Cell therapy for diabetic neuropathy using adult stem or progenitor cells

Efficacy of adipose-derived mesenchymal stem cell therapy in the treatment of chronic micro- and macrovascular complications of diabetes

Diabetes mellitus is a highly prevalent disease characterized by hyperglycaemia that damages the vascular system, leading to micro- (retinopathy, neuropathy, nephropathy) and macrovascular diseases (cardiovascular disease). There are also secondary complications of diabetes (cardiomyopathy, erectile dysfunction or diabetic foot ulcers). Stem cell-based therapies have become a promising tool targeting diabetes symptoms and its chronic complications. Among all stem cells, adipose-derived mesenchymal stem cells (ADMSCs) are of great importance because of their abundance, non-invasive isolation and no ethical limitations. Characteristics that make ADMSCs good candidates for cell-based therapy are their wide immunomodulatory properties and paracrine activities through the secretion of an array of growth factors, chemokines, cytokines, angiogenic factors and anti-apoptotic molecules. Besides, after transplantation, ADMSCs show great ex vivo expansion capacity and differentiation to other cell types, including insulin-producing cells, cardiomyocytes, chondrocytes, hepatocyte-like cells, neurons, endothelial cells, photoreceptor-like cells, or astrocytes. Preclinical studies have shown that ADMSC-based therapy effectively improved visual acuity, ameliorated polyneuropathy and foot ulceration, arrested the development and progression of diabetic kidney disease, or alleviated the diabetes-induced cardiomyocyte hypertrophy. However, despite the positive results obtained in animal models, there are still several challenges that need to be overcome before the results of preclinical studies can be translated into clinical applications. To date, there are several clinical trials or ongoing trials using ADMSCs in the treatment of diabetic complications, most of them in the treatment of diabetic foot ulcers. This narrative review summarizes the most recent outcomes on the usage of ADMSCs in the treatment of long-term complications of diabetes in both animal models and clinical trials.

Interferon-gamma Treatment of Human Umbilical Cord Mesenchymal Stem Cells can Significantly Reduce Damage Associated with Diabetic Peripheral Neuropathy in Mice

BACKGROUND

Diabetic peripheral neuropathy causes significant pain to patients. Umbilical cord mesenchymal stem cells have been shown to be useful in the treatment of diabetes and its complications. The aim of this study was to investigate whether human umbilical cord mesenchymal stem cells treated with interferon-gamma can ameliorate nerve injury associated with diabetes better than human umbilical cord mesenchymal stem cells without interferon-gamma treatment.

METHODS

Human umbilical cord mesenchymal stem cells were assessed for adipogenic differentiation, osteogenic differentiation, and proliferation ability. Vonfry and a hot disc pain tester were used to evaluate tactile sensation and thermal pain sensation in mice. Hematoxylin-eosin and TUNEL staining were performed to visualize sciatic nerve fiber lesions and Schwann cell apoptosis in diabetic mice. Western blotting was used to detect expression of the apoptosis-related proteins Bax, B-cell lymphoma-2, and caspase-3 in mouse sciatic nerve fibers and Schwann cells. Real-Time Quantitative PCR was used to detect mRNA levels of the C-X-C motif chemokine ligand 1, C-X-C motif chemokine ligand 2, C-X-C motif chemokine ligand 9, and C-X-C motif chemokine ligand 10 in mouse sciatic nerve fibers and Schwann cells. Enzyme-linked immunosorbent assay was used to detect levels of the inflammatory cytokines, interleukin- 1β, interleukin-6, and tumor necrosis factor-α in serum and Schwann cells.

RESULTS

The adipogenic differentiation capacity, osteogenic differentiation capacity, and proliferation ability of human umbilical cord mesenchymal stem cells were enhanced after interferon-gamma treatment. Real-Time Quantitative PCR revealed that interferon-gamma promoted expression of the adipogenic markers, PPAR-γ and CEBP-α, as well as of the osteogenic markers secreted phosphoprotein 1, bone gamma-carboxyglutamate protein, collagen type I alpha1 chain, and Runt-related transcription factor 2. The results of hematoxylin-eosin and TUNEL staining showed that pathological nerve fiber damage and Schwann cell apoptosis were reduced after the injection of interferon-gamma-treated human umbilical cord mesenchymal stem cells. Expression of the apoptosis-related proteins, caspase-3 and Bax, was significantly reduced, while expression of the anti-apoptotic protein B-cell lymphoma-2 was significantly increased. mRNA levels of the cell chemokines, C-X-C motif chemokine ligand 1, C-X-C motif chemokine ligand 2, C-X-C motif chemokine ligand 9, and C-X-C motif chemokine ligand 10, were significantly reduced, and levels of the inflammatory cytokines, interleukin-1β, interleukin-6, and tumor necrosis factor-α, were decreased. Tactile and thermal pain sensations were improved in diabetic mice.

CONCLUSION

Interferon-gamma treatment of umbilical cord mesenchymal stem cells enhanced osteogenic differentiation, adipogenic differentiation, and proliferative potential. It can enhance the ability of human umbilical cord mesenchymal stem cells to alleviate damage to diabetic nerve fibers and Schwann cells, in addition to improving the neurological function of diabetic mice.

A Receptor Story: Insulin Resistance Pathophysiology and Physiologic Insulin Resensitization's Role as a Treatment Modality

Physiologic insulin secretion consists of an oscillating pattern of secretion followed by distinct trough periods that stimulate ligand and receptor activation. Apart from the large postprandial bolus release of insulin, β cells also secrete small amounts of insulin every 4-8 min independent of a meal. Insulin resistance is associated with a disruption in the normal cyclical pattern of insulin secretion. In the case of type-2 diabetes, β-cell mass is reduced due to apoptosis and β cells secrete insulin asynchronously. When ligand/receptors are constantly exposed to insulin, a negative feedback loop down regulates insulin receptor availability to insulin, creating a relative hyperinsulinemia. The relative excess of insulin leads to insulin resistance (IR) due to decreased receptor availability. Over time, progressive insulin resistance compromises carbohydrate metabolism, and may progress to type-2 diabetes (T2D). In this review, we discuss insulin resistance pathophysiology and the use of dynamic exogenous insulin administration in a manner consistent with more normal insulin secretion periodicity to reverse insulin resistance. Administration of insulin in such a physiologic manner appears to improve insulin sensitivity, lower HgbA1c, and, in some instances, has been associated with the reversal of end-organ damage that leads to complications of diabetes. This review outlines the rationale for how the physiologic secretion of insulin orchestrates glucose metabolism, and how mimicking this secretion profile may serve to improve glycemic control, reduce cellular inflammation, and potentially improve outcomes in patients with diabetes.

Nanochannel-Based Poration Drives Benign and Effective Nonviral Gene Delivery to Peripheral Nerve Tissue

While gene and cell therapies have emerged as promising treatment strategies for various neurological conditions, heavy reliance on viral vectors can hamper widespread clinical implementation. Here, the use of tissue nanotransfection as a platform nanotechnology to drive nonviral gene delivery to nerve tissue via nanochannels, in an effective, controlled, and benign manner is explored. TNT facilitates plasmid DNA delivery to the sciatic nerve of mice in a voltage-dependent manner. Compared to standard bulk electroporation (BEP), impairment in toe-spread and pinprick response is not caused by TNT, and has limited to no impact on electrophysiological parameters. BEP, however, induces significant nerve damage and increases macrophage immunoreactivity. TNT is subsequently used to deliver vasculogenic cell therapies to crushed nerves via delivery of reprogramming factor genes Etv2, Foxc2, and Fli1 (EFF). The results indicate the TNT-based delivery of EFF in a sciatic nerve crush model leads to increased vascularity, reduced macrophage infiltration, and improved recovery in electrophysiological parameters compared to crushed nerves that are TNT-treated with sham/empty plasmids. Altogether, the results indicate that TNT can be a powerful platform nanotechnology for localized nonviral gene delivery to nerve tissue, in vivo, and the deployment of reprogramming-based cell therapies for nerve repair/regeneration.

Autologous Bone Marrow Mononuclear Cell Transplantation Therapy Improved Symptoms in Patients with Refractory Diabetic Sensorimotor Polyneuropathy via the Mechanisms of Paracrine and Immunomodulation: A Controlled Study

We recently reported that transplantation of autologous bone marrow mononuclear cells (BM-MNCs) may be an effective and promising therapy to treat refractory diabetic sensorimotor polyneuropathy (DSPN) in patients with type 2 diabetes mellitus (T2DM). This study was designed to investigate the potential mechanisms of BM-MNCs therapy, which recruited 60 patients with DSPN, 30 T2DM patients without complications, and 30 healthy control participants. All clinical parameters, the levels of inflammatory markers, and growth factors in the three groups were compared. Patients in DSPN group had higher level of tumor necrosis factor-α (TNF-α) (DSPN vs control, 412.90 ± 64.58 vs 374.81 ± 63.18 pg/mL, P < 0.01) and lower level of vascular endothelial growth factor (VEGF) (DSPN vs control, 140.93 ± 24.78 vs 157.39 ± 25.11 pg/mL, P < 0.01) than those in control group. DSPN group had the highest level of soluble intercellular adhesion molecule-1 (sICAM-1) among three groups (DSPN and DM vs control, 1477.56 ± 228.00 and 1342.17 ± 237.54 vs 1308.00 ± 200.94 ng/mL, P < 0.05). The level of nerve growth factor in the DSPN group was slightly lower than that in the DM group (DSPN vs DM, 3509.11 ± 438.39 vs 3734.87 ± 647.50 pg/mL, P < 0.05). All patients with DSPN received one intramuscular injection of BM-MNCs and clinical follow-ups after the therapy for 2 days, 1, 4, 12, 24, and 48 weeks. Neuropathic symptoms of foot pain, numbness, and weakness were significantly improved within 4 weeks after BM-MNCs injection. Patients with DSPN were divided into the responder (n = 35) and nonresponder groups (n = 19) based on the improvement of nerve conduction velocity at 12 weeks post-transplantation. Compared with nonresponders, responders were younger (57.3 ± 5.2 vs 62.0 ± 4.8, P < 0.01), had a shorter history of diabetes (7.1 ± 2.7 vs 11.2 ± 5.4 years, P < 0.01), and had higher numbers of mobilized CD34⁺ cells (17.61 ± 2.64 vs 14.79 ± 1.62 ×10⁵/L, P < 0.01) and BM-MNCs (12.05 ± 2.16 vs 9.84 ± 1.53 ×10⁸/L, P < 0.01). The levels of TNF-α and sICAM-1 decreased just after BM-MNCs injection in both groups and slowly reverted to baseline levels. The duration of the downtrend of TNF-α and sICAM-1 in the responder group lasted longer than that in the nonresponder group. Serum level of VEGF in the responder group increased immediately after BM-MNC therapy and reached the highest point after the injection for 12 weeks. On the other hand, VEGF levels in the nonresponder group only increased slightly. Binary logistic regression was performed to evaluate the corresponding prognostic factors for BM-MNCs treatment. The number of applied CD34⁺ cells and the duration of diabetes were the independent predictors of responding to BM-MNCs therapy. No adverse event associated with the treatment was observed during follow-up observations. These results indicated that BM-MNCs transplantation is an effective and promising therapeutic strategy to treat refractory DSPN. The immune regulation and paracrine function of BM-MNCs may contribute to the improvement of DSPN.

Endothelial progenitor cells and peripheral neuropathy in subjects with type 2 diabetes mellitus

AIMS

To examine for differences in circulating progenitor cells (CPCs) and endothelial progenitor cells (EPCs) in patients with and without diabetic peripheral neuropathy (DPN).

METHODS

A total of 105 participants were included: 50 patients with type 2 diabetes (T2DM) and DPN, 30 patients with T2DM without DPN and 25 healthy individuals. CPCs and 6 different EPCs phenotypes were assessed with flow cytometry. We also measured plasma levels of vascular endothelial growth factor (VEGF), stromal cell-derived factor 1 (SDF-1), vascular cell adhesion protein-1 (VCAM-1), intracellular adhesion molecule-1 (ICAM) and tumor necrosis factor a (TNFa).

RESULTS

No difference was observed in the number of CPCs among the 3 groups. Patients with DPN had higher numbers of all 6 EPCs phenotypes when compared with patients without DPN and higher number of 5 EPCs phenotypes when compared with healthy individuals. Plasma VEFG, VCAM-1, ICAM-1 and TNFa levels did not differ among the 3 groups. Patients with DPN had lower SDF-1 levels in comparison with healthy individuals.

CONCLUSION

Circulating EPCs are increased while SDF-1 levels are decreased in the presence of DPN. Our findings suggest that DPN may be associated with impaired trafficking of EPCs and impaired EPCs homing to the injured endothelium.

Sodium nitrate preconditioning prevents progression of the neuropathic pain in streptozotocin-induced diabetes Wistar rats

Purpose

The purpose of the study was to evaluate the possible protective effects of low dose sodium nitrate preconditioning on the peripheral neuropathy in streptozotocin (STZ)-induced diabetic model.

Methods

Male Wistar rats were randomly divided into five groups: control (no intervention), control treated sodium nitrate (100 mg/L in drinking water), diabetic (no intervention), diabetic treated NPH insulin (2-4 U), and diabetic treated sodium nitrate (100 mg/L in drinking water). Diabetes was induced by intraperitoneal injection of STZ (60 mg/kg). All interventions were done for 60 days immediately following diabetes confirmation. Thermal and mechanical algesia thresholds were measured by means of hot-plate test, von Frey test, and tail-withdrawal test before the diabetic induction and after diabetes confirmation. At the end of the experiment, serum NOx level and serum insulin level were assessed. Blood glucose concentration and body weight have recorded at the base and duration of the experiment.

Results

Both hypoalgesia, hyperalgesia along with allodynia developed in diabetic rats. Significant alterations including, decrease in tail withdrawal latency (30th day), decreased mechanical threshold (60th day), and an increase in hot plate latency (61st day) were displayed in diabetic rats compared to control rats. Nitrate and insulin preconditioning produced protective effects against diabetes-induced peripheral neuropathy. Data analysis also showed a significant increase in glucose level as well as a considerable reduction in serum insulin and body weight of diabetic rats, which restored by both insulin and nitrate preconditioning.

Conclusion

Sodium nitrate preconditioning produces a protective effect in diabetic neuropathy, which may be mediated by its antihyperglycemic effects and increased serum insulin level.

The Influence of Diabetic Foot Exercise in Sensory Peripheral Neuropathy with Monofilament Test on Diabetes Mellitus Clients

Background: Peripheral neuropathy is a long-term complication that attacks the nerves and loses the sensation of protection which affects about 50% of people with diabetes mellitus (DM). Diabetic foot exercises can help blood circulation, especially in the legs or lower limbs. This researched aimed to analyze the effect of diabetic foot exercise on sensory peripheral neuropathy in DM clients.Method: The study design used quasi-experimental pre-post test with control group. Samples were 28 respondents using purposive sampling and divided into two groups of 14 respondents each. The independent variable is diabetic foot training, and the dependent variable is peripheral sensory neuropathy. Interventions are carried out 3 times a week for 4 weeks. The research instrument was Weinstein Monofilament 10 g Semmes and a diabetic foot training checklist. Data analysis using the Wilcoxon-signed rank test and Mann Whitney test with α≤0.05.Result: The Wilcoxon-signed rank test in the treatment group showed differences in sensory peripheral neuropathy after treatment (p=0,000) and no difference in the control group (p=0.564). The Mann Whitney test results showed differences in sensory peripheral neuropathy between the treatment group and the control group after treatment p=0.039.Conclusion: Diabetic foot exercises can be used as an alternative measure to improve sensory peripheral neuropathy.

Effects of mesenchymal stromal cells on motor function and collagen in the skeletal muscles of rats with type I diabetes

The present study aimed to evaluate the effects of mesenchymal stromal cell (MSC) transplantation on motor function and collagen organization in the muscles of rats with type 1 diabetes mellitus. Male Wistar rats were randomly assigned to three groups: control (C), diabetic (DM) and diabetic treated with MSCs (DM-MSCs). Diabetes was induced by streptozotocin (50 µg/kg). Bone marrow cells were isolated from the tibia and femur. After 10 weeks of DM induction, the DM-MSC rats received four i.p. injections of MSCs (1 × 106). Ten weeks after MSC transplantation, motor performance was evaluated by the rotarod test and the anterior tibial (TA) muscles were collected for morphometric and quantification of collagen birefringence by polarizing microscopy analysis. Motor performance of the DM group was significantly reduced when compared to the C group and increased significantly in the DM + MSC group. The TA muscle mass was significantly reduced in the DM and DM + MSC groups compared to the C group. The connective tissue increased in the DM group compared to the C group and decreased in the DM + MSC group. The percentage collagen birefringence decreased significantly in the DM group when compared to the C group and increased in the DM + MSC group. Motor performance was positively correlated with collagen birefringence and negatively correlated with percentage of connective tissue. The results indicate that MSC transplantation improves both motor function and the collagen macromolecular organization in type 1 DM.

Effects of adipose derived stromal vascular fraction on diabetic neuropathy: an experimental study

The stromal vascular fraction (SVF) obtained from inguinal adipose tissue was injected into the sciatic nerve region in diabetic rats. The effects of the SVF on the sciatic nerve and functional, electrophysiological and histopathological changes were examined in this study. Rats were divided into five groups; a non-diabetic control group, and four diabetic groups. In the first diabetic rat group, the SVF was obtained from inguinal adipose tissue. The remaining diabetic groups included a sham control group, a phosphate-buffered saline (PBS) injection group and an SVF injection group. Injections were made into the sciatic nerve region. Electromyography and walking track analyses were conducted on all groups at the beginning of the experiment. Diabetes was induced via a single dose of streptozotocin. Walking track analysis and electromyography measurements were repeated in week 8. SVF or PBS was injected into the right sciatic nerve region on week 8 of experiment group rats. Walking track analysis and electromyography were repeated in week 12 and all sciatic nerves were examined histopathologically. In the diabetic SVF group, the sciatic functional index calculated from walking track analysis in week 12 was better than week 8. Additionally, the myelin sheaths of the right sciatic nerve were thicker and more uniform and the nerve fibers were thicker than those of the left, untreated sciatic nerve. No statistical differences were detected in electromyographic measurements. The adipose-derived SVF may be beneficial for nerve regeneration in diabetic neuropathy.

Impaired Regeneration Potential in Urinary Stem Cells Diagnosed from the Patients with Diabetic Nephropathy

Stem cells present in urine possess regenerative capacity to repair kidney injury. However, the unique characteristics of urinary stem cells (USC) from patients with diabetic nephropathy (d-USC) are unknown. The goal of this study was to investigate stemness properties in cell phenotype and regenerative potential of d-USC, compared to USC from healthy individuals. Methods: Thirty-six urine samples collected from patients (n=12, age range 60-75 years) with diabetic nephropathy (stages 3-4 stage chronic kidney disease [CKD]) were compared with 30 urine samples from healthy age-matched donors (n=10, age range 60-74 years). Results: There were approximately six times as many cells in urine samples from patients with diabetic nephropathy, including twice as many USC clones as healthy donors. However, approximately 70% of d-USC had weaker regenerative capacity as assessed by cell proliferation, less secretion of paracrine factors, weaker telomerase activity, and lower renal tubular epithelial differentiation potential compared to healthy controls. In addition, the levels of inflammatory factors (IL-1β and Cx43) and apoptotic markers (Caspase-3, and TUNEL) were significantly increased in d-USC compared to USC (p<0.01). Protein levels of autophagy marker (LC3-II) and mTOR signaling molecules (p-mTOR/mTOR, p-Raptor/Raptor and p-S6K1) were significantly lower in patient with diabetic nephropathy (p<0.01). Nevertheless, up to 30% of d-USC possessed similar regenerative capacity as USC from healthy donors. Conclusions: Regenerative performance of most d-USC was significantly lower than normal controls. Understanding the specific changes in d-USC regeneration capability will help elucidate the pathobiology of diabetic nephropathy and lead to prevent USC from diabetic insults, recover the stemness function and also identify novel biomarkers to predict progression of this chronic kidney disease.

Efficacy of autologous bone marrow mononuclear cell transplantation therapy in patients with refractory diabetic peripheral neuropathy

BACKGROUND

Owing to the multifactorial nature of the pathogenesis of diabetic peripheral neuropathy (DPN), conventional drug therapies have not been effective. The application of stem cells transplantation may be useful for the treatment of DPN. This study was designed to assess the safety and therapeutic effects of autologous bone marrow mononuclear cells (BMMNCs) transplantation on the treatment of refractory DPN.

METHODS

One hundred and sixty-eight patients with refractory DPN were recruited and enrolled in the study. They received intramuscular injection of BMMNCs and followed at 1, 3, 6, 12, 18, 24, and 36 months after the transplantation. Clinical data, Toronto Clinical Scoring System (TCSS), and nerve conduction studies (NCSs) were compared before and after the transplantation.

RESULTS

The signs and symptoms of neuropathy were significantly improved after BMMNCs transplantation. The values of the TCSS scores at 1 month (9.68 ± 2.49 vs. 12.55 ± 2.19, P < 0.001) and 3 months (8.47 ± 2.39 vs. 12.55 ± 2.19, P < 0.001) after the treatment reduced significantly compared with the baseline value. This decrement remained persistent until the end of the study. The conduction velocity and action potential and sensory nerves were significantly improved after transplantation (3 and 12 months after the treatment vs. the baseline: motor nerve conduction velocity, 40.24 ± 2.80 and 41.00 ± 2.22 m/s vs. 38.21 ± 2.28 m/s, P < 0.001; sensory nerve conduction velocity, 36.96 ± 2.26 and 39.15 ± 2.61 m/s vs. 40.41 ± 2.22 m/s, P < 0.001; compound muscle action potential, 4.67 ± 1.05 and 5.50 ± 1.20 μV vs. 5.68 ± 1.08 μV, P < 0.001; sensory nerve action potential, 4.29 ± 0.99 and 5.14 ± 1.26 μV vs. 5.41 ± 1.14 μV, P < 0.001). No adverse event associated with the treatment was observed during the follow-up period.

CONCLUSIONS

Autologous transplantation of BMMNCs may be an effective and promising therapeutic strategy for the treatment of refractory DPN.

Transplantation of human mobilized mononuclear cells improved diabetic neuropathy

Rodent stem cells demonstrated regenerative effects in diabetic neuropathy via improvement in nerve perfusion. As a pre-clinical step, we explored if human mobilized mononuclear cells (hMNC) would have the same effects in rats. hMNC were injected into Rt. hind-limb muscles of streptozotocin-induced diabetic nude rats, and the grafts were monitored using with MRI. After 4 weeks, the effects were compared with those in the vehicle-injected Lt. hind limbs. Nerve conduction, muscle perfusion and gene expression of sciatic nerves were assessed. Induction of diabetes decreased nerve function and expression of Mpz and Met in the sciatic nerves, which are related with myelination. hMNC injection significantly improved the amplitude of compound muscle action potentials along with muscle perfusion and sciatic nerve Mpz expression. On MRI, hypointense signals were observed for 4 weeks at the graft site, but their correlation with the presence of hMNC was detectable for only 1 week. To evaluate paracrine effects of hMNC, IMS32 cells were tested with hepatocyte growth factor (HGF), which had been reported as a myelination-related factor from stem cells. We could observe that HGF enhanced Mpz expression in the IMS32 cells. Because hMNC secreted HGF, IMS32 cells were co-cultured with hMNC, and the expression of Mpz increased along with morphologic maturation. The hMNC-induced Mpz expression was abrogated by treatment of anti-HGF. These results suggest that hMNC could improve diabetic neuropathy, possibly through enhancement of myelination as well as perfusion. According to in vitro studies, HGF was involved in the hMNC-induced myelination activity, at least in part.

Fluoxetine pretreatment enhances neurogenic, angiogenic and immunomodulatory effects of MSCs on experimentally induced diabetic neuropathy

Being one of the most debilitating complications among diabetic patients, diabetic polyneuropathy (DPN) is a paramount point of continuous research. Stem cell therapies have shown promising results. However, limited cell survival and paracrine activities hinder its transfer from bench to bedside. We designed this study to evaluate fluoxetine-pretreatment technique of mesenchymal stem cells (MSCs) as an approach to enhance their paracrine and immunomodulatory properties in DPN. Effects of fluoxetine treatment of MSCs were tested in vitro. Forty-two adult Wistar male albino rats were utilized, further subdivided into control, diabetic, MSC-treated and fluoxetine-pretreated MSC groups. Sciatic nerve sections were prepared for light and electron microscope examination and immunohistochemical detection of neurofilament (NF) protein. Also, we assessed in vitro survival and paracrine properties of fluoxetine-pretreated MSCs. Real time PCR of BDNF, VEGF, IL-1β, and IL-10 expression in tissue homogenate was performed. Our results showed restoration of normal neuronal histomorphology and ultrastructure, moreover, immunohistochemical expression of anti-neurofilament protein was significantly elevated in MSC-treated groups compared to the diabetic one. Fluoxetine enhanced the MSC survival and their paracrine properties of MSCs in vitro. Furthermore, the fluoxetine-pretreated MSC group revealed a significant elevation of mRNA expression of BDNF (neurotrophic factor) and VEGF (angiogenic factor), denoting ameliorated MSC paracrine properties. Similarly, improved immunomodulatory functions were evident by a significant reduction of interleukin-1β mRNA expression (pro-inflammatory) and a reciprocal significant increase of interleukin-10 (anti-inflammatory). We concluded that fluoxetine-pretreatment of MSCs boosts their survival, paracrine, and immunomodulatory traits and directly influenced neuronal histomorphology. Hence, it presents a promising intervention of diabetic polyneuropathy. Graphical Abstract.

Addressing Stem Cell Therapeutic Approaches in Pathobiology of Diabetes and Its Complications

High morbidity and mortality of diabetes mellitus (DM) throughout the human population is a serious threat which needs to be addressed cautiously. Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) are most prevalent forms. Disruption in insulin regulation and resistance leads to increased formation and accumulation of advanced end products (AGEs), which further enhance oxidative and nitrosative stress leading to microvascular (retinopathy, neuropathy, and nephropathy) and macrovascular complications. These complications affect the normal function of organ and tissues and may cause life-threatening disorders, if hyperglycemia persists and improperly controlled. Current and traditional treatment procedures are only focused on to regulate the insulin level and do not cure the diabetic complications. Pancreatic transplantation seemed a viable alternative; however, it is limited due to lack of donors. Cell-based therapy such as stem cells is considered as a promising therapeutic agent against DM and diabetic complications owing to their multilineage differentiation and regeneration potential. Previous studies have demonstrated the various impacts of both pluripotent and multipotent stem cells on DM and its micro- and macrovascular complications. Therefore, this review summarizes the potential of stem cells to treat DM and its related complications.

Autologous Bone Marrow-Derived Stem Cells for Treating Diabetic Neuropathy in Metabolic Syndrome

Diabetic neuropathy is one of the most common and serious complications of diabetes mellitus and metabolic syndrome. The current therapy strategies, including glucose control and pain management, are not effective for most patients. Growing evidence suggests that infiltration of inflammation factors and deficiency of local neurotrophic and angiogenic factors contribute significantly to the pathologies of diabetic neuropathy. Experimental and clinical studies have shown that bone marrow-derived stem cells (BMCs) therapy represents a novel and promising strategy for tissue repair through paracrine secretion of multiple cytokines, which has a potential to inhibit inflammation and promote angiogenesis and neurotrophy in diabetic neuropathy. In this review, we discuss the clinical practice in diabetic neuropathy and the therapeutic effect of BMC. We subsequently illustrate the functional impairment of autologous BMCs due to the interrupted bone marrow niche in diabetic neuropathy. We anticipate that the functional restoration of BMCs could improve their therapeutic effect and enable their wide applications in diabetic neuropathy.

Impaired olfactory function is related to the presence of neuropathy in adults with type 1 diabetes

INTRODUCTION

Olfactory dysfunction is suggested to be a clinical manifestation of central diabetic neuropathy. The aim of the study was to assess olfactory function in adult patients with type 1 diabetes.

MATERIALS AND METHODS

A total of 106 patients with type 1 diabetes and 30 healthy subjects were included in the study. We evaluated the metabolic control of diabetes and the presence of chronic complications. Olfactory function was assessed with Sniffin' Sticks.

RESULTS

We found a negative correlation between olfactory identification scores and body mass index ( Rs -0.2; p = 0.04) and triglycerides ( Rs = -0.2; p = 0.04). We showed lower olfactory identification scores in neuropathy group versus non-neuropathy group [8 (interquartile range, 7-9) vs 10 (interquartile range, 9-11) points; p = 0.005]. In multivariate linear regression, impaired olfaction was independently associated with neuropathy (beta, -0.3; p = 0.005). In multivariate logistic regression, diabetes duration (odds ratio, 1.06; 95% confidence interval, 1.00-1.11; p = 0.04) and olfactory identification score (odds ratio, 0.61; 95% confidence interval, 0.43-0.85; p = 0.003) were independently associated with neuropathy.

CONCLUSION

Olfactory dysfunction is observed in patients with type 1 diabetes and diabetic peripheral neuropathy.

New insights into the ameliorative effects of ferulic acid in pathophysiological conditions

Ferulic acid, a natural phytochemical has gained importance as a potential therapeutic agent by virtue of its easy commercial availability, low cost and minimal side-effects. It is a derivative of curcumin and possesses the necessary pharmacokinetic properties to be retained in the general circulation for several hours. The therapeutic effects of ferulic acid are mediated through its antioxidant and anti-inflammatory properties. It exhibits different biological activities such as anti-inflammatory, anti-apoptotic, anti-carcinogenic, anti-diabetic, hepatoprotective, cardioprotective, neuroprotective actions, etc. The current review addresses its therapeutic effects under different pathophysiological conditions (eg. cancer, cardiomyopathy, skin disorders, brain disorders, viral infections, diabetes etc.).

Mesenchymal stem cells to treat diabetic neuropathy: a long and strenuous way from bench to the clinic

As one of the most common complications of diabetes, diabetic neuropathy often causes foot ulcers and even limb amputations. Inspite of continuous development in antidiabetic drugs, there is still no efficient therapy to cure diabetic neuropathy. Diabetic neuropathy shows declined vascularity in peripheral nerves and lack of angiogenic and neurotrophic factors. Mesenchymal stem cells (MSCs) have been indicated as a novel emerging regenerative therapy for diabetic neuropathy because of their multipotency. We will briefly review the pathogenesis of diabetic neuropathy, characteristic of MSCs, effects of MSC therapies for diabetic neuropathy and its related mechanisms. In order to treat diabetic neuropathy, neurotrophic or angiogenic factors in the form of protein or gene therapy are delivered to diabetic neuropathy, but therapeutic efficiencies are very modest if not ineffective. MSC treatment reverses manifestations of diabetic neuropathy. MSCs have an important role to repair tissue and to lower blood glucose level. MSCs even paracrinely secrete neurotrophic factors, angiogenic factors, cytokines, and immunomodulatory substances to ameliorate diabetic neuropathy. There are still several challenges in the clinical translation of MSC therapy, such as safety, optimal dose of administration, optimal mode of cell delivery, issues of MSC heterogeneity, clinically meaningful engraftment, autologous or allogeneic approach, challenges with cell manufacture, and further mechanisms.

Microvessel permeability correlates with diabetic peripheral neuropathy in early stage of streptozotocin-induced diabetes rats

AIMS

This study aims to explore the alterations in microvessel permeability in the sciatic nerve and whether they are associated with the development of diabetic peripheral neuropathy (DPN) during the early stage of diabetes in rats.

METHODS

Sprague-Dawley rats were injected with streptozotocin and assessed at 0, 2, 4, and 8 weeks. Rats in the control group received the vehicle. Changes in sciatic nerve pathology, nerve conductive velocity (NCV), permeability of microvessel, and levels of vascular endothelial growth factor (VEGF) were examined.

RESULTS

The morphology and NCV of sciatic nerves showed signs of abnormality as early as 2 weeks after streptozotocin injection. The microvessel permeability as monitored by water and Evans blue content of sciatic nerve had increased dramatically at 4 and 8 weeks. The water and Evans blue content both negatively correlated with NCV. VEGF was found in axons as well as the myelin sheaths in diabetic rats but not in control rats.

CONCLUSIONS

The permeability of sciatic nerves was associated with the development of DPN in the early stage of diabetes in rats. Increased expression of VEGF may have a crucial role in changes in microvessel permeability and DPN.

Diabetes mellitus related bone metabolism and periodontal disease

Diabetes mellitus and periodontal disease are chronic diseases affecting a large number of populations worldwide. Changed bone metabolism is one of the important long-term complications associated with diabetes mellitus. Alveolar bone loss is one of the main outcomes of periodontitis, and diabetes is among the primary risk factors for periodontal disease. In this review, we summarise the adverse effects of diabetes on the periodontium in periodontitis subjects, focusing on alveolar bone loss. Bone remodelling begins with osteoclasts resorbing bone, followed by new bone formation by osteoblasts in the resorption lacunae. Therefore, we discuss the potential mechanism of diabetes-enhanced bone loss in relation to osteoblasts and osteoclasts.

Emerging roles of hematopoietic cells in the pathobiology of diabetic complications

Diabetic complications encompass macrovascular events, mainly the result of accelerated atherosclerosis, and microvascular events that strike the eye (retinopathy), kidney (nephropathy), and nervous system (neuropathy). The traditional view is that hyperglycemia-induced dysregulated biochemical pathways cause injury and death of cells intrinsic to the organs affected. There is emerging evidence that diabetes compromises the function of the bone marrow (BM), producing a stem cell niche-dependent defect in hematopoietic stem cell mobilization. Furthermore, dysfunctional BM-derived hematopoietic cells contribute to diabetic complications. Thus, BM cells are not only a victim but also an accomplice in diabetes and diabetic complications. Understanding the underlying molecular mechanisms may lead to the development of new therapies to prevent and/or treat diabetic complications by specifically targeting these perpetrators.

Mesenchymal stem cell-based treatment for microvascular and secondary complications of diabetes mellitus

The worldwide increase in the prevalence of Diabetes mellitus (DM) has highlighted the need for increased research efforts into treatment options for both the disease itself and its associated complications. In recent years, mesenchymal stromal cells (MSCs) have been highlighted as a new emerging regenerative therapy due to their multipotency but also due to their paracrine secretion of angiogenic factors, cytokines, and immunomodulatory substances. This review focuses on the potential use of MSCs as a regenerative medicine in microvascular and secondary complications of DM and will discuss the challenges and future prospects of MSCs as a regenerative therapy in this field. MSCs are believed to have an important role in tissue repair. Evidence in recent years has demonstrated that MSCs have potent immunomodulatory functions resulting in active suppression of various components of the host immune response. MSCs may also have glucose lowering properties providing another attractive and unique feature of this therapeutic approach. Through a combination of the above characteristics, MSCs have been shown to exert beneficial effects in pre-clinical models of diabetic complications prompting initial clinical studies in diabetic wound healing and nephropathy. Challenges that remain in the clinical translation of MSC therapy include issues of MSC heterogeneity, optimal mode of cell delivery, homing of these cells to tissues of interest with high efficiency, clinically meaningful engraftment, and challenges with cell manufacture. An issue of added importance is whether an autologous or allogeneic approach will be used. In summary, MSC administration has significant potential in the treatment of diabetic microvascular and secondary complications but challenges remain in terms of engraftment, persistence, tissue targeting, and cell manufacture.