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The role of mesenchymal-stem-cell-derived exosomes (MSCs-Exo) in the regulation of macrophage polarization has been recognized in several diseases. There is emerging evidence that MSCs-Exo partially prevent the progression of diabetic nephropathy (DN). This study aimed to investigate whether exosomes secreted by MSCs pre-treated with a diabetic environment (Exo-pre) have a more pronounced protective effect against DN by regulating the balance of macrophages. Exo-pre and Exo-Con were isolated from the culture medium of UC-MSCs pre-treated with a diabetic mimic environment and natural UC-MSCs, respectively. Exo-pre and Exo-Con were injected into the tail veins of db/db mice three times a week for 6 weeks. Serum creatinine and serum urea nitrogen levels, the urinary protein/creatinine ratio, and histological staining were used to determine renal function and morphology. Macrophage phenotypes were analyzed by immunofluorescence, western blotting, and quantitative reverse transcription polymerase chain reaction. In vitro, lipopolysaccharide-induced M1 macrophages were incubated separately with Exo-Con and Exo-pre. We performed microRNA (miRNA) sequencing to identify candidate miRNAs and predict their target genes. An miRNA inhibitor was used to confirm the role of miRNAs in macrophage modulation. Exo-pre were more potent than Exo-Con at alleviating DN. Exo-pre administration significantly reduced the number of M1 macrophages and increased the number of M2 macrophages in the kidney compared to Exo-Con administration. Parallel outcomes were observed in the co-culture experiments. Moreover, miR-486-5p was distinctly expressed in Exo-Con and Exo-pre groups, and it played an important role in macrophage polarization by targeting PIK3R1 through the PI3K/Akt pathway. Reducing miR-486-5p levels in Exo-pre abolished macrophage polarization modulation. Exo-pre administration exhibited a superior effect on DN by remodeling the macrophage balance by shuttling miR-486-5p, which targets PIK3R1., (© 2024 Federation of American Societies for Experimental Biology.)

Background: Infusion of mesenchymal stem cells (MSCs) induces polarization of M2 macrophages in adipose tissue of type 2 diabetes (T2D) mice. Studies have shown that M2 macrophages were divided into four sub-phenotypes (M2a, M2b, M2c and M2d) with different functions, and manuscripts have also confirmed that macrophages co-cultured with MSCs were not matched with known four phenotype macrophages. Therefore, our study explored the phenotype and related gene expressions of macrophages in the adipose tissue of T2D mice with/without MSCs infusion., Methods: We induced a T2D mouse model by using high-fat diets and streptozotocin (STZ) injection. The mice were divided into three groups: the control group, the T2D group, and the MSCs group. MSCs were systemically injected once a week for 6 weeks. The phenotype of macrophages in adipose tissue was detected via flow cytometric analysis. We also investigated the gene expression of macrophages in different groups via SMART-RNA-sequencing and quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR)., Results: The present study found that the macrophages of adipose tissue in the MSCs group were polarized to the M2 phenotype mixed with four sub-phenotypes. Besides, M2a and M2c held a dominant position, while M2b and M2d (tumor-associated macrophages, TAMs) exhibited a decreasing trend after infusion of MSCs. Moreover, the MSCs group did not appear to express higher levels of tumor-associated, inflammation-associated, or fibrosis-associated genes in comparison to the T2D group., Conclusion: The present results unveiled that the macrophage phenotype was inclined to be present in a hybridity state of four M2 sub-phenotypes and the genes related to tumor-promoting, pro-inflammation and pro-fibrosis were not increased after MSCs injection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Background: Our previous single-center, randomized, double-blinded, placebo-controlled phase 2 study evaluated the safety and effectiveness of human umbilical cord mesenchymal stromal cell (UC-MSC) transfusion for treating patients with type 2 diabetes mellitus (T2DM). Indeed, this potential treatment strategy was able to reduce insulin use by half in a considerable number of patients. However, many other patients' responses to UC-MSC transfusion were insignificant. The selection of patients who might benefit from UC-MSC treatment is crucial from a clinical standpoint., Methods: In this post hoc analysis, 37 patients who received UC-MSC transfusions were divided into two groups based on whether their glycated hemoglobin (hemoglobin A1c, or HbA1c) level was less than 7% after receiving UC-MSC treatment. The baseline differences between the two groups were summarized, and potential factors influencing efficacy of UC-MSCs for T2DM were analyzed by univariate and multivariate logistic regression. The correlations between the relevant hormone levels and the treatment effect were further analyzed., Results: At the 9-week follow-up, 59.5% of patients achieved their targeted HbA1c level. Male patients with lower baseline HbA1c and greater C-peptide area under the curve (AUCC-pep) values responded favorably to UC-MSC transfusion, according to multivariate analysis. The effectiveness of UC-MSCs transfusion was predicted by AUCC-pep (cutoff value: 14.22 ng/h/mL). Further investigation revealed that AUCC-pep was increased in male patients with greater baseline testosterone levels., Conclusions: Male patients with T2DM with greater AUCC-pep may be more likely to respond clinically to UC-MSC therapy, and further large-scale multi-ethnic clinical studies should be performed to confirm the conclusion., Competing Interests: Declaration of Competing Interest The authors have no commercial, proprietary or financial interest in the products or companies described in this article., (Copyright © 2024 International Society for Cell & Gene Therapy. Published by Elsevier Inc. All rights reserved.)

Umbilical cord-derived mesenchymal stem cells (UC-MSCs) have been proved a promising clinical strategy for the treatment of diabetes, and time in range (TIR) has been demonstrated a new metric of glycemic control links to diabetes complications. To further assess the therapeutic effect of UC-MSCs on TIR, a phase II study investigating the efficacy of UC-MSCs in Chinese adults with type 2 diabetes (T2D) assessed by retrospective continuous glucose monitoring (CGM) was conducted. In this randomized and placebo-controlled trial, a total of 73 patients were randomly assigned to receive intravenous infusion of UC-MSCs (n = 37) or placebo (n = 36) 3 times at 4-week intervals and followed up for 48 weeks. The primary endpoint was the changes in TIR and glycosylated hemoglobin (HbA1c). TIR and HbA1c were both significantly improved in UC-MSCs and placebo groups after 48 weeks of therapy compared with baseline. Compared with placebo group, UC-MSCs group exhibited more pronounced changes at 9 and 48 weeks from baseline in TIR (26.54 vs. 15.84 and 21.36 vs. 6.32) and HbA1c (-1.79 vs. -0.96 and -1.36 vs. -0.51). More patients in UC-MSCs group achieved the glycemic control target of TIR ≥ 70% and HbA1c < 7% at 9 and 48 weeks than in placebo group (59.5% vs. 27.8% and 43.2% vs. 11.1%). The C-peptide area under the curve (AUCC-pep) was an independent risk factor associated with efficacy in T2D undergoing UC-MSCs intervention. These results illustrate that UC-MSCs administration via intravenous infusion is an effective approach for ameliorating TIR., (© The Author(s) 2023. Published by Oxford University Press.)

Background: Mesenchymal stem cells (MSCs) exert anti-diabetic effects and improve long-term complications via secretory effects that regulate macrophage polarisation and attenuate inflammation. Enhancing the efficacy of MSCs needs to be explored further. The in vitro culture microenvironment influences the secretory profile of MSCs. Therefore, we hypothesised that a diabetic microenvironment would promote the secretion of cytokines responsible for macrophage polarisation, further attenuating systemic inflammation and enhancing the effects of MSCs on type 2 diabetes (T2D) and long-term diabetic complications., Methods: Preconditioned adipose-derived mesenchymal stem cells (pre-ADSCs) were obtained after co-cultivating ADSCs in a diabetic metabolic environment (including high sugar, advanced glycation end-product, and lipopolysaccharides). The regulatory effects of pre-ADSCs on macrophages were observed in vitro. A T2D rat model was induced with a high-fat diet for 32 weeks combined with an intraperitoneal injection of streptozotocin. Sprague-Dawley (SD) rats were divided into four groups: normal group, diabetes without treatment group (PBS), ADSC treatment group, and pre-ADSC treatment group. ADSCs and pre-ADSCs were intravenously administered weekly to SD rats for 6 months, and then glucose homeostasis and long-term diabetic complications were evaluated in each group., Results: The secretion of cytokines related to M2 macrophage polarisation (IL-6, MCP-1, etc.) was increased in the pre-ADSC group in the in vitro model. Pre-ADSC treatment significantly maintained blood glucose homeostasis, reduced insulin resistance, promoted islet regeneration, and ameliorated the complications related to diabetes in rats (chronic kidney disease, non-alcoholic steatohepatitis, lung fibrosis, and cataract) compared to the ADSC group (P < 0.05). Additionally, the number of anti-inflammatory M2 macrophage phenotypes was enhanced in tissues following pre-ADSC injections. Moreover, the expression of pro-inflammatory genes (iNOS, TNF-α, IL-1β) was reduced whereas that of anti-inflammatory genes (Arg1, CD206, and Il-10) was increased after cultivation with pre-ADSCs., Conclusion: Diabetic microenvironment-preconditioned ADSCs effectively strengthen the capacity against inflammation and modulate the progress of long-term T2D complications., (© 2022. The Author(s).)

Background: To determine the efficacy and safety of umbilical cord-derived mesenchymal stem cells (UC-MSCs) in Chinese adults with type 2 diabetes mellitus (T2DM)., Methods: In this single-center, double-blinded, randomized, placebo-controlled phase II trial, 91 patients were randomly assigned to receive intravenous infusion of UC-MSCs (n = 45) or placebo (n = 46) three times with 4-week intervals and followed up for 48 weeks from October 2015 to December 2018. The primary endpoint was the percentage of patients with glycated hemoglobin (HbA1c) levels of < 7.0% and daily insulin reduction of ≥ 50% at 48 weeks. Additional endpoints were changes of metabolic control, islet β-cell function, insulin resistance, and safety., Results: At 48 weeks, 20% of the patients in the UC-MSCs group and 4.55% in the placebo group reached the primary endpoint (p < 0.05, 95% confidence interval (CI) 2.25-28.66%). The percentage of insulin reduction of the UC-MSCs group was significantly higher than that of the placebo group (27.78% versus 15.62%, p < 0.05). The levels of HbA1c decreased 1.31% (9.02 ± 1.27% to 7.52 ± 1.07%, p < 0.01) in the UC-MSCs group, and only 0.63% in the placebo group (8.89 ± 1.11% to 8.19 ± 1.02%, p˃0.05; p = 0.0081 between both groups). The glucose infusion rate (GIR) increased significantly in the UC-MSCs group (from 3.12 to 4.76 mg/min/kg, p < 0.01), whereas no significant change was observed in the placebo group (from 3.26 to 3.60 mg/min/kg, p ˃ 0.05; p < 0.01 between both groups). There was no improvement in islet β-cell function in both groups. No major UC-MSCs transplantation-related adverse events occurred., Conclusions: UC-MSCs transplantation could be a potential therapeutic approach for Chinese adults with T2DM. Trial registration This study was registered on ClinicalTrials.gov (identifier: NCT02302599)., (© 2022. The Author(s).)

Background: Previous research has demonstrated that the spleen plays an important role in mesenchymal stem cell (MSC)-mediated alleviation of acute inflammation, as MSC infusion increases the spleen-derived anti-inflammatory cytokine interleukin 10 (IL-10) levels. However, studies on splenic involvement in MSC-induced protection against chronic inflammatory diseases are limited. Obesity is characterized by chronic low-grade inflammation, a key driver of insulin resistance. This study aims to evaluate the effects of MSCs on obesity-related insulin resistance and explore the underlying mechanism, particularly regarding splenic involvement., Methods: We induced obesity in mice by feeding them high-fat diets for 20 weeks. Human umbilical cord-derived MSCs (UC-MSCs) were systemically infused into the obese mice once per week for 6 weeks. Systemic glucose metabolic homeostasis and insulin sensitivity in epididymal adipose tissue (EAT) were evaluated. Then, we conducted in vivo blockade of IL-10 during UC-MSC infusion by intraperitoneally administrating an IL-10-neutralizing antibody twice per week. We also investigated the therapeutic effects of UC-MSCs on obese mice after removal of the spleen by splenectomy., Results: UC-MSC infusions improved systemic metabolic homeostasis and alleviated insulin resistance in EAT but elicited no change in weight. Despite rare engraftment of UC-MSCs in EAT, UC-MSC infusions attenuated insulin resistance in EAT by polarizing macrophages into the M2 phenotype, coupled with elevated serum IL-10 levels. In vivo blockade of IL-10 blunted the effects of UC-MSCs on obese mice. Furthermore, UC-MSCs overwhelmingly homed to the spleen, and the ability of UC-MSCs to elevate serum IL-10 levels and alleviate insulin resistance was impaired in the absence of the spleen. Further in vivo and in vitro studies revealed that UC-MSCs promoted the capacity of regulatory T cells (Treg cells) to produce IL-10 in the spleen., Conclusions: Our results demonstrated that UC-MSCs elevated serum IL-10 levels and subsequently promoted macrophage polarization, leading to alleviation of insulin resistance in EAT. The underlying mechanism was that UC-MSCs improved the capacity of Treg cells to produce IL-10 in the spleen. Our findings indicated that the spleen played a critical role in amplifying MSC-mediated immunomodulatory effects, which may contribute to maximizing MSC efficacy in clinical applications in the future., (© 2022. The Author(s).)

Background Aims: The authors aimed to observe β-cell dedifferentiation in type 2 diabetes mellitus (T2DM) and investigate the reversal effect of umbilical cord-derived mesenchymal stem cells (UC-MSCs) on early- and late-stage β-cell dedifferentiation., Methods: In high-fat diet (HFD)/streptozotocin (STZ)-induced T2DM mice, the authors examined the predominant role of β-cell dedifferentiation over apoptosis in the development of T2DM and observed the reversion of β-cell dedifferentiation by UC-MSCs. Next, the authors used db/db mice to observe the progress of β-cell dedifferentiation from early to late stage, after which UC-MSC infusions of the same amount were performed in the early and late stages of dedifferentiation. Improvement in metabolic indices and restoration of β-cell dedifferentiation markers were examined., Results: In HFD/STZ-induced T2DM mice, the proportion of β-cell dedifferentiation was much greater than that of apoptosis, demonstrating that β-cell dedifferentiation was the predominant contributor to T2DM. UC-MSC infusions significantly improved glucose homeostasis and reversed β-cell dedifferentiation. In db/db mice, UC-MSC infusions in the early stage significantly improved glucose homeostasis and reversed β-cell dedifferentiation. In the late stage, UC-MSC infusions mildly improved glucose homeostasis and partially reversed β-cell dedifferentiation. Combining with other studies, the authors found that the reversal effect of UC-MSCs on β-cell dedifferentiation relied on the simultaneous relief of glucose and lipid metabolic disorders., Conclusions: UC-MSC therapy is a promising strategy for reversing β-cell dedifferentiation in T2DM, and the reversal effect is greater in the early stage than in the late stage of β-cell dedifferentiation., (Copyright © 2021 International Society for Cell & Gene Therapy. Published by Elsevier Inc. All rights reserved.)

This study was designed to assess whether the combination of the glucagon-like peptide-1 (GLP-1) analog exendin-4 (Ex4) and bone marrow-derived mesenchymal stem cell (BM-MSC) could enhance β-cell action in streptozotocin (STZ)-induced diabetic rats. Forty male Sprague-Dawley rats were randomly assigned to five groups: the normal control group (Normal), diabetes mellitus (DM) group, MSC-treated group (MSC), Ex4-treated group (Ex4), and MSC plus Ex4-treated group (MSC+Ex4). Body weight, blood glucose level, intraperitoneal glucose tolerance test, and in vitro glucose-stimulated insulin secretion were used to assess the treatment efficacy. The expression level of insulin, glucagon, pancreatic duodenal homeobox-1 (PDX-1), v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (MafA), glucagon-like peptide-1 receptor (GLP-1R), and forkhead transcription factor 1 (FoxO1) was estimated by immunofluorescence analysis. Proliferation was assessed by Ki67 staining, and apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining in β-cells. Glucose-induced insulin secretion in the MSC+Ex4 group was significantly increased compared to that in the MSC group in vitro and in vivo. Compared to that of the other groups, the number of insulin-immunopositive cells was increased in both the MSC and MSC+Ex4 groups. However, β-cell proliferation and apoptosis in the MSC group and MSC+Ex4 group were not significantly different. Importantly, the expression level of PDX-1, MafA, FoxO1, and GLP-1R in β-cells in the MSC+Ex4 group was significantly higher than those in the MSC group. The numbers of insulin + glucagon + double positive cells and glucagon + GLP-1 + double positive cells were significantly increased after MSC treatment and MSC+Ex4 combined treatment, suggesting the enhanced function of newly formed islet β-cells. Our findings showed that the combination of MSC and Ex4 enhanced the function of newly formed β-cells in STZ-induced diabetic rats by acting on multiple insulin transcription factors. Thus, combined MSC and Ex4 therapy provides a feasible approach for future diabetes treatments.

Background: Long-term diabetes-associated complications are the major causes of morbidity and mortality in individuals with diabetes. These diabetic complications are closely linked to immune system activation along with chronic, non-resolving inflammation, but therapies to directly reverse these complications are still not available. Our previous study demonstrated that mesenchymal stem cells (MSCs) attenuated chronic inflammation in type 2 diabetes mellitus (T2DM), resulting in improved insulin sensitivity and islet function. Therefore, we speculated that MSCs might exert anti-inflammatory effects and promote the reversal of diabetes-induced kidney, liver, lung, heart, and lens diseases in T2DM rats., Methods: We induced a long-term T2DM complication rat model by using a combination of a low dose of streptozotocin (STZ) with a high-fat diet (HFD) for 32 weeks. Adipose-derived mesenchymal stem cells (ADSCs) were systemically administered once a week for 24 weeks. Then, we investigated the role of ADSCs in modulating the progress of long-term diabetic complications., Results: Multiple infusions of ADSCs attenuated chronic kidney disease (CKD), nonalcoholic steatohepatitis (NASH), lung fibrosis, and cataracts; improved cardiac function; and lowered serum lipid levels in T2DM rats. Moreover, the levels of inflammatory cytokines in the serum of each animal group revealed that ADSC infusions were able to not only inhibit pro-inflammatory cytokines IL-6, IL-1β, and TNF-α expression but also increase anti-inflammatory cytokine IL-10 systematically. Additionally, MSCs reduced the number of iNOS(+) M1 macrophages and restored the number of CD163(+) M2 macrophages., Conclusions: Multiple intravenous infusions of ADSCs produced significant protective effects against long-term T2DM complications by alleviating inflammation and promoting tissue repair. The present study suggests ADSCs may be a novel, alternative cell therapy for long-term diabetic complications.

Background: Mesenchymal stem cells (MSCs) have emerged as a promising therapy for type 2 diabetes (T2D). Mechanistic researches demonstrate that the anti-diabetic effect of MSCs is partially mediated by eliciting macrophages into an anti-inflammatory phenotype thus alleviating insulin resistance. However, single MSC infusion is insufficient to ameliorate sustained hyperglycemia or normalize blood glucose levels. In this study, we used decitabine (DAC), which is involved in the regulation of macrophage polarization, to test whether MSCs combined with decitabine can prolong and enhance the anti-diabetic effect in T2D mice., Methods: High-fat diet (HFD) and streptozocin (STZ) were given to induce T2D mouse model. Successfully induced T2D mice were randomly divided into four groups: T2D group, MSC group, DAC group, and MSC + DAC group. Blood glucose was monitored, and glucose tolerance and insulin sensitivity were evaluated during the entire analysis period. Epididymal fat was extracted for analysis of macrophage phenotype and inflammation in adipose tissue. In vitro, we examined the effect of MSC + DAC on macrophage polarization in bone marrow-derived macrophages (BMDMs) and explore the possible mechanism., Results: MSC infusion effectively improved insulin sensitivity and glucose homeostasis in T2D mice within 1 week, whereas combination therapy of MSCs + DAC extended the anti-diabetic effects of MSCs from 1 to 4 weeks (the end of the observation). Correspondingly, more M2 macrophages in adipose tissue were observed in the combination therapy group over the entire study period. In vitro, compared with the MSC group, MSCs combined with decitabine more effectively polarized M1 macrophages to M2 macrophages. Further analysis showed that the effect of MSC + DAC on macrophage polarization was largely abrogated by the peroxisome proliferator-activated receptor gamma (PPARγ) antagonist GW9662., Conclusions: Our data suggest that MSCs combined with decitabine can more effectively alleviate insulin resistance and prolong and enhance the anti-diabetic effect of MSCs in T2D mice in part by prompting M2 polarization in a PPARγ-dependent manner. Thus, decitabine may be an applicable addition to MSCs for diabetes therapy. UC-MSCs combined with decitabine activate the IL4R/STAT6/STAT3/PPARγ axis to further promote M2 macrophage polarization in adipose tissue, reduce inflammation, improve insulin sensitivity, and lead to better glucose metabolism and long-term hypoglycemic effects.

Progressive pancreatic β-cell dysfunction is recognized as a fundamental pathology of type 2 diabetes (T2D). Recently, mesenchymal stem cells (MSCs) have been identified in protection of islets function in T2D individuals. However, the underlying mechanisms remain elusive. It is widely accepted that β-cell dysfunction is closely related to improper accumulation of macrophages in the islets, and a series of reports suggest that MSCs possess great immunomodulatory properties by which they could elicit macrophages into an anti-inflammatory M2 state. In this study, we induced a T2D mouse model with a combination of high-fat diet (HFD) and low-dose streptozotocin (STZ), and then performed human umbilical cord-derived MSCs (hUC-MSCs) infusion to investigate whether the effect of MSCs on islets protection was related to regulation on macrophages in pancreatic islets. hUC-MSCs infusion exerted anti-diabetic effects and significantly promoted islets recovery in T2D mice. Interestingly, pancreatic inflammation was remarkably suppressed, and local M1 macrophages were directed toward an anti-inflammatory M2-like state after hUC-MSC infusion. In vitro study also proved that hUC-MSCs inhibited the activation of the M1 phenotype and induced the generation of the M2 phenotype in isolated mouse bone marrow-derived macrophages (BMDMs), peritoneal macrophages (PMs) and in THP-1 cells. Further analysis showed that M1-stimulated hUC-MSCs increased the secretion of interleukin (IL)-6, blocking which by small interfering RNA (siRNA) largely abrogated the hUC-MSCs effects on macrophages both in vitro and in vivo, resulting in dampened restoration of β-cell function and glucose homeostasis in T2D mice. In addition, MCP-1 was found to work in accordance with IL-6 in directing macrophage polarization from M1 to M2 state. These data may provide new clues for searching for the target of β-cell protection. Furthermore, hUC-MSCs may be a superior alternative in treating T2D for their macrophage polarization effects.

Umbilical cord-derived mesenchymal stem cells (UC-MSCs), with both immunomodulatory and pro-regenerative properties, are promising for the treatment of type 2 diabetes mellitus (T2DM). As efficient cell therapy largely relies on appropriate homing to target tissues, knowing where and to what extent injected UC-MSCs have homed is critically important. However, bio-distribution data for UC-MSCs in T2DM subjects are extremely limited. Beneficial effects of UC-MSCs on T2DM subjects are associated with increased M2 macrophages, but no systemic evaluation of M2 macrophages has been performed in T2DM individuals. In this study, we treated T2DM mice with CM-Dil-labelled UC-MSCs. UC-MSC infusion not only exerted anti-diabetic effects but also alleviated dyslipidemia and improved liver function in T2DM mice. To compare UC-MSC migration between T2DM and normal subjects, a collection of normal mice also received UC-MSC transplantation. UC-MSCs homed to the lung, liver and spleen in both normal and T2DM recipients. Specifically, the spleen harbored the largest number of UC-MSCs. Unlike normal mice, a certain number of UC-MSCs also homed to pancreatic islets in T2DM mice, which suggested that UC-MSC homing may be closely related to tissue damage. Moreover, the number of M2 macrophages in the islets, liver, fat and muscle significantly increased after UC-MSC infusion, which implied a strong link between the increased M2 macrophages and the improved condition in T2DM mice. Additionally, an M2 macrophage increase was also observed in the spleen, suggesting that UC-MSCs might exert systemic effects in T2DM individuals by modulating macrophages in immune organs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: To investigate the distinct effects of intermittent and continuous administration of parathyroid hormone (PTH) on bone and mesenchymal stem cell (MSC). Methods: Six weeks old mice with C57/BL6J background and SOX9-creERT/Td-tomato/Osteocalcin-GFP genotype were divided into 6 groups: intermittent administration and withdraw group (subcutaneous injection with PTH 500 μg·kg -1 ·d -1 ), continuous administration and withdraw group (subcutaneous implantation of PTH pump, 80 μg·kg -1 ·d -1, with a rate of 0.25 μl/h), control administration and withdraw group, with 8 mice in each group. Serum calcium level and bone mineral density (BMD) were measured after two weeks' treatment and two weeks after drug withdraw. Histopathology and immunofluorescence analyses were performed to assess the effects of PTH on bone and mesenchymal stem cell. Results: Serum calcium level increased transiently in intermittent group[(1.36±0.03) mmol/L]and increased gradually in continuous group[up to (2.33±0.03) mmol/L], but reduced to normal level (1.12-1.27 mmol/L) 14 days after drug withdraw. BMD of both intermittent[(0.047±0.002) g/cm 2 ]and continuous[(0.046±0.001) g/cm 2 ]PTH administration groups increased compared with control group[(0.044±0.001) g/cm 2 ], but there was no significant difference among three groups 2 weeks after drug withdraw. Femoral histopathology showed that bone mass, trabecular number and little fibrous tissue hyperplasia in intermittent PTH group increased. Osteoblasts number increased, but lining cells decreased. There was no significant difference in osteocyte and osteoclast numbers. After withdrawing of intermittent PTH, osteocyte and osteoblast number declined significantly, but there was an increased number of lining cells. Continuous PTH caused very high amount of fibrosis, and osteoclast number increased significantly, while osteoblast and osteocyte number increased slightly. After withdrawing of continuous PTH, fibrosis disappeared significantly, and lining cell number increased. Immunofluorescence staining in the epiphyseal-metaphyseal regions in fibula showed intermittent PTH increased undifferentiated Td-Tomato MSC, but declined significantly after withdrawing. Undifferentiated Td-Tomato MSC in continuous PTH increased slightly and decreased after drug withdraw. Conclusions: Intermittent PTH increased undifferentiated Td-Tomato MSC and osteoblast number, and might transform lining cell into osteocytes and osteoblasts, and thus lead to bone formation. Continuous PTH increased undifferentiated Td/Tomato MSC, osteoblast and osteocyte number slightly, but high amount of fibrosis and osteoclasts can be seen, leading to metabolic bone disease. However, lining cell ascended after drug withdraw, which may be beneficial to bone remodeling.

Background: Insulin resistance is one of the most common and important pathological features of type 2 diabetes (T2D). Recently, insulin resistance is increasingly considered to be associated with systemic chronic inflammation. Elevated levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in blood are predictive indicators of the development of T2D. Mesenchymal stem cell (MSC)-based therapies have been proven to have potential immunomodulation and anti-inflammatory properties through their paracrine effects; however, the mechanism for the anti-inflammatory effect of MSCs in enhancing insulin sensitivity is still uncertain., Methods: In the present experiment, we used HepG2 cells, a human hepatoma cell line, and a MSC-HepG2 transwell culturing system to investigate the anti-inflammatory mechanism of human umbilical cord-derived MSCs (UC-MSCs) under palmitic acid (PA) and lipopolysaccharide (LPS)-induced insulin resistance in vitro. Insulin resistance was confirmed by glycogen assay kit and glucose assay kit. Inflammatory factor release was detected by ELISA, gene expression was tested by quantitative real-time PCR, and insulin signaling activation was determined by western blotting analysis. The changes of inflammatory factors and insulin signaling protein were also tested in T2D rats injected with UC-MSCs., Results: Treating HepG2 cells with PA-LPS caused NLRP3 inflammation activation, including overexpression of NLRP3 and caspase-1, and overproduction of IL-1β and IL-18 as well as TNF-α from HepG2 cells. The elevated levels of these inflammatory cytokines impaired insulin receptor action and thereby prevented downstream signaling pathways, exacerbating insulin resistance in HepG2 cells. Importantly, UC-MSCs cocultured with HepG2 could effectively alleviate PA and LPS-induced insulin resistance by blocking the NLRP3 inflammasome activation and inflammatory agents. Furthermore, knockdown of NLRP3 or IL-1β partially improved PA and LPS-induced insulin signaling impairments in the presence of UC-MSCs. Similarly, UC-MSC infusion significantly ameliorated hyperglycemia in T2D rats and decreased inflammatory activity, which resulted in improved insulin sensitivity in insulin target tissues., Conclusions: Our results indicated that UC-MSCs could attenuate insulin resistance and this regulation was correlated with their anti-inflammatory activity. Thus, MSCs might become a novel therapeutic strategy for insulin resistance and T2D in the near future.

The worldwide rapid increase in diabetes poses a significant challenge to current therapeutic approaches. Single-dose mesenchymal stem cell (MSC) infusion ameliorates hyperglycemia but fails to restore normoglycemia in diabetic animals. We therefore hypothesized that multiple intravenous MSC infusions may reverse hyperglycemia in type 2 diabetes (T2D) rats. We administered serial allogenous bone-marrow derived MSC infusions (1 × 10(6)cells/infusion) via the tail vein once every 2 weeks to T2D rats, induced by high-fat diet and streptozocin (STZ) administration. Hyperglycemia decreased only transiently after a single infusion in early-phase (1 week) T2D rats, but approximated normal levels after at least three-time infusions. This normal blood level was maintained for at least 9 weeks. Serum concentrations of both insulin and C-peptide were dramatically increased after serial MSC infusions. Oral glucose tolerance tests revealed that glucose metabolism was significantly ameliorated. Immunofluorescence analysis of insulin/glucagon staining revealed the restoration of islet structure and number after multiple MSC treatments. When multiple-MSC treatment was initiated in late-phase (5 week) T2D rats, the results were slightly different. The results of this study suggested that a multiple-MSC infusion strategy offers a viable clinical option for T2D patients., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Infusion of mesenchymal stem cells (MSCs) has been shown to effectively lower blood glucose in diabetic individuals, but the mechanism involved could not be adequately explained by their potential role in promoting islet regeneration. We therefore hypothesized that infused MSCs might also contribute to amelioration of the insulin resistance of peripheral insulin target tissues. To test the hypothesis, we induced a diabetic rat model by high-fat diet/streptozotocin (STZ) administration, performed MSC infusion during the early phase (7 days) or late phase (21 days) after STZ injection, and then evaluated the therapeutic effects of MSC infusion and explored the possible mechanisms involved. MSC infusion ameliorated hyperglycemia in rats with type 2 diabetes (T2D). Infusion of MSCs during the early phase not only promoted β-cell function but also ameliorated insulin resistance, whereas infusion in the late phase merely ameliorated insulin resistance. Infusion of MSCs resulted in an increase of GLUT4 expression and an elevation of phosphorylated insulin receptor substrate 1 (IRS-1) and Akt (protein kinase B) in insulin target tissues. This is the first report of MSC treatment improving insulin sensitivity in T2D. These data indicate that multiple roles and mechanisms are involved in the efficacy of MSCs in ameliorating hyperglycemia in T2D.

Background. Progressive β-cell dysfunction, a major characteristic of type 2 diabetes (T2D), is closely related to the infiltration of inflammatory macrophages within islets. Mesenchymal stem cells (MSCs) have been identified to alleviate β-cell dysfunction by modulating macrophage phenotype in T2D, but the restoration of β-cells by a single MSC infusion is relatively transient. Decitabine (DAC) has been reported to polarize macrophages towards the anti-inflammatory phenotype at low doses. We therefore investigated whether low-dose decitabine could enhance the antidiabetic effect of MSCs and further promote the restoration of β-cell function. Methods. We induced a T2D mice model by high-fat diets and streptozotocin (STZ) injection. Mice were divided into five groups: the normal group, the T2D group, the DAC group, the MSC group, and the MSC plus DAC group (MD group). We examined the blood glucose and serum insulin levels of mice 1, 2, and 4 weeks after MSC and/or DAC treatment. Dynamic changes in islets and the phenotype of intraislet macrophages were detected via immunofluorescence. In vitro, we explored the effect of MSCs and DAC on macrophage polarization. Results. The blood glucose and serum insulin levels revealed that DAC prolonged the antidiabetic effect of MSCs to 4 weeks in T2D mice. Immunofluorescence staining demonstrated more sustainable morphological and structural amelioration in islets of the MD group than in the MSC group. Interestingly, further analysis showed more alternatively activated macrophages (M2, anti-inflammatory) and fewer classically activated macrophages (M1, proinflammatory) in islets of the MD group 4 weeks after treatment. An in vitro study demonstrated that DAC together with MSCs further polarized macrophages from the M1 to M2 phenotype via the PI3K/AKT pathway. Conclusion. These data unveiled that DAC prolonged the antidiabetic effect of MSCs and promoted sustainable β-cell restoration, possibly by modulating the macrophage phenotype. Our results offer a preferable therapeutic strategy for T2D. [ABSTRACT FROM AUTHOR]

Insulin resistance, a major characteristic of type 2 diabetes (T2D), is closely associated with adipose tissue macrophages (ATMs) that induce chronic low-grade inflammation. Recently, mesenchymal stem cells (MSCs) have been identified in alleviation of insulin resistance. However, the underlying mechanism still remains elusive. Thus, we aimed to investigate whether the effect of MSCs on insulin resistance was related to macrophages phenotypes in adipose tissues of T2D rats. In this study, human umbilical cord-derived MSCs (UC-MSCs) infusion produced significantly anti-diabetic effects and promoted insulin sensitivity in T2D rats that were induced by a high-fat diet combined with streptozotocin and directed ATMs into an alternatively activated phenotype (M2, anti-inflammatory). In vitro, MSC-induced M2 macrophages alleviated insulin resistance caused by classically activated macrophages (M1, pro-inflammatory). Further analysis showed that M1 stimulated UC-MSCs to increase expression of interleukin (IL)-6, a molecule which upregulated IL4R expression, promoted phosphorylation of STAT6 in macrophages, and eventually polarized macrophages into M2 phenotype. Moreover, the UC-MSCs effect on macrophages was largely abrogated by small interfering RNA (siRNA) knockdown of IL-6. Together, our results indicate that UC-MSCs can alleviate insulin resistance in part via production of IL-6 that elicits M2 polarization. Additionally, human obesity and insulin resistance were associated with increased pro-inflammatory ATMs infiltration. Thus, MSCs may be a new treatment for obesity-related insulin resistance and T2D concerning macrophage polarized effects. S tem C ells 2016;34:627-639 [ABSTRACT FROM AUTHOR]