Journal of Molecular Medicine-Jmm最新文献

Osteoarthritis (OA) is a prevalent degenerative joint disease affecting over 530 million individuals worldwide. Recent studies suggest a potential link between iron overload, a condition characterised by the excessive accumulation of iron in the body, and the onset of OA. Iron is essential for various biological processes, and any disruption in its homeostasis can trigger significant health effects, including OA. This study aimed to elucidate the effects of excess iron on joint tissue and the underlying mechanisms associated with excess iron and OA development. Human articular cartilage (n = 6) and synovium (n = 4) were collected from patients who underwent total knee arthroplasty. Cartilage and synovium explants were incubated with a gradually increasing concentration of ferric ammonium citrate for 3 days respectively. The effects of iron homeostasis in tissue explants were analysed using a Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). To further study the effects of iron excess on OA initiation and development, male 3-week-old Hfe^-/- and 5-week-old Tfr2^-/- mice, animal models of hereditary haemochromatosis were established. Littermate wild-type mice were fed a high-iron diet to induce dietary overload. All animals were sacrificed at 8 weeks of age, and knee joints were harvested for histological analysis. The LA-ICP-MS analysis unveiled changes in the elemental composition related to iron metabolism, which included alterations in FTH1, FPN1, and HAMP within iron(III)-treated cartilage explants. While chondrocyte viability remained stable under different iron concentrations, ex vivo treatment with a high concentration of Fe³⁺ increased the catabolic gene expression of MMP13. Similar alterations were observed in the synovium, with added increases in GAG content and inflammation markers. In vivo studies further supported the role of iron overload in OA development as evidenced by spontaneous OA symptoms, proteoglycan loss, increased Mankin scores, synovial thickening, and enhanced immunohistochemical expression of MMP13, ADAMTS5, and P21 in Hfe^-/-, Tfr2^-/-, and diet-induced iron overload mouse models. Our findings elucidate the specific pathways through which excess iron accelerates OA progression and highlights potential targets for therapeutic intervention aimed at modulating iron levels to mitigate OA symptoms. KEY MESSAGES: Iron overload alters joint iron metabolism, increasing OA markers in cartilage and synovium. High iron levels in mice accelerate OA, highlighting genetic and dietary impacts. Excess iron prompts chondrocyte iron storage response, signalling potential OA pathways. Iron dysregulation linked to increased cartilage degradation and synovial inflammation. Our findings support targeted therapies for OA based on iron modulation strategies.

A fundamental event in the formation of heart valves involves the transformation of endocardial cells within the outflow tract (OFT) and atrioventricular canal (AVC) cushions through a process known as endothelial-to-mesenchymal transition (EndMT). Aberrant EndMT is a primary cause of congenital valvular malformations. Manic Fringe (MFNG) has been previously associated with cardiovascular development, although its role in heart valve development remains underexplored. In this study, we seek to enhance our understanding of MFNG's involvement in valve formation and its association with EndMT. Staining results of histological section revealed the expression of MFNG in the AVC and OFT from embryonic day 9.5 to 10.5 (E9.5-E10.5), when EndMT takes place. Cellular data demonstrated that MFNG exerts a positive regulatory influence on the EndMT process, promoting endothelial cell (EC) migration by enhancing the activity of the Notch signalling pathway. MFNG knockdown mediated by antisense morpholino oligonucleotides (MO) injection caused abnormal development of the heart and valves in zebrafish. Furthermore, through whole-exome sequencing (WES), we identified a heterozygous MFNG mutation in patients diagnosed with tetralogy of Fallot-pulmonary valve stenosis (TOF-PS). Cellular and molecular assays confirmed that this deleterious mutation reduced MFNG expression and hindered the EndMT process. In summary, our study verifies that MFNG plays a role in promoting EndMT mediated by the Notch signalling pathway during the heart and valve development. The MFNG deleterious variant induces MFNG loss of function, potentially elucidating the underlying molecular mechanisms of MFNG's involvement in the pathogenesis of congenital heart valve defects. These observations contribute to our current genetic understanding of congenital heart valve disease and may provide a potential target for prenatal diagnosis and treatment. KEY MESSAGES: Our examination revealed, for the first time, that MFNG exhibited high expression levels during EndMT of heart valve development in mice. Our findings provide compelling evidence that MFNG plays a role in promoting EndMT mediated by the Notch signalling pathway. Our results identified, for the first time, a deleterious MFNG p. T77M variant that inhibited the EndMT process by downregulating the activity of the Notch signalling pathway, thereby preventing the normal valve formation. MFNG may serve as an early diagnostic marker and an effective therapeutic target for the clinical treatment of congenital heart valve defects.