Exosomes originate from endosomal vesicles within the cell and exhibit distinctive characteristics that set them apart from other cell-secreted microvesicles (103). They are enclosed by a phospholipid bilayer architecture, with a size ranging from 30 to 150 nanometers and a density falling within the range of 1.13 to 1.19 grams per milliliter (104, 105). When observed through transmission electron microscopy (TEM), exosomes present a cup-shaped morphology, further confirming their identity. Moreover, the presence of specific proteins, including tetraspanins (e.g., CD63, CD9, and CD81) and β-actin, serves as additional markers to differentiate exosomes from other vesicular structures (101, 104). To emphasize their prevalence, it is noteworthy that approximately 1 × 10¹² exosomes can be found in just 1 milliliter of blood (105). These distinct characteristics and abundance make exosomes a subject of significant interest in various fields of research and clinical applications (106).

Exosome biogenesis is a highly regulated process that occurs in various cell types under both pathological and physiological conditions. The secretion of exosomes is governed by the modulation of Rab27a and Rab27b expression (107). A diverse array of cell types, including lymphocytes, dendritic cells, fibroblasts, erythrocytes, platelets, mast cells, tumor cells, stem cells, monocytes, macrophages, natural killer (NK) cells, B lymphocytes, and T lymphocytes, are known to synthesize exosomes (108).

The process of exosome biogenesis commences with the internalization of the cell membrane, leading to the formation of small intracellular structures referred to as early endosomes (103–107). Early endosome development involves a progressive maturation process that culminates in the generation of intraluminal vesicles (ILVs). On the other hand, late endosomes, known as multivesicular bodies (MVBs), are formed through the inward folding of segments of the endosomal membrane (106). The fusion of MVBs with the plasma membrane results in the exocytotic release of ILVs into the extracellular space, where they ultimately undergo transformation into exosomes (99–102, 105). This intricate process is visually depicted in Figure 1.

Notably, exosomes are present in a variety of physiological fluids, including serum, as well as in saliva, amniotic fluid, and breast milk (106). Their presence in these fluids underscores the ubiquity of exosomes in biological systems and their potential significance in various biological and clinical contexts.

Exosomes, which are minuscule in size and invisible to the naked eye and standard light microscopes, can only be observed using electron microscopy. Their morphology is characterized by flattened spheres, which can result from the dehydration process required for electron microscopy preparation, leading to their collapse (108, 109). Exosomes are complex structures composed of proteins, particularly those derived from the plasma or endosomal membrane, lipids, and various cytosolic components (Figure 2). It’s important to note that exosomes lack proteins originating from the Golgi apparatus, nuclear pore complex, mitochondria, and endoplasmic reticulum (Figure 2). Exosomes lack proteins of the Golgi apparatus, nuclear pore complex, mitochondria and endoplasmic reticulum (110). Data on exosomal content are systematically curated and updated in databases such as ExoCarta, Vesiclepedia, and EVpedia (111). Although initial investigations suggest the presence of proteins from the cytosol, endosomes, and plasma membrane in exosomes, it is essential to acknowledge that cellular organelles such as mitochondria, the Golgi apparatus, or the nucleus do not exclusively consist of proteins. The establishment of exosomal protein databases has been a collaborative effort among multiple research teams. Exosome repositories like ExoCarta¹ and Vesiclepedia² have cataloged a total of 9,769 proteins, 1,116 lipids, 3,408 mRNAs, and 2,838 miRNAs within exosomes originating from various cellular sources and organisms up to the present day (110). Exosome protein sorting, a newly explored field of study, relies, at least in part, on the endosomal sorting complex required for transport (ESCRT) machinery and protein ubiquitylation (112). During exosome biogenesis, ESCRT orchestrates the formation of intricate structures on the plasma membrane, resembling membranous necks. These structures encompass conical funnels, tubular arrangements, planar spirals, and filaments, which are hypothesized to regulate membrane remodeling processes.

Exosomes encompass a substantial number of transport proteins, including tubulin, actin, and actin-binding molecules (110), in addition to various proteins intricately involved in specific roles within secretory cells (113). Exosomal proteins are categorized into diverse groups based on their family, function, and subcellular localization (114). The most frequently encountered protein categories in exosomes include those related to (i) the formation of multivesicular bodies (MVBs), (ii) transmembrane proteins acting as targeting or adhesion molecules, such as tetraspanins like CD9, CD63, and CD81, which play roles in membrane fusion, (iii) signal transduction proteins such as annexin and 14-3-3 proteins, (iv) cytoskeletal proteins including actin, syntenin, and myosin, (v) chaperones like HSPA8 and HSP90, and (vi) metabolic enzymes, such as GAPDH, LDHA, PGK1, aldolase, and PKM (111, 113). Each individual exosome also contains MHC class I molecules, among distinct components (114), and heat shock proteins (112). These proteins participate in antigen presentation and antigenic peptide attachment to MHC class I molecules (113). Tetraspanin family members CD9, CD63, CD81, and CD82 interact with other transmembrane proteins to facilitate antigen presentation and adhesion. The interaction of CD9 and CD82 with integrins can inhibit the migration and invasion of tumor cells (111). Exosomes exhibit distinctive lipid compositions in addition to their protein content (113). Intriguingly, they are deficient in lysobisphosphatidic acid and intraluminal vesicle (ILV) lipids (115) but contain high levels of sphingomyelin, phosphatidylserine, ceramide, and cholesterol.

Exosomes are recognized for their substantial content of DNA and RNA, alongside lipids and proteins. The term “EV-DNA” refers to DNA enclosed within EVs, spanning a size range of 100 base pairs to 2.5 kilobases (115). Analysis of complete RNA sequencing data from EVs isolated from serum suggests that RNA repeats constitute approximately 50% of the total EV-RNA content. Additionally, miRNAs and tRNAs are estimated to account for up to 15% of the EV-RNA content (115, 116). Certain RNAs are found in higher concentrations in exosomes than in the originating cells, particularly in exosomes from MSCs (116). Numerous studies have provided evidence that RNA can indeed be transferred between cells via exosomes (117). However, the extent to which transferred RNA retains its functionality in recipient cells, as well as the proportion that undergoes fragmentation and subsequent transport, remains an area of ongoing investigation.

The subcortical endothelium of the umbilical cord, Wharton’s jelly (WJ), and the perivascular area are the primary locations where UC-MSCs are commonly found. Wharton’s Jelly has a structure primarily resembling a sponge, with collagen fibers, proteoglycans, and stromal cells intertwined within it (20). When analyzing UC-MSCs from Wharton’s Jelly using flow cytometry, it was discovered that CD24 and CD108 were abundantly expressed, while the dermal fibroblast marker CD40 and fibroblast-specific markers (FAP and FSP) were not discernible, which highlights the abundance of MSCs in the Wharton’s Jelly region (128, 129). UC-MSCs can exhibit distinctive markers corresponding to various cell lineages, exemplifying their pluripotent nature (130). In contrast to hematopoietic stem cells, UC-MSCs exhibit the expression of MSC-specific markers such as CD105, CD90, and CD73, along with adhesion molecule markers including CD54, CD13, CD29, and CD44. Conversely, UC-MSCs shows reduced or absent expression of surface antigens CD31, CD14, CD34, and CD45 (131). Additionally, these cells are deficient in immune response-related antigens necessary for T lymphocyte activation, including CD80, CD86, CD40, and CD40L, as well as the MHC class II antigen HLA-DR. (132) UC-MSCs exhibit reduced immunogenicity compared to BM-derived cells due to their considerably lower expression levels of CD106 and HLA-ABC (133).

WJ-MSCs, which exhibited the highest proliferation rate, outperformed adipose tissue and BM-MSCs by a factor of three to four in terms of proliferation (134). Based on the inquiry conducted by the Mennan research team, no significant disparity in the rate of proliferation was observed. The population of UC-MSCs exhibited an average twofold increase between passages P0 and P3 within a span of 2–3 days. This rate of expansion significantly exceeds the duration observed for BM-MSCs (135). UC-MSCs have the capacity for multidirectional differentiation, enabling them to differentiate into various tissues such as bone, fat, cartilage, and others (136). Therefore, in the field of regenerative medicine, these cells are considered ideal seed cells due to their potential to facilitate the healing of various tissues and organs (137). According to studies, chemokines are produced by biological tissues that undergo damage due to ischemia-anoxia or persistent inflammation (138). These chemokines aid in recruiting MSCs to the injury site and subsequently regulate their migration to facilitate their differentiation into various cell lineages (139). Under specific conditions in an in vitro setting, UC-MSCs have been observed to exhibit the ability to undergo “trans-differentiation,” resulting in their differentiation into osteoblast-like mesodermal cell types (140), endothelial cells (141), cardiomyocytes (142), as well as ectoderm-derived hepatocytes with potential for neuronal transformation (143), and pancreatic cells (144), bridging the germinal layers within the endoderm.

To maximize the therapeutic effects of EVs, it is essential for researchers to isolate and characterize them. The isolation and characterization of hUC-MSC-EVs hold great importance for their potential therapeutic use in IBD and other associated illnesses (145). However, the extraction of EVs from biological fluids, such as serum or conditioned media, can be challenging due to the heterogeneity of EV populations and the presence of impurities (93). In response to this challenge, various methodologies have been developed to achieve optimal purity and cost-effectiveness of EVs. These techniques include ultracentrifugation, density gradient centrifugation, and size-exclusion chromatography, all aiming to achieve high levels of purity (146). Ultracentrifugation, are commonly used technique for EV extraction, involves differential centrifugation at high speeds, reaching up to 100,000 x g, to pellet EVs (147). This method can be further optimized by utilizing sucrose or iodixanol gradients to separate EVs from other subcellular components (148). Another technique, density gradient centrifugation, employs a continuous gradient to separate EVs based on their buoyant density. This method is often used for isolating specific EV subpopulations, such as exosomes (149). Size-exclusion chromatography (SEC) is another method used for EV isolation, where EVs are separated based on their size characteristics. This technology is useful for removing unwanted contaminants, such as proteins and lipoproteins, which may be present during the isolation process (150). Once the isolation process is complete, hUC-MSC-EVs can be characterized by analyzing their physical and biochemical properties. Physical characterization includes assessing various attributes of EVs, such as their dimensions, structure, and abundance. Techniques such as dynamic light scattering (DLS), transmission electron microscopy (TEM), and nanoparticle tracking analysis (NTA) are commonly employed for this purpose (151). Biochemical characterization involves the detection and analysis of specific EV markers, including CD9, CD63, and CD81, using techniques like western blotting, flow cytometry, or immunogold labeling (152). Furthermore, the cargo of hUC-MSC-EVs can be characterized through proteomics, RNA sequencing, and lipidomics, providing insights into their functional properties and potential therapeutic targets (153).

It is important to acknowledge the inherent challenges associated with the extraction and characterization of EVs, which stem from the diverse nature of EV populations and the potential risk of contamination (154). Therefore, it is crucial to employ a range of isolation and characterization methodologies to ensure the integrity and homogeneity of hUC-MSC-EVs for their potential clinical application. By improving separation and characterization techniques and tailoring the cargo of EVs to therapeutic targets, researchers can develop novel IBD medications that are more effective and exhibit fewer side effects than current treatments. For a comprehensive overview of different techniques for exosome isolation and characterization, please refer to Table 2.

At the site of intestinal inflammation, MSC-Exos bind to macrophages and release encapsulated miRNA, which in turn selectively modulates the mRNA within macrophages and influences the polarization of M2 macrophages. Research has demonstrated that the ExomiRNAs of MSCs, including miR-146a, can downregulate the expression of TNF receptor-related factor 6 (TRAF-6) and IL-1 receptor-related kinase 1 (IRAK-1), thereby suppressing the release of proinflammatory cytokines and promoting the expression of the anti-inflammatory factor IL-10 (192).

MSC-Exo contains a multitude of proteins, notably metallothionein-2 (MT-2), renowned for its capacity to suppress colitis activity. This protein plays a pivotal role in mitigating the intestinal inflammatory response by upholding the integrity of the intestinal barrier and fostering the polarization of M2b macrophages (179).

MSC-Exos penetrate macrophages, potentially triggering the myeloid differentiation primary response gene 88 (MyD88)-dependent signaling pathway in macrophages upon recognition of TLR3 by the enclosed dsRNA. This activation leads to the induction of M2 polarization in macrophages, the release of anti-inflammatory factors, and the inhibition of the inflammatory response (193).

In the presence of inflammatory stimuli, the interaction between CC chemokine receptor 2 (CCR2) expressed on the surface of monocytes and CC chemokine ligand 2 expressed on the surface of macrophages triggers the migration of monocytes to inflammatory sites, where they transform into macrophages, thereby intensifying the inflammatory response and exacerbating tissue damage. Notably, MSC-Exos exhibit high expression of CCR2, which competitively binds to the chemokine ligand 2 on the surface of macrophages. This competitive binding inhibits the recruitment and activation of monocytes, prevents the polarization of M1 macrophages, and reduces the expression of proinflammatory cytokines, such as IL-1β, IL-6, and TNF-α, thereby effectively restraining inflammatory responses (194).

Firstly, MSC-Exos derived from MSCs, induced by specific inflammatory factors, encapsulate numerous anti-inflammatory cytokines and chemokines. Upon uptake by macrophages, these components are released into the surrounding environment. Secondly, the aforementioned pathways, once activated, govern or initiate the polarization of M2 macrophages, leading to the upregulation of anti-inflammatory cytokines and the downregulation of proinflammatory cytokines. This orchestration serves to sustain the equilibrium of anti-inflammatory factors at inflammatory sites and effectively suppress excessive inflammatory responses (195).

Th1 and Th2 cells represent the two primary subtypes of Th0 differentiation. Th1 cells primarily express IFN-γ and IL-12, while Th2 cells predominantly express IL-4 (196, 197). The dysregulation of Th1/Th2 subsets is intricately linked to the chronic inflammation observed in IBD (197, 198). The direction of differentiation is largely influenced by the concentration of IL-12 in the environment and the activation status of antigen-presenting cells. Through the regulation of DCs and macrophages, MSC-Exos induce the polarization of M2 macrophages, impede the antigen presentation of DCs, and diminish the release of proinflammatory cytokines, such as IL-12. This environment is conducive to the transition of T cells into Th2 cells. Studies have demonstrated that MSC-Exos can markedly diminish the expression of IL-12, hinder the differentiation and proliferation of Th1 cells, and facilitate the transition of T cells into Th2 cells following co-cultivation with T cells activated by phytohemagglutinin (199, 200). Furthermore, research has revealed that the TSG-6 protein detected in hUC-MSC-exo regulates the immune response of Th2 and Th17 cells in mesenteric lymph nodes (MLN), downregulates proinflammatory cytokines in colon tissue, and upregulates anti-inflammatory cytokines, thereby safeguarding the integrity of the intestinal barrier (162).

Treg cells play a pivotal role in inhibiting the transformation of effector T cells and adaptive mucosal immunity in the intestine, thereby reducing immune-related tissue damage in IBD. A study has revealed that MSC-Exos induce T lymphocyte apoptosis and modulate the differentiation and proliferation of Treg cells through programmed death ligand and galactosin-1 (201). Treg cells express anti-inflammatory cytokines, such as IL-10 and TGF-β, to achieve immunosuppressive effects (193, 202, 203). In contrast, Th17 cells express proinflammatory cytokines that contribute to the inflammatory activity in IBD. Notably, the ratio of Th17/Treg in the peripheral blood of IBD patients has been found to be significantly increased, as demonstrated (204). Furthermore, Chen et al. (133) discovered a significant increase in the ratio of Th17/Treg cells in the mesenteric lymphoid tissue of colitis rats. Conversely, the ratio of Th17/Treg cells was markedly decreased, leading to a notable amelioration of colitis after the injection of MSC-Exos via the caudal vein (180, 205). Additionally, it was found that adipose-MSC-Exos (AD-MSC-Exos) can restore the proportion of Treg cells in the spleen of the IBD mouse model to the baseline level, akin to that of normal mice, and also improve the inflammation of dextran sulfate sodium (DSS)-induced colitis (166).

The intestinal barrier encompasses the IEB, mucosal innate immune system, intestinal mucus, and intestinal microbiota. The IEB, constituted by the tight junctions of IECs, forms a crucial mechanical barrier and represents the most pivotal component of the intestinal barrier. Dysregulation and disturbances in various aspects, including mucosal immunity, surface mucus, intestinal microbiota, and oxidative stress, can compromise the integrity of the IEB, leading to the necrosis and apoptosis of IECs and an escalation in wall permeability. These changes underlie the pathological alterations observed in IBD (213–216). MSC-Exos exhibit the capacity to repair IEC injury, inhibit IEC apoptosis, preserve the equilibrium of oxidative stress, and diminish intestinal wall permeability, thereby facilitating the restoration of the IEB, refer to Figure 6.

Colonic fibrosis is a chronic complication of IBD, with more than 30% of CDpatients developing fibrosis, which rapidly leads to intestinal stenosis and adversely impacts patient prognosis (228, 229). Pathological stimuli such as chronic intestinal inflammation, oxidative stress, damage to and repair of the IEB, promote epithelial-mesenchymal transition (EMT). This transition involves the loss of epithelial cell polarity and intercellular connections, morphological and functional transformation, and significant extracellular matrix (ECM) accumulation, culminating in intestinal fibrosis (230). During tissue repair or response, fibroblast activation is crucial for fibrosis development (230). The TGF-β signaling pathway has been identified as a key activator of fibroblasts, inducing their differentiation into myofibroblasts, which is central to the pathogenesis of intestinal fibrosis (231). Yang et al. (232) demonstrated that BM-MSC-Exos can significantly reverse EMT in TGF-β1-treated (IEC-6) through miR-200b, thereby mitigating intestinal fibrosis. Various studies have shown that MSCs from different sources regulate EMT by activating TGF-β and Wnt signaling pathways, reducing ECM aggregation, and exerting antifibrotic effects (233). While MSCs have been shown to reduce fibrosis in the heart, lungs, liver, and kidneys, research on their effects on intestinal fibrosis remains limited (234). Choi et al. (234) hUCMSC-Exos suppress TGF-β1-induced fibroblast activation by inhibiting the Rho/MRTF/SRF pathway, thereby reducing intestinal fibrosis. Additionally, Duan and Cao (235) discovered that human placental MSC-Exos can decrease collagen deposition in the intestinal wall by reducing collagen production and promoting its degradation through inhibition of TGF-β1 protein expression.

The induction of M1 to M2 phenotypic transition in bone marrow-derived macrophages (BM-DM) can be effectively achieved through the utilization of hUC-MSC-derived exosomes, which are characterized by an average particle size of 70 nm. In vivo studies have provided compelling evidence that hUC-MSC-derived exosomes facilitate the process of functional recuperation subsequent to SCI through the downregulation of inflammatory cytokines, including TNF-α, MIP-1, IL-6, and IFN-γ (61). The role of hUC-MSC-exo in the transformation of macrophages from the M1 to the M2 phenotype has been established (236). Intravenous administration of these exosomes shows promise as a therapeutic approach for mitigating inflammation and facilitating the restoration of locomotor function following SCI. These findings highlight the potential of exosomes to significantly contribute to the future of SCI therapy (237).

In the treatment of SCI mice, hUC-MSC transplantation has been shown to greatly enhance the survival and regeneration of myelin and nerve cells in the injured area of the spinal cord (238). This transplantation approach also leads to a significant improvement in the motor function of the animals. These positive therapeutic outcomes may be attributed, at least in part, to the effects of hUC-MSC transplantation, which include reducing the production of IL-7 at the site of injury, enhancing the activation of M2 macrophages, and preventing inflammatory infiltration (239). A study conducted in 2022 suggests that the ability of hUC-MSCs to modulate the inflammatory response following nerve injury plays a critical role in their effectiveness in treating acute SCI. This information may guide future applications of hUC-MSCs and enhance the effectiveness of their clinical translation (240). Moreover, hUC-MSC-EVs, acting through the miR-29b-3p/PTEN/Akt/mTOR axis, have demonstrated the ability to reduce pathological alterations, enhance motor function, and promote nerve function repair in SCI rats (241).

Globally, traumatic brain injury (TBI) is a leading cause of fatalities and long-term impairment (242). TBI treatments have recently gained significant attention. However, the therapeutic application of hUC-MSC transplantation in TBI has been limited by challenges such as immunological rejection, ethical considerations, and the potential for tumorigenicity. Notably, hUC-MSC-exo have demonstrated the ability to enhance neurological performance, reduce cerebral edema, and decrease lesion volume following TBI (243). According to a study, hUC-MSC-exo may provide neuroprotection against TBI by exerting inhibitory effects on cell death processes, including apoptosis, pyroptosis, and ferroptosis, through the PINK1/Parkin-mediated mitophagy pathway (238). Recent studies have shed light on the emerging significance of pyroptosis in the context of brain damage. It has been demonstrated that pyroptosis plays a significant role in the development of neonatal cerebral ischemia-reperfusion (I/R) injury, exerting a substantial influence on the pathological processes involved (244). hUC-MSC-exo possesses the potential to mitigate apoptosis following TBI, reduce neuroinflammation, and promote neurogenesis (245). In order to evaluate the efficacy of exosome therapy in facilitating neurological recovery, a rat model of TBI was established. Subsequent analysis revealed a significant improvement in sensorimotor function and spatial learning in rats upon administration of hUC-MSC-exo (246). Moreover, through the inhibition of the NF-kB signaling pathway, hUC-MSC-exo exhibited a substantial reduction in the synthesis of proinflammatory cytokines. Furthermore, noteworthy observations were made regarding the neuroprotective effects of hUC-MSC-exos, including the prevention of neuronal apoptosis, attenuation of inflammation, and facilitation of neuronal regeneration within the injured cortex of rats subjected to TBI (247).

A myocardial infarction (MI) is a significant inflammatory disorder triggered by an imbalance in substrate and oxygen supply versus demand, leading to ischemia or cellular demise (248, 249). Despite the frequent utilization of early revascularization and the widespread implementation of quality measures, notable variations exist at the local and regional levels regarding the management and outcomes of MI (250, 251). The therapeutic effectiveness of stem cell-based therapy in MI for the purposes of heart repair and regeneration has been substantiated through preclinical investigations as well as clinical trials (252). A potential therapeutic approach for MI involves the utilization of MSC-EVs. To investigate the effects of hUC-MSC-EVs loaded with miR-223 in the context of MI, experiments were conducted employing both an in vitro cellular model of oxidative stress and cardiac fibrosis, as well as in vivo rat models of MI. The transfer of miR-223 via EVs demonstrated improved cardiac function in MI rat models, along with reduced fibrosis and inflammation (253). The pathogenesis of MI is primarily attributed to the presence of inflammation, wherein the detrimental effects of MI are intricately associated with the orchestrated activation of multiple inflammatory cascades and the recruitment of inflammatory cells (254). Before the widespread implementation of cardiomyocyte regeneration in clinical trials, substantial further research and development are required. In the realm of cell therapy, extensive investigations have been conducted to explore the differentiating capabilities of (hUC-MSCs). It is widely recognized that the utilization of 5-Azacytidine (5-Aza) effectively triggers the differentiation of hUC-MSCs into cardiomyocytes, resulting in morphological changes and the expression of cardiac-specific proteins, irrespective of the presence of basic fibroblast growth factor (bFGF) (255). An additional investigation has revealed that 5-Azacytidine (5-Aza) may facilitate the in vitro differentiation of hUC-MSCs into cardiomyocytes through the sustained phosphorylation of extracellular signal-regulated kinase (ERK) (256). Recent scientific investigations have demonstrated that the administration of injected hUC-MSCs exerts beneficial effects on cardiac function in rats with dilated cardiomyopathy (DCM) through the attenuation of myocardial fibrosis and dysfunction. These effects are achieved by the downregulation of Transforming Growth Factor-β1 (TGF-β1) and TNF-α production (257). Furthermore, emerging scientific evidence suggests that exosomes possess potential protective properties in the context of acute myocardial infarction. These exosomes have been shown to potentially facilitate cell repair mechanisms by modulating the expression of Smad7 in cardiomyocytes (257).

Depending on the concentration of serum creatinine (Scr) or glomerular filtration rate (GFR), nephrologists have classified kidney failure into two distinct syndromes: acute renal failure and chronic renal failure (258). Currently, clinical treatments for kidney injury primarily involve medication, surgery, and renal transplantation (259). As stem cell research has advanced, the preventive effects of hUC-MSCs and hUC-MSC-exo on renal tissue injury have been demonstrated (260). Acute kidney injury (AKI) refers to the clinical condition that arises from a rapid loss of renal function caused by various factors (260). Pre-renal acute kidney injury commonly arises from diminished blood volume caused by fluid loss and bleeding from various etiologies, as well as a decrease in effective arterial blood volume and alterations in intrarenal hemodynamics. Recent research has focused on the role of sepsis in causing AKI. To investigate this, a sepsis model was induced using cecal ligation and puncture (CLP), followed by treatment with hUC-MSCs (261). The data presented in the study provided evidence that the administration of hUC-MSCs resulted in substantial improvement in renal function, reduction in tissue damage, and significant enhancement of overall health in mice with sepsis (262, 263). According to the data reported, pre-treatment of hUC-MSCs with IL-1 exhibited a statistically significant augmentation in their capacity to modulate the immune system (264). In response to IL-1 stimulation, exosomes selectively encapsulated a widely recognized anti-inflammatory microRNA, MiR-146a. Subsequent delivery of exosomal MiR-146a to macrophages induced M2 polarization, leading to a reduction in kidney damage in septic mice (265). According to a study, the administration of hUC-MSCs have been demonstrated to effectively ameliorate renal ischemia-reperfusion injury (IRI) in mice. This beneficial effect is achieved through a dual mechanism involving a reduction in the infiltration of macrophages into the injured kidneys and a concomitant increase in the population of M2-like macrophages during the healing process (265). Through the modulation of inflammatory cytokine production and promotion of renal tubular cell proliferation, hUC-MSCs have been observed to expedite the recovery of renal function. Additionally, it was discovered that hUC-MSC transplantation resulted in a reduction in the levels of malondialdehyde (MDA) in renal tissues, indicating a potential protective effect of hUC-MSCs against oxidative damage and mitochondrial dysfunction in renal cells (266). Subsequent investigations revealed that the underlying mechanism responsible for cisplatin-induced nephrotoxicity was primarily attributed to the induction of oxidative stress. However, this detrimental effect can be mitigated by the administration of hUC-MSC-exo, which exert their protective effects by suppressing the activation of the p38 mitogen-activated protein kinase (MAPK) pathway (267). Renal fibrosis is a common pathway in the progression of chronic kidney disease (CKD) that often culminates in end-stage renal failure. Huang et al. provided insights into the potential therapeutic role of MSCs in mitigating obstructive chronic progressive renal interstitial fibrosis (RIF) in the context of kidney failure. Their study demonstrated that infused MSCs could effectively reach the damaged kidney tissues, offering a promising approach for addressing the underlying mechanisms involved in renal fibrosis (268).

Inflammatory, proliferative, and remodeling stages are just a few of the many phases that make up the complex process of cutaneous wound healing (268). Recent years have witnessed extensive exploration into benefits of direct stem cell infusion for tissue regeneration (269, 270). A degradable, dual-sensitive hydrogel incorporating exosomes extracted from hUC-MSC was synthesized. Afterwards, the in vivo wound healing potential, exosome identification and material properties of the hydrogel were assessed. The exosome-loaded hydrogel demonstrated substantial improvements in wound closure rates, re-epithelialization rates and collagen deposition at the wound sites, as evidenced by the in vivo results (269). The administration of exosomes-loaded hydrogel to the wounded sites resulted in a higher density of skin appendages, indicating a potential for achieving full skin regeneration (271).

Clinicians persistently encounter challenges in managing diabetic wounds due to the prevalence of multiple bacterial infections and oxidative damage (272). Exosomes have been widely employed as a promising nanodrug delivery strategy for the treatment of diabetic (273). To ascertain their participation in the modulation of diabetic wound healing, a co-culture of human umbilical vein endothelial cells (HU-VECs) and hUC-MSCs was established, and hUC-MSC-exo were subsequently utilized in both in vitro and in vivo experiments (274). The findings demonstrated that hUC-MSCs possess the ability to mitigate oxidative stress-induced damage to endothelial cells via exosomal mechanisms, thereby accelerating the healing process of diabetic cutaneous wounds in an in vitro setting (273). In vivo setting, it was observed that wounds treated with hUC-MSC-exo exhibited significantly accelerated re-epithelialization and elevated expression levels of CK19, PCNA, and collagen I (in contrast to collagen III) (274).

Acute lung injury (ALI) leads to the early onset of lung inflammation, capillary rupture, destruction of endothelial and epithelial cells, and breakdown of tight epithelial junctions. These factors increase alveolar epithelial permeability, causing significant pulmonary edema and, in severe cases, even death (275). In animal models, transplantation of MSCs effectively enhances the recovery from ALI (276). In the LPS-induced ALI rat model, hUC-MSCs can enhance the activity of antioxidant enzymes in lung tissue (277). Based on this, photobiomodulation (PBM) was utilized to modulate the release of pro-inflammatory chemicals, reduce their levels to a certain extent, and enhance the balance of oxidative stress at the site of injury (278). Bronchopulmonary dysplasia (BPD) is a dangerous chronic lung condition characterized by a high rate of morbidity and mortality in premature neonates (279). Transplantation of MSCs is a promising strategy for treating BPD. In a rat model of BPD, the transplantation of hUC-MSC-EVs resulted in the improvement of pulmonary hypertension, restoration of lung function, and alveolar structure (280). In a BPD model treated with hUC-MSC-EVs, the proportion of Ki-67-positive lung cells increased, indicating an upregulation of cell proliferation, whereas the proportion of TUNEL-positive lung cells decreased, suggesting a downregulation of cell apoptosis (263). Furthermore, in a hyperoxia-induced BPD model treated with hUC-MSC-EVs, there was an increase in SP-C staining, a marker of type II alveolar epithelial cells (TIIAECs), as well as CD31 staining, a marker of pulmonary vascular endothelial cells (PVECs) (281). Another study has demonstrated that intervention with PBM in hUC-MSCs naturally reduces the thickness of the alveolar septum, suppresses excessive secretion of inflammatory factors, and alleviates in vivo conditions of bleeding, edema, and fibrosis (278). PBM is a physical intervention that enhances the therapeutic effect of hUC-MSCs and shows promise as a therapy for the treatment of ALI. Furthermore, the use of hUC-MSCs may potentially reduce bleomycin-induced mouse mortality and attenuate lung collagen buildup (282). The transplantation of hUC-MSCs induced the proliferation of alveolar type 2 (AT2) cells, while concurrently suppressing the proliferation of lung fibroblasts (283). After the transplantation of hUC-MSCs, there is an induction of AT2 cell proliferation, concomitant with the suppression of lung fibroblast proliferation. Additionally, this transplantation leads to increased release of CXCL9 and CXCL10 by interferon-stimulated cells (IFNSMs), thereby attracting additional Treg cells to the injured lung (284). In a study, hUC-MSCs were administered, and lung morphometry was successfully enhanced (285). Further research has revealed the crucial role of exosome-resident miR-377-3p in controlling autophagy, thereby preventing LPS-induced ALI (286).

The liver, which is widely considered to be the most critical organ in the body, plays a pivotal role in the detoxification, secretion, and metabolism of medications and toxins (287). Acute liver failure (ALF), a pathological condition resulting from rapid deterioration in hepatic function, and is clinically characterized by jaundice, coagulopathy, and encephalopathy (288). In recent years, increasing scientific research has indicated that the transplantation of MSCs holds promise as a potential therapeutic strategy for the treatment of ALF (289, 290). Findings of ta study revealed that the administration of hUC-MSC-exo via a single tail vein injection resulted in a significant improvement in the survival rate, prevention of hepatocyte death, and enhancement of liver function in an experimental mouse model of ALF induced by APAP (291). Furthermore, the administration of hUC-MSCs effectively mitigated APAP-induced hepatocyte apoptosis by modulating oxidative stress markers (292). This was evident through the downregulation of glutathione (GSH) and superoxide dismutase (SOD) levels, as well as the attenuation of MDA production. Additionally, the excessive expression of cytochrome P450 E1 (CYP2E1) and 4-hydroxynonenal (4-HNE), which are known contributors to oxidative stress, was significantly suppressed. These findings highlight the ability of hUC-MSC-exo to regulate oxidative stress pathways, thereby conferring protection against APAP-induced hepatocyte death in the context of acute liver failure (293). In a study, mouse models of acute and chronic liver damage, as well as liver tumors, were generated by intraperitoneal injection of carbon tetrachloride (CCl4) followed by the intravenous infusion of hUC-MSC-exo. The results of the study demonstrated the hepatoprotective effect of hUC-MSC-exo, as evidenced by a significant reduction in liver damage (294). hUC-MSC-exo treatment has been shown to mitigate the expression of the NLRP3 inflammasome and associated inflammatory factors (295), offering a potential therapeutic approach for the management of acute liver failure. Furthermore, in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, hUC-MSC-exo demonstrated inhibitory effects on the expression of NLRP3, caspase-1, IL-1β, and IL-6. These findings highlight the immunomodulatory properties of hUC-MSC-exo, which could contribute to the attenuation of inflammatory responses in various pathological conditions (296). The proteolytic activation of pro-IL-1β is facilitated by activated caspase-1. Caspase-1, IL-1β, and NLRP3 play pivotal roles in the development of acute pancreatic and hepatic injury, inflammation, and subsequent organ damage. These factors are crucial in the pathophysiological processes associated with inflammatory responses and tissue injury in the pancreas and liver (297). The primary outcome of a recent study revealed that T-Exo treatment effectively reduces circulating levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and proinflammatory cytokines. Additionally, T-Exo therapy attenuates the activation of proteins involved in the NLRP3 inflammation-associated pathway, thereby mitigating the pathological liver damage associated with acute ALF (298). Notably, TNF stimulation of MSCs leads to the selective packaging of anti-inflammatory microRNA-299-3p into exosomes, which can be utilized for exosomal therapy purposes (299).

Diabetes mellitus (DM), a collective term referring to a group of metabolic disorders, is distinguished by the presence of elevated blood glucose levels, commonly known as hyperglycemia (300). Over the preceding half-century, the dynamics of lifestyles and the process of globalization have imparted profound ramifications on political, environmental, societal, and human behavioral domains. DM represents a complex disorder influenced by a combination of genetic predisposition and environmental factors, leading to compromised insulin secretion or insulin resistance (IR). These physiological aberrations contribute to the characteristic pathophysiology of DM and its associated metabolic dysregulation (300, 301). In recent years, obesity and physical inactivity have become more common, and rapid population expansion, aging, and urbanization have all contributed to the worldwide health issue that is DM (302). To maintain physiological equilibrium within the body’s ecosystem, it is imperative to regulate the homeostasis of blood glucose, which is contingent upon the management of vital life processes (303). In the year 2018, a team of researchers conducted an investigation into the correlation between hUC-MSC-exo and hyperglycemia induced by type 2 diabetes mellitus (T2DM) (304). The findings unequivocally indicate that hUC-MSC-exo consistently mitigated blood glucose levels in T2DM-afflicted rats subjected to a high-fat diet (HFD) and streptozotocin (STZ). Notably, hUC-MSC-exo enhanced the uptake of the fluorescent glucose analogue 2-NBDG in myotubes and hepatocytes, thereby substantiating their role in facilitating glucose absorption. Additionally, hUC-MSC-exo promoted glucose uptake in the muscles, upregulated the expression of the glucose-responsive transporter (GLUT4) in T2DM rats, and reinstated hepatic glucose homeostasis through the activation of insulin signaling. The activation of the insulin/AKT signaling pathway further corroborated the potential of hUC-MSC-exo to enhance insulin sensitivity in both in vivo and in vitro settings. Moreover, an evidence demonstrated that hUC-MSC-exo facilitated insulin secretion and islet regeneration by preventing STZ-induced caspase-3 alterations that lead to cellular apoptosis (305).