Retracted : In vivo and in vitro effects of PTH1‐34 on osteogenic and adipogenic differentiation of human bone marrow‐derived mesenchymal stem cells through regulating microRNA‐155

Noncoding RNA miR-205-5p mediates osteoporosis pathogenesis and osteoblast differentiation by regulating RUNX2

As a kind of noncoding RNAs, microRNAs (miRNAs) play important roles in disease pathogenesis by regulating gene expression. However, the molecular mechanism of miRNAs in osteoporosis remains largely unknown. In the present study, we aim to explore the genome-wide miRNAs expression profile and the regulatory mechanism of miR-205-5p in osteoporosis. A total of 72 differentially expressed miRNAs were identified in osteoporosis via microarray technology and bioinformatics analysis. We focused on one of the abnormally expressed miRNAs, miR-205-5p, which was previously unknown in osteoporosis. Quantitative real-time polymerase chain reaction (qRT-PCR) results showed that miR-205-5p was upregulated in osteoporosis samples and its expression was gradually decreased during osteogenic differentiation. Besides, miR-205-5p overexpression could inhibit the activity of osteoblast markers, including collagen, type I, α 1 (COL1A1) and alkaline phosphatase (ALP) while miR-205-5p inhibition showed the opposite results. Moreover, bioinformatics analysis identified the potential targets of miR-205-5p, including runt-related transcription factor 2 (RUNX2), SMAD1 and BCL6, etc. The dual-luciferase reporter assay confirmed RUNX2 was directly targeted by miR-205-5p. Furthermore, the rescue experiments showed that RUNX2 overexpression could significantly weaken the effect of miR-205-5p on osteoblast markers, indicating that miR-205-5p may inhibit osteogenic differentiation by targeting RUNX2.

Strategy for achieving standardized bone models

Reliably producing functional in vitro organ models, such as organ-on-chip systems, has the potential to considerably advance biology research, drug development time, and resource efficiency. However, despite the ongoing major progress in the field, three-dimensional bone tissue models remain elusive. In this review, we specifically investigate the control of perfusion flow effects as the missing link between isolated culture systems and scientifically exploitable bone models and propose a roadmap toward this goal.

Loss of Nmp4 optimizes osteogenic metabolism and secretion to enhance bone quality

A goal of osteoporosis therapy is to restore lost bone with structurally sound tissue. Mice lacking the transcription factor nuclear matrix protein 4 (Nmp4, Zfp384, Ciz, ZNF384) respond to several classes of osteoporosis drugs with enhanced bone formation compared with wild-type (WT) animals. Nmp4-/- mesenchymal stem/progenitor cells (MSPCs) exhibit an accelerated and enhanced mineralization during osteoblast differentiation. To address the mechanisms underlying this hyperanabolic phenotype, we carried out RNA-sequencing and molecular and cellular analyses of WT and Nmp4-/- MSPCs during osteogenesis to define pathways and mechanisms associated with elevated matrix production. We determined that Nmp4 has a broad impact on the transcriptome during osteogenic differentiation, contributing to the expression of over 5,000 genes. Phenotypic anchoring of transcriptional data was performed for the hypothesis-testing arm through analysis of cell metabolism, protein synthesis and secretion, and bone material properties. Mechanistic studies confirmed that Nmp4-/- MSPCs exhibited an enhanced capacity for glycolytic conversion: a key step in bone anabolism. Nmp4-/- cells showed elevated collagen translation and secretion. The expression of matrix genes that contribute to bone material-level mechanical properties was elevated in Nmp4-/- cells, an observation that was supported by biomechanical testing of bone samples from Nmp4-/- and WT mice. We conclude that loss of Nmp4 increases the magnitude of glycolysis upon the metabolic switch, which fuels the conversion of the osteoblast into a super-secretor of matrix resulting in more bone with improvements in intrinsic quality.

miR-431 inhibits adipogenic differentiation of human bone marrow-derived mesenchymal stem cells via targeting insulin receptor substance 2

Background

An understanding of the mechanism underlying adipogenic differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) will provide new therapeutic approaches for many diseases, including osteoporosis. This study aimed to investigate the role of miR-431 in adipogenic differentiation of hMSCs.

Methods

hMSCs were induced for adipogenic differentiation and miR-431 was detected by polymerase chain reaction (PCR). hMSCs were transfected by miR-431 or small interfering RNA (siRNA) for insulin receptor substance 2 (IRS2). The expression of IRS2 was detected by PCR and Western blot analysis. The targeting of the 3′-untranslated region (UTR) of IRS2 by miR-431 was examined by luciferase assay.

Results

miR-431 expression was decreased during adipogenesis of hMSCs. Overexpression of miR-431 inhibited adipogenic differentiation, accompanied by the downregulation of CCAAT/enhancer binding protein α (C/EBPα) and peroxisome proliferator-activated receptor γ (PPARγ), two key regulators of adipogenesis. Moreover, miR-431 decreased both protein and mRNA levels of IRS2. The expression of IRS2 was increased during adipogenic differentiation of hMSCs in conjunction with decreased levels of miR-431, and knockdown of IRS2 in hMSCs inhibited adipogenic differentiation. Luciferase assay confirmed that miR-431 targeted the 3′-UTR of IRS2 in hMSCs.

Conclusions

This is the first study to show that miR-431 inhibits adipogenic differentiation of hMSCs via targeting IRS2.