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Effects of negative pressure wound therapy on mesenchymal stem cells proliferation and osteogenic differentiation in a fibrin matrix.

ABSTRACT: Vacuum-assisted closure (VAC) negative pressure wound therapy (NPWT) has been proven to be an effective therapeutic method for the treatment of recalcitrant wounds. However, its role in bone healing remains to be unclear. Here, we investigated the effects of NPWT on rat periosteum-derived mesenchymal stem cells (P-MSCs) proliferation and osteoblastic differentiation in a 3D fibrin matrix. P-MSCs underwent primary culture for three passages before being used to construct cell clots. The fibrin clots were incubated with NPWT under continuous suction at -125 mmHg in a subatmospheric perfusion bioreactor. Clots exposed to atmospheric pressure served as the static control. Compared to the control group, cell proliferation significantly increased in NPWT group after incubation for 3 days. There was no statistical difference in apoptosis rate between two groups. The ALP activity and mineralization of P-MSCs all increased under continuous suction. The expressions of collagen type 1 and transcription factor Cbfa-1 were higher at the 1-, 3-, and 7-day timepoints and the expressions of osteocalcin and integrin ?5 were higher at the 3-, and 7-day timepoints in the NPWT group. These results indicate that a short time treatment with NPWT, applied with continuous suction at -125 mmHg, can enhance cellular proliferation of P-MSCs and induce the differentiation toward an osteogenic phenotype. The mechanotransduction molecule integrin ?5 was found to be highly expressed after NPWT treatment, which indicates that NPWT may play a positive role in fracture healing through enhance bone formation and decrease bone resorption.

SUBMITTER: Zhu J

PROVIDER: S-EPMC4162584 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Human mesenchymal stem cell (hMSC) differentiation into osteoblasts has important clinical significance in treating bone injury, and the stiffness of the extracellular matrix (ECM) has been shown to be an important regulatory factor for hMSC differentiation. The aim of this study was to further delineate how matrix stiffness affects intracellular signaling through integrin α5/β1, FAK, and Wnt signaling, subsequently regulating the osteogenic phenotype of hMSCs. METHODS:hMSCs were cultured on tunable polyacrylamide hydrogels coated with fibronectin with stiffness corresponding to a Young's modulus of 13-16 kPa and 62-68 kPa. After hMSCs were cultured on gels for 1 week, gene expression of alpha-1 type I collagen, BGLAP, and RUNX2 were evaluated by real-time PCR. After hMSCs were cultured on gels for 24 h, signaling molecules relating to integrin α5 (FAK, ERK, p-ERK, Akt, p-Akt, GSK-3β, p-GSK-3β, and β-catenin) were evaluated by western blot analysis. RESULTS:Osteogenic differentiation was increased on 62-68 kPa ECM, as evidenced by alpha-1 type I collagen, BGLAP, and RUNX2 gene expression, calcium deposition, and ALP staining. In the process of differentiation, gene and protein expression of integrin α5/β1 increased, together with protein expression of the downstream signaling molecules FAK, p-ERK, p-Akt, GSK-3β, p-GSK-3β, and β-catenin, indicating that these molecules can affect the osteogenic differentiation of hMSCs. An antibody blocking integrin α5 suppressed the stiffness-induced expression of all osteoblast markers examined. In particular, alpha-1 type I collagen, RUNX2, and BGLAP were significantly downregulated, indicating that integrin α5 regulates hMSC osteogenic differentiation. Downstream expression of FAK, ERK, p-ERK, and β-catenin protein was unchanged, whereas Akt, p-Akt, GSK-3β, and p-GSK-3β were upregulated. Moreover, expression of Akt and p-Akt was upregulated with anti-integrin α5 antibody, but no difference was observed for FAK, ERK, and p-ERK between the with or without anti-integrin α5 antibody groups. At the same time, expression of GSK-3β and p-GSK-3β was upregulated and β-catenin levels showed no difference between the groups with or without anti-integrin α5 antibody. Since Akt, p-Akt, GSK-3β, and p-GSK-3β displayed the same changes between the groups with or without anti-integrin α5 antibody, we then detected the links among them. Expression of p-Akt and p-GSK-3β was reduced effectively in the presence of the Akt inhibitor Triciribine. However, Akt, GSK-3β, and β-catenin were unchanged. These results suggested that expression of p-GSK-3β was regulated by p-Akt on 62-68 kPa ECM. CONCLUSIONS:Taken together, our results provide evidence that matrix stiffness (62-68 kPa) affects the osteogenic outcome of hMSCs through mechanotransduction events that are mediated by integrin α5.

Project description:Deficient bone regeneration causes bone defects or nonunion in a substantial proportion of trauma patients that urges for novel therapies. To develop a reliable therapy, we investigated the effect of negative pressure wound therapy (NPWT) on bone regeneration in vivo in a rat calvarial defect model. Negative pressure (NP) treatment in vitro was mimicked to test its effect on osteoblast differentiation in rat mesenchymal stem cells (MSCs) and MC3T3-E1 cells. Transcriptomic analyses, pharmaceutical interventions, and shRNA knockdowns were conducted to explore the underlying mechanism and their clinical relevance was investigated in samples from patients with nonunion. The potential application of a combined therapy of MSCs in hydrogels with negative pressure was tested in the rat critical-size calvarial defect model. We found that NPWT promoted bone regeneration in vivo and NP treatment induced osteoblast differentiation in vitro. NP induced osteogenesis via activating macroautophagy/autophagy by AMPK-ULK1 signaling that was impaired in clinical samples from patients with nonunion. More importantly, the combined therapy involving MSCs in hydrogels with negative pressure significantly improved bone regeneration in rat critical-size calvarial defect model. Thus, our study identifies a novel AMPK-ULK1-autophagy axis by which negative pressure promotes osteoblast differentiation of MSCs and bone regeneration. NPWT treatment can potentially be adopted for therapy of bone defects.Abbreviations: ADP, adenosine diphosphate; AICAR/Aic, acadesine; ALP, alkaline phosphatase; ALPL, alkaline phosphatase, biomineralization associated; AMP, adenosine monophosphate; AMPK, AMP-activated protein kinase; ARS, alizarin red S staining; ATG7, autophagy related 7; ATP, adenosine triphosphate; BA1, bafilomycin A1; BGLAP/OCN, bone gamma-carboxyglutamate protein; BL, BL-918; BS, bone surface; BS/TV, bone surface per tissue volume; BV/TV, bone volume per tissue volume; C.C, compound C; CCN1, cellular communication network factor 1; COL1A1, collagen type I alpha 1 chain; COL4A3, collagen type IV alpha 3 chain; COL4A4, collagen type IV alpha 4 chain; COL18A1, collagen type XVIII alpha 1 chain; CQ, chloroquine; GelMA, gelatin methacryloyl hydrogel; GO, Gene Ontology; GSEA, gene set enrichment analysis; HIF1A, hypoxia inducible factor 1 subunit alpha; HPLC, high-performance liquid chromatography; ITGAM/CD11B, integrin subunit alpha M; ITGAX/CD11C, integrin subunit alpha X; ITGB1/CdD9, integrin subunit beta 1; KEGG, Kyoto Encyclopedia of Genes and Genomes; MAP1LC3B/LC3B, microtubule associated protein 1 light chain 3 beta; micro-CT, microcomputed tomography; MSCs, mesenchymal stem cells; MTOR, mechanistic target of rapamycin kinase; NP, negative pressure; NPWT, negative pressure wound therapy; PRKAA1/AMPKα1, protein kinase AMP-activated catalytic subunit alpha 1; PRKAA2, protein kinase AMP-activated catalytic subunit alpha 2; PTPRC/CD45, protein tyrosine phosphatase receptor type C; ROS, reactive oxygen species; RUNX2, RUNX family transcription factor 2; SBI, SBI-0206965; SPP1/OPN, secreted phosphoprotein 1; THY1/CD90, Thy-1 cell surface antigen; SQSTM1, sequestosome 1; TGFB3, transforming growth factor beta 3; ULK1/Atg1, unc-51 like autophagy activating kinase 1.

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Effects of negative pressure wound therapy on mesenchymal stem cells proliferation and osteogenic differentiation in a fibrin matrix.

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