MiR-181a Targets RSPO2 and Regulates Bone Morphogenetic Protein – WNT Signaling Crosstalk During Chondrogenic Differentiation of Mesenchymal Stromal Cells

Abstract

Mechanisms of WNT and bone morphogenetic protein (BMP) signaling crosstalk is in the focus of multiple biological studies, and it also has been discovered to play important roles in human mesenchymal stromal cells (MSC) that are of great interest for neocartilage engineering due to their high chondrogenic differentiation potential. However, MSC-derived chondrocytes undergo hypertrophic degeneration that impedes their clinical application for cartilage regeneration. In our previous study, we established that several microRNAs (miRs) are differentially expressed between articular chondrocytes (AC) – and MSC-derived neocartilage, with miR-181a being the most prominent candidate as key microRNA involved in the regulation of a balance between chondral and endochondral differentiation. The aim of this study was the identification of precise mRNA targets and signaling pathways regulated by miR-181a in MSC during chondrogenesis. MiR-181a was upregulated during chondrogenesis of MSC, along with an increase of the hypertrophic phenotype in resulting cartilaginous tissue. By in silico analysis combined with miR reporter assay, the WNT signaling activator and BMP signaling repressor RSPO2 was suggested as a target of miR-181a. Further validation experiments confirmed that miR-181a targets RSPO2 mRNA in MSC. It was found that in human MSC miR-181a activated BMP signaling manifested by the accumulation of SOX9 protein and increased phosphorylation of SMAD1/5/9. These effects, together with the concomitant reduction of canonical WNT signaling induced by miR-181a mimic, were in accordance with the effects expected by the loss of RSPO2, thus indicating the causative link between miR-181a and RSPO2. Moreover, we observed that a tight correlation between miR-181a and miR-218 expression levels in healthy human cartilage tissue was disrupted in osteoarthritis (OA) highlighting the importance of the WNT-BMP signaling crosstalk for preventing OA.

Mesenchymal Stem Cells Cultured in a 3D Microgel Environment Containing Platelet-Rich Plasma Significantly Modify Their Chondrogenesis-Related miRNA Expression

“…We found that the expression of this miRNA increased by 3.17-fold. We also found a significant upregulation of miR182a and b, which have been shown to induce chondrogenesis through mechanisms involving downregulation of the Wnt/β-catenin pathway [36], in association with other miRNAs such as miR-185 (whose expression increased 2.08-fold).…”

The miR‐181 family: Wide‐ranging pathophysiological effects on cell fate and function

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“…Two studies reported increased levels of miR‐181a during bone marrow MSC chondrogenesis although a correlation with enhancing hypertrophy was not discussed (Barter et al, 2015; Vail et al, 2022). More recently, Melnik et al identified R‐Spondin 2 ( RSPO2 ) as a key target for miR‐181a in regulating MSC hypertrophy (Melnik et al, 2021).…”

Ethanolic Extract of Propolis Modulates Autophagy-Related microRNAs in Osteoarthritic Chondrocytes

“…A differential expression of miR-181a has also been described in the different stages of maturation of chondrocytes with an upregulation in hypertrophic chondrocytes [3]. It is postulated that miR-181a regulates the balance of WNT and BMP pathways in cartilage [83]. miR-181a also regulates the expression of endogenous CCN1 and ACAN genes with a repressive role in cartilage metabolism via CCN1 as well as ECM construction via aggrecan [84].…”