H Vessel Formation as a Marker for Enhanced Bone Healing in Irradiated Distraction Osteogenesis.

In the setting of bone defects, the injured vasculature and loss of hemodynamic inflow leads to hematoma formation and low oxygen tension which stimulates vascular expansion through the HIf-1α pathway. Most importantly, this pathway upregulates sprouting of type H vessels (CD31hiEmcnhi vessels). H vessels engage in direct interaction with perivascular osteoprogenitor cells (OPCs), osteoblasts, and preosteoclasts of bone formation and remodeling. This angiogenic-osteogenic coupling leads to synchronous propagation of vascular and bony tissue for regenerative healing. A growing body of literature demonstrates that H vessels constitute a large portion of bone's innate capacity for osteogenic healing. We believe that CD31hiEmcnhi vessels play a role in bone healing during distraction osteogenesis (DO). DO is a procedure that utilizes traction forces to facilitate induction of endogenous bone formation and regeneration of surrounding soft tissues such as skin, muscle, tendon, and neurovascular structures. While the H vessel response to mechanical injury is adequate to facilitate healing in normal healthy tissue, it remains inadequate to overcome the devastation of radiation. We posit that the destruction of CD31hiEmcnhi vessels plays a role in precluding DO's effectiveness in irradiated bone defect healing. We aim, therefore, to recapitulate the normal pathway of bony healing by utilizing the regenerative capacity of H vessels. We hypothesize that using localized application of deferoxamine (DFO) will enhance the H vessel-mediated vasculogenic response to radiation damage and ultimately enable osteogenic healing during DO. This discovery could potentially be exploited by developing translational therapeutics to hopefully accelerate bone formation and shorten the DO consolidation period, thereby potentially expanding DO's utilization in irradiated bone healing. Sprague-Dawley rats were divided into three groups: DO, radiation with DO (xDO), and radiation with DO and DFO implantation (xDODFO). Experimental groups received 35 Gy of radiation. All groups underwent DO. The treatment group received injections into the osteotomy site, every other day, beginning on postoperative day (POD) 4 of DFO. Animals were sacrificed on POD 40. For immunohistochemical analysis, mandibles were dissected and fixed in 4% paraformaldehyde for 48 hours, decalcified in Cal-Ex II for 2 days, dehydrated through graded ethanol of increasing concentration, and then embedded in paraffin. Samples were cut into 7-µm thick longitudinally oriented sections including the metaphysis and diaphysis. CD31 and Emcn double immunofluorescent staining were performed to evaluate the extent of CD31hiEmcnhi vessel formation. Bone sections were then stained with conjugated antibodies overnight at 4°C. Nuclei were stained with Hoechst. Slides were also double stained with Osterix and CD31 to study the quantity of H vessel-mediated recruitment of OPCs to accelerate bone healing. Images were acquired with a Nikon Ti2 widefield microscope and analyzed in NIS- Elements Advanced Research 5.41.02 software. The abundance of type H vessels is represented by the area fraction of CD31 + Emcn+ vessel area inside the regenerate sample. OPC concomitant proliferation into the distraction gap is represented by the area fraction of Osterix+ cell area inside of the regenerate sample. There were 6× more type H vessels in DO groups than in xDO groups. Localized DFO significantly increased the abundance of type H vessels of irradiated DO animals compared to xDO by 15× ( p = 0.00133531). Moreover, the DO and xDODFO groups with higher abundance of type H vessels also demonstrated better angiogenesis and osteogenesis outcomes. Interestingly, xDODFO groups doubled the quantity of H vessel formation compared to DO, indicating a supraphysiologic response ( p = 0.044655055). Furthermore, H vessel-mediated recruitment of OPCs mimicked the described H vessel formation trend in our study groups. Irradiated DO groups contained 3× less OPCs compared to DO controls. DFO treatment to xDO animals remediated irradiation damage by containing 12× Osterix+ cells. Finally, DFO treatment of irradiated animals quadrupled osteoprogenitor recruitment into the distraction gap compared to DO controls. In this study, we developed a novel approach to visualize CD31hiEmcnhi in paraffin sections to study DO regeneration. Normal DO demonstrated a significant upregulation of H vessel formation and associated angiogenic-osteogenic coupling. Radiation severely decreased H vessel formation along with an associated significant diminution of new bone formation and nonunion. DFO administration, however, resulted in vascular replenishment and the restoration of high quantities of CD31hiEmcnhi and OPCs, recapitulating the normal process of bony regeneration and repair. DFO treatment remediated new bone formation and bony union in irradiated fields associated with increased H vessel angiogenic-osteogenic coupling. While further studies are required to optimize this approach, the results of this study are incredibly promising for the long-awaited translation of localized DFO into the clinical arena.

Polystyrene microplastics mitigate lead-induced neurotoxicity by reducing heavy metal uptake in zebrafish larvae.

The combined pollution of lead (Pb) and polystyrene microplastics (PS-MPs) is common in aquatic environments. However, the combined neurotoxicity of these two pollutants is still poorly understood. In this study, zebrafish (Danio rerio) larvae were used to assess the combined neurotoxicity and mechanism of Pb and PS-MPs at environmentally relevant concentrations. The results showed that Pb (10 µg/L) induced abnormal behavior including significantly reduced movement distance, maximum acceleration, and average velocity (P < 0.05) along with altered expression of neurodevelopment-related genes (gap43 and α1-tubulin) (P < 0.05). PS-MPs (25 µg/L, 250 µg/L; diameter at 25 µm) co-exposure not only significantly reduced the concentration of Pb in the exposed solution (P < 0.01), but also decreased the uptake of Pb by downregulating the divalent metal transporter 1 gene (dmt1) (P < 0.01), thereby alleviating Pb-induced neurotoxicity. However, to demonstrate that PS-MPs alleviate the neurotoxicity of Pb by reducing Pb uptake, upregulation of dmt1 by addition of deferoxamine (DFO, an efficient iron chelator, 100 µM) significantly increased the Pb uptake and exacerbated neurotoxicity in zebrafish. In summary, our results demonstrated that PS-MPs alleviate Pb neurotoxicity by downregulating the mRNA level of dmt1 and decreasing the Pb uptake. This study provides a new insight into the combined neurotoxicity and underlying mechanisms of PS-MPs and Pb on zebrafish.

Mechanism of damage of HIF-1 signaling in chronic diabetic foot ulcers and its related therapeutic perspectives.

Diabetic foot ulcer (DFU) is a chronic complication of diabetes. Wound healing in patients with DFU is generally very slow, with a high recurrence rate even after the ulcer healed. The DFU remains a major clinical challenge due to a lack of understanding of its pathogenesis. Given the significant impact of DFU on patient health and medical costs, enhancing our understanding of pathophysiological alterations and wound healing in DFU is critical. A growing body of research has shown that impaired activation of the HIF-1 pathway in diabetics, which weakens HIF-1 mediated responses to hypoxia and leads to down-regulation of its downstream target genes, leading to incurable diabetic foot ulcers. By analyzing and summarizing the literature in recent years, this review summarizes the mechanism of HIF-1 signaling pathway damage in the development of DFU, analyzes and compares the application of PHD inhibitors, VHL inhibitors, biomaterials and stem cell therapy in chronic wounds of diabetes, and proposes a new treatment scheme mediated by participation in the HIF-1 signaling pathway, which provides new ideas for the treatment of DFU.

Mechanisms of exacerbation of Th2-mediated eosinophilic allergic asthma induced by plastic pollution derivatives (PPD): A molecular toxicological study involving lung cell ferroptosis and metabolomics.

Polystyrene microplastics (PS-MP) and dibutyl phthalate (DBP) are plastic pollution derivatives (PPDs) commonly found in the natural environment. To investigate the effects of PPD exposure on the risk of allergic asthma, we established a PPD exposure group in a mouse model. The dose administered for PS-MP was 0.1 mg/d and for DBP was 30 mg/kg/d, with a 5-week oral administration period. The pathological changes of airway tissue and the increase of oxidative stress and inflammatory response confirmed that PPD aggravated eosinophilic allergic asthma in mice. The mitochondrial morphological changes and metabolomics of mice confirmed that ferrotosis and oxidative stress played key roles in this process. Treatment with 100 mg/Kg deferoxamine (DFO) provided significant relief, and metabolomic analysis of lung tissue supported the molecular toxicological. Our findings suggest that the increased levels of reactive oxygen species (ROS) in the lungs lead to Th2-mediated eosinophilic inflammation, characterized by elevated IL-4, IL-5, and eosinophils, and reduced INF-γ levels. This inflammatory response is mediated by the NFκB pathway and exacerbates type I hypersensitivity through increased IL-4 production. In this study, the molecular mechanism by which PPD aggravates asthma in mice was elucidated, which helps to improve the understanding of the health effects of PPD and lays a theoretical foundation for addressing the health risks posed by PPD.