HSPB7 regulates osteogenic differentiation of human adipose derived stem cells via ERK signaling pathway

Chanyuan Jin,Zhihui Tang,Ting Shuai

doi:10.1186/s13287-020-01965-4

Abstract

BackgroundHeat shock protein B7 (HSPB7), which belongs to small heat shock protein family, has been reported to be involved in diverse biological processes and diseases. However, whether HSPB7 regulates osteogenic differentiation of human adipose derived stem cells (hASCs) remains unexplored.MethodsThe expression level of HSPB7 during the osteogenesis of hASCs was examined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analysis. Lentivirus transfection was used to knock down or overexpress HSPB7, which enabled us to investigate the effect of HSPB7 on osteogenic differentiation of hASCs. U0126 and extracellular signal-regulated protein kinase 1/2 (ERK1/2) siRNA were used to identify the mechanism of the HSPB7/ERK1/2 axis in regulating osteogenic differentiation of hASCs. Moreover, ectopic bone formation in nude mice and osteoporosis mice model was used to investigate the effect of HSPB7 on osteogenesis in vivo.ResultsIn this study, we found the expression of HSPB7 was significantly downregulated during the osteogenic differentiation of hASCs. HSPB7 knockdown remarkably promoted osteogenic differentiation of hASCs, while HSPB7 overexpression suppressed osteogenic differentiation of hASCs both in vitro and in vivo. Moreover, we discovered that the enhancing effect of HSPB7 knockdown on osteogenic differentiation was related to the activation of extracellular signal-regulated protein kinase (ERK) signaling pathway. Inhibition of ERK signaling pathway with U0126 or silencing ERK1/2 effectively blocked the stimulation of osteogenic differentiation induced by HSPB7 knockdown. Additionally, we found that HSPB7 expression was markedly increased in mouse bone marrow mesenchymal stem cells (mBMSCs) from the osteoporotic mice which suggested that HSPB7 might be utilized as a potential target in the development of effective therapeutic strategies to treat osteoporosis and other bone diseases.ConclusionTaken together, these findings uncover a previously unrecognized function of HSPB7 in regulating osteogenic differentiation of hASCs, partly via the ERK signaling pathway.

Highlights

Human adipose derived stem cells are multipotential mesenchymal stem cells (MSCs) that have the ability to differentiate into different lineages such as chondrocytes, adipocytes, and osteocytes [1]
Heat shock protein B7 (HSPB7) was downregulated during osteogenic differentiation of human adipose derived stem cells (hASCs) In order to determine the effect of HSPB7 in the process of osteogenesis, we first detected the expression level of HSPB7 during osteogenic differentiation of hASCs. quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis showed the mRNA expression of HSPB7 was remarkably decreased during osteogenesis, while the expression levels of osteogenic markers Runt-related transcription factor 2 (RUNX2), Alkaline phosphatase (ALP), and OCN were significantly upregulated (Fig. 1a–d)
Results showed that HSPB7 was expressed at a much lower level in U2OS cells compared with hASCs and human bone marrow mesenchymal stem cells (hBMSCs) (SFig. 1A)

Summary

Introduction

Human adipose derived stem cells (hASCs) are multipotential mesenchymal stem cells (MSCs) that have the ability to differentiate into different lineages such as chondrocytes, adipocytes, and osteocytes [1]. As a type of MSCs, hASCs offer new therapeutic solutions for bone defects and metabolic diseases due to their abundant sources, ease of acquisition, low immunogenicity, and osteogenic differentiation capacity [2, 3]. The extracellular signal-regulated kinase (ERK)/MAPK signaling pathway plays important roles in driving the commitment of MSCs into osteogenic lineage [8]. Fibroblast growth factor receptor 1 (FGFR1), a transmembrane receptor which transduces extracellular signals to multiple intracellular downstream pathways, is indispensable for skeletal development via regulating osteoblast growth and differentiation [11]. Whether HSPB7 regulates osteogenic differentiation of human adipose derived stem cells (hASCs) remains unexplored

Methods

Results

Conclusion