Background: Age-related bone loss plays a vital role in the development of osteoporosis and osteoporotic fracture. Bone marrow stromal cell (BMSC) senescence is highly associated with osteoporosis and limits the application of BMSCs in regenerative medicine. Hypoxia is an essential component for maintaining the normal physiology of BMSCs. We have reported that activation of hypoxia-induced factor by deletion of von Hippel-Lindau gene in osteochondral progenitor cells protected mice from aging-induced bone loss. However, whether pharmacologically manipulation of hypoxic niche would attenuate age-related bone loss and dysfunction of BMSCs is not well understood. Methods: Twelve-month-old Sprague-Dawley rats were used as an aged model and were intraperitoneally injected with Desferal® (20, 60 mg/kg weight or vehicle), three times a week for a continuous 8-week period. Two-month-old young rats were set as a reference. After 8 weeks, micro-CT and HE staining were performed to determine the effect of Desferal® on bone loss. In order to investigate the effects of Desferal® on BMSC senescence, 12-month-old rats were treated with high-dose Desferal® (60 mg/kg weight) daily for 10 days. BMSCs were isolated and evaluated using CCK-8 assay, colony-forming cell assay, cell differentiation assay, laser confocal for reactive oxygen species (ROS) level, senescence-associated β-galactosidase (SA-β-gal) staining, and molecular expression test for stemness/senescence-associated genes. Results: Micro-CT and HE staining showed that high-dose Desferal® significantly prevented bone loss in aged rats. Compared with vehicle group, the ex vivo experiments showed that short-term Desferal® administration could promote the potential of BMSC growth (proliferation and colony formation ability) and improve the rebalance of osteogenic and adipogenic differentiation, as well as rejuvenate senescent BMSCs (ROS level and SA-β-gal staining) and revise the expression of stemness/senescence-associated genes. The potential of BMSCs from 12M-H-Desferal® group at least partly revised to the level close to 2-month-old group. Conclusions: The current study suggested that Desferal®, an iron-chelating agent, could alleviate age-related bone loss in middle-aged rats. Meanwhile, we found that short-term intraperitoneal injection of Desferal® partly rejuvenate BMSCs from aged rats. Overall, we demonstrated a novel role of Desferal® in rejuvenating aged BMSCs and preventing age-related bone loss.

Cell-based therapy serves as an effective way for cartilage repair. Compared with a limited source of autologous chondrocytes, adipose-derived stem cells (ADSCs) are proposed as an attractive cell source for cartilage regeneration. How to drive chondrogenic differentiation of ADSCs efficiently remains to be further investigated. TGF-β3 has shown a strong chondrogenic action on ADSCs. Recently, fibroblast growth factor 18 (FGF-18) has gained marked attention due to its anabolic effects on cartilage metabolism, but existing data regarding the role of FGF-18 on the chondrogenic potential of mesenchymal stem cells (MSCs) are conflicting. In addition, whether the combined application of FGF-18 and TGF-β3 would improve the efficiency of the chondrogenic potential of ADSCs has not been thoroughly studied. In the current study, we isolated human ADSCs and characterized the expression of their surface antigens. Also, we evaluated the chondrogenic potential of FGF-18 on ADSCs using an in vitro pellet model by measuring glycosaminoglycan (GAG) content, collagen level, histologic appearance, and expression of cartilage-related genes. We found that FGF-18, similarly to TGF-β3, had a positive impact on chondrogenic differentiation and matrix deposition when presented throughout the culture period. More importantly, we observed synergistic effects of FGF-18 and TGF-β3 on the chondrogenic differentiation of ADSCs in the in vitro pellet model. Our results provide critical information on the therapeutic use of ADSCs with the help of FGF-18 and TGF-β3 for cartilage regeneration.

Septic lung injury is strongly associated with polarization of M1 macrophages and excessive cytokine release. Fibroblast growth factor (FGF) signaling plays a role in both processes. However, the impact of FGF2 deficiency on macrophage polarization and septic acute lung injury remains unclear. To investigate this, we obtained macrophages from FGF2 knockout mice and examined their polarization and inflammatory cytokine expression. We also eliminated endogenous macrophages using clodronate liposomes and administered FGF2 knockout or WT macrophages intravenously in conjunction with cecal ligation and puncture (CLP) surgery to induce sepsis. In vitro analysis by flow cytometry and real-time PCR analysis demonstrated that FGF2 deficiency resulted in increased expression of M1 markers (iNOS and CD86) and inflammatory cytokines (CXCL1, IL1β, and IL6), especially after LPS stimulation. Additionally, immunofluorescence demonstrated increased nuclear translocation of p65 NF-κB in FGF2 knockout macrophages and RNA-seq analysis showed enrichment of differentially expressed genes in the IL17 and TNFα inflammatory signaling pathways. Furthermore, in vivo experiments revealed that depletion of FGF2 in macrophages worsened sepsis-induced lung inflammation, lung vascular leak, and lung histological injury, accompanied by an increase in CD86-positive cells and apoptosis. Our study suggests that FGF2 deficiency in macrophages plays a critical role in the pathogenesis of septic ALI, possibly because of the enhanced M1 macrophage polarization and production of proinflammatory cytokines. These findings provide empirical evidence for potential therapeutic interventions targeting FGF2 signaling to modulate the polarization of M1 and M2 macrophages in the management of sepsis-induced acute lung injury.

Mesenchymal stem cells (MSCs) have potential for treating degenerative and immune diseases, but their clinical efficacy is limited by senescence, characterized by mitochondrial dysfunction, impaired mitophagy, and metabolic imbalance. The goal of this study was to investigate the effects of dimethyloxalylglycine (DMOG), a hypoxia-mimetic agent that stabilizes hypoxia-inducible factor 1 alpha (HIF-1α), on rejuvenating senescent MSCs by enhancing mitochondrial function, mitophagy, and metabolic reprogramming. Two models of MSC senescence were established: oxidative stress-induced senescence using hydrogen peroxide and replicative senescence through serial passaging. Umbilical cord derived MSCs were treated with DMOG for 48 h under normoxic conditions. Mitochondrial function, mitophagy, and metabolism were assessed using assays that measured mitochondrial membrane potential, reactive oxygen species levels, ATP production, and mitophagy. Western blotting and real-time PCR were employed to analyze the expression changes of relevant molecules. RNA sequencing (RNA-seq) was performed to identify key genes and pathways regulated by DMOG. Additionally, to evaluate the therapeutic potential of rejuvenated MSCs, a co-culture system was established, where DMOG-treated senescent MSCs were co-cultured with IL-1β-treated chondrocytes. DMOG treatment significantly reduced key senescence markers, including senescence-associated beta-galactosidase, p53, and p21, in both senescence models. DMOG treatment restored mitochondrial morphology and function, improving mitochondrial membrane potential, reducing mitochondrial reactive oxygen species, and enhancing ATP production. DMOG also promoted mitophagy, as evidenced by increased colocalization of mitochondria with lysosomes. RNA-seq analysis revealed that DMOG activated key pathways, including HIF-1 signaling, calcium signaling, and mitophagy-related gene (BNIP3 and BNIP3L). Notably, BNIP3 knockdown greatly abolished DMOG-induced mitophagy and its anti-senescence effects. Furthermore, DMOG treatment improved metabolic flexibility by enhancing both mitochondrial respiration and glycolysis in senescent MSCs. Moreover, DMOG-treated senescent MSCs partially restored their therapeutic efficacy in an osteoarthritis model by improving extracellular matrix regulation in IL-1β-stimulated chondrocytes. Short-term DMOG treatment rejuvenates senescent MSCs by enhancing mitochondrial function, promoting mitophagy via HIF-1α/BNIP3, and improving metabolic reprogramming. DMOG-treated MSCs also showed enhanced therapeutic efficacy in co-culture with IL-1β-treated chondrocytes, suggesting its potential to improve MSC-based therapies in regenerative medicine.