MicroRNA-584-5p/RUNX family transcription factor 2 axis mediates hypoxia-induced osteogenic differentiation of periosteal stem cells

Identification and function of periosteal skeletal stem cells in skeletal development, homeostasis, and disease

Background

Periosteum-resident skeletal stem cells (SSCs) are essential for the growth, maintenance, and repair of the skeletal system. These cells exhibit self-renewal ability and clonal pluripotency. Compared to the diverse bone marrow mesenchymal stem cells (BMSCs), periosteal skeletal stem cells (P-SSCs) represent a purified stem cell population and are preferable for bone tissue engineering.

Methods

This review covers the histological structure of the periosteum, process of isolating and characterising P-SSCs, and spatiotemporal distribution and characteristics of P-SSCs from different lineages. Additionally, the roles of P-SSCs in bone injury, disease, and periosteal niche regulation are discussed.

Results

Intramembrane and intraconal ossification of P-SSCs exhibits favourable therapeutic potential. Osteogenesis using P-SSCs is an ideal process for bone repair.

Conclusions

P-SSCs are vital for bone formation, maintenance, and repair. P-SSCs are essential components of the periosteal microenvironment. Therefore, it is essential to investigate their critical clinical applications and translational functions. By targeting and inducing endogenous stem cells, the in situ repair of bone defects can be facilitated, leading to the development of more effective novel therapies.

The translational potential of this article

To enhance our understanding of the function of P-SSCs in bone repair and skeleton-related diseases, it is imperative to elucidate the current research status of P-SSCs and ascertain the prospective trajectory for their advancement and refinement in bone tissue engineering. P-SSCs are expected to play an expanded role in treating bone abnormalities, leading to the optimisation of bone tissue treatment.

Mechanism of hyperbaric oxygen therapy downregulating H-type angiogenesis in subchondral bone of knee osteoarthritis through the PHD2/HIF-1α pathway

OBJECTIVE

To explore the mechanism of hyperbaric oxygen therapy in inhibiting subchondral bone angiogenesis and delaying the progression of osteoarthritis through the PHD2/HIF-1α signaling pathway.

METHODS

Mice were randomly divided into three groups (control group, osteoarthritis group, and hyperbaric oxygen treatment group). The effect of hyperbaric oxygen therapy on osteoarthritis was evaluated using Micro-CT, Safranin O-Fast Green staining, and detection of osteoarthritis inflammation markers (MMP-13, ADAMTS-5, Col2a1, and Aggrecan). The activation relationship between PHD2 and downstream signaling pathways was investigated through gene knockout and overexpression experiments. Finally, cell scratch assays, tube formation assays, and chondrogenic differentiation experiments were conducted to verify the mechanism of the PHD2/HIF-1α signaling pathway under hyperbaric oxygen stimulation.

RESULTS

Hyperbaric oxygen therapy delayed the progression of osteoarthritis in mice. It promoted chondrogenic differentiation of mesenchymal stem cells, inhibited angiogenesis, enhanced PHD2 expression, and suppressed the production of HIF-1α and VEGFA. Silencing/overexpression of PHD2 resulted in increased/decreased production of HIF-1α and VEGFA, respectively.

CONCLUSION

The hyperbaric oxygen environment promotes the expression of PHD2, accelerates the degradation of HIF-1α, and inhibits the production of VEGFA, thereby reducing the generation of type H vessels in subchondral bone.

RUNX2 regulation in osteoblast differentiation: A possible therapeutic function of the lncRNA and miRNA-mediated network

Osteogenic differentiation is a crucial process in the formation of the skeleton and the remodeling of bones. It relies on a complex system of signaling pathways and transcription factors, including Runt-related transcription factor 2 (RUNX2). Non-coding RNAs (ncRNAs) control the bone-specific transcription factor RUNX2 through post-transcriptional mechanisms to regulate osteogenic differentiation. The most research has focused on microRNAs (miRNAs) and long ncRNAs (lncRNAs) in studying how they regulate RUNX2 for osteogenesis in both normal and pathological situations. This article provides a concise overview of the recent advancements in understanding the critical roles of lncRNA/miRNA/axes in controlling the expression of RUNX2 during bone formation. The possible application of miRNAs and lncRNAs as therapeutic agents for the treatment of disorders involving the bones and bones itself is also covered.

Runx2 and Polycystins in Bone Mechanotransduction: Challenges for Therapeutic Opportunities

Bone mechanotransduction is a critical process during skeletal development in embryogenesis and organogenesis. At the same time, the type and level of mechanical loading regulates bone remodeling throughout the adult life. The aberrant mechanosensing of bone cells has been implicated in the development and progression of bone loss disorders, but also in the bone-specific aspect of other clinical entities, such as the tumorigenesis of solid organs. Novel treatment options have come into sight that exploit the mechanosensitivity of osteoblasts, osteocytes, and chondrocytes to achieve efficient bone regeneration. In this regard, runt-related transcription factor 2 (Runx2) has emerged as a chief skeletal-specific molecule of differentiation, which is prominent to induction by mechanical stimuli. Polycystins represent a family of mechanosensitive proteins that interact with Runx2 in mechano-induced signaling cascades and foster the regulation of alternative effectors of mechanotransuction. In the present narrative review, we employed a PubMed search to extract the literature concerning Runx2, polycystins, and their association from 2000 to March 2024. The keywords stated below were used for the article search. We discuss recent advances regarding the implication of Runx2 and polycystins in bone remodeling and regeneration and elaborate on the targeting strategies that may potentially be applied for the treatment of patients with bone loss diseases.