Apoptotic vesicles restore liver macrophage homeostasis to counteract type 2 diabetes

Promotion of osteochondral repair through immune microenvironment regulation and activation of endogenous chondrogenesis via the release of apoptotic vesicles from donor MSCs

Utilizing transplanted human umbilical cord mesenchymal stem cells (HUMSCs) for cartilage defects yielded advanced tissue regeneration, but the underlying mechanism remain elucidated. Early after HUMSCs delivery to the defects, we observed substantial apoptosis. The released apoptotic vesicles (apoVs) of HUMSCs promoted cartilage regeneration by alleviating the chondro-immune microenvironment. ApoVs triggered M2 polarization in macrophages while simultaneously facilitating the chondrogenic differentiation of endogenous MSCs. Mechanistically, in macrophages, miR-100-5p delivered by apoVs activated the MAPK/ERK signaling pathway to promote M2 polarization. In MSCs, let-7i-5p delivered by apoVs promoted chondrogenic differentiation by targeting the eEF2K/p38 MAPK axis. Consequently, a cell-free cartilage regeneration strategy using apoVs combined with a decellularized cartilage extracellular matrix (DCM) scaffold effectively promoted the regeneration of osteochondral defects. Overall, new mechanisms of cartilage regeneration by transplanted MSCs were unconcealed in this study. Moreover, we provided a novel experimental basis for cell-free tissue engineering-based cartilage regeneration utilizing apoVs.

Extracellular vesicles from the dead: the final message

Communication between dying and neighbouring cells is vital to ensure appropriate processes such as tissue repair or inflammation are initiated in response to cell death. As a mechanism to aid intercellular communication, cells undergoing apoptosis can release membrane-bound extracellular vesicles (EVs) called apoptotic-cell-derived EVs (ApoEVs) that can influence downstream processes through biomolecules within or on ApoEVs. ApoEVs are broadly categorised based on size as either large ApoEVs known as apoptotic bodies (ApoBDs) or small ApoEVs (s-ApoEVs). Notably, the mechanisms of ApoBD and s-ApoEV formation are different, and the functions of these two ApoEV subsets are distinct. This Review focuses on the biogenesis and functional properties of both ApoBDs and s-ApoEVs, particularly in the context of cell clearance, cell signalling and disease progression.

Microenvironment-responsive nano-bioconjugated vesicles for the multi-pronged treatment of liver fibrosis

Liver fibrosis represents an inevitable stage of various chronic liver diseases. The activated hepatic stellate cells (aHSCs) are the main drivers for promoting the development of liver fibrosis. Meanwhile, liver macrophages can secrete pro-inflammatory cytokines, thus accelerating the deterioration of the liver. Regulating both aHSCs and the inflammatory microenvironment in the liver simultaneously may be an effective strategy for treating liver fibrosis. A multi-pronged nano-bioconjugated system, HNP-B-aEV, was developed according to the above strategy. Based on cell aggregate-derived extracellular vesicles (aEVs) and hydroxychloroquine (HCQ)-loaded nanoparticles (HNP) modified with retinol, HNP-B-aEV is prepared via a reactive oxygen species (ROS)-responsive boronate linker. In the ROS-rich microenvironment of liver fibrosis, aEVs and HNP are released, eliminating ROS, and targeting aHSCs and macrophages respectively to inhibit the activation of HSCs. Both in vitro and in vivo studies demonstrated that HNP-B-aEV can significantly inhibit the release of inflammatory factors from M1 macrophages, remodeling the microenvironment and preventing the activation of HSCs, offering a multi-pronged treatment for liver fibrosis. This strategy can inhibit the progression of liver fibrosis at its source, providing a new perspective for the clinical treatment of liver fibrosis.

Apoptotic Vesicles: Therapeutic Mechanisms and Critical Issues

Apoptosis is the most prominent mode of programmed cell death and is necessary for the maintenance of tissue homeostasis. During cell apoptosis, a distinctive population of extracellular vesicles is generated, termed apoptotic vesicles (apoVs). ApoVs inherit a variety of biological molecules such as proteins, RNAs, nuclear components, lipids, and gasotransmitters from their parent cells. ApoVs have shown promising therapeutic potential for inflammation, tumors, immune disorders, and tissue regeneration. In addition, apoVs can be used as drug carriers, vaccine development, and disease diagnosis. Recently, apoVs have been used in clinical trials to treat a variety of diseases, such as temporomandibular joint osteoarthritis and the regeneration of functional alveolar bone. Here, we review the history of apoV research, current preclinical and clinical studies, and the potential issues of apoV application.

Odontogenesis-Empowered Extracellular Vesicles Safeguard Donor-Recipient Stem Cell Interplay to Support Tooth Regeneration

Harnessing the developmental events of mesenchymal condensation to direct postnatal dental stem cell aggregation represents a cutting-edge and promising approach to tooth regeneration. Tooth avulsion is among the most prevalent and serious dental injuries, and odontogenic aggregates assembled by stem cells from human exfoliated deciduous teeth (SHED) have proven effective in revitalizing avulsed teeth after replantation in the clinical trial. However, whether and how SHED aggregates (SA) communicate with recipient components and promote synergistic tissue regeneration to support replanted teeth remains elusive. Here, it is shown that SA-mediated avulsed tooth regeneration involves periodontal restoration and recovery of recipient Gli1+ stem cells, which are mobilized and necessarily contribute to the reestablishment of the tooth-periodontal ligament-bone interface. Mechanistically, the release of extracellular vesicles (EVs) is revealed indispensable for the implanted SA to mobilize recipient Gli1+ cells and regenerate avulsed teeth. Furthermore, SHED aggregates-released EVs (SA-EVs) are featured with odontogenic properties linked to tissue regeneration, which enhance migration, proliferation, and differentiation of Gli1+ cells. Importantly, local application of SA-EVs per se empowers recipient Gli1+ cells and safeguards regeneration of avulsed teeth. Collectively, the findings establish a paradigm in which odontogenesis-featured EVs govern donor-recipient stem cell interplay to achieve tooth regeneration, inspiring cell-free translational regenerative strategies.

Contribution of PKS+ Escherichia coli to colon carcinogenesis through the inhibition of exosomal miR-885-5p

Objectives

About 90 % of all colorectal cancer (CRC) fatalities are caused by the metastatic spread of primary tumors, which is closely correlated with patient survival and spreads by circulating tumor cells (CTCs). The epithelial-mesenchymal transition (EMT) that characterizes CTCs is associated with a poor prognosis. Organotropic metastasis is dictated by the transmission of miRNAs by cancer-derived exosomes. The purpose of this research is to examine PKS + E's function. Coli in CRC metastases and exosomal miR-885-5p suppression.

Methods

A cohort of 100 patients (50 CRC, 50 healthy) underwent colonoscopy screenings from February 2018 to August 2021. Exosomes were isolated using ultracentrifugation, and exosomal miRNA was analyzed using sequencing and qPCR.

Results

Among the patients, 40 tested positive for E. coli (12 CRC, 23 healthy). Serotyping revealed that 68.57 % harbored the PKS gene. Exosomal miR-885-5p levels were significantly altered in CRC patients with PKS + E. coli. Intriguingly, our findings indicate that exosomes derived from EMT-CRC cells did not affect miR-885-5p synthesis in HUVECs. Moreover, we observed that the levels of miR-885-5p in both exosomes and the total CRC-conditioned medium were comparable upon isolation of exosomes from CRC cells. What's more, an increased expression of miR-558-5p within the tumors, and the group that received exosome treatment, as well as the EMT-HCT116 group, exhibited a higher occurrence of distant metastasis.

Conclusion

PKS + E. By inhibiting exosomal miR-885-5p, coli is linked to CRC metastases, offering a possible target for therapeutic intervention.

Apoptotic vesicles rescue impaired mesenchymal stem cells and their therapeutic capacity for osteoporosis by restoring miR-145a-5p deficiency

Apoptotic vesicles (apoVs) play a vital role in various physiological and pathological conditions. However, we have yet to fully understand their precise biological effects in rescuing impaired mesenchymal stem cells (MSCs). Here, we proved that systemic infusion of MSCs derived from wild-type (WT) mice rather than from ovariectomized (OVX) mice effectively improved the osteopenia phenotype and rescued the impaired recipient MSCs in osteoporotic mice. Meanwhile, apoVs derived from WT MSCs (WT apoVs) instead of OVX apoVs efficiently restored the impaired biological function of OVX MSCs and their ability to improve osteoporosis. Mechanistically, the reduced miR-145a-5p expression hindered the osteogenic differentiation and immunomodulatory capacity of OVX MSCs by affecting the TGF-β/Smad 2/3-Wnt/β-catenin signaling axis, resulting in the development of osteoporosis. WT apoVs directly transferred miR-145a-5p to OVX MSCs, which were then reused to restore their impaired biological functions. The differential expression of miR-145a-5p is responsible for the distinct efficacy between the two types of apoVs. Overall, our findings unveil the remarkable potential of apoVs, as a novel nongenetic engineering approach, in rescuing the biological function and therapeutic capability of MSCs derived from patients. This discovery offers a new avenue for exploring apoVs-based stem cell engineering and expands the application scope of stem cell therapy, contributing to the maintenance of bone homeostasis through a previously unrecognized mechanism.

Apoptotic metabolites ameliorate bone aging phenotypes via TCOF1/FLVCR1-mediated mitochondrial homeostasis

Over 50 billion cells undergo apoptosis each day in an adult human to maintain tissue homeostasis by eliminating damaged or unwanted cells. Apoptotic deficiency can lead to age-related diseases with reduced apoptotic metabolites. However, whether apoptotic metabolism regulates aging is unclear. Here, we show that aging mice and apoptosis-deficient MRL/lpr (B6.MRL-Faslpr/J) mice exhibit decreased apoptotic levels along with increased aging phenotypes in the skeletal bones, which can be rescued by the treatment with apoptosis inducer staurosporine (STS) and stem cell-derived apoptotic vesicles (apoVs). Moreover, embryonic stem cells (ESC)-apoVs can significantly reduce senescent hallmarks and mtDNA leakage to rejuvenate aging bone marrow mesenchymal stem cells (MSCs) and ameliorate senile osteoporosis when compared to MSC-apoVs. Mechanistically, ESC-apoVs use TCOF1 to upregulate mitochondrial protein transcription, resulting in FLVCR1-mediated mitochondrial functional homeostasis. Taken together, this study reveals a previously unknown role of apoptotic metabolites in ameliorating bone aging phenotypes and the unique role of TCOF1/FLVCR1 in maintaining mitochondrial homeostasis.

Tailoring of apoptotic bodies for diagnostic and therapeutic applications:advances, challenges, and prospects

Apoptotic bodies (ABs) are extracellular vesicles released during apoptosis and possess diverse biological activities. Initially, ABs were regarded as garbage bags with the main function of apoptotic cell clearance. Recent research has found that ABs carry and deliver various biological agents and are taken by surrounding and distant cells, affecting cell functions and behavior. ABs-mediated intercellular communications are involved in various physiological processes including anti-inflammation and tissue regeneration as well as the pathogenesis of a variety of diseases including cancer, cardiovascular diseases, neurodegeneration, and inflammatory diseases. ABs in biological fluids can be used as a window of altered cellular and tissue states which can be applied in the diagnosis and prognosis of various diseases. The structural and constituent versatility of ABs provides flexibility for tailoring ABs according to disease diagnostic and therapeutic needs. An in-depth understanding of ABs' constituents and biological functions is mandatory for the effective tailoring of ABs including modification of bio membrane and cargo constituents. ABs' tailoring approaches including physical, chemical, biological, and genetic have been proposed for bench-to-bed translation in disease diagnosis, prognosis, and therapy. This review summarizes the updates on ABs tailoring approaches, discusses the existing challenges, and speculates the prospects for effective diagnostic and therapeutic applications.

Engineering strategies for apoptotic bodies

Extracellular vesicles (EVs) are lipid bilayer vesicles containing proteins, lipids, nucleic acids, and metabolites secreted by cells under various physiological and pathological conditions that mediate intercellular communication. The main types of EVs include exosomes, microvesicles, and apoptotic bodies (ABs). ABs are vesicles released during the terminal stages of cellular apoptosis, enriched with diverse biological entities and characterized by distinct morphological features. As a result, ABs possess great potential in fields like disease diagnosis, immunotherapy, regenerative therapy, and drug delivery due to their specificity, targeting capacity, and biocompatibility. However, their therapeutic efficacy is notably heterogeneous, and an overdose can lead to side effects such as accumulation in the liver, spleen, lungs, and gastrointestinal system. Through bioengineering, the properties of ABs can be optimized to enhance drug-loading efficiency, targeting precision, and multifunctionality for clinical implementations. This review focuses on strategies such as transfection, sonication, electroporation, surface engineering, and integration with biomaterials to enable ABs to load cargoes and enhance targeting, providing insights into the engineering of ABs.

Apoptotic vesicle-mediated senolytics requires mechanical loading

Rationale: Mechanical force plays crucial roles in extracellular vesicle biogenesis, release, composition and activity. However, it is unknown whether mechanical force regulates apoptotic vesicle (apoV) production. Methods: The effects of mechanical unloading on extracellular vesicles of bone marrow were evaluated through morphology, size distribution, yield, and protein mass spectrometry analysis using hindlimb unloading (HU) mouse model. Apoptosis resistance and aging related phenotype were assessed using HU mouse model in vivo and cell microgravity model in vitro. The therapeutic effects of apoVs on HU mouse model were assessed by using microcomputed tomography, histochemical and immunohistochemical, as well as histomorphometry analyses. SiRNA and chemicals were used for gain and loss-of-function assay. Results: In this study, we show that loss of mechanical force led to cellular apoptotic resistance and aging related phenotype, thus reducing the number of apoVs in the circulation due to down-regulated expression of Piezo1 and reduced calcium influx. And systemic infusion of apoVs was able to rescue Piezo1 expression and calcium influx, thereby, rescuing mechanical unloading-induced cellular apoptotic resistance, senescent cell accumulation. Conclusions: This study identified a previously unknown role of mechanical force in maintaining apoptotic homeostasis and eliminating senescent cells. Systemic infusion of mesenchymal stem cell-derived apoVs can effectively rescue apoptotic resistance and eliminate senescent cells in mechanical unloading mice.

Resolution of inflammation, an active process to restore the immune microenvironment balance: A novel drug target for treating arterial hypertension

The resolution of inflammation, the other side of the inflammatory response, is defined as an active and highly coordinated process that promotes the restoration of immune microenvironment balance and tissue repair. Inflammation resolution involves several key processes, including dampening proinflammatory signaling, specialized proresolving lipid mediator (SPM) production, nonlipid proresolving mediator production, efferocytosis and regulatory T-cell (Treg) induction. In recent years, increasing attention has been given to the effects of inflammation resolution on hypertension. Furthermore, our previous studies reported the antihypertensive effects of SPMs. Therefore, in this review, we aim to summarize and discuss the detailed association between arterial hypertension and inflammation resolution. Additional, the association between gut microbe-mediated immune and hypertension is discussed. This findings suggested that accelerating the resolution of inflammation can have beneficial effects on hypertension and its related organ damage. Exploring novel drug targets by focusing on various pathways involved in accelerating inflammation resolution will contribute to the treatment and control of hypertensive diseases in the future.

Apoptotic Extracellular Vesicles from Supernumerary Tooth-Derived Pulp Stem Cells Transfer COL1A1 to Promote Angiogenesis via PI3K/Akt/VEGF Pathway

Purpose

Angiogenesis is a tightly controlled process that initiates the formation of new vessels and its dysfunction can lead to life-threatening diseases. Apoptotic extracellular vesicles (ApoEVs) have emerged as a proangiogenic agent with high safety and isolation efficiency profile, and ApoEVs from supernumerary tooth-derived pulp stem cells (SNTSC-ApoEVs) have their unique advantages with an easily accessible parental cell source and non-invasive cell harvesting. However, the detailed characteristics of SNTSC-ApoEVs are largely unknown. This study aimed to investigate the proangiogenic capacity and function molecule of SNTSC-ApoEVs.

Methods

SNTSC-ApoEVs were isolated and characterized. In vitro effects of SNTSC-ApoEVs on the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) were evaluated by CCK-8, wound healing, transwell, and tube formation assays. The mRNA and protein levels of proangiogenic genes were quantified by qRT-PCR, Western blot, and immunofluorescence analysis. A Matrigel plug model was established in 6-week-old male nu/nu mice for one week, and the in vivo impact of SNTSC-ApoEVs on micro-vessel formation was assessed by histological analysis. Proteomic analysis and RNA sequencing were performed to explore the active ingredients and underlying mechanisms.

Results

SNTSC-ApoEVs enhanced the proliferation, migration, and angiogenesis of HUVECs in vitro. In the Matrigel plug model in vivo, SNTSC-ApoEVs promoted CD31-positive luminal structure formation. Apart from expressing general ApoEV markers, SNTSC-ApoEVs were enriched with multiple proteins related to extracellular matrix-cell interactions. Mechanistically, SNTSC-ApoEVs transferred COL1A1 to HUVECs and promoted endothelial functions by activating the PI3K/Akt/VEGF cascade.

Conclusion

SNTSC-ApoEVs can promote angiogenesis by transferring the functional molecule COL1A1 and activating the PI3K/Akt/VEGF pathway, making SNTSC-ApoEVs a promising strategy for the treatment of angiogenesis-related diseases.

Carbon Dot-Loaded Apoptotic Vesicles Improve the Liver Kupffer Cell-Mediated Antibacterial Effect to Synergistically Alleviate Sepsis

Sepsis is a lethal systemic inflammatory disease against infection that lacks effective therapeutic approaches. Liver resident macrophage Kupffer cell (KC)-initiated bacterial clearance is crucial for the host to defend against infection. However, it remains unclear whether this process also governs the antibacterial therapy of sepsis that would be used to improve therapeutic outcomes. Here, we found that copper-doped carbon dots (Cu-CDs) exhibited superior antibacterial capabilities in vitro but displayed limited therapeutic effects in septic mice due to their limited ability to target the liver and restore KC antimicrobial capacity. Thus, we developed a composite nanodrug of copper-doped carbon dot-loaded apoVs (CC-apoVs) that combined the antibacterial ability of Cu-CDs and liver KC targeting features of apoV. Moreover, intravenous injection of CC-apoVs markedly alleviated the systemic infection and decreased the mortality of septic mice compared to Cu-CD and apoV infusion alone. Mechanistically, CC-apoV injection rescued impaired liver KCs during sepsis and enhanced their ability to capture and kill bloodborne bacteria. In addition, apoV-promoted macrophage killing of bacteria could be blocked by the inhibition of small GTPase Rab5. This study reveals a liver KC-targeted therapeutic strategy for sepsis and provides a nanodrug CC-apoV to improve the host antibacterial defense and amplify the therapeutic effect of the nanodrug.

Apoptotic Vesicles Modulate Endothelial Metabolism and Ameliorate Ischemic Retinopathy via PD1/PDL1 Axis

Pathological angiogenesis with subsequent disturbed microvascular remodeling is a major cause of irreversible blindness in a number of ischemic retinal diseases. The current anti-vascular endothelial growth factor therapy can effectively inhibit angiogenesis, but it also brings significant side effects. The emergence of stem cell derived extracellular vesicles provides a new underlining strategy for ischemic retinopathy. Apoptotic vesicles (apoVs) are extracted from stem cells from human exfoliated deciduous teeth (SHED). SHED-apoVs are delivered into the eyeballs of oxygen-induced retinopathy (a most common model of angiogenic retinal dieseases) mice through intravitreal injection. The retinal neovascularization and nonperfusion area, vascular structure, and density changes are observed during the neovascularization phase (P17) and vascular remodeling phase (P21), and visual function is measured. The expression of extracellular acidification rate and lactic acid testing are used to detect endothelial cells (ECs) glycolytic activity. Furthermore, lentivirus and neutralizing antibody are used to block PD1-PDL1 axis, investigating the effects of SHED-apoVs on glycolysis and angiogenic activities. This work shows that SHED-apoVs are taken up by ECs and modulate the ECs glycolysis, leading to the decrease of abnormal neovessels and vascular remodeling. Furthermore, it is found that, at the molecular level, apoVs-carried PD1 interacts with PDL1 on hypoxic ECs to regulate the angiogenic activation. SHED-apoVs inhibit pathological angiogenesis and promote vascular remodeling in ischemic retinopathy partially by modulating ECs glycolysis through PD1/PDL1 axis. This study provides a new potential strategy for the clinical treatment of pathological retinal neovascularization.

Integrating network pharmacology and experimental validation reveals therapeutic effects of D-mannose on NAFLD through mTOR suppression

Non-alcoholic fatty liver disease (NAFLD), a chronic liver condition and metabolic disorder, has emerged as a significant health issue worldwide. D-mannose, a natural monosaccharide widely existing in plants and animals, has demonstrated metabolic regulatory properties. However, the effect and mechanism by which D-mannose may counteract NAFLD have not been studied. In this study, network pharmacology followed by molecular docking analysis was utilized to identify potential targets of mannose against NAFLD, and the leptin receptor-deficient, genetically obese db/db mice was employed as an animal model of NAFLD to validate the regulation of D-mannose on core targets. As a result, 67 targets of mannose are predicted associated with NAFLD, which are surprisingly centered on the mechanistic target of rapamycin (mTOR). Further analyses suggest that mTOR signaling is functionally enriched in potential targets of mannose treating NAFLD, and that mannose putatively binds to mTOR as a core mechanism. Expectedly, repeated oral gavage of supraphysiological D-mannose ameliorates liver steatosis of db/db mice, which is based on suppression of hepatic mTOR signaling. Moreover, daily D-mannose administration reduced hepatic expression of lipogenic regulatory genes in counteracting NAFLD. Together, these findings reveal D-mannose as an effective and potential NAFLD therapeutic through mTOR suppression, which holds translational promise.

Apoptotic vesicles rescue impaired mesenchymal stem cells and their therapeutic capacity for osteoporosis by restoring miR-145a-5p deficiency

Apoptotic vesicles (apoVs) play a vital role in various pathological conditions; however, we have yet to fully understand their precise biological effects in rescuing impaired mesenchymal stem cells (MSCs) and regulating tissue homeostasis. Here, we proved that systemic infusion of bone marrow MSCs derived from wild-type (WT) mice effectively improved the osteopenia phenotype and hyperimmune state in ovariectomized (OVX) mice. Importantly, the WT MSCs rescued the impairment of OVX MSCs both in vivo and in vitro, whereas OVX MSCs did not show the same efficacy. Interestingly, treatment with apoVs derived from WT MSCs (WT apoVs) restored the impaired biological function of OVX MSCs and their ability to improve osteoporosis. This effect was not observed with OVX MSCs-derived apoVs (OVX apoVs) treatment. Mechanistically, the reduced miR-145a-5p expression hindered the osteogenic differentiation and immunomodulatory capacity of OVX MSCs by affecting the TGF-β/Smad 2/3-Wnt/β-catenin signaling axis, resulting in the development of osteoporosis. WT apoVs directly transferred miR-145a-5p to OVX MSCs, which were then reused to restore their impaired biological functions. Conversely, treatment with OVX apoVs did not produce significant effects due to their limited expression of miR-145a-5p. Overall, our findings unveil the remarkable potential of apoVs in rescuing the biological function and therapeutic capability of MSCs derived from individuals with diseases. This discovery offers a new avenue for exploring apoVs-based MSC engineering and expands the application scope of stem cell therapy, contributing to the maintenance of bone homeostasis through a previously unrecognized mechanism.

Extracellular vesicles from apoptotic BMSCs ameliorate osteoporosis via transporting regenerative signals

Rationale: Mesenchymal stromal cells (MSCs) are considered a promising resource for cell therapy, exhibiting efficacy in ameliorating diverse bone diseases. However, most MSCs undergo apoptosis shortly after transplantation and produce apoptotic extracellular vesicles (ApoEVs). This study aims to clarify the potential role of ApoEVs from apoptotic MSCs in ameliorating osteoporosis and molecular mechanism. Methods: In this study, Dio-labeled bone marrow mesenchymal stem cells (BMSCs) were injected into mice to track BMSCs apoptosis and ApoEVs production. ApoEVs were isolated from BMSCs after inducing apoptosis, the morphology, size distribution, marker proteins expression of ApoEVs were characterized. Protein mass spectrometry analysis revealed functional differences in proteins between ApoEVs and BMSCs. BMSCs were adopted to test the cellular response to ApoEVs. Ovariectomy mice were used to further compare the ability of ApoEVs in promoting bone formation. SiRNA and lentivirus were used for gain and loss-of-function assay. Results: The results showed that BMSCs underwent apoptosis within 2 days after being injected into mice and produce a substantial quantity of ApoEVs. Proteomic analysis revealed that ApoEVs carried a diverse functional array of proteins, and easily traversed the circulation to reach the bone. After being phagocytized by endogenous BMSCs, ApoEVs efficiently promoted the proliferation, migration, and osteogenic differentiation of BMSCs. In an osteoporosis mouse model, treatment of ApoEVs alleviated bone loss and promoted bone formation. Mechanistically, ApoEVs carried Ras protein and activated the Ras/Raf1/Mek/Erk pathway to promote osteogenesis and bone formation in vitro and in vivo. Conclusion: Given that BMSC-derived ApoEVs are high-yield and easily obtained, our data underscore the substantive role of ApoEVs from dying BMSCs to treat bone loss, presenting broad implications for cell-free therapeutic modalities.

Roles of extracellular vesicles on macrophages in inflammatory bone diseases

Inflammatory bone disease is a general term for a series of diseases caused by chronic inflammation, which leads to the destruction of bone homeostasis, that is, the osteolytic activity of osteoclasts increases, and the osteogenic activity of osteoblasts decreases, leading to osteolysis. Macrophages are innate immune cell with plasticity, and their polarization is related to inflammatory bone diseases. The dynamic balance of macrophages between the M1 phenotype and the M2 phenotype affects the occurrence and development of diseases. In recent years, an increasing number of studies have shown that extracellular vesicles existing in the extracellular environment can act on macrophages, affecting the progress of inflammatory diseases. This process is realized by influencing the physiological activity or functional activity of macrophages, inducing macrophages to secrete cytokines, and playing an anti-inflammatory or pro-inflammatory role. In addition, by modifying and editing extracellular vesicles, the potential of targeting macrophages can be used to provide new ideas for developing new drug carriers for inflammatory bone diseases.

Mesenchymal stem cell-derived apoptotic vesicles ameliorate impaired ovarian folliculogenesis in polycystic ovary syndrome and ovarian aging by targeting WNT signaling

Rationale: It has been emergingly recognized that apoptosis generates plenty of heterogeneous apoptotic vesicles (apoVs), which play a pivotal role in the maintenance of organ and tissue homeostasis. However, it is unknown whether apoVs influence postnatal ovarian folliculogenesis. Methods: Apoptotic pathway deficient mice including Fas mutant (Fasmut ) and Fas ligand mutant (FasLmut ) mice were used with apoV replenishment to evaluate the biological function of apoVs during ovarian folliculogenesis. Ovarian function was characterized by morphological analysis, biochemical examination and cellular assays. Mechanistical studies were assessed by combinations of transcriptomic and proteomic analysis as well as molecular assays. CYP17A1-Cre; Axin1fl /fl mice was established to verify the role of WNT signaling during ovarian folliculogenesis. Polycystic ovarian syndrome (PCOS) mice and 15-month-old mice were used with apoV replenishment to further validate the therapeutic effects of apoVs based on WNT signaling regulation. Results: We show that systemic administration of mesenchymal stem cell (MSC)-derived apoptotic vesicles (MSC-apoVs) can ameliorate impaired ovarian folliculogenesis, PCOS phenotype, and reduced birth rate in Fasmut and FasLmut mice. Mechanistically, transcriptome analysis results revealed that MSC-apoVs downregulated a number of aberrant gene expression in Fasmut mice, which were enriched by kyoto encyclopedia of genes and genomes (KEGG) pathway analysis in WNT signaling and sex hormone biosynthesis. Furthermore, we found that apoptotic deficiency resulted in aberrant WNT/β-catenin activation in theca and mural granulosa cells, leading to responsive action of dickkopf1 (DKK1) in the cumulus cell and oocyte zone, which downregulated WNT/β-catenin expression in oocytes and, therefore, impaired ovarian folliculogenesis via NPPC/cGMP/PDE3A/cAMP cascade. When WNT/β-catenin was specially activated in theca cells of CYP17A1-Cre; Axin1fl /fl mice, the same ovarian impairment phenotypes observed in apoptosis-deficient mice were established, confirming that aberrant activation of WNT/β-catenin in theca cells caused the impairment of ovarian folliculogenesis. We firstly revealed that apoVs delivered WNT membrane receptor inhibitor protein RNF43 to ovarian theca cells to balance follicle homeostasis through vesicle-cell membrane integration. Systemically infused RNF43-apoVs down-regulated aberrantly activated WNT/β-catenin signaling in theca cells, contributing to ovarian functional maintenance. Since aging mice have down-regulated expression of WNT/β-catenin in oocytes, we used MSC-apoVs to treat 15-month-old mice and found that MSC-apoVs effectively ameliorated the ovarian function and fertility capacity of these aging mice through rescuing WNT/β-catenin expression in oocytes. Conclusion: Our studies reveal a previously unknown association between apoVs and ovarian folliculogenesis and suggest an apoV-based therapeutic approach to improve oocyte function and birth rates in PCOS and aging.

Mesenchymal Stromal Cells: New Generation Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract, which has a high recurrence rate and is incurable due to a lack of effective treatment. Mesenchymal stromal cells (MSCs) are a class of pluripotent stem cells that have recently received a lot of attention due to their strong self-renewal ability and immunomodulatory effects, and a large number of experimental and clinical models have confirmed the positive therapeutic effect of MSCs on IBD. In preclinical studies, MSC treatment for IBD relies on MSCs paracrine effects, cell-to-cell contact, and its mediated mitochondrial transfer for immune regulation. It also plays a therapeutic role in restoring the intestinal mucosal barrier through the homing effect, regulation of the intestinal microbiome, and repair of intestinal epithelial cells. In the latest clinical trials, the safety and efficacy of MSCs in the treatment of IBD have been confirmed by transfusion of autologous or allogeneic bone marrow, umbilical cord, and adipose MSCs, as well as their derived extracellular vesicles. However, regarding the stable and effective clinical use of MSCs, several concerns emerge, including the cell sources, clinical management (dose, route and frequency of administration, and pretreatment of MSCs) and adverse reactions. This article comprehensively summarizes the effects and mechanisms of MSCs in the treatment of IBD and its advantages over conventional drugs, as well as the latest clinical trial progress of MSCs in the treatment of IBD. The current challenges and future directions are also discussed. This review would add knowledge into the understanding of IBD treatment by applying MSCs.

Apoptotic extracellular vesicles restore homeostasis of the articular microenvironment for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a severe autoimmune disease with symptoms including synovial inflammation, cartilage erosion, and bone loss in RA lesions, which eventually lead to joint deformity and function loss. Most current treatments fail to achieve satisfying therapeutic outcomes with some adverse effects. Extracellular vesicles derived from apoptotic cells (apoEVs) have emerged as important mediators in intercellular communication regulating diverse physiological and pathological processes. In this study, we investigated the therapeutic efficacy of macrophage-derived and osteoclast-derived apoEVs (Mφ-apoEVs and OC-apoEVs) on RA. The in vitro results showed that both Mφ-apoEVs and OC-apoEVs induced macrophage repolarization toward the anti-inflammatory M2 phenotype, promoted chondrocyte functions and chondrogenesis, and inhibited osteoclast formation and maturation. In addition, OC-apoEVs promoted osteogenic differentiation. The in vivo study on the CIA mouse model further demonstrated that apoEVs could couple various functions and exert synergistic effects on the joint with RA, as evidenced by the regression of synovial inflammation, the reversal of cartilage damage and bone erosion, and the preservation of joint structure. These findings demonstrated that Mφ-apoEVs and OC-apoEVs contributed to restoring the homeostasis of the overall microenvironment in the RA joint and highlighted their potential application as a promising alternative to treat RA.

Interplay between mesenchymal stem cells and macrophages: Promoting bone tissue repair

The repair of bone tissue damage is a complex process that is well-orchestrated in time and space, a focus and difficulty in orthopedic treatment. In recent years, the success of mesenchymal stem cells (MSCs)-mediated bone repair in clinical trials of large-area bone defects and bone necrosis has made it a candidate in bone tissue repair engineering and regenerative medicine. MSCs are closely related to macrophages. On one hand, MSCs regulate the immune regulatory function by influencing macrophages proliferation, infiltration, and phenotype polarization, while also affecting the osteoclasts differentiation of macrophages. On the other hand, macrophages activate MSCs and mediate the multilineage differentiation of MSCs by regulating the immune microenvironment. The cross-talk between MSCs and macrophages plays a crucial role in regulating the immune system and in promoting tissue regeneration. Making full use of the relationship between MSCs and macrophages will enhance the efficacy of MSCs therapy in bone tissue repair, and will also provide a reference for further application of MSCs in other diseases.

Tailored apoptotic vesicles promote bone regeneration by releasing the osteoinductive brake

Accumulating evidence has demonstrated that apoptotic vesicles (apoVs) derived from mesenchymal stem cells (MSCs; MSC-apoVs) are vital for bone regeneration, and possess superior capabilities compared to MSCs and other extracellular vesicles derived from MSCs (such as exosomes). The osteoinductive effect of MSC-apoVs is attributed to their diverse contents, especially enriched proteins or microRNAs (miRNAs). To optimize their osteoinduction activity, it is necessary to determine the unique cargo profiles of MSC-apoVs. We previously established the protein landscape and identified proteins specific to MSC-apoVs. However, the features and functions of miRNAs enriched in MSC-apoVs are unclear. In this study, we compared MSCs, MSC-apoVs, and MSC-exosomes from two types of MSC. We generated a map of miRNAs specific to MSC-apoVs and identified seven miRNAs specifically enriched in MSC-apoVs compared to MSCs and MSC-exosomes, which we classified as apoV-specific miRNAs. Among these seven specific miRNAs, hsa-miR-4485-3p was the most abundant and stable. Next, we explored its function in apoV-mediated osteoinduction. Unexpectedly, hsa-miR-4485-3p enriched in MSC-apoVs inhibited osteogenesis and promoted adipogenesis by targeting the AKT pathway. Tailored apoVs with downregulated hsa-miR-4485-3p exhibited a greater effect on bone regeneration than control apoVs. Like releasing the brake, we acquired more powerful osteoinductive apoVs. In summary, we identified the miRNA cargos, including miRNAs specific to MSC-apoVs, and generated tailored apoVs with high osteoinduction activity, which is promising in apoV-based therapies for bone regeneration.

Apoptotic vesicles are required to repair DNA damage and suppress premature cellular senescence

It is well known that DNA damage can cause apoptosis. However, whether apoptosis and its metabolites contribute to DNA repair is largely unknown. In this study, we found that apoptosis-deficient Fasmut and Bim- /- mice show significantly elevated DNA damage and premature cellular senescence, along with a significantly reduced number of 16,000 g apoptotic vesicles (apoVs). Intravenous infusion of mesenchymal stromal cell (MSC)-derived 16,000 g apoVs rescued the DNA damage and premature senescence in Fasmut and Bim-/- mice. Moreover, a sublethal dose of radiation exposure caused more severe DNA damage, reduced survival rate, and loss of body weight in Fasmut mice than in wild-type mice, which can be recovered by the infusion of MSC-apoVs. Mechanistically, we showed that apoptosis can assemble multiple nuclear DNA repair enzymes, such as the full-length PARP1, into 16,000 g apoVs. These DNA repair components are directly transferred by 16,000 g apoVs to recipient cells, leading to the rescue of DNA damage and elimination of senescent cells. Finally, we showed that embryonic stem cell-derived 16,000 g apoVs have superior DNA repair capacity due to containing a high level of nuclear DNA repair enzymes to rescue lethal dose-irradiated mice. This study uncovers a previously unknown role of 16,000 g apoVs in safeguarding tissues from DNA damage and demonstrates a strategy for using stem cell-derived apoVs to ameliorate irradiation-induced DNA damage.

Apoptotic body-inspired nanotherapeutics efficiently attenuate osteoarthritis by targeting BRD4-regulated synovial macrophage polarization

Bromodomain-containing protein 4 (BRD4) is the most well-studied BET protein that is important for the innate immune response. We recently revealed that targeting BRD4 triggers apoptosis in tumor-associated macrophages, but its role in synovial macrophages and joint inflammation is largely unknown. Herein, we demonstrated that BRD4 was highly expressed in the iNOS-positive M1 macrophages in the human and mouse osteoarthritis (OA) synovium, and conditional knockout of BRD4 in the myeloid lineage using Lyz2-cre; BRD4flox/flox mice significantly abolished anterior cruciate ligament transection (ACLT)-induced M1 macrophage accumulation and synovial inflammation. Accordingly, we successfully constructed apoptotic body-inspired phosphatidylserine-containing nanoliposomes (PSLs) loaded with the BRD4 inhibitor JQ1 to regulate inflammatory macrophages. JQ1-loaded PSLs (JQ1@PSLs) exhibited a higher cellular uptake by macrophages than fibroblast-like synoviocytes (FLSs) in vitro and in vivo, as well as the reduction in proinflammatory M1 macrophage polarization. Intra-articular injections of JQ1@PSLs showed prolonged retention within the joint, and remarkably reduced synovial inflammation and joint pain via suppressing M1 polarization accompanied by reduced TRPA1 expression by targeted inhibition of BRD4 in the macrophages, thus attenuating cartilage degradation during OA development. The results show that BRD4-inhibiting JQ1@PSLs can targeted-modulate macrophage polarization, which opens a new avenue for efficient OA therapy via a "Trojan horse".

Calcified apoptotic vesicles from PROCR+ fibroblasts initiate heterotopic ossification

Heterotopic ossification (HO) comprises the abnormal formation of ectopic bone in extraskeletal soft tissue. The factors that initiate HO remain elusive. Herein, we found that calcified apoptotic vesicles (apoVs) led to increased calcification and stiffness of tendon extracellular matrix (ECM), which initiated M2 macrophage polarization and HO progression. Specifically, single-cell transcriptome analyses of different stages of HO revealed that calcified apoVs were primarily secreted by a PROCR+ fibroblast population. In addition, calcified apoVs enriched calcium by annexin channels, absorbed to collagen I via electrostatic interaction, and aggregated to produce calcifying nodules in the ECM, leading to tendon calcification and stiffening. More importantly, apoV-releasing inhibition or macrophage deletion both successfully reversed HO development. Thus, we are the first to identify calcified apoVs from PROCR+ fibroblasts as the initiating factor of HO, and might serve as the therapeutic target for inhibiting pathological calcification.

Sympathetic innervation induces exosomal miR-125 transfer from osteoarthritic chondrocytes, disrupting subchondral bone homeostasis and aggravating cartilage damage in aging mice

INTRODUCTION

Osteoarthritis (OA) is a progressive disease that poses a significant threat to human health, particularly in aging individuals: Although sympathetic activation has been implicated in bone metabolism, its role in the development of OA related to aging remains poorly understood. Therefore, this study aimed to investigate how sympathetic regulation impacts aging-related OA through experiments conducted both in vivo and in vitro.

METHODS

To analyze the effect of sympathetic regulation on aging-related OA, we conducted experiments using various mouse models. These models included a natural aging model, a medial meniscus instability model, and a load-induced model, which were used to examine the involvement of sympathetic nerves. In order to evaluate the expression levels of β1-adrenergic receptor (Adrβ1) and sirtuin-6 (Sirt6) in chondrocytes of naturally aging OA mouse models, we performed assessments. Additionally, we investigated the influence of β1-adrenergic receptor knockout or treatment with a β1-adrenergic receptor blocker on the progression of OA in aging mice and detected exosome release and detected downstream signaling expression by inhibiting exosome release. Furthermore, we explored the impact of sympathetic depletion through tyrosine hydroxylase (TH) on OA progression in aging mice. Moreover, we studied the effects of norepinephrine(NE)-induced activation of the β1-adrenergic receptor signaling pathway on the release of exosomes and miR-125 from chondrocytes, subsequently affecting osteoblast differentiation in subchondral bone.

RESULTS

Our findings demonstrated a significant increase in sympathetic activity, such as NE levels, in various mouse models of OA including natural aging, medial meniscus instability, and load-induced models. Notably, we observed alterations in the expression levels of β1-adrenergic receptor and Sirt6 in chondrocytes in OA mouse models associated with natural aging, leading to an improvement in the progression of OA. Critically, we found that the knockout of β1-adrenergic receptor or treatment with a β1-adrenergic receptor blocker attenuated OA progression in aging mice and the degraded cartilage explants produced more exosome than the nondegraded ones, Moreover, sympathetic depletion through TH was shown to ameliorate OA progression in aging mice. Additionally, we discovered that NE-induced activation of the β1-adrenergic receptor signaling pathway facilitated the release of exosomes and miR-125 from chondrocytes, promoting osteoblast differentiation in subchondral bone.

CONCLUSION

In conclusion, our study highlights the role of sympathetic innervation in facilitating the transfer of exosomal miR-125 from osteoarthritic chondrocytes, ultimately disrupting subchondral bone homeostasis and exacerbating cartilage damage in aging mice. These findings provide valuable insights into the potential contribution of sympathetic regulation to the pathogenesis of aging-related OA.

Apoptotic Extracellular Vesicles Induced Endothelial Cell-Mediated Autologous Stem Cell Recruitment Dominates Allogeneic Stem Cell Therapeutic Mechanism for Bone Repair

Although stem cell therapy is proved to be a promising strategy for bone repair and regeneration, transplanted allogeneic stem cells generally suffer from unfavorable apoptosis instead of differentiation into osteocytes. How the apoptotic stem cells promote bone regeneration still needs to be uncovered. In this work, we found that apoptotic extracellular vesicles released by allogeneic stem cells are critical mediators for promoting bone regeneration. Based on the results of in vivo experiments, a mechanism of apoptotic stem cells determined autologous stem cell recruitment and enhance osteogenesis was proposed. The nanoscaled apoptotic extracellular vesicles released from transplanted stem cells were endocytosed by vascular endothelial cells and preferentially distribute at endoplasmic reticular region. The oxidized phosphatidylcholine enriched in the vesicles activated the endoplasmic reticulum stress and triggered the reflective elevation of adhesion molecules, which induced the recruitment of autologous stem cells located in the blood vessels, transported them into the defect region, and promoted osteogenesis and bone repair. These findings not only reveal the mechanism of stem cell therapy of bone defects but also provide a cue for investigation of the biological process of stem cell therapy for other diseases and develop stem cell therapeutic strategies.

Apoptotic extracellular vesicles derived from hypoxia-preconditioned mesenchymal stem cells within a modified gelatine hydrogel promote osteochondral regeneration by enhancing stem cell activity and regulating immunity

Due to its unique structure, articular cartilage has limited abilities to undergo self-repair after injury. Additionally, the repair of articular cartilage after injury has always been a difficult problem in the field of sports medicine. Previous studies have shown that the therapeutic use of mesenchymal stem cells (MSCs) and their extracellular vesicles (EVs) has great potential for promoting cartilage repair. Recent studies have demonstrated that most transplanted stem cells undergo apoptosis in vivo, and the apoptotic EVs (ApoEVs) that are subsequently generated play crucial roles in tissue repair. Additionally, MSCs are known to exist under low-oxygen conditions in the physiological environment, and these hypoxic conditions can alter the functional and secretory properties of MSCs as well as their secretomes. This study aimed to investigate whether ApoEVs that are isolated from adipose-derived MSCs cultured under hypoxic conditions (hypoxic apoptotic EVs [H-ApoEVs]) exert greater effects on cartilage repair than those that are isolated from cells cultured under normoxic conditions. Through in vitro cell proliferation and migration experiments, we demonstrated that H-ApoEVs exerted enhanced effects on stem cell proliferation, stem cell migration, and bone marrow derived macrophages (BMDMs) M2 polarization compared to ApoEVs. Furthermore, we utilized a modified gelatine matrix/3D-printed extracellular matrix (ECM) scaffold complex as a carrier to deliver H-ApoEVs into the joint cavity, thus establishing a cartilage regeneration system. The 3D-printed ECM scaffold provided mechanical support and created a microenvironment that was conducive to cartilage regeneration, and the H-ApoEVs further enhanced the regenerative capacity of endogenous stem cells and the immunomodulatory microenvironment of the joint cavity; thus, this approach significantly promoted cartilage repair. In conclusion, this study confirmed that a ApoEVs delivery system based on a modified gelatine matrix/3D-printed ECM scaffold together with hypoxic preconditioning enhances the functionality of stem cell-derived ApoEVs and represents a promising approach for promoting cartilage regeneration.

The Landscape of Biomimetic Nanovesicles in Brain Diseases

Brain diseases, such as brain tumors, neurodegenerative diseases, cerebrovascular diseases, and brain injuries, are caused by various pathophysiological changes, which pose a serious health threat. Brain disorders are often difficult to treat due to the presence of the blood-brain barrier (BBB). Biomimetic nanovesicles (BNVs), including endogenous extracellular vesicles (EVs) derived from various cells and artificial nanovesicles, possess the ability to penetrate the BBB and thus can be utilized for drug delivery to the brain. BNVs, especially endogenous EVs, are widely distributed in body fluids and usually carry various disease-related signal molecules such as proteins, RNA, and DNA, and may also be analyzed to understand the etiology and pathogenesis of brain diseases. This review covers the exhaustive classification and characterization of BNVs and pathophysiological roles involved in various brain diseases, and emphatically focuses on nanotechnology-integrated BNVs for brain disease theranostics, including various diagnosis strategies and precise therapeutic regulations (e.g., immunity regulation, disordered protein clearance, anti-neuroinflammation, neuroregeneration, angiogenesis, and the gut-brain axis regulation). The remaining challenges and future perspectives regarding the nanotechnology-integrated BNVs for the diagnosis and treatment of brain diseases are also discussed and outlined.

Apoptotic vesicles derived from human red blood cells promote bone regeneration via carbonic anhydrase 1

Apoptotic vesicles (apoVs) are nanoscale vesicles derived from billions of apoptotic cells involved in the maintenance of the human body's homeostasis. Previous researches have shown that some apoVs, such as those derived from mesenchymal stem cells, contribute to bone formation. However, those apoVs cannot be extracted from patients in large quantities, and cell expansion is needed before apoV isolation, which limits their clinical translation. Mature RBCs, which have no nuclei or genetic material, are easy to obtain, showing high biological safety as a source of extracellular vesicles (EVs). Previous studies have demonstrated that RBC-derived EVs have multiple biological functions, but it is unknown whether RBCs produce apoVs and what effect these apoVs have on bone regeneration. In this study, we isolated and characterized RBC-derived apoVs (RBC-apoVs) from human venous blood and investigated their role in the osteogenesis of human bone mesenchymal stem cells (hBMSCs). We showed that RBCs could produce RBC-apoVs that expressed both general apoVs markers and RBC markers. RBC-apoVs significantly promoted osteogenesis of hBMSCs and enhanced bone regeneration in rat calvarial defects. Mechanistically, RBC-apoVs regulated osteogenesis by transferring carbonic anhydrase 1 (CA1) into hBMSCs and activating the P38 MAPK pathway. Our results indicated that RBC-apoVs could deliver functional molecules from RBCs to hBMSCs and promote bone regeneration, pointing to possible therapeutic use in bone tissue engineering.

Bone-Targeting Peptide and RNF146 Modified Apoptotic Extracellular Vesicles Alleviate Osteoporosis

Background

Osteoporosis is a highly prevalent disease that causes fractures and loss of motor function. Current drugs targeted for osteoporosis often have inevitable side effects. Bone marrow mesenchymal stem cell (BMSCs)-derived apoptotic extracellular vesicles (ApoEVs) are nanoscale extracellular vesicles, which has been shown to promote bone regeneration with low immunogenicity and high biological compatibility. However, natural ApoEVs cannot inherently target bones, and are often eliminated by macrophages in the liver and spleen. Thus, our study aimed to reconstruct ApoEVs to enhance their bone-targeting capabilities and bone-promoting function and to provide a new method for osteoporosis treatment.

Methods

We conjugated a bone-targeting peptide, (Asp-Ser-Ser)6 ((DSS)6), onto the surface of ApoEVs using standard carbodiimide chemistry with DSPE-PEG-COOH serving as the linker. The bone-targeting ability of (DSS)6-ApoEVs was determined using an in vivo imaging system and confocal laser scanning microscopy (CLSM). We then loaded ubiquitin ligase RING finger protein146 (RNF146) into BMSCs via adenovirus transduction to obtain functional ApoEVs. The bone-promoting abilities of (DSS)6-ApoEVs and (DSS)6-ApoEVsRNF146 were measured in vitro and in vivo.

Results

Our study successfully synthesized bone-targeting and gained functional (DSS)6-ApoEVsRNF146 and found that engineered ApoEVs could promote osteogenesis in vitro and exert significant bone-targeting and osteogenesis-promoting effects to alleviate osteoporosis in a mouse model.

Conclusion

To promote the bone-targeting ability of natural ApoEVs, we successfully synthesized engineered ApoEVs, (DSS)6-ApoEVsRNF146 and found that they could significantly promote osteogenesis and alleviate osteoporosis compared with natural ApoEVs, which holds great promise for the treatment of osteoporosis.

Apoptotic Extracellular Vesicles Derived from Human Umbilical Vein Endothelial Cells Promote Skin Repair by Enhancing Angiogenesis: From Death to Regeneration

Purpose

The promotion of angiogenesis is an effective strategy for skin wound repair. While the transplantation of endothelial cells has shown promise in vascularization, the underlying mechanism remains unclear. Recent studies have suggested that transplanted cells undergo apoptosis in a short period and release apoptotic extracellular vesicles (ApoEVs) that may have therapeutic potential.

Methods

In this study, we isolated ApoEVs from human umbilical vein endothelial cells (HUVECs) and characterized their properties. In vitro, we assessed the effects of ApoEVs on the proliferation, migration, and differentiation of endothelial cells and fibroblasts. In vivo, we investigated the therapeutic role of ApoEVs-AT in full-thickness skin wounds, evaluating wound closure rate, re-epithelialization, granulation tissue formation, vascularization, scar area, and collagen 3(Col3)/collagen 1(Col 1) ratio.

Results

ApoEVs derived from HUVECs displayed typical characteristics. In vitro, ApoEVs significantly enhanced the proliferation, migration, tube formation, and expression of angiogenic-related genes in endothelial cells and slightly promoted the proliferation and migration of fibroblasts. In vivo, ApoEVs improved the wound closure rate, re-epithelialization, the formation of granulation tissue, and vascularization. Besides, ApoEVs reduced scar formation, accompanied by an increase in the Col 3/ Col 1 ratio.

Conclusion

Given their abundant source and effectiveness, this study provided a novel approach for angiogenesis in tissue regeneration and deepened the understanding of from death to regeneration.

The Role of Mesenchymal Stem/Stromal Cells Secretome in Macrophage Polarization: Perspectives on Treating Inflammatory Diseases

Mesenchymal stem/stromal cells (MSCs) have exhibited potential for treating multiple inflammation- related diseases (IRDs) due to their easy acquisition, unique immunomodulatory and tissue repair properties, and immune-privileged characteristics. It is worth mentioning that MSCs release a wide array of soluble bioactive components in the secretome that modulate host innate and adaptive immune responses and promote the resolution of inflammation. As the first line of defense, macrophages exist throughout the entire inflammation process. They continuously switch their molecular phenotypes accompanied by complementary functional regulation ranging from classically activated pro-inflammatory M1-type (M1) to alternatively activated anti-inflammatory M2-type macrophages (M2). Recent studies have shown that the active intercommunication between MSCs and macrophages is indispensable for the immunomodulatory and regenerative behavior of MSCs in pharmacological cell therapy products. In this review, we systematically summarized the emerging capacities and detailed the molecular mechanisms of the MSC-derived secretome (MSC-SE) in immunomodulating macrophage polarization and preventing excessive inflammation, providing novel insights into the clinical applications of MSC-based therapy in IRD management.

Effects of microenvironment and biological behavior on the paracrine function of stem cells

Mesenchymal stem cells (MSCs), the most well-studied cell type in the field of stem cell therapy, have multi-lineage differentiation and self-renewal potential. MSC-based therapies have been used to treat diverse diseases because of their ability to potently repair tissue and locally restore function. An increasing body of evidence demonstrates that paracrine function is central to the effects of MSC-based therapy. Growth factors, cytokines, chemokines, extracellular matrix components, and extracellular vehicles all contribute to the beneficial effects of MSCs on tissue regeneration and repair. The paracrine substances secreted by MSCs change depending on the tissue microenvironment and biological behavior. In this review, we discuss the bioactive substances secreted by MSCs depending on the microenvironment and biological behavior and their regulatory mechanisms, which explain their potential to treat human diseases, to provide new ideas for further research and clinical cell-free therapy.

The Role of Extracellular Vesicles in Efferocytosis

Efferocytosis is the physiological process of phagocytic clearance of apoptotic cells by both professional phagocytic cells, such as macrophages, and non-professional phagocytic cells, such as epithelial cells. This process is crucial for maintaining tissue homeostasis in normal physiology. Any defects in efferocytosis can lead to pathological consequences and result in inflammatory diseases. Extracellular vesicles (EVs), including exosomes, microvesicles (MVs), and apoptotic vesicles (ApoVs), play a crucial role in proper efferocytosis. These EVs can significantly impact efferocytosis by affecting the polarization of macrophages and impacting calreticulin (CRT), TAM receptors, and MFG-E8. With further knowledge of these effects, new treatment strategies can be proposed for many inflammatory diseases caused by efferocytosis disorders. This review article aims to investigate the role of EVs during efferocytosis and its potential clinical applications in inflammatory diseases.

Apoptotic bodies inhibit inflammation by PDL1-PD1-mediated macrophage metabolic reprogramming

Apoptosis triggers immunoregulation to prevent and suppress inflammation and autoimmunity. However, the mechanism by which apoptotic cells modulate immune responses remains largely elusive. In the context of allogeneic mesenchymal stem cells (MSCs) transplantation, long-term immunoregulation is observed in the host despite the short survive of the injected MSCs. In this study, utilizing a mouse model of acute lung injury (ALI), we demonstrate that apoptotic bodies (ABs) released by transplanted human umbilical cord MSCs (UC-MSCs) convert the macrophages from a pro-inflammatory to an anti-inflammatory state, thereby ameliorating the disease. Mechanistically, we identify the expression of programmed cell death 1 ligand 1 (PDL1) on the membrane of UC-MSCs-derived ABs, which interacts with programmed cell death protein 1 (PD1) on host macrophages. This interaction leads to the reprogramming of macrophage metabolism, shifting from glycolysis to mitochondrial oxidative phosphorylation via the Erk-dependent pathway in ALI. Importantly, we have reproduced the PDL1-PD1 effects of ABs on metabolic switch using alveolar macrophages from patients with ALI, suggesting the potential clinical implications of developing therapeutic strategies for the patients.

Platelet-Derived Apoptotic Vesicles Promote Bone Regeneration via Golgi Phosphoprotein 2 (GOLPH2)-AKT Signaling Axis

Apoptotic vesicles (apoVs) are apoptotic-cell-derived nanosized vesicles that take on dominant roles in regulating bone homeostasis. We have demonstrated that mesenchymal stem cell (MSC)-derived apoVs are promising therapeutic agents for bone regeneration. However, clinical translation of MSC-derived apoVs has been hindered due to cell expansion and nuclear substance. As another appealing source for apoV therapy, blood cells could potentially eliminate these limitations. However, whether blood cells can release apoVs during apoptosis is uncertain, and the detailed characteristics and biological properties of respective apoVs are not elucidated. In this study, we showed that platelets (PLTs) could rapidly release abundant apoVs during apoptosis in a short time. To recognize the different protein expressions between PLT-derived apoVs and PLTs, we established their precise protein landscape. Furthermore, we identified six proteins specifically enriched in PLT-derived apoVs, which could be considered as specific biomarkers. More importantly, PLT-derived apoVs promoted osteogenesis of MSCs and rescued bone loss via Golgi phosphoprotein 2 (GOLPH2)-induced AKT phosphorylation, therefore, leading to the emergence of their potential in bone regeneration. In summary, we comprehensively determined characteristics of PLT-derived apoVs and confirmed their roles in bone metabolism through previously unrecognized GOPLH2-dependent AKT signaling, providing more understanding for exploring apoV-based therapy in bone tissue engineering.

Macrophage-hitchhiked arsenic/AB bionic preparations for liver cancer

Macrophage-hitchhiked arsenic/AB bionic preparations were developed to improve the therapeutic effect on liver cancer by means of the tumor-targeting ability of macrophages in vivo. In vitro and in vivo cellular uptake assays demonstrated that arsenic/AB, with negatively charged particles of around 100-200 nm size, could hitchhike to macrophages. Dissolution experiments of arsenic/AB showed that arsenic/AB could delay the release of arsenic and ensure the safety of macrophages during its transport. Histological examination confirmed the safety of the preparations for major organs. In vivo distribution experiment showed that the arsenic/AB bionic preparations could rapidly accumulate in tumors, and in vivo treatment experiment showed a significant tumor inhibition of arsenic/AB. The therapeutic mechanism of liver cancer might be that the arsenic/AB bionic preparations could inhibit tumor growth by reducing inflammatory response and inhibiting CSF1 secretion to block CSF1R activation to induce more differentiation of tumor-associated macrophages (TAMs) towards the anti-tumor M1 phenotype. Therefore, we concluded that the arsenic/AB bionic preparations could improve the distribution of arsenic in vivo by hitchhiking on macrophages as well as make it have tumor targeting and deep penetration abilities, thus increasing the therapeutic effect of arsenic on liver cancer with reduced side effects.

Impaired Efferocytosis Enables Apoptotic Osteoblasts to Escape Osteoimmune Surveillance During Aging

Macrophage efferocytosis of apoptotic osteoblasts (apoOBs) is a key osteoimmune process for bone homeostasis. However, apoOBs frequently accumulate in aged bone marrow, where they may mount proinflammatory responses and progressive bone loss. The reason why apoOBs are not cleared during aging remains unclear. In this study, it is demonstrated that aged apoOBs upregulate the immune checkpoint molecule CD47, which is controlled by SIRT6-regulated transcriptional pausing, to evade clearance by macrophages. Using osteoblast- and myeloid-specific gene knockout mice, SIRT6 is further revealed to be a critical modulator for apoOBs clearance via targeting CD47-SIRPα checkpoint. Moreover, apoOBs activate SIRT6-mediated chemotaxis to recruit macrophages by releasing apoptotic vesicles. Two targeting delivery strategies are developed to enhance SIRT6 activity, resulting in rejuvenated apoOBs clearance and delayed age-related bone loss. Collectively, the findings reveal a previously unknown linkage between immune surveillance and bone homeostasis and targeting the SIRT6-regulated mechanism can be a promising therapeutic strategy for age-related bone diseases.

ApoSEVs-Mediated Modulation of Versatile Target Cells Promotes Diabetic Wound Healing: Unveiling a Promising Strategy

Background

Diabetic chronic wounds present a formidable challenge in clinical management, lacking effective treatment options. Mesenchymal stem cell (MSC) transplantation has emerged as a promising therapy for tissue repair and regeneration. However, transplanted MSCs often undergo rapid apoptosis, giving rise to heterogeneous extracellular vesicles (EVs), including apoptotic bodies (apoBDs) and apoptotic small extracellular vesicles (apoSEVs). The potential stimulatory role of these EVs in diabetic wound healing remains unknown.

Methods

In this study, we investigated the effects of apoSEVs derived from adipose-derived mesenchymal/stromal cells (ADSCs) on the recovery of diabetic wounds by modulating the function of versatile target cells. First, we characterized the apoSEVs and apoBDs derived from apoptotic ADSCs. Subsequently, we evaluated the effects of apoSEVs and apoBDs on macrophages, endothelial cells, and fibroblasts, three essential cell types in wound healing, under high-glucose conditions. Furthermore, we developed a gelatin methacryloyl (GelMA) hydrogel for the sustained release of apoSEVs and investigated its therapeutic effects on wound healing in type 2 diabetic mice in vivo.

Results

apoSEVs facilitated the polarization of M1 phenotype macrophages to M2 phenotype, promoted proliferation, migration, and tube formation of endothelial cells, and enhanced fibroblast proliferation and migration. However, apoBDs failed to improve the function of endothelial cells and fibroblasts. In vivo, the apoSEVs-loaded GelMA effectively promoted wound healing by facilitating collagen fiber deposition, angiogenesis, and immune regulation.

Conclusion

Our study elucidates the beneficial effects of apoSEVs on wound recovery in diabetes and introduces a novel strategy for diabetic wound treatment based on apoSEVs.

Hepatic Macrophages as Targets for the MSC-Based Cell Therapy in Non-Alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a serious public health issue associated with the obesity pandemic. Obesity is the main risk factor for the non-alcoholic fatty liver disease (NAFLD), which progresses to NASH and then to end-stage liver disease. Currently, there are no specific pharmacotherapies of NAFLD/NASH approved by the FDA or other national regulatory bodies and the treatment includes lifestyle adjustment and medicines for improving lipid metabolism, enhancing sensitivity to insulin, balancing oxidation, and counteracting fibrosis. Accordingly, further basic research and development of new therapeutic approaches are greatly needed. Mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles prevent induced hepatocyte death in vitro and attenuate NASH symptoms in animal models of the disease. They interact with hepatocytes directly, but also target other liver cells, including Kupffer cells and macrophages recruited from the blood flow. This review provides an update on the pathogenesis of NAFLD/NASH and the key role of macrophages in the development of the disease. We examine in detail the mechanisms of the cross-talk between the MSCs and the macrophages, which are likely to be among the key targets of MSCs and their derivatives in the course of NAFLD/NASH cell therapy.

Lyophilized apoptotic vesicle-encapsulated adhesive hydrogel sponge as a rapid hemostat for traumatic hemorrhage in coagulopathy

Rapid hemostasis of uncontrolled bleeding following traumatic injuries, especially accompanied by coagulopathies, remains a significant clinical challenge. Extracellular vesicles (EVs) show therapeutic effects for fast clotting. However, low yield, specific storage conditions, and lack of proper carriers have hindered EVs' clinical application. Herein, we establish an optimized procedure method to generate lyophilized mesenchymal stem cell-derived apoptotic vesicles (apoVs) with adhesive hydrogel sponge to show superior procoagulant activity for traumatic hemorrhage. Mechanistically, apoVs' procoagulant ability stems from their high tissue factor (TF) and phosphatidylserine (PS) expression independent of hemocytes and circulating procoagulant microparticles (cMPs). Their stable hemostatic capability was maintained after 2-month room temperature storage. Subsequently, we mixed apoVs with both phenylboronic acid grafted oxidized hyaluronic acid (PBA-HA) and poly(vinyl alcohol) (PVA) simultaneously, followed by lyophilization to construct a novel apoV-encapsulated hydrogel sponge (apoV-HS). Compared to commercial hemostats, apoV-HS exhibits rapid procoagulant ability in liver-laceration and femoral artery hemorrhage in rat and rabbit models of coagulopathies. The combination of high productivity, physiological stability, injectability, plasticity, excellent adhesivity, biocompatibility, and rapid coagulant property indicates that apoV-HS is a promising therapeutic approach for heavy hemorrhage in civilian and military populations.

Apoptotic Vesicles of MSCs: The Natural Therapeutic Agents and Bio-Vehicles for Targeting Drug Delivery

Mesenchymal stem cell (MSC)-based therapies are increasingly recognized as promising cellular therapeutics and show the ability to treat various diseases. However, the underlying mechanism is not fully elucidated. Some recent studies have shown an unexpected result whereby MSCs undergo rapid apoptosis following administration but still exert therapeutic effects in some disease treatments. Such a therapeutic mechanism is believed to associate with the released apoptotic vesicles from apoptotic MSCs (MSC-ApoVs). This finding inspires a novel therapeutic strategy for using MSC-ApoVs for disease treatment. The present review aims to summarize the biogenesis, physiological functions, therapeutic potentials, and related mechanisms of apoptotic vesicles in MSC-based therapy. In addition, the potential applications of MSC-ApoVs as natural therapeutic agents and natural drug delivery vehicles are proposed and highlighted. The present review is hoped to provide a general understanding of MSC-ApoVs in disease treatment and inspire potential applications in targeted drug delivery.

Encapsulation of Nano-Bortezomib in Apoptotic Stem Cell-Derived Vesicles for the Treatment of Multiple Myeloma

Extracellular vesicles (EVs) are lipid bilayer nanovesicles released from living or apoptotic cells that can transport DNA, RNA, protein, and lipid cargo. EVs play critical roles in cell-cell communication and tissue homeostasis, and have numerous therapeutic uses including serving as carriers for nanodrug delivery. There are multiple ways to load EVs with nanodrugs, such as electroporation, extrusion, and ultrasound. However, these approaches may have limited drug-loading rates, poor EV membrane stability, and high cost for large-scale production. Here, it is shown that apoptotic mesenchymal stem cells (MSCs) can encapsulate exogenously added nanoparticles into apoptotic vesicles (apoVs) with a high loading efficiency. When nano-bortezomib is incorporated into apoVs in culture-expanded apoptotic MSCs, nano-bortezomib-apoVs show a synergistic combination effect of bortezomib and apoVs to ameliorate multiple myeloma (MM) in a mouse model, along with significantly reduced side effects of nano-bortezomib. Moreover, it is shown that Rab7 regulates the nanoparticle encapsulation efficiency in apoptotic MSCs and that activation of Rab7 can increase nanoparticle-apoV production. In this study, a previously unknown mechanism to naturally synthesize nano-bortezomib-apoVs to improve MM therapy is revealed.

Harnessing strategies for enhancing diabetic wound healing from the perspective of spatial inflammation patterns

Diabetic wound is a great threat to patient's health and lives. The refractory diabetic wound shows spatial inflammation patterns, in which the early-wound pattern depicts a deprived acute inflammatory response, and the long-term non-healing wound pattern delineates an excessive and persistent inflammation due to the delayed immune cell infiltration in a positive feedback loop. In this work, we give points to some strategies to normalize the dysregulated immune process based on the spatial inflammation pattern differences in diabetic wound healing. First of all, inhibiting inflammatory response to avoid subsequent persistent and excessive immune infiltration for the early diabetic wound is proposed. However, diabetic wounds are unperceptive trauma that makes patients miss the best treatment time. Therefore, we also introduce two strategies for the long-term non-healing diabetic wound. One strategy is about changing chronic wounds to acute ones, which aims to rejuvenate M1 macrophages in diabetic wounds and make spontaneous M2 polarization possible. To activate the controllable proinflammatory response, western medicine delivers proinflammatory molecules while traditional Chinese medicine develops "wound-pus promoting granulation tissue growth theory". Another strategy to solve long-term non-healing wounds is seeking switches that target M1/M2 transition directly. These investigations draw a map that delineates strategies for enhancing diabetic wound healing from the perspective of spatial inflammation patterns systematically.

Cell culture-derived extracellular vesicles: Considerations for reporting cell culturing parameters

Cell culture-conditioned medium (CCM) is a valuable source of extracellular vesicles (EVs) for basic scientific, therapeutic and diagnostic applications. Cell culturing parameters affect the biochemical composition, release and possibly the function of CCM-derived EVs (CCM-EV). The CCM-EV task force of the Rigor and Standardization Subcommittee of the International Society for Extracellular Vesicles aims to identify relevant cell culturing parameters, describe their effects based on current knowledge, recommend reporting parameters and identify outstanding questions. While some recommendations are valid for all cell types, cell-specific recommendations may need to be established for non-mammalian sources, such as bacteria, yeast and plant cells. Current progress towards these goals is summarized in this perspective paper, along with a checklist to facilitate transparent reporting of cell culturing parameters to improve the reproducibility of CCM-EV research.

Advances in biological functions and applications of apoptotic vesicles

BACKGROUND

Apoptotic vesicles are extracellular vesicles generated by apoptotic cells that were previously regarded as containing waste or harmful substances but are now thought to play an important role in signal transduction and homeostasis regulation.

METHODS

In the present review, we reviewed many articles published over the past decades on the subtypes and formation of apoptotic vesicles and the existing applications of these vesicles.

RESULTS

Apoptotic bodies were once regarded as vesicles released by apoptotic cells, however, apoptotic vesicles are now regarded to include apoptotic bodies, apoptotic microvesicles and apoptotic exosomes, which exhibit variation in terms of biogenesis, sizes and properties. Applications of apoptotic vesicles were first reported long ago, but such reports have been rarer than those of other extracellular vesicles. At present, apoptotic vesicles have been utilized mainly in four aspects, including in direct therapeutic applications, in their engineering as carriers, in their construction as vaccines and in their utilization in diagnosis.

CONCLUSION

Building on a deeper understanding of their composition and characteristics, some studies have utilized apoptotic vesicles to treat diseases in more novel ways. However, their limitations for clinical translation, such as heterogeneity, have also emerged. In general, apoptotic vesicles have great application potential, but there are still many barriers to overcome in their investigation. Video Abstract.

Umbilical cord mesenchymal stem cell-derived apoptotic extracellular vesicles ameliorate cutaneous wound healing in type 2 diabetic mice via macrophage pyroptosis inhibition

BACKGROUND

Delayed healing of diabetic cutaneous wounds is one of the most common complications of type 2 diabetes mellitus (T2DM), which can bring great distress to patients. In diabetic patients, macrophages accumulate around skin wounds and produce NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) inflammasomes, which in turn undergo pyroptosis and produce inflammatory factors such as interleukin-1β that affect wound healing. Although our previous study revealed that apoptotic extracellular vesicles (ApoEVs) produced from mesenchymal stem cells (MSCs) improve cutaneous wound healing in normal C57BL/6 mice, whether ApoEVs can also improve diabetic wound healing remains unclear.

METHODS

Umbilical cord mesenchymal stem cells (UCMSCs) were cultured in vitro and apoptosis was induced. ApoEVs were extracted and identified and used in a T2DM mouse cutaneous wound model to evaluate the efficacy. The inhibitory effect of ApoEVs on macrophage pyroptosis was verified in vivo and in vitro, and the level of oxidative stress in macrophages was assessed to explore the mechanism by which ApoEVs play a role.

RESULTS

UCMSC-derived ApoEVs improved skin defect healing in T2DM mice. Moreover, UCMSC-derived ApoEVs inhibited macrophage pyroptosis in T2DM mice in vivo as well as in vitro under high-glucose culture conditions. In addition, we demonstrated that ApoEVs reduce oxidative stress levels, which is a possible mechanism by which they inhibit macrophage pyroptosis.

CONCLUSIONS

Our study confirmed that local application of UCMSC-derived ApoEVs improved cutaneous wound healing in T2DM mice. ApoEVs, as products of MSC apoptosis, can inhibit macrophage pyroptosis and regulate the death process by decreasing the level of oxidative stress.