Downregulation of the RNA-binding protein PUM2 facilitates MSC-driven bone regeneration and prevents OVX-induced bone loss

Abstract

Background Although mRNA dysregulation can induce changes in mesenchymal stem cell (MSC) homeostasis, the mechanisms by which post-transcriptional regulation influences MSC differentiation potential remain understudied. PUMILIO2 (PUM2) represses translation by binding target mRNAs in a sequence-specific manner. Methods In vitro osteogenic differentiation assays were conducted using human bone marrow-derived MSCs. Alkaline phosphatase and alizarin red S staining were used to evaluate the osteogenic potential of MSCs. A rat xenograft model featuring a calvarial defect to examine effects of MSC-driven bone regeneration. RNA-immunoprecipitation (RNA-IP) assay was used to determine the interaction between PUM2 protein and Distal-Less Homeobox 5 (DLX5) mRNA. Ovariectomized (OVX) mice were employed to evaluate the effect of gene therapy for postmenopausal osteoporosis. Results Here, we elucidated the molecular mechanism of PUM2 in MSC osteogenesis and evaluated the applicability of PUM2 knockdown (KD) as a potential cell-based or gene therapy. PUM2 level was downregulated during MSC osteogenic differentiation, and PUM2 KD enhanced MSC osteogenic potential. Following PUM2 KD, MSCs were transplanted onto calvarial defects in 12-week-old rats; after 8 weeks, transplanted MSCs promoted bone regeneration. PUM2 KD upregulated the expression of DLX5 mRNA and protein and the reporter activity of its 3'-untranslated region. RNA-IP revealed direct binding of PUM2 to DLX5 mRNA. We then evaluated the potential of adeno-associated virus serotype 9 (AAV9)-siPum2 as a gene therapy for osteoporosis in OVX mice. Conclusion Our findings suggest a novel role for PUM2 in MSC osteogenesis and highlight the potential of PUM2 KD-MSCs in bone regeneration. Additionally, we showed that AAV9-siPum2 is a potential gene therapy for osteoporosis.

Injectable Nano‐Micro Composites with Anti‐bacterial and Osteogenic Capabilities for Minimally Invasive Treatment of Osteomyelitis

“…The ability of the nano‐micro CaP@MS‐Oligo‐Van composites to stimulate the mineralization of BMSCs was further analyzed using Alizarin Red S staining. [ 58 ] CaP@MS and CaP@MS‐Oligo‐Van generated a substantial number of mineralized nodules (Figure 5d ). Quantitative analysis confirmed that the composites containing CaP nanosheets could improve osteogenic activity in BMSCs (Figure 5e ).…”

A Biomimetic Fibrous Composite Scaffold with Nanotopography-Regulated Mineralization for Bone Defect Repair

“…The potential of the bone fibril-like scaffold for the osteogenic differentiation of BMSCs was explored. Alkaline phosphatase (ALP) is an early biomarker of the osteogenic phenotype and plays a critical role in the initial stage of bone formation. , As shown in Figure A, the deepest ALP staining is found for BMSCs after they were cocultured for 7 days with MNTS. Alizarin Red S staining was also conducted on day 14 to determine whether mineralized nodules were present during late osteogenesis.…”

RNA-binding proteins in bone pathophysiology

“…As described above, in bone physiology PUM2 is essential to maintain balance in the MSCs differentiation, and, for this reason, it could have a potential role in OP ( Spassov and Jurecic, 2003 ). In this regard, Yoon et al (2023) , identified PUM2 as a potential therapeutic target for bone-related diseases, including OP. By performing in vivo experiments on a rat model of calvarial defects and on an OVX mice model of postmenopausal OP, the authors have observed that a KO of PUM2 and systemic delivery of PUM2 siRNA prevented bone loss, promoting respectively bone regeneration and alleviation of OP symptoms.…”