Role of TGF‑β1 expressed in bone marrow‑derived mesenchymal stem cells in promoting bone formation in a rabbit femoral defect model

FOXC1 Promotes Osteoblastic Differentiation of Bone Marrow Mesenchymal Stem Cells via the Dnmt3b/CXCL12 Axis

Bone defects have remained a clinical problem in current orthopedics. Bone marrow mesenchymal stem cells (BM-MSCs) with multi-directional differentiation ability have become a research hotspot for repairing bone defects. In vitro and in vivo models were constructed, respectively. Alkaline phosphatase (ALP) staining and alizarin red staining were performed to detect osteogenic differentiation ability. Western blotting (WB) was used to detect the expression of osteogenic differentiation-related proteins. Serum inflammatory cytokine levels were detected by ELISA. Fracture recovery was evaluated by HE staining. The binding relationship between FOXC1 and Dnmt3b was verified by dual-luciferase reporter assay. The relationship between Dnmt3b and CXCL12 was explored by MSP and ChIP assays. FOXC1 overexpression promoted calcium nodule formation, upregulated osteogenic differentiation-related protein expression, promoted osteogenic differentiation, and decreased inflammatory factor levels in BM-MSCs, and promoted callus formation, upregulated osteogenic differentiation-related protein expression, and downregulated CXCL12 expression in the mouse model. Furthermore, FOXC1 targeted Dnmt3b, with Dnmt3b knockdown decreasing calcium nodule formation and downregulating osteogenic differentiation-related protein expression. Additionally, inhibiting Dnmt3b expression upregulated CXCL12 protein expression and inhibited CXCL12 methylation. Dnmt3b could be binded to CXCL12. CXCL12 overexpression attenuated the effects of FOXC1 overexpression and inhibited BM-MSCs osteogenic differentiation. This study confirmed that the FOXC1-mediated regulation of the Dnmt3b/CXCL12 axis had positive effects on the osteogenic differentiation of BM-MSCs.

Alkaline shear-thinning micro-nanocomposite hydrogels initiate endogenous TGFβ signaling for in situ bone regeneration

Recruiting endogenous stem cells to bone defects without stem cell transplantation and exogenous factor delivery represents a promising strategy for bone regeneration. Herein, we develop an alkaline shear-thinning micro-nanocomposite hydrogel (10-MmN), aiming to alkaline-activate endogenous TGFβ1 and achieve in situ bone regeneration. It contains polyethyleneimine (PEI)-modified gelatin, laponite nanoplatelets (LAP), a bicarbonate buffer with a pH of 10, and gelatin microspheres (MSs). PEI-modified gelatin plays a pivotal role in hydrogel fabrication. It endows the system with sufficient positive charges, and forms a shear-thinning nanocomposite matrix in the pH 10 buffer (10-mN) with negatively charged LAP via electrostatic gelation. For biological functions, the pH 10 buffer dominates alkaline activation of endogenous serum TGFβ1 to recruit rat bone marrow stem cells through the Smad pathway, followed by improved osteogenic differentiation. In addition, MSs are incorporated into 10-mN to form 10-MmN, and function as substrates to provide good attachment sites for the recruited stem cells and facilitate further their osteogenic differentiation. In a rat critical-sized calvarial defect model, 10-MmN exhibits excellent biocompatibility, biodegradability, hydrogel infusion and retention in bone defects with flexible shapes and active bleeding. Importantly, it repairs ~95% of the defect areas in 3 months by recruiting TGFβR2+ and CD90+CD146+ stem cells, and promoting cell proliferation, osteogenic differentiation and bone formation. The present study provides a biomaterial-based strategy to regulate alkalinity in bone defects for the initiation of endogenous TGFβ signaling, which can be extended to treat other diseases.

Emerging roles of growth factors in osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a potentially disabling orthopedic condition that requires total hip arthroplasty in most late-stage cases. However, mechanisms underlying the development of ONFH remain unknown, and the therapeutic strategies remain limited. Growth factors play a crucial role in different physiological processes, including cell proliferation, invasion, metabolism, apoptosis, and stem cell differentiation. Recent studies have reported that polymorphisms of growth factor-related genes are involved in the pathogenesis of ONFH. Tissue and genetic engineering are attractive strategies for treating early-stage ONFH. In this review, we summarized dysregulated growth factor-related genes and their role in the occurrence and development of ONFH. In addition, we discussed their potential clinical applications in tissue and genetic engineering for the treatment of ONFH.

The Effects of Transforming Growth Factor-β1 on the Differentiation of Cell Organoids Composed of Gingiva-Derived Stem Cells

This study was aimed at evaluating the effects of transforming growth factor-β on the differentiation and mRNA expression of organoids made out of human mesenchymal stem cells. Cell organoids composed of gingiva-derived stem cells were cultured in the presence of transforming growth factor-β1 at concentrations ranging from 0, 1, 10, to 20 ng/ml. Evaluations of the cell morphology of the organoids were performed on days 7, 9, 11, and 14. Quantitative cellular viability was completed on day 14. Alkaline phosphatase activity assays were performed to evaluate the differentiation of stem cells on day 14. Real-time polymerase chain reactions were used to determine the expression levels of TGF-β1, RUNX2, OCN, SOX9, and COL1A1 mRNA on day 14. The stem cells produced well-formed organoids on day 7, and the addition of transforming growth factor-β1 did not result in relevant changes in their shape. The organoids grew in size and became more intact with longer incubation times. On day 14, the diameters were 222.2 ± 9.6, 186.1 ± 4.8, 197.2 ± 9.6, and 211.1 ± 19.2 m for transforming growth factor-β1 at final concentrations of 0, 1, 10, and 20 ng/ml, respectively. Quantitative cell viability results from day 14 exhibited no significant difference between the groups (P > 0.05). There was significantly higher alkaline phosphatase activity with the addition of transforming growth factor-β1 with the highest value for the 1 ng/ml group (P < 0.05). Real-time polymerase chain reaction results demonstrated that the mRNA expression levels of RUNX2, OCN, and SOX were higher in 1 ng/ml but did not reach statistical significance. Treatment with 1 ng/ml of transforming growth factor-β1 significantly increased COL1A1 mRNA expression at day 14. The application of transforming growth factor-β1 increased differentiation, which was confirmed by alkaline phosphatase activity and mRNA expression while maintaining cell viability.

The Effect of Mesenchymal Stem Cell-Enriched Scaffolds on MMP-8 and TGF-β Levels of Vertebrae Postlaminoplasty in Rabbit Model

INTRODUCTION

Some laminoplasty procedures still have restenosis because of bony-bridging failure of the laminar hinge. The present study aimed to determine the effect of mesenchymal stem cell (MSC)-enriched scaffolds on vertebral regeneration after laminoplasty on the basis of the number of osteoblasts, matrix metalloproteinase-8 (MMP-8), and transforming growth factor-beta (TGF-β) levels.

METHODS

Laminoplasty procedure using the Hirabayashi technique was conducted at the lumbar level in 32 rabbits that were divided into four and three groups of the control (C) and treatment groups, respectively, with different types of laminoplasty spacer (T1, autograft; T2, scaffold; and T3, scaffold with MSCs). Histopathological studies were conducted to calculate the number of osteoblasts and enzyme-linked immunosorbent assay tests to detect MMP-8 and TGF-β 4 weeks after the surgery.

RESULTS

The results showed a significant decrease in MMP-8 level in the T3 group compared with that in the control group (p < 0.05). A significant difference exists between the average number of newly formed osteoblasts in the control group compared with that in the T3 group (p < 0.05) with a higher mean blood TGF-β level of all experimental groups compared with that of the control group (p = 0.58).

CONCLUSION

The significant decrease in MMP-8 levels, increase in TGF-β levels, and increased number of osteoblasts on MSC-seeded polylactic acid scaffolds could be useful to support the laminoplasty procedure to prevent restenosis because it was biocompatible and promoted the bone healing process.

COX-2 promotes the osteogenic potential of BMP9 through TGF-β1/p38 signaling in mesenchymal stem cells

This study investigated the effects of transforming growth factor-β1 (TGF-β1) and cyclooxygenase-2 (COX-2) on bone morphogenetic protein 9 (BMP9) in mesenchymal stem cells (MSCs). We found that BMP9 increased mRNA levels of TGF-β1 and COX-2 in C3H10T1/2 cells. BMP9-induced osteogenic markers were enhanced by TGF-β1 and reduced by TGF-βRI-specific inhibitor LY364947. BMP9 increased level of p-Smad2/3, which were either enhanced or reduced by COX-2 and its inhibitor NS398. BMP9-induced osteogenic markers were decreased by NS398 and it was partially reversed by TGF-β1. COX-2 increased BMP9-induced osteogenic marker levels, which almost abolished by LY364947. BMP9-induced bone formation was enhanced by TGF-β1 but reduced by silencing TGF-β1 or COX-2. BMP9’s osteogenic ability was inhibited by silencing COX-2 but partially reversed by TGF-β1. TGF-β1 and COX-2 enhanced activation of p38 signaling, which was induced by BMP9 and reduced by LY364947. The ability of TGF-β1 to increase the BMP9-induced osteogenic markers was reduced by p38-specific inhibitor, while BMP9-induced TGF-β1 expression was reduced by NS398, but enhanced by COX-2. Furthermore, CREB interacted with Smad1/5/8 to regulate TGF-β1 expression in MSCs. These findings suggest that COX-2 overexpression leads to increase BMP9’s osteogenic ability, resulting from TGF-β1 upregulation which then activates p38 signaling in MSCs.