence microscope. Under high glucose (HG) condition, the effect of BVHP66 scaffold on rat bone marrow mesenchymal stem cells’ (rBMSCs) adherent, proliferative, and differentiate capacities and human umbilical vein endothelial cells’ (HUVECs) proliferative and tube formation capacities was assessed. Finally, the BVHP66 scaffold was applied to fracture of diabetic rats, and its effect on osteogenesis and angiogenesis was evaluated. In vitro, the peptide loaded on the BVHP66 scaffold was in a sustained-release mode of 14 days. The BVHP66 scaffold significantly promoted rBMSCs’ and HUVECs’ proliferation and improved osteogenic differentiation of rBMSCs and tube formation of HUVECs in HG environment. In vivo, the BVHP66 scaffold enhanced osteogenesis and angiogenesis, rescuing the poor fracture healing in diabetic rats. Comparing with single peptide modification, the dual peptide-modified scaffold had a synergetic effect on bone regeneration in vivo. Overall, this study reported a novel BVHP66 scaffold with excellent biocompatibility and bioactive property and its application in diabetic fracture.

Semaphorin 3A promotes the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells in inflammatory environments by suppressing the Wnt/β-catenin signaling pathway

After periodontal treatment, the local inflammatory environment surrounding periodontal tissues cannot be entirely eliminated. The means by which alveolar bone repair and regeneration are promoted in inflammatory environments have important clinical significance. As a powerful protein that promotes the differentiation of osteocytes, semaphorin 3A (Sema3A) shows potential for bone regeneration therapy. However, the effect of Sema3A on osteogenic differentiation in an inflammatory environment, as well as the underlying mechanism, have not yet been explored. We used lentivirus to transduce rat bone marrow-derived mesenchymal stem cells (rBMSCs) to stably overexpress Sema3A. Lipopolysaccharide from Escherichia coli (E. coli LPS) was used to stimulate rBMSCs to establish an inflammatory environment. ALP staining, Alizarin red staining, ALP activity tests, quantitative RT-PCR (qRT-PCR), and Western blotting were used to elucidate the effect of Sema3A on the osteogenesis of rBMSCs in inflammatory environments. XAV939 and LiCl were used to determine whether the Wnt/β-catenin signaling pathway was involved in attenuating the inhibition of Sema3A-induced osteogenic differentiation by LPS. The qRT-PCR and Western blot results demonstrated that the lentiviral vector (LV-NC) and lentiviral-Sema3A (LV-Sema3A) were successfully transduced into rBMSCs. An inflammatory environment could be established by stimulating rBMSCs with 1 μg/ml E. coli LPS. After Sema3A overexpression, mineral deposition was exacerbated, and the BSP and Runx2 gene and protein expression levels were increased. Furthermore, E. coli LPS activated the Wnt/β-catenin signaling pathway and decreased rBMSC osteogenesis, but these effects were attenuated by Sema3A. In conclusion, Sema3A could protect BMSCs from LPS-mediated inhibition of osteogenic differentiation in inflammatory environments by suppressing the Wnt/β-catenin pathway.

MicroRNA-145 suppresses osteogenic differentiation of human jaw bone marrow mesenchymal stem cells partially via targeting semaphorin 3A

Purpose: Human jaw bone marrow mesenchymal stem cells (h-JBMMSCs) are multipotent progenitor cells with osteogenic differentiation potential. MicroRNAs (miRNAs) have emerged as crucial modulators of osteoblast differentiation. In this study, we focus on the role of miR-145 and its target protein in osteoblast differentiation of h-JBMMSCs. Materials and Methods: h-JBMMSCs were isolated and cultured in osteogenic medium. miR-145 mimics and inhibitors were used to elevate and inhibit miR-145 expression, respectively. Osteogenic differentiation was determined by Alkaline phosphatase (ALP) and Alizarin red S (ARS) staining, and osteogenic marker detection using quantitative real-time reverse transcription PCR (qRT-PCR) assay. Bioinformatic analysis and luciferase reporter assay were used to identify the target gene of miR-145. Results: MiR-145 was down-regulated during osteogenesis of h-JBMMSCs. Inhibition of miR-145 promoted osteogenic differentiation of h-JBMMSCs, revealed by enhanced activity of alkaline phosphatase (ALP), greater mineralisation, and increased expression levels of the osteogenic markers, such as Runt-related transcription factor 2 (RUNX2), Osterix (OSX), ALP and COL1A1. MiR-145 could negatively regulate semaphorin3A (SEMA3A), which acts as a positive regulator of osteogenesis. MiR-145 inhibitor induced osteogenesis could be partially attenuated by SEMA3A siRNA treatment in h-JBMMSCs. Conclusions: Our data show that miR-145 directly targets SEMA3A, and also suggest miR-145 as a suppressor, plays an important role in the osteogenic differentiation of h-JBMMSCs.

The Role of Semaphorins in Metabolic Disorders

Semaphorins are a family originally identified as axonal guidance molecules. They are also involved in tumor growth, angiogenesis, immune regulation, as well as other biological and pathological processes. Recent studies have shown that semaphorins play a role in metabolic diseases including obesity, adipose inflammation, and diabetic complications, including diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, diabetic wound healing, and diabetic osteoporosis. Evidence provides mechanistic insights regarding the role of semaphorins in metabolic diseases by regulating adipogenesis, hypothalamic melanocortin circuit, immune responses, and angiogenesis. In this review, we summarize recent progress regarding the role of semaphorins in obesity, adipose inflammation, and diabetic complications.

Niches for Skeletal Stem Cells of Mesenchymal Origin

With very few exceptions, all adult tissues in mammals are maintained and can be renewed by stem cells that self-renew and generate the committed progeny required. These functions are regulated by a specific and in many ways unique microenvironment in stem cell niches. In most cases disruption of an adult stem cell niche leads to depletion of stem cells, followed by impairment of the ability of the tissue in question to maintain its functions. The presence of stem cells, often referred to as mesenchymal stem cells (MSCs) or multipotent bone marrow stromal cells (BMSCs), in the adult skeleton has long been realized. In recent years there has been exceptional progress in identifying and characterizing BMSCs in terms of their capacity to generate specific types of skeletal cells in vivo. Such BMSCs are often referred to as skeletal stem cells (SSCs) or skeletal stem and progenitor cells (SSPCs), with the latter term being used throughout this review. SSPCs have been detected in the bone marrow, periosteum, and growth plate and characterized in vivo on the basis of various genetic markers (i.e., Nestin, Leptin receptor, Gremlin1, Cathepsin-K, etc.). However, the niches in which these cells reside have received less attention. Here, we summarize the current scientific literature on stem cell niches for the SSPCs identified so far and discuss potential factors and environmental cues of importance in these niches in vivo. In this context we focus on (i) articular cartilage, (ii) growth plate cartilage, (iii) periosteum, (iv) the adult endosteal compartment, and (v) the developing endosteal compartment, in that order.

Local Application of Semaphorin 3A Combined with Adipose-Derived Stem Cell Sheet and Anorganic Bovine Bone Granules Enhances Bone Regeneration in Type 2 Diabetes Mellitus Rats

Bone tissue regeneration is considered to be the optimal solution for bone loss. However, diabetic patients have a greater risk of poor bone healing or bone grafting failure than nondiabetics. The purpose of this study was to investigate the influence of the complexes of an adipose-derived stem cell sheet (ASC sheet) and Bio-Oss® bone granules on bone healing in type 2 diabetes mellitus (T2DM) rats with the addition of semaphorin 3A (Sema3A). The rat ASC sheets showed stronger osteogenic ability than ASCs in vitro, as indicated by the extracellular matrix mineralization and the expression of osteogenesis-related genes at mRNA level. An ASC sheet combined with Bio-Oss® bone granules promoted bone formation in T2DM rats as indicated by microcomputed tomography (micro-CT) and histological analysis. In addition, Sema3A promoted the osteogenic differentiation of ASC sheets in vitro and local injection of Sema3A promoted T2DM rats' calvarial bone regeneration based on ASC sheet and Bio-Oss® bone granule complex treatment. In conclusion, the local injection of Sema3A and the complexes of ASC sheet and Bio-Oss® bone granules could promote osseous healing and are potentially useful to improve bone healing for T2DM patients.