HWJMSC-EVs promote cartilage regeneration and repair via the ITGB1/TGF-ß/Smad2/3 axis mediated by microfractures.

The current first-line treatment for repairing cartilage defects in clinical practice is the creation of microfractures (MF) to stimulate the release of mesenchymal stem cells (MSCs); however, this method has many limitations. Recent studies have found that MSC-derived extracellular vesicles (MSC-EVs) play an important role in tissue regeneration. This study aimed to verify whether MSC-EVs promote cartilage damage repair mediated by MFs and to explore the repair mechanisms. In vitro experiments showed that human umbilical cord Wharton's jelly MSC-EVs (hWJMSC-EVs) promoted the vitality of chondrocytes and the proliferation and differentiation ability of bone marrow-derived MSCs. This was mainly because hWJMSC-EVs carry integrin beta-1 (ITGB1), and cartilage and bone marrow-derived MSCs overexpress ITGB1 after absorbing EVs, thereby activating the transforming growth factor-ß/Smad2/3 axis. In a rabbit knee joint model of osteochondral defect repair, the injection of different concentrations of hWJMSC-EVs into the joint cavity showed that a concentration of 50 µg/ml significantly improved the formation of transparent cartilage after MF surgery. Extraction of regenerated cartilage revealed that the changes in ITGB1, transforming growth factor-ß, and Smad2/3 were directly proportional to the repair of regenerated cartilage. In summary, this study showed that hWJMSC-EVs promoted cartilage repair after MF surgery.

Intra-articular injection of ascorbic acid enhances microfracture-mediated cartilage repair.

Previous studies have confirmed that ascorbic acid (AA) can promote cartilage repair and improve cartilage differentiation in bone marrow mesenchymal stem cells. However, the use of microfracture (MFX) combined with AA to repair cartilage damage has not been studied. This study established a rabbit animal model and treated cartilage injury with different concentrations of AA combined with MFX. Macroscopic observations, histological analysis, immunohistochemical analysis and reverse transcription quantitative polymerase chain reaction analysis of TGF-ß, AKT/Nrf2, and VEGF mRNA expression were performed. The results showed that intra-articular injection of AA had a positive effect on cartilage repair mediated by microfractures. Moreover, 10 mg/ml AA was the most effective at promoting cartilage repair mediated by microfractures. Intra-articular injection of AA promoted the synthesis of type II collagen and the formation of glycosaminoglycans by downregulating the mRNA expression of TGF-ß and VEGF. In summary, this study confirmed that AA could promote cartilage repair after MFX surgery.

Lack of tumorigenesis and protumorigenic activity of human umbilical cord mesenchymal stem cells in NOD SCID mice.

BACKGROUND: The tumorigenesis of infused umbilical cord mesenchymal stem cells (UC-MSCs) is being preclinically evaluated. METHODS: We observed tumor formation in NOD SCID mice after a single subcutaneous injection of hUC-MSCs and the effect of these cells on tumor growth in tumor-bearing mice. Three generations (P5, P7, and P10) of hUC-MSCs (1 × 107) from two donors (hUC-MSC1 and hUC-MSC2) were inoculated subcutaneously into NOD SCID mice. Subcutaneous transplantation models were established in NOD SCID mice with human cervical cancer HeLa cells (solid tumor) and human B cell lymphoma Raji cells (hematological tumor). Then, the animals were euthanized, gross dissection was performed, and tissues were collected. Various organs were observed microscopically to identify pathological changes and tumor metastasis. RESULTS: In the tumorigenesis experiment, no general anatomical abnormalities were observed. In the tumor promotion experiment, some animals in the HeLa groups experienced tumor rupture, and one animal died in each of the low- and medium-dose hUC-MSC groups. The results may have occurred due to the longer feeding time, and the tumor may have caused spontaneous infection and death. Pathological examination revealed no metastasis to distant organs in any group. In the Raji tumor model, some animals in each group experienced tumor rupture, and one animal in the medium-dose hUC-MSC group died, perhaps due to increased tumor malignancy. Thus, hUC-MSCs neither promoted nor inhibited tumor growth. No cancer cell metastasis was observed in the heart, liver, spleen, lungs, kidneys or other important organs, except that pulmonary venule metastasis was observed in 1 animal in the model group. CONCLUSIONS: Injected hUC-MSCs were not tumorigenic and did not significantly promote or inhibit solid or hematological tumor growth or metastasis in NOD SCID mice.

Effects and mechanisms of mUCMSCs on ovarian structure and function in naturally ageing C57 mice.

BACKGROUND: The ovaries are the core reproductive organs in women and are critical for maintaining normal reproductive function and endocrine system stability. An ageing C57 mouse model was used to evaluate the efficacy and mechanism of mouse umbilical cord mesenchymal stem cells (mUCMSCs) and to explore the mechanism by which mUCMSCs promote the antioxidant repair of mouse granulosa cells (mGCs). RESULTS: Eighteen-month-old C57 mice were randomly divided into a model group and a treatment group. At the same time, 2-month-old C57 mice were established as a young group (15 mice per group). The mice in the treatment group were injected via the tail vein with GFP-labelled mUCMSCs. The ovarian volume in ageing C57 mice was decreased, and there were no follicles at any stage. After mUCMSC transplantation, the mouse ovaries increased in size, follicles at various stages were observed in the cortex, and the antral follicle counts increased. The serum E2, AMH, and INH-B levels of mice in the treatment group were significantly higher than those of mice in the model control group (P < 0.05). mUCMSCs downregulated the expression of the autophagy-related gene LC3b and the apoptosis-related genes Bax and Caspase-3, upregulated the expression of SOD2 and the peroxidase gene PRDX IV, and reduced apoptosis rates and reactive oxygen species (ROS) levels in granulosa cells. CONCLUSIONS: mUCMSCs play roles in promoting the repair of ageing ovaries by regulating immunity, anti-inflammatory responses and the PI3K-Akt signalling pathway.

Establishment of a Systemic Inflammatory Response Syndrome Model and Evaluation of the Efficacy of Umbilical Cord Mesenchymal Stem Cell Transplantation.

Based on the characteristics of modern weapon injury, a repetitive model of traumatic systemic inflammatory response syndrome (SIRS) and an evaluation system were established. The models were treated with GFP-labeled tree shrew umbilical cord mesenchymal stem cells (UCMSCs). Forty out of 50 tree shrews were used to make a unilateral femoral comminuted fracture. Lipopolysaccharide was injected intravenously to create a traumatic SIRS model. The other 10 shrews were used as normal controls. After the model was established for 10 days, 20 tree shrews were injected intravenously with GFP-labeled UCMSCs, and 18 tree shrews were not injected as the model control group. The distribution of GFP-labeled cells in vivo was measured at 2 and 10 days after injection. Twenty days after treatment, the model group, the normal control group, and the treatment group were taken to observe the pathological changes in each tissue, and blood samples were taken for the changes in liver, renal, and heart function. Distribution of GFP-positive cells was observed in all tissues at 2 and 10 days after injection. After treatment, the HE staining results of the treatment group were close to those of the normal group, and the model group had a certain degree of lesions. The results of liver, renal, and heart function tests in the treatment group were returned to normal, and the results in the model group were abnormally increased. UCMSCs have a certain effect on the treatment of traumatic SIRS and provide a new technical solution for modern weapon trauma treatment.

Transplantation of chicken egg white extract-induced rabbit PBMCs as a treatment for renal ischemia-reperfusion injury in rabbits.

Ischemia-reperfusion injury is an important contributor to acute kidney injury and a major factor affecting early functional recovery after kidney transplantation. We conducted this experiment to investigate the protective effect of induced multipotent stem cell transplantation on renal ischemia-reperfusion injury. Forty rabbits were divided into four groups of 10 rabbits each. Thirty rabbits were used to establish the renal ischemia-reperfusion injury model, and ten rabbits served as the model group and were not treated. Among the 30 rabbits with renal ischemia-reperfusion injury, 10 rabbits were treated with induced peripheral blood mononuclear cells (PBMCs), and 10 other rabbits were treated with noninduced PBMCs. After three weekly treatments, the serum creatinine levels, urea nitrogen levels and urine protein concentrations were quantified. The kidneys were stained with hematoxylin-eosin (HE), periodic acid-Schiff (PAS) and Masson's trichrome and then sent for commercial metabolomic testing. The kidneys of the rabbits in the model group showed different degrees of pathological changes, and the recovery of renal function was observed in the group treated with induced cells. The results indicate that PBMCs differentiate into multipotent stem cells after induction and exert a therapeutic effect on renal ischemia-reperfusion injury.

Effect and mechanism of human umbilical cord mesenchymal stem cells in treating allergic rhinitis in mice.

A model of allergic rhinitis (AR) in BALB/c mice was established and evaluated to provide experimental subjects for further research. Preparation of human umbilical cord mesenchymal stem cells (hUCMSCs), including isolation, expansion culture, passaging, cryopreservation, and preparation of cell suspensions, provided materials for experimental research and clinical treatment. The mouse AR model was established by ovalbumin (OVA) intraperitoneal injection and the nasal stimulation induction method, and the model had a good effect and high repeatability. GFP-labeled hUCMSCs had good effects and were stable cells that could be used for tracking in animals. Transplantation of hUCMSCs by intraperitoneal and tail vein injections had a specific effect on the AR model of mice, and tail vein injection had a better effect. Tracking of hUCMSCs in vivo showed that the three groups of mice had the greatest number of hUCMSCs in the nose at week 2. The mouse AR model was used to evaluate the efficacy of hUCMSC transplantation via multiple methods for AR. The distribution of hUCMSCs in vivo was tracked by detecting green fluorescent protein (GFP), and the treatment mechanism of hUCMSCs was elucidated. This study provides technical methods and a theoretical basis for the clinical application of hUCMSCs.

Umbilical cord mesenchymal stem cells protect thymus structure and function in aged C57 mice by downregulating aging-related genes and upregulating autophagy- and anti-oxidative stress-related genes.

BACKGROUND: To study the effect of allogeneic umbilical cord mesenchymal stem cell transplantation on the structure and function of the thymus in aged C57 mice and provide a new method for the treatment of senile thymic atrophy. RESULTS: The changes in the thymus cortex and medulla volume and the lymphocyte ratio were analyzed by immunofluorescence. For thymus tissue sections, immunohistochemical staining was performed to detect p16, p53, SOD, becline1, LC3b, p62, sirt1, and sirt3. Changes in CK5, CK8, CD4 and CD8 expression were observed. Treatment with mUCMSCs could promote hair regeneration in aging mice and regenerate the thymus structure. CONCLUSIONS: mUCMSCs inhibited senescence of the thymus and promoted structural and functional thymus regeneration by downregulating the senescence genes p53 and p16 and upregulating the SOD, Sirt1 and Sirt3 genes, but the mechanism requires further research. METHODS: C57 mice were obtained and met the requirements of thymic aging. mUCMSCs were infused via the tail vein at a dose of 1×107 cells/kg twice per week for 3 weeks. Six weeks after the last transplantation, the thymus was weighed, and the thymus-to-body weight ratio was calculated. The thymus tissue was stained with HE.

Mechanism and therapeutic effect of umbilical cord mesenchymal stem cells in inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a persistent and chronic disease that is characterized by destructive gastrointestinal (GI) inflammation. Researchers are trying to identify and develop new and more effective treatments with no side effects. Acute and chronic mouse models of IBD were established using dextran sulfate sodium (DSS) solution. To evaluate the efficacy and mechanism, umbilical cord mesenchymal stem cells (UCMSCs) were obtained from Kunming (KM) mice and humans. In the chronic IBD study, the survival rates of the normal control, model, mouse UCMSC (mUCMSC) and human UCMSC (hUCMSC) groups were 100%, 40%, 86.7%, and 100%, respectively. The histopathological scores of the normal control, intraperitoneal injection, intravenous treatment, and model groups were 0.5 ± 0.30, 5.9 ± 1.10, 8.7 ± 1.39, and 8.8 ± 1.33 (p = 0.021). UCMSCs promoted the expression of the intestinal tight junction protein occludin, downregulated the protein expression of the autophagy marker LC3A/B in colon tissue, and upregulated the expression of VEGF-A and VEGFR-1 at the injured site. This study provides an experimental model for elucidating the therapeutic effects of UCMSCs in IBD. We provide a theoretical basis and method for the clinical treatment of IBD using UCMSCs.

Relationship between senescence in macaques and bone marrow mesenchymal stem cells and the molecular mechanism.

The relationship between bone marrow mesenchymal stem cells (BMSCs) and aging, as well as the antiaging effects of BMSCs, was observed. An aging macaque BMSC model was established. We isolated BMSCs from young and aged macaques and used RT-PCR and Western blot to confirm the aging-related mRNAs and their expression, revealing that TERT, SIRT1 and SIRT6 expression was decreased in the aged BMSCs. The morphology, immunophenotype, differentiation potential, proliferation potential, and antiaging effects of aged and young BMSCs on 293T cells were compared. The expression of aging-related genes and the difference between the secreted cytokines in natural aging and induced aging BMSCs were observed. The transcriptome of peripheral blood mononuclear cells from macaques was analyzed by high-throughput sequencing. Finally, the transcriptional characteristics and regulatory mechanisms of gene transcription in aging macaques were investigated.

Efficacy and mechanisms underlying the effects of allogeneic umbilical cord mesenchymal stem cell transplantation on acute radiation injury in tree shrews.

Umbilical cord mesenchymal stem cells (UC-MSCs) exert strong immunomodulatory effects and can repair organs. However, their roles in radiation injury remain unclear. We show that in tree shrews with acute radiation injury, injected UC-MSCs significantly improved survival rates, reduced lung inflammation and apoptosis, prevented pulmonary fibrotic processes, recovered hematopoiesis, and increased blood counts. A protein microarray analysis showed that serum levels of the anti-inflammatory cytokines IL-10 and IL-13 and the growth factors BMP-5, BMP-7, HGF, insulin, NT-4, VEGFR3, and SCF were significantly higher, while those of the inflammatory cytokines IL-2, TIMP-2, TNF-α, IFN-γ, IL-1ra, and IL-8 and the fibrosis-related factors PDGF-BB, PDGF-AA, TGF-ß1, IGFBP-2, and IGFBP-4 were significantly lower in UC-MSC-injected animals. A transcriptome analysis of PBMCs showed that the mRNA expression of C1q was upregulated, while that of HLA-DP was downregulated after UC-MSC injection. These results confirm the immunohistochemistry results. eGFP-labeled UC-MSCs were traced in vivo and found in the heart, liver, spleen, lungs, kidneys, thymus, small intestine and bone marrow. Our findings suggest that UC-MSC transplantation may be a novel therapeutic approach for treating acute radiation injury.

Chronic Toxicity Test in Cynomolgus Monkeys For 98 Days with Repeated Intravenous Infusion of Cynomolgus Umbilical Cord Mesenchymal Stem Cells.

BACKGROUND/AIMS: Stem cell-based therapy is attractive in many clinical studies, but current data on the safety of stem cell applications remains inadequate. This study observed the safety, immunological effect of cynomolgus monkey umbilical cord mesenchymal stem cells (mUC-MSCs) injected into cynomolgus monkeys, in order to evaluate the safety of human umbilical cord mesenchymal stem cells (hUC-MSCs) prepared for human clinical application. METHODS: Eighteen cynomolgus monkeys were divided into three groups. Group 1 is control group, Group 2 is low-dose group, Group 3 is high-dose group. After repeated administrations of mUC-MSCs, cynomolgus monkeys were observed for possible toxic reactions. RESULTS: During the experiment, no animal died. There were no toxicological abnormalities in body weight, body temperature, electrocardiogram, coagulation and pathology. In the groups 2 and 3, AST and CK transiently increased, and serum inorganic P slightly decreased. All animals were able to recover at 28 days after the infusion was stopped. In the groups 2 and 3, CD3+ and IL-6 levels significantly increased, and recovery was after 28 days of infusion. There were no obvious pathological changes associated with the infusion of cells in the general and microscopic examinations. CONCLUSIONS: The safe dosage of repeated intravenous infusion of mUC-MSCs in cynomolgus monkeys is 1.0 × 107/kg, which is 10 times of that in clinical human use.

Transplantation of induced mesenchymal stem cells for treating chronic renal insufficiency.

Discovering a new cell transplantation approach for treating chronic renal insufficiency is a goal of many nephrologists. In vitro-cultured peripheral blood mononuclear cells (PBMCs) were reprogrammed into induced mesenchymal stem cells (iMSCs) by using natural inducing agents made in our laboratory. The stem cell phenotype of the iMSCs was then identified. Unilateral ureteral obstruction (UUO) was used to create an animal model of chronic renal insufficiency characterized by renal interstitial fibrosis. The induced and non-induced PBMCs were transplanted, and the efficacy of iMSCs in treating chronic renal insufficiency was evaluated using a variety of methods. The ultimate goal was to explore the effects of iMSC transplantation on the treatment of chronic renal insufficiency, with the aim of providing a new therapeutic modality for this disease.

Umbilical cord mesenchymal stem cells are able to undergo differentiation into functional islet-like cells in type 2 diabetic tree shrews.

Islet transplantation is arguably one of the most promising strategies to treat patients suffering with diabetes mellitus. However, a combination of a lack of donors and chronic immune rejection limit clinical applications. Here, we evaluated the efficacy of cell therapy using islet-like cells differentiated from umbilical cord mesenchymal stem cells (UC-MSCs) of tree shrews for the treatment of type 2 diabetes. Enhanced green fluorescent protein (eGFP) labeled UC-MSCs were directly injected into type 2 diabetic tree shrews, where UC-MSC differentiated into functional islet-like cells and alleviated disease severity, as evidenced by improved biochemical features and reduced concentrations of inflammatory cytokines. We also demonstrated that in vitro culture of UC-MSCs for six days in a high-glucose environment (40 mmol/L or 60 mmol/L glucose) resulted in significant gene methylation. The potency of UC-MSCs differentiated into insulin-secreting cells was attributed to the activation of Notch signal pathways. This study provides evidence that cell therapy of islet-like cells differentiated from UC-MSCs is a feasible, simple and inexpensive approach in the treatment of type 2 diabetes.

Overexpression of Jagged1 Ameliorates Aged Rat-Derived Endothelial Progenitor Cell Functions and Improves Its Transfusion Efficiency for Rat Balloon-Induced Arterial Injury.

BACKGROUND: Endothelial progenitor cell (EPC) has significant age-dependent alterations in properties, but the role of Jagged1 in aging-induced decline of EPC functions remains unclear. METHODS: 2- and 20-month old healthy male Sprague-Dawley rats were used in present study. Jagged1 gene transfection was performed in EPC isolated from aged (AEPC) and young rats (YEPC), respectively. Experiments were divided into 4 groups: (1) pIRES2-EGFP (PE) group, (2) PE-combined N-[N-(3, 5-difluoro-phenacetyl)-1- alany1]-S-phenyglycine t-butyl ester (DAPT) (PE + D) group, (3) pIRES2 EGFP-Jagged1 (PEJ) group, and (4) PEJ combined DAPT (PEJ + D) group. Notch molecules were detected by real-time quantitative polymerase chain reaction or Western blotting. CD34, CD133, CD45, and KDR markers were detected by flow cytometry. EPC migration and proliferation were detected with a modified Boyden chamber and 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay, respectively; the tube formation ability was assayed by in vitro angiogenesis kit; EPC transfusion after Jagged1 gene transfection was performed in rat carotid artery injury models. RESULTS: Jagged1 gene transfection effectively activates notch-signaling pathway. Compared with PE groups, overexpression of Jagged1 significantly promoted AEPC functions including proliferation, migration, the tube formation ability, and cell differentiation, these effects could be reasonably diminished by DAPT. In vivo study demonstrated that Jagged1 overexpressing also significantly promoted AEPC homing to the vascular injury sites and decreases the neointima formation after vascular injury. CONCLUSIONS: Overexpression of Jagged1 ameliorates aged rat-derived EPC functions and increases its transfusion efficiency for balloon-induced rat arterial injury.

Umbilical Cord-Derived Mesenchymal Stem Cells Relieve Hindlimb Ischemia through Enhancing Angiogenesis in Tree Shrews.

Hindlimb ischemia is still a clinical problem with high morbidity and mortality. Patients suffer from consequent rest pain, ulcers, cool limbs, and even amputation. Angiogenesis is a promising target for the treatment of ischemic limbs, providing extra blood for the ischemic region. In the present study, we investigated the role of umbilical cord-derived mesenchymal stem cells (UC-MSCs) in regulating angiogenesis and relieving hindlimb ischemia. UC-MSCs were isolated from the umbilical cord of tree shrews. Angiography results showed that UC-MSCs injection significantly promoted angiogenesis in tree shrews. Moreover, the ankle brachial index, transcutaneous oxygen pressure, blood perfusion, and capillary/muscle fiber ratio were all markedly increased by the application of UC-MSCs. In addition, the conditioned culture of human umbilical vein endothelial cells using medium collected from UC-MSCs showed higher expression of angiogenic markers and improved migration ability. In short, the isolated UC-MSCs notably contributed to restoring blood supply and alleviating the symptoms of limb ischemia through enhancing angiogenesis.

Establishing a tree shrew model of systemic lupus erythematosus and cell transplantation treatment.

BACKGROUND: The establishment of a tree shrew model for systemic lupus erythematosus (SLE) provides a new method to evaluate the pathogenesis of autoimmune diseases. METHODS: Eighty tree shrews were randomly divided into four groups receiving either an intraperitoneal injection of pristane, lipopolysaccharide (LPS), or pristane and LPS, or no injection. Three weeks after injection, the SLE model tree shrews were divided into the model group and the treatment group. Tree shrews in the treatment group and the normal control group were infused with umbilical cord mesenchymal stem cells (UC-MSCs). The cells were labeled with DiR. Two weeks after transplantation, three groups of tree shrews were analyzed for urine protein, serum antinuclear antibodies and antiphospholipid, and inflammatory cytokine antibody microarray detection. The heart, liver, spleen, lung, and kidney were collected from the three groups and subjected to hematoxylin and eosin (HE) staining and detection of renal immune complex deposition. RESULTS: HE staining indicated pathology in the model group. Red fluorescence revealed immune complex deposition in the kidneys from the model group. CONCLUSIONS: The combined intraperitoneal injection of pristane and LPS is the best way to induce SLE pathological changes. The pathological changes improved after UC-MSC treatment.

Serum CXCL16 as a Novel Biomarker of Coronary Artery Disease in Type 2 Diabetes Mellitus: a Pilot Study.

OBJECTIVE: To explore the diagnostic value of serum C-X-C chemokine ligand 16 (CXCL16) in subjects with diabetic coronary artery disease (T2DM-CAD). METHODS: One hundred twenty Chinese subjects, including patients with coronary artery disease (CAD group), diabetic coronary artery disease (T2DM-CAD group), type 2 diabetes mellitus (T2DM group), and healthy controls of similar age and gender (control group), were enrolled in this study. Serum CXCL16 was detected by a sandwich-type enzyme linked immunosorbent assay (ELISA). Simultaneously, other clinical biochemical parameters such as high-sensitivity C-reactive protein (hs-CRP), uric acid (UA), and glucose (Glu) were tested based on standard methods. RESULTS: Compared to the levels in the CAD group (3.912±1.061 mg/L) and the T2DM group (4.115±0.876 mg/L), the levels of serum CXCL16 in the T2DM-CAD group were significantly increased (5.707±1.404 mg/L, P<0.01). In the T2DM-CAD group, serum CXCL16 concentrations correlated positively with hs-CRP (r=0.772, P<0.001) and uric acid levels (r=0.476, P<0.01). Multiple linear regression analysis indicated that hs-CRP might be the only influencing factor for serum CXCL16 levels (ß=0.772, P<0.001). Furthermore, in the T2DM-CAD group/T2DM group, the area under the curve of CXCL16 was 0.824, and the area under the curve of hs-CRP was 0.842; no significant difference was found (z=0.245, P>0.05). CONCLUSIONS: Serum CXCL16 may be a novel biomarker for the diagnosis of patients with T2DM-CAD.

Irisin Increased the Number and Improved the Function of Endothelial Progenitor Cells in Diabetes Mellitus Mice.

The dysfunction of endothelial progenitor cells (EPCs) was found to be associated with vascular complications in diabetes mellitus (DM) patients. Previous studies found that regular exercise could improve the function of EPCs in DM patients, but the underling mechanism was unclear. Irisin, a newly identified myokine, was induced by exercise and has been demonstrated to mediate some of the positive effects of exercise. In this study, we hypothesize that irisin may have direct effects on EPC function in DM mice. These data showed for the first time that irisin increased the number of EPCs in peripheral blood of DM mice and improved the function of EPCs derived from DM mice bone marrow. The mechanism for the effect of irisin is related to the PI3K/Akt/eNOS pathway. Furthermore, irisin was demonstrated to improve endothelial repair in DM mice that received EPC transplants after carotid artery injury. The results of this study indicate a novel effect of irisin in regulating the number and function of EPCs via the PI3K/Akt/eNOS pathway, suggesting a potential for the administration of exogenous irisin as a succedaneum to improve EPC function in diabetic patients who fail to achieve such improvements through regular exercise.