Increased BMPR1A Expression Enhances the Adipogenic Differentiation of Mesenchymal Stem Cells in Patients with Ankylosing Spondylitis.

Zhenhua Liu,Liangbin Gao,Zhongyu Xie,Hongjun Su,Peng Wang,Huiyong Shen,Shuizhong Cen,Yanfeng Wu,Xiaohua Wu

doi:10.1155/2019/4143167

Abstract

Objective To investigate the adipogenic differentiation capacity of mesenchymal stem cells (MSCs) from ankylosing spondylitis (AS) patients and explore the mechanism of abnormal MSC adipogenesis in AS. Methods MSCs from patients with AS (ASMSCs) and healthy donors (HDMSCs) were cultured in adipogenic differentiation medium for up to 21 days. Adipogenic differentiation was determined using oil red O (ORO) staining and quantification and was confirmed by assessing adipogenic marker expression (PPAR-γ, FABP4, and adiponectin). Gene expression of adipogenic markers was detected using qRT-PCR. Protein levels of adipogenic markers and signaling pathway-related molecules were assessed via Western blotting. Levels of bone morphogenetic proteins 4, 6, 7, and 9 were determined using enzyme-linked immunosorbent assays. Lentiviruses encoding short hairpin RNAs (shRNAs) were constructed to reverse abnormal bone morphogenetic protein receptor 1A (BMPR1A) expression and evaluate its role in abnormal ASMSC adipogenic differentiation. Bone marrow fat content was assessed using hematoxylin and eosin (HE) staining. BMPR1A expression in bone marrow MSCs was measured using immunofluorescence staining. Results ASMSCs exhibited a greater adipogenic differentiation capacity than HDMSCs. During adipogenesis, ASMSCs expressed BMPR1A at higher levels, which activated the BMP-pSmad1/5/8 signaling pathway and increased adipogenesis. BMPR1A silencing using an shRNA eliminated the difference in adipogenic differentiation between HDMSCs and ASMSCs. Moreover, HE and immunofluorescence staining showed higher bone marrow fat content and BMPR1A expression in patients with AS than in healthy donors. Conclusion Increased BMPR1A expression induces abnormal ASMSC adipogenic differentiation, potentially contributing to fat metaplasia and thus new bone formation in patients with AS.

Highlights

Ankylosing spondylitis (AS) is a chronic inflammatory and potentially disabling disease that mainly affects the axial spinal joints [1]
HDMSCs and ASMSCs were cultured in adipogenic differentiation medium (AM) for 0-21 days
In both HDMSCs and ASMSCs, the levels of the fatty acid binding protein 4 (FABP4) and adiponectin mRNAs and proteins increased continuously from day 0 to day 21, but the levels of PPAR-γ mRNA and protein peaked on day 10 and decreased thereafter

Summary

Introduction

Ankylosing spondylitis (AS) is a chronic inflammatory and potentially disabling disease that mainly affects the axial spinal joints [1]. Fat metaplasia, defined as focally enhanced MRI signals on T1-weighted sequences and reduced signals on short tau inversion recovery sequences, is a common MRI finding in patients with AS [7,8,9] These MRI signals, which imply adipocyte accumulation [10, 11], often occur in the sacroiliac joint or vertebral corner of patients with AS. New bone often forms at the same sites as these signals, suggesting that fat metaplasia is an important intermediary step in new bone development [5, 7, 12]

Methods

Results

Conclusion