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Diabetes reduces mesenchymal stem cells in fracture healing through a TNF?-mediated mechanism.

ABSTRACT: Diabetes interferes with bone formation and impairs fracture healing, an important complication in humans and animal models. The aim of this study was to examine the impact of diabetes on mesenchymal stem cells (MSCs) during fracture repair.Fracture of the long bones was induced in a streptozotocin-induced type 1 diabetic mouse model with or without insulin or a specific TNF? inhibitor, pegsunercept. MSCs were detected with cluster designation-271 (also known as p75 neurotrophin receptor) or stem cell antigen-1 (Sca-1) antibodies in areas of new endochondral bone formation in the calluses. MSC apoptosis was measured by TUNEL assay and proliferation was measured by Ki67 antibody. In vitro apoptosis and proliferation were examined in C3H10T1/2 and human-bone-marrow-derived MSCs following transfection with FOXO1 small interfering (si)RNA.Diabetes significantly increased TNF? levels and reduced MSC numbers in new bone area. MSC numbers were restored to normal levels with insulin or pegsunercept treatment. Inhibition of TNF? significantly reduced MSC loss by increasing MSC proliferation and decreasing MSC apoptosis in diabetic animals, but had no effect on MSCs in normoglycaemic animals. In vitro experiments established that TNF? alone was sufficient to induce apoptosis and inhibit proliferation of MSCs. Furthermore, silencing forkhead box protein O1 (FOXO1) prevented TNF?-induced MSC apoptosis and reduced proliferation by regulating apoptotic and cell cycle genes.Diabetes-enhanced TNF? significantly reduced MSC numbers in new bone areas during fracture healing. Mechanistically, diabetes-enhanced TNF? reduced MSC proliferation and increased MSC apoptosis. Reducing the activity of TNF? in vivo may help to preserve endogenous MSCs and maximise regenerative potential in diabetic patients.

SUBMITTER: Ko KI

PROVIDER: S-EPMC4346353 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Diabetes reduces mesenchymal stem cells in fracture healing through a TNFα-mediated mechanism.

Ko Kang I KI Coimbra Leila S LS Tian Chen C Alblowi Jazia J Kayal Rayyan A RA Einhorn Thomas A TA Gerstenfeld Louis C LC Pignolo Robert J RJ Graves Dana T DT

Diabetologia 20150107 3

<h4>Aims/hypothesis</h4>Diabetes interferes with bone formation and impairs fracture healing, an important complication in humans and animal models. The aim of this study was to examine the impact of diabetes on mesenchymal stem cells (MSCs) during fracture repair.<h4>Methods</h4>Fracture of the long bones was induced in a streptozotocin-induced type 1 diabetic mouse model with or without insulin or a specific TNFα inhibitor, pegsunercept. MSCs were detected with cluster designation-271 (also kn ...[more]

PMID: 25563724

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Project description:To gain insight into the effect of diabetes on fracture healing, experiments were carried out focusing on chondrocyte apoptosis during the transition from cartilage to bone. Type 1 diabetes was induced in mice by multiple low-dose streptozotocin injections, and simple transverse fractures of the tibia or femur was carried out. Large-scale transcriptional profiling and gene set enrichment analysis were performed to examine apoptotic pathways on total RNA isolated from fracture calluses on days 12, 16, and 22, a period of endochondral bone formation when cartilage is resorbed and chondrocyte numbers decrease. Tumor necrosis factor alpha (TNF-alpha) protein levels were assessed by ELISA and caspase-3 by bioactivity assay. The role of TNF was examined by treating mice with the TNF-specific inhibitor pegsunercept. In vitro studies investigated the proapoptotic transcription factor FOXO1 in regulating TNF-induced apoptosis of chondrogenic ATDC5 and C3H10T1/2 cells as representative of differentiated chondrocytes, which are important during endochondral ossification. mRNA profiling revealed an upregulation of gene sets related to apoptosis in the diabetic group on day 16 when cartilage resorption is active but not day 12 or day 22. This coincided with elevated TNF-alpha protein levels, chondrocyte apoptosis, enhanced caspase-3 activity, and increased FOXO1 nuclear translocation (p < .05). Inhibition of TNF significantly reduced these parameters in the diabetic mice but not in normoglycemic control mice (p < .05). Silencing FOXO1 using siRNA in vitro significantly reduced TNF-induced apoptosis and caspase activity in differentiated chondrocytes. The mRNA levels of the proapoptotic genes caspase-3, caspase-8, caspase-9, and TRAIL were significantly reduced with silencing of FOXO1 in chondrocytic cells. Inhibiting caspase-8 and caspase-9 significantly reduced TNF-induced apoptosis in chondrogenic cells. These results suggest that diabetes causes an upregulation of proapoptotic genes during the transition from cartilage to bone in fracture healing. Diabetes increased chondrocyte apoptosis through a mechanism that involved enhanced production of TNF-alpha, which stimulates chondrocyte apoptosis and upregulates mRNA levels of apoptotic genes through FOXO1 activation.

Project description:BackgroundMesenchymal stem cells (MSCs) are promising targets for therapeutic use in regenerative medicine and tissue engineering. In the previous study, we have found that MSCs could be reverted to a primitive stem cell population after in vitro induction of osteogenic and de-osteogenic differentiation (de-osteogenic differentiated MSCs, De-Os-MSCs). De-Os-MSCs showed improved cell survival and osteogenic potential. However, the underlying mechanism and its potential effect on fracture healing has not been explored.MethodsMSCs were isolated from the rat bone marrow. MicroRNAs were cloned into lentiviral vectors and transduced into MSCs to observe the effects on osteogenesis. The expression levels of marker genes were evaluated by quantitative RT-PCR. Ectopic bone formation model was used to evaluate the bone regeneration ability of mir-92b transduced MSCs in vivo. An open femur fracture model was established, and MSCs or De-Os-MSCs were administrated to the fracture sites. Histological, biomechanical and microCT analysis were used to evaluate the quality of bone.ResultsIn the present study, we found that mir-92b was significantly increased in the secretions of De-Os-MSCs. And mir-92b could promote the osteogenic differentiation potential of MSCs by activating pERK and JNK signaling pathways. The ectopic bone formation assay showed that MSCs overexpressing mir-92b formed more bone like tissues in vivo. Most importantly, we found local administration of De-Os-MSCs could accelerate fracture healing using an open femur fracture model in rats. The quality of bone property was much better as shown by microCT and biomechanical testing.ConclusionTaken together, our study demonstrated that mir-92b promoted osteogenesis of MSCs, which was partially accounted for the enhanced osteogenic differentiation potential of De-Os-MSCs. And De-Os-MSCs had shown better regenerative capacity in accelerating fracture healing when they were locally given.The translational potential of this articleDe-Os-MSCs could be used to accelerate fracture healing, and reduce the occurrence of delayed unions and non-unions.

Project description:: Paracrine signaling by bone-marrow-derived mesenchymal stem cells (MSCs) plays a major role in tissue repair. Although the production of regulatory cytokines by MSC transplantation is a critical modulator of tissue regeneration, we focused on exosomes, which are extracellular vesicles that contain proteins and nucleic acids, as a novel additional modulator of cell-to-cell communication and tissue regeneration. To address this, we used radiologic imaging, histological examination, and immunohistochemical analysis to evaluate the role of exosomes isolated from MSC-conditioned medium (CM) in the healing process in a femur fracture model of CD9-/- mice, a strain that is known to produce reduced levels of exosomes. We found that the bone union rate in CD9-/- mice was significantly lower than wild-type mice because of the retardation of callus formation. The retardation of fracture healing in CD9-/- mice was rescued by the injection of exosomes, but this was not the case after the injection of exosomes-free conditioned medium (CM-Exo). The levels of the bone repair-related cytokines, monocyte chemotactic protein-1 (MCP-1), MCP-3, and stromal cell-derived factor-1 in exosomes were low compared with levels in CM and CM-Exo, suggesting that bone repair may be in part mediated by other exosome components, such as microRNAs. These results suggest that exosomes in CM facilitate the acceleration of fracture healing, and we conclude that exosomes are a novel factor of MSC paracrine signaling with an important role in the tissue repair process.SignificanceThis work focuses on exosomes, which are extracellular vesicles, as a novel additional modulator of cell-to-cell communication. This study evaluated the role of exosomes isolated from mesenchymal stem cell (MSC)-conditioned medium (MSC-CM) in the fracture-healing process of CD9-/- mice, a strain that is known to produce reduced levels of exosomes. Retardation of fracture healing in CD9-/- mice was rescued by the injection of MSC exosomes, but this was not the case after the injection of exosome-free CM. This study finds that MSC exosomes are a novel factor of MSC paracrine signaling, with an important role in the tissue repair process.

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Diabetes reduces mesenchymal stem cells in fracture healing through a TNF?-mediated mechanism.

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Diabetes reduces mesenchymal stem cells in fracture healing through a TNFα-mediated mechanism.

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