N6 methyladenosine (m6A) is one of the most prevalent epitranscriptomic modifications of mRNAs, and plays a critical role in various bioprocesses. Bone-derived mesenchymal stem cells (BMSCs) can attenuate apoptosis of nucleus pulposus cells (NPCs) under compression; however, the underlying mechanisms are poorly understood. This study showed that the level of m6A mRNA modifications was decreased, and the autophagic flux was increased in NPCs under compression when they were cocultured with BMSCs. We report that under coculture conditions, RNA demethylase ALKBH5-mediated FIP200 mRNA demethylation enhanced autophagic flux and attenuated the apoptosis of NPCs under compression. Specific silencing of ALKBH5 results in impaired autophagic flux and a higher proportion of apoptotic NPCs under compression, even when cocultured with BMSCs. Mechanistically, we further identify that the m6A "reader" YTHDF2 is likely to be involved in the regulation of autophagy, and lower m6A levels in the coding region of FIP200 lead to a reduction in YTHDF2-mediated mRNA degradation of FIP200, a core molecular component of the ULK1 complex that participates in the initiating process of autophagy. Taken together, our study reveals the roles of ALKBH5-mediated FIP200 mRNA demethylation in enhancing autophagy and reducing apoptosis in NPCs when cocultured with BMSCs.

Macrophages eliminate apoptotic cells produced daily in the body through efferocytosis. Restricted clearance can cause inflammation-related diseases. In intervertebral discs (IVDs), apoptotic nucleus pulposus cells (NPCs) are difficult to effectively remove, and their accumulation can cause changes in the inflammatory microenvironment, disrupt IVD homeostasis, and lead to IVD degeneration (IDD). Here, we present chimeric antigen receptor-M-like engineered macrophages (CAR-eMs) with enhanced efferocytosis capacity for IDD treatment. Macrophages undergo phenotypic transformation and a reduction in phagocytic ability after phagocyting apoptotic NPCs, but their efferocytosis capacity recovers with upregulated brain-specific angiogenesis inhibitor 1 (BAI1) expression. We develop a CAR-eM system with enhanced BAI1 expression and an IVD circular microneedle (MN) delivery system that utilizes arrays of MNs to deliver CAR-eMs into the deep IVD layers, thereby clearing apoptotic NPCs, ameliorating the inflammatory microenvironment, and repairing damaged IVDs. Our study explores the therapeutic potential of CAR-eM efferocytosis for IDD treatment.

Complex craniocervical malformations pose significant challenges to surgical fixation. The biomechanical advantage of occipital plate fixation versus short-lever modified C1 lateral mass screw fixation remains controversial, and finite element analysis (FEA) is a reliable tool for implant performance evaluation. To compare biomechanical characteristics of occipital plate fixation and modified C1 lateral mass screw fixation in AOZ-BI and AOZ-AAD models via FEA, and guide surgical decision-making. A validated healthy occipito-atlantoaxial (C0-C2) FEA model was established using CT data. Two pathological models were constructed: AOZ-BI (Group A, atlantoaxial distance [ADI] < 5 mm) and AOZ-AAD (Group B, ADI ≥ 5 mm with transverse ligament dysfunction), each divided into occipital plate and modified C1 lateral mass screw subgroups. Static loads (40 N preload + 1.5 N·m torque) simulated flexion (Fe), extension (Ex), lateral bending (LB), and axial rotation (AR). C1-C2 range of motion (ROM) and screw-rod peak Von Mises stress (PVMS) were measured. Modified C1 lateral mass screw fixation reduced C1-C2 ROM by 19.67

Low back pain (LBP) is a highly prevalent musculoskeletal disorder worldwide. Nucleus pulposus cell (NPC) pyroptosis contributes to intervertebral disc degeneration (IVDD), but the underlying mechanisms remain unclear. We identified TMEM2, a transmembrane protein not previously linked to IVDD, as markedly upregulated in degenerated NPCs by single‑cell RNA sequencing. TMEM2 expression correlated positively with IVDD severity and NPC pyroptosis, and its knockdown alleviated pyroptosis. Mechanistically, TMEM2 binds BAX to promote mPTP opening, leading to mtDNA release and activation of the STING–TBK1–NF‑κB pathway, ultimately triggering NLRP3 inflammasome‑mediated pyroptosis. To address the avascular nature of the disc, we developed an injectable ROS‑responsive hydrogel microsphere system encapsulating shTMEM2‑loaded liposomes (Lipo/shTMEM2@MS). This platform enables sustained release, on‑demand degradation, and single‑dose intradiscal administration. In a rat model, Lipo/shTMEM2@MS effectively ameliorated disc degeneration. Collectively, these findings identify TMEM2 as a key driver of NPC pyroptosis and establish a ROS‑responsive microsphere strategy as a promising translational approach for IVDD.

Intervertebral disc degeneration (IDD) is characterized by excessive apoptosis of nucleus pulposus (NP) cells and hyperactive extracellular matrix (ECM) catabolism. Our previous studies revealed the relationship between human islet amyloid polypeptide (hIAPP) and NP cell apoptosis. However, the role of hIAPP aggregates in IDD has not yet been investigated. This study aimed to determine whether the accumulation of hIAPP aggregates promotes IDD progression. The aggregation of hIAPP increased in human NP tissues during IDD. The deposition of hIAPP aggravated the compression-induced IDD that promoted NP cell apoptosis and ECM degradation via IL-1β/IL-1Ra signaling in an ex vivo rat disc model. Moreover, neutralizing IL-1β augmented the protective effects of hIAPP overexpression by decreasing hIAPP aggregation in human NP cells. These results suggest that the aggregation of hIAPP promotes NP cell apoptosis and ECM degradation ex vivo and in vitro by disrupting the balance of IL-1β/IL-1Ra signaling.

Post-translational modifications (PTMs) dynamically regulate cellular processes by modifying protein function. Among these, lactylation, a modification derived from lactate, functions through direct or indirect modification of histones or nonhistone proteins. While glycosylation and phosphorylation have established roles in bone metabolism and joint disorders, the biological significance of lactylation in musculoskeletal diseases remains underexplored. This study synthesizes current evidence investigating lactylation in four major orthopedic diseases: intervertebral disc degeneration (IVDD), osteoporosis (OP), osteoarthritis (OA), and spinal cord injury (SCI). The evidence indicates that lactylation modulates disease progression through dual mechanisms: coordinating cellular metabolism with extracellular matrix remodeling in IVDD and OA and regulating neuroimmune responses during SCI recovery. Notably, lactylation’s regulatory patterns differ from classical PTMs by serving as a molecular bridge linking metabolic reprogramming to pathological tissue remodeling. This contrasts with phosphorylation, which primarily dominates signal transduction pathways. These insights reposition lactate from a metabolic byproduct to a disease-modifying signaling molecule, suggesting lactylation could inform therapeutic strategies for inflammatory, degenerative, and regenerative musculoskeletal disorders.

This retrospective observational study aimed to explore the associations of AI-assisted CT-quantified C4/C5 skeletal muscle and adipose tissue indices with postoperative cervical kyphosis and long-term functional outcomes in patients undergoing laminoplasty. Postoperative cervical kyphosis is a prevalent complication of laminoplasty with incompletely elucidated pathogenesis, and the role of neck muscle and adipose tissue in this complication lacks validation via standardized 3D quantification. We enrolled 114 patients with cervical spondylosis who underwent laminoplasty at Wuhan Union Hospital between 2018 and 2022, excluding those with severe comorbidities. Preoperative CT scans (obtained within 3 months before surgery) were processed using a ResU-Net model to quantify C4/C5 tissue indices. Statistical analyses (SPSS 27.0) included multivariate logistic regression, and receiver operating characteristic (ROC) curves with the Youden index were used to determine predictive thresholds. Postoperative kyphosis was diagnosed based on routine follow-up cervical X-rays. Multivariate logistic regression revealed that C4 and C5 subcutaneous fat volume (SFV) were independently associated with postoperative kyphosis (p<0.05). The combined model integrating tissue indices and clinical variables achieved area under the curve (AUC) values of 0.706 (C4 SFV) and 0.717 (C5 SFV) (p<0.05). AI-assisted CT-quantified C4/C5 SFV is correlated with postoperative cervical kyphosis. Integration of CT-derived tissue metrics and clinical indicators improves the prediction of laminoplasty outcomes, providing a data-driven foundation for optimizing surgical planning and postoperative rehabilitation in cervical spondylosis patients.

Intervertebral disc degeneration (IVDD) is a leading cause of discogenic low back pain, contributing significantly to global disability and economic burden. Current treatments provide only short-term pain relief without addressing the underlying pathogenesis. Herein we report engineering of biomimetic therapies for IVDD guided by single-cell RNA-sequencing data from human nucleus pulposus tissues, along with validation using animal models. In-depth analyses revealed the critical role of mitochondrial dysfunction in fibrotic phenotype polarization of nucleus pulposus cells (NPCs) during IVDD progression. Consequently, mitochondrial transplantation was proposed as a novel therapeutic strategy. Transplanted exogeneous mitochondria improved mitochondrial quality control in NPCs under pathological conditions, following endocytosis, separate distribution or fusion with endogenous mitochondria, and transfer to neighboring cells by tunneling nanotubes. Correspondingly, intradiscal mitochondrial transplantation significantly delayed puncture-induced IVDD progression in rats, demonstrating efficacy in maintaining mitochondrial homeostasis and alleviating pathological abnormalities. Furthermore, exogenous mitochondria were engineered with a bioactive, mitochondrial-targeting macromolecule to impart anti-oxidative and anti-inflammatory activities. The obtained multi-bioactive biotherapy exhibited significantly enhanced benefits in IVDD treatment, in terms of reversing IVDD progression and restoring structural integrity through the mtDNA/SPARC-STING signaling pathways. Overall, our engineered mitochondrial therapies hold great promise for treating IVDD and other musculoskeletal diseases linked to mitochondrial dysfunction.

Intervertebral disc degeneration (IVDD) is a common cause of low back pain. Procyanidin C1 (PCC1) has been demonstrated to exert a protective effect on nucleus pulposus (NP) cells, and therefore, plays a critical role in the prevention and therapy of IVDD. Clarifying the pathophysiological characteristics and molecular mechanisms of IVDD may be helpful in establishing novel preventive and therapeutic strategies. This study aimed to investigate the probable mechanisms underlying the protection against acidic pH stress induced human NP cell injury. In vitro, acidic pH stress induced degeneration, mitochondrial dynamics imbalance, mitophagy, and mitochondria-mediated apoptosis in NP cells, all of which were ameliorated by PCC1. Autophagy inhibition partially eliminated the protective effects of PCC1 on mitochondrial homeostasis in NP cells. Moreover, PCC1 activated the sirtuin 3 (SIRT3)/forkhead box O3 (FOXO3) signaling pathway, a pivotal signaling pathway involved in the regulation of mitochondrial homeostasis in NP cells. In vivo, PCC1 ameliorated IVDD in a rat model and preserved the extracellular matrix of NP cells. Consequently, the protective effects of PCC1 on NP cells may inhibit IVDD progression via regulation of the SIRT3/FOXO3 signaling pathway. Therefore, regulation of the SIRT3/FOXO3 signaling pathway may be a novel preventive and therapeutic strategy for IVDD.

In recent years, research has increasingly focused on the biogenesis of extracellular vesicles (EVs) and the sorting mechanisms for their contents. Mitochondria can be selectively loaded into EVs, serving as a way to maintain cellular mitochondrial homeostasis. EV-mediated mitochondrial transfer has also been shown to greatly impact the function of target cells. Based on the mechanism of EV-mediated mitochondrial transfer, therapies can be developed to treat human diseases. This review summarizes the recent advances in the biogenesis and molecular composition of EVs. It also highlights the sorting and trafficking mechanisms of mitochondrial components into EVs. Furthermore, it explores the current role of EV-mediated mitochondrial transfer in the development of human diseases, as well as its diagnostic and therapeutic applications.

Study design:Systematic review. Background:Conservative treatment is clinically preferred for lumbar disc herniation (LDH), and surgery is considered when patients' life quality is still affected by LDH symptoms after three months' conservative treatment. Spontaneous resorption of nucleus pulposus (NP) is common during conservative treatment. However, the current understanding for the mechanism of NP spontaneous resorption is lacking. Purpose:The aim of this study was to elucidate the rate of NP spontaneous resorption, the evidence of predicting spontaneous resorption, and the pathophysiologic mechanisms of spontaneous resorption in the conservative management of LDH based on existing evidence from literature. Methods:Studies related to NP spontaneous resorption of LDH were retried from PubMed, Embase, and Cochrane databases. Based on the studies conforming to inclusion criteria, a systematic review was generated for describing the proportion of NP spontaneous resorption, evidence of predicted resorption, and pathophysiologic mechanisms of spontaneous resorption. Results:We reviewed a total of 34 articles dealing with the percentage of LDH resorption. The percentage of NP spontaneous resorption after conservative treatment was 76.6% (1684/2199), ranging from 20% to 96.2%. A total of 25 papers were reviewed, involving evidence of predicting resorption using predictors including NP size, inflammatory response to NP herniation, NP prolapse, the percentages edge-enhancing area and posterior longitudinal ligament coverage of the herniation measured by enhanced MRI. Moreover, we analyzed a total of 22 papers describing the pathophysiologic mechanisms of NP spontaneous resorption, where main mechanisms include inflammatory response, neovascular growth, macrophage infiltration, immune intervention, and matrix degradation. Conclusions:A percentage of 76.6% in LDH patients undergo NP resorption. Prolapsed NP has a greater contact surface with blood system, which is easily to trigger immune response and thus promote spontaneous resorption. The mechanism of NP spontaneous resorption is mainly due to macrophage infiltration leading to immune response.

Intervertebral disc degeneration (IDD) is the most critical pathological factor in the development of low back pain. The maintenance of nucleus pulposus (NP) cell and intervertebral disc integrity benefits largely from well-controlled mitochondrial quality, surveilled by mitochondrial dynamics (fission and fusion) and mitophagy, but the outcome is cellular context-dependent that remain to be clarified. Our studies revealed that the loss of NLRX1 is correlated with NP cell senescence and IDD progression, which involve disordered mitochondrial quality. Further using animal and in vitro tissue and cell models, we demonstrated that NLRX1 could facilitate mitochondrial quality by coupling mitochondrial dynamic factors (p-DNM1L, L-OPA1:S-OPA1, OMA1) and mitophagy activity. Conversely, mitochondrial collapse occurred in NLRX1-defective NP cells and switched on the compensatory PINK1-PRKN pathway that led to excessive mitophagy and aggressive NP cell senescence. Mechanistically, NLRX1 was originally shown to interact with zinc transporter SLC39A7 and modulate mitochondrial Zn2+ trafficking via the formation of an NLRX1-SLC39A7 complex on the mitochondrial membrane of NP cells, subsequently orchestrating mitochondrial dynamics and mitophagy. The restoration of NLRX1 function by gene overexpression or pharmacological agonist (NX-13) treatment showed great potential for regulating mitochondrial fission with synchronous fusion and mitophagy, thus sustaining mitochondrial homeostasis, ameliorating NP cell senescence and rejuvenating intervertebral discs. Collectively, our findings highlight a working model whereby the NLRX1-SLC39A7 complex coupled mitochondrial dynamics and mitophagy activity to surveil and target damaged mitochondria for degradation, which determines the beneficial function of the mitochondrial surveillance system and ultimately rejuvenates intervertebral discs.

BACKGROUND Crowned dens syndrome (CDS) is a rare condition characterized by deposition of calcium pyrophosphate crystals on the odontoid process of the second cervical vertebra, forming a calcified 'crown', with neck pain being a common symptom. The disorder exhibits unique clinical and radiological features, resembling manifestations of meningitis, such as acute headaches and cervical stiffness. There are few case reports and case series related to CDS. Patients generally respond well to treatment with nonsteroidal anti-inflammatory drugs (NSAIDs), although there is a certain rate of recurrence. Since there are few reports of CDS, we sought to publish this case report, aiming of increasing clinicians' awareness and reducing misdiagnosis rates. CASE REPORT A 62-year-old man presented to the Emergency Department with "cutting-like" headaches and neck pain for 2 days, and was subsequently diagnosed with CDS by cervical computed tomography (CT) scan, and hematological tests revealed inflammatory manifestations. He was advised to take oral nonsteroidal anti-inflammatory drugs and to rest; his symptoms improved after 3 days and his neck pain had almost resolved after 2 months. CONCLUSIONS In older patients experiencing new headaches and neck pain, along with increased inflammatory markers, particularly those with a history of pseudogout, the possibility of CDS should be considered. Case reports suggest that oral NSAIDs and short courses of corticosteroids can generally alleviate symptoms. Further research is needed on CDS diagnosis and treatment.

ObjectiveConventional correction techniques were challenging and of high risk of neurological complications for the correction of severe and rigid kyphoscoliosis. A new technical note we developed and named as sequential correction, was used to treat severe and rigid kyphoscoliosis. The present study was to compare the clinical outcomes of sequential correction versus conventional correction for the treatment of severe and rigid kyphoscoliosis.MethodsThis is a respectively case–control study. Between January 2014 and December 2019, 36 adults underwent the surgical correction of severe and rigid kyphoscoliosis and were included in the present study. Among them, 20 adults underwent conventional correction, 16 adults underwent sequential correction. Major curve Cobb angle, kyphotic angle, coronal imbalance, and sagittal vertical axis were compared between two groups. The patient‐reported health‐related quality of life outcomes, including the Oswestry disability index score, and SRS‐22 questionnaire, were recorded. Independent samples t‐test, Mann–Whitney U test, and Wilcoxon signed‐rank test, were used to compare the differences between two groups according to the results of normal distribution test.ResultsIn conventional correction group, the mean major curve Cobb angle was 122.50° preoperatively, 40.35° immediately after surgery, and 43.95° at final follow‐up postoperatively; the mean kyphotic angle was 97.45° preoperatively, 34.45° immediately after surgery, and 38.30° at final follow‐up postoperatively. In the sequential correction group, the mean major angle was 134.44° preoperatively, 44.56° immediately after surgery, and 46.25° at final follow‐up postoperatively; the mean kyphotic angle was 112.31° preoperatively, 39.00° immediately after surgery, and 40.38° at final follow‐up postoperatively. The mean major curve Cobb angle and kyphotic angle of both groups were improved significantly, while there were no significant differences between two groups (p > 0.001). Improved self‐reported quality of life scores were achieved postoperatively and at final follow‐up postoperatively, and there were no significant differences between the two groups. The total complication rate of the patients underwent conventional correction was 55%, and the total complication rate of the patients underwent sequential correction was 43.75%. The complication rate of the two groups showed no significant difference.ConclusionsSequential correction is an excellent and safe treatment for severe and rigid kyphoscoliosis in adults, with similar clinical outcomes with conventional correction. The total complication rate of the patients who underwent sequential correction was slightly lower than conventional correction.

Objective: A study has been conducted to investigate the relationship between DDX3X and nucleus pulposus (NP) pyroptosis.Methods: DDX3X and pyroptosis-related proteins (Caspase-1, Full-length GSDMD, Cleaved GSDMD) were measured in compression-induced human NP cells and tissue. DDX3X was overexpressed or knocked down by gene transfection. The expressions of NLRP3, ASC, and pyroptosis-related proteins were detected by Western blot assay. IL-10 and IL-18 were detected by ELISA. HE staining and immunohis-tochemistry were used to observe the expression of DDX3X, NLRP3, and Caspase-1 in the rat model of compression-induced disc degeneration.Results: DDX3X, NLRP3, and Caspase-1 were highly expressed in degenerated NP tissue. Overexpression of DDX3X induced pyroptosis in NP cells and increased levels of NLRP3, IL-10, IL-18, and pyroptosis-related proteins. Knockdown of DDX3X showed an opposite trend to overexpression of DDX3X. The NLRP3 inhibitor CY-09 effectively prevented the up-regulation of the expression of IL-10, IL-18, ASC, Pro-caspase-1, Full-length GSDMD, and Cleaved GSDMD. Increased expression of DDX3X, NLRP3, and Caspase-1 was observed in the rat model of compression-induced disc degeneration.Conclusion: Our study showed that DDX3X mediates pyroptosis of NP cells by upregulating NLRP3 expression, which ultimately leads to intervertebral disc degeneration (IDD). This discovery deepens the understanding of IDD pathogenesis and provides a promising and novel therapeutic target for IDD.(c) 2023 Elsevier Inc. All rights reserved.

目的 探讨Wiltse入路后路固定骨水泥强化技术治疗高龄Ⅲ期Kümmell病的安全性与有效性.方法 回顾性分析武汉市江夏区第一人民医院骨科2016年5月至2022年6月采用Wiltse入路后路固定联合伤椎强化技术治疗的39例高龄Ⅲ型Kümmell病病人的临床资料,其中男17例,女22例;年龄为(73.0±4.2)岁(70～85岁).记录手术时间、失血量、住院时间及手术并发症.比较术前、术后第2天及末次随访的疼痛视觉模拟量表(VAS)评分、Oswestry功能障碍指数(ODI)、伤椎高度及脊柱后凸Cobb角.结果 所有病人均获得随访,随访时间为(14.5±2.3)月(9～21个月).手术时间(75.0±12.1)min(65～92 min),失血量(93.0±11.2)mL(75～110 mL),住院时间(7.2±1.2)d(6～10 d).术后第2天CT检查发现骨水泥椎间隙漏2例,骨水泥椎旁漏3例,随访过程中未见内固定物松动及断裂.术后第2天的VAS评分、ODI分别为(2.7±0.8)分、33.0%±2.5%,均较术前显著降低,术后第2天的椎体中线高度百分比(87.5%±9.8%)较术前(45.3%±11.2%)明显恢复,后凸Cobb角(6.5°±2.3°)较术前(25.8°±5.1°)明显减小,差异均有统计学意义(P＜0.05).末次随访时的数据虽较术后第2天时进一步改善,但差异无统计学意义(P＞0.05).结论 Wiltse入路后路固定联合骨水泥强化技术治疗高龄Ⅲ期Kümmell病安全有效,可以明显减轻胸背部疼痛,恢复伤椎高度,纠正脊柱后凸畸形,改善病人生活质量.

The present study is to evaluate the clinical outcomes of the sequential correction of severe and rigid kyphoscoliosis.Between January 2014 and December 2020, 27 adults with severe and rigid kyphoscoliosis underwent sequential correction combined with posterior grade 4 or grade 5 spinal osteotomy. Radiological parameters, including the major curve Cobb angle, kyphotic angle, coronal imbalance, and sagittal vertical axis (SVA), were compared. Patient self-reported health-related quality of life (HRQOL) scores were used to evaluate clinical outcomes.The mean major curve Cobb angle improved from 134.30 ± 13.24° to 44.48 ± 9.34° immediately after surgery and to 46.11 ± 8.94° at the final follow-up. The mean kyphotic angle improved from 112.15 ± 20.28° to 38.63 ± 15.00° immediately after surgery and to 39.85 ± 14.92° at the final follow-up. The mean preoperative major curve Cobb angle of grade 5 spinal osteotomy group was higher than that of grade 4 spinal osteotomy group. Coronal imbalance and SVA slightly improved. The patient self-reported HRQOL scores improved postoperatively and at the final follow-up. Activity, appearance and total scores of the SRS-22 of the grade 5 spinal osteotomy group at the final follow-up were significantly better than those of the grade 4 spinal osteotomy group.Sequential correction combined with posterior grade 4 or grade 5 spinal osteotomies is an excellent and safe treatment for severe and rigid kyphoscoliosis in adults. Sequential correction combined with posterior grade 5 spinal osteotomies can be used to correct severe and rigid kyphoscoliosis with higher major curve Cobb angle.

As mesenchymal stem-cell-derived small extracellular vesicles (MSC-sEVs) have been widely applied in treatment of degenerative diseases, it is essential to improve their cargo delivery efficiency in specific microenvironments of lesions. However, the interaction between the microenvironment of recipient cells and MSC-sEVs remains poorly understood. Herein, we find that the cargo delivery efficiency of MSC-sEVs was significantly reduced under hypoxia in inflammaging nucleus pulposus cells due to activated endocytic recycling of MSC-sEVs. Hypoxia-inducible factor-1 (HIF-1)-induced upregulated RCP (also known as RAB11FIP1) is shown to promote the Rab11a-dependent recycling of internalized MSC-sEVs under hypoxia via enhancing the interaction between Rab11a and MSC-sEV. Based on this finding, si-RCP is loaded into MSC-sEVs using electroporation to overcome the hypoxic microenvironment of intervertebral disks. The engineered MSC-sEVs significantly inhibit the endocytic recycling process and exhibit higher delivery efficiency under hypoxia. In a rat model of intervertebral disk degeneration (IDD), the si-RCP-loaded MSC-sEVs successfully treat IDD with improved regenerative capacity compared with natural MSC-sEV. Collectively, the findings illustrate the intracellular traffic mechanism of MSC-sEVs under hypoxia and demonstrate that the therapeutic capacity of MSC-sEVs can be improved via inhibiting endocytic recycling. This modifying strategy may further facilitate the application of extracellular vesicles in hypoxic tissues.