Influence of heme oxygenase-1 gene transfer on the viability and function of rat islets in in vitro culture

Viability and Functionality of Neonatal Porcine Islet-like Cell Clusters Bioprinted in Alginate-Based Bioinks

The transplantation of pancreatic islets can prevent severe long-term complications in diabetes mellitus type 1 patients. With respect to a shortage of donor organs, the transplantation of xenogeneic islets is highly attractive. To avoid rejection, islets can be encapsulated in immuno-protective hydrogel-macrocapsules, whereby 3D bioprinted structures with macropores allow for a high surface-to-volume ratio and reduced diffusion distances. In the present study, we applied 3D bioprinting to encapsulate the potentially clinically applicable neonatal porcine islet-like cell clusters (NICC) in alginate-methylcellulose. The material was additionally supplemented with bovine serum albumin or the human blood plasma derivatives platelet lysate and fresh frozen plasma. NICC were analysed for viability, proliferation, the presence of hormones, and the release of insulin in reaction to glucose stimulation. Bioprinted NICC are homogeneously distributed, remain morphologically intact, and show a comparable viability and proliferation to control NICC. The number of insulin-positive cells is comparable between the groups and over time. The amount of insulin release increases over time and is released in response to glucose stimulation over 4 weeks. In summary, we show the successful bioprinting of NICC and could demonstrate functionality over the long-term in vitro. Supplementation resulted in a trend for higher viability, but no additional benefit on functionality was observed.

3D Bioprinting of Functional Islets of Langerhans in an Alginate/Methylcellulose Hydrogel Blend

Transplantation of pancreatic islets is a promising strategy to alleviate the unstable blood-glucose control that some patients with diabetes type 1 exhibit and has seen many advances over the years. Protection of transplanted islets from the immune system can be accomplished by encapsulation within a hydrogel, the most investigated of which is alginate. In this study, islet encapsulation is combined with 3D extrusion bioprinting, an additive manufacturing method which enables the fabrication of 3D structures with a precise geometry to produce macroporous hydrogel constructs with embedded islets. Using a plottable hydrogel blend consisting of clinically approved ultrapure alginate and methylcellulose (Alg/MC) enables encapsulating pancreatic islets in macroporous 3D hydrogel constructs of defined geometry while retaining their viability, morphology, and functionality. Diffusion of glucose and insulin in the Alg/MC hydrogel is comparable to diffusion in plain alginate; the embedded islets continuously produce insulin and glucagon throughout the observation and still react to glucose stimulation albeit to a lesser degree than control islets.

Human mesenchymal stem cells improve rat islet functionality under cytokine stress with combined upregulation of heme oxygenase-1 and ferritin

Background

Islets of Langerhans transplantation is a promising therapy for type 1 diabetes mellitus, but this technique is compromised by transplantation stresses including inflammation. In other tissues, co-transplantation with mesenchymal stem cells has been shown to reduce damage by improving anti-inflammatory and anti-oxidant defences. Therefore, we probed the protection afforded by bone marrow mesenchymal stem cells to islets under pro-inflammatory cytokine stress.

Methods

In order to evaluate the cytoprotective potential of mesenchymal stem cells on rat islets, co-cultures were exposed to the interleukin-1, tumour necrosis factor α and interferon γ cocktail for 24 h. Islet viability and functionality tests were performed. Reactive oxygen species and malondialdehyde were measured. Expression of stress-inducible genes acting as anti-oxidants and detoxifiers, such as superoxide dismutases 1 and 2, NAD(P)H quinone oxidoreductase 1, heme oxygenase-1 and ferritin H, was compared to non-stressed cells, and the corresponding proteins were measured. Data were analysed by a two-way ANOVA followed by a Holm-Sidak post hoc analysis.

Results

Exposure of rat islets to cytokines induces a reduction in islet viability and functionality concomitant with an oxidative status shift with an increase of cytosolic ROS production. Mesenchymal stem cells did not significantly increase rat islet viability under exposure to cytokines but protected islets from the loss of insulin secretion. A drastic reduction of the antioxidant factors heme oxygenase-1 and ferritin H protein levels was observed in islets exposed to the cytokine cocktail with a prevention of this effect by the presence of mesenchymal stem cells.

Conclusions

Our data evidenced that MSCs are able to preserve islet insulin secretion through a modulation of the oxidative imbalance mediated by heme and iron via heme oxygenase-1 and ferritin in a context of cytokine exposure.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1190-4) contains supplementary material, which is available to authorized users.

Physiologic Doses of Bilirubin Contribute to Tolerance of Islet Transplants by Suppressing the Innate Immune Response

Bilirubin has been recognized as a powerful cytoprotectant when used at physiologic doses and was recently shown to have immunomodulatory effects in islet allograft transplantation, conveying donor-specific tolerance in a murine model. We hypothesized that bilirubin, an antioxidant, acts to suppress the innate immune response to islet allografts through two mechanisms: 1) by suppressing graft release of damage-associated molecular patterns (DAMPs) and inflammatory cytokines, and 2) by producing a tolerogenic phenotype in antigen-presenting cells. Bilirubin was administered intraperitoneally before pancreatic procurement or was added to culture media after islet isolation in AJ mice. Islets were exposed to transplant-associated nutrient deprivation and hypoxia. Bilirubin significantly decreased islet cell death after isolation and hypoxic stress. Bilirubin supplementation of islet media also decreased the release of DAMPs (HMGB1), inflammatory cytokines (IL-1β and IL-6), and chemokines (MCP-1). Cytoprotection was mediated by the antioxidant effects of bilirubin. Treatment of macrophages with bilirubin induced a regulatory phenotype, with increased expression of PD-L1. Coculture of these macrophages with splenocytes led to expansion of Foxp3+ Tregs. In conclusion, exogenous bilirubin supplementation showed cytoprotective and antioxidant effects in a relevant model of islet isolation and hypoxic stress. Suppression of DAMP release, alterations in cytokine profiles, and tolerogenic effects on macrophages suggest that the use of this natural antioxidant may provide a method of preconditioning to improve outcomes after allograft transplantation.

Nucleotide sequencing, cloning, and expression of Capra hircus Heme Oxygenase-1 in caprine islets to promote insulin secretion in vitro

Transplantation of islets of Langerhans that have been isolated from whole pancreas is an attractive alternative for the reversal of Type 1 diabetes. However, in vitro culture of isolated pancreatic islets has been reported to cause a decrease in glucose response over time. Hence, the improvement in islet culture conditions is an important goal in islet transplantation. Heme Oxygenase-1 (HO-1) is a stress protein that has been described as an inducible protein with the capacity of preventing apoptosis and cytoprotection via radical scavenging. Therefore, this study was aimed to assess the influence of endogenous HO-1 gene transfer on insulin secretion of caprine islets. The full-length cDNA sequence of Capra hircus HO-1 was determined using specific designed primers and rapid amplification of cDNA ends of pancreatic tissue. The HO-1 cDNA was then cloned into the prokaryotic expression vectors and transfected into caprine islets using lipid carriers. Efficiency of lipid carriers to transfect caprine islets was determined by flow cytometry. Insulin secretion assay was carried out by ovine insulin ELISA. The finding demonstrated that endogenous HO-1 gene transfer could improve caprine islet function in in vitro culture. Consequently, strategies using HO-1 gene transfer to islets might lead to better outcome in islet transplantation.

Exendin-4 protects hypoxic islets from oxidative stress and improves islet transplantation outcome

Oxidative stress produced during pancreatic islet isolation leads to significant β-cell damage. Homeostatic cytokines secreted subsequently to islet transplantation damage β-cells by generating oxygen free radicals. In this study, exendin-4, a glucagon-like peptide-1 analog improved islet transplantation outcome by increasing the survival of diabetic recipient mice from 58% to 100%. We hypothesized that this beneficial effect was due to the ability of exendin-4 to reduce oxidative stress. Further experiments showed that it significantly reduced the apoptotic rate of cultured β-cells subjected to hypoxia or to IL-1β. Reduction of apoptotic events was confirmed in pancreatic islet grafts of exendin-4-treated mice. Exendin-4 enhanced Akt phosphorylation of β-cells and insulin released from them. It even augmented insulin secretion from islets cultivated at hypoxic conditions. Exposure to hypoxia led to a decrease in the activation of Akt, which was reversed when β-cells were pretreated with exendin-4. Moreover, exendin-4 increased the activity of redox enzymes in a hypoxia-treated β-cell line and reduced reactive oxygen species production in isolated pancreatic islets. Recovery from diabetes in mice transplanted with hypoxic islets was more efficient when they received exendin-4. In conclusion, exendin-4 rescued islets from oxidative stress caused by hypoxia or due to cytokine exposure. It improved the outcome of syngenic and xenogenic islet transplantation.

Heme oxygenase-1 expression and its significance for acute rejection following kidney transplantation in rats

OBJECTIVE

To analyze rejection and antiapoptotic effects of heme oxygenase-1 (HO-1) in kidney transplantations, to investigate the protective effects of endogenous HO-1 induced by hemin on acute rat kidney allograft rejection.

METHODS

We selected 27 Brown-Norway rats and 27 male Lewis rats as donors and recipients, respectively, randomly dividing them into three groups: kidney transplantation alone, hemin treatment group, and cyclosporine (CsA) group (n = 18). Six recipient rats were harvested on the first, fifth, or seventh days after operation among each group to examine histopathologic changes in renal tissue, HO-1 protein expression, and acute rejection as well as to measure serum creatinine values.

RESULTS

HO-1 expression in both the kidney transplantation model group and the hemin-induced groups were higher compared with the CsA group (P < .05-.01). The expression increased with the aggravation of rejection; the expression in the CsA group also increased after transplantation but was obviously lower than that of the hemin-induced group (P < .01). The rejection process was relatively mild as indenset by histopathologic examination. The serum creatinine levels among the hemin-induced group were lower compared to the kidney transplantation control group (P < .05), but higher compared to the CsA group (P < .05).

CONCLUSION

HO-1 provided protection of allografts against rejection in rats, but such effects were poorer than those achieved using potent immunosuppressive agents like CsA.

Reversible immortalization of rat pancreatic β cells with a novel immortalizing and tamoxifen-mediated self-recombination tricistronic vector

Although the strategy of "Cre/LoxP-based reversible immortalization" holds great promise to overcome the cellular senescence of primary cell cultures for their further use, a secondary gene transfer for Cre expression is usually utilized to trigger the excision of the immortalizing genes in a large number of cells, thus presenting a formidable hurdle for large-scale application. We modified the strategy by utilizing a tricistronic retroviral vector pLCRSTP, in which Cre-ER, simian virus 40 large T antigen (SV40LTAg) oncogene, and a reporter gene were flanked by the same pair of LoxA sites. Five immortalized rat pancreatic β cell clones transduced with pLCRSTP, and six immortalized rat pancreatic β cell clones co-transduced with pLCRSTP and another vector encoding the human telomerase reverse transcriptase (hTERT) gene, were obtained, respectively. The Cre-ER protein could be induced to translocate from the cytoplasm to the nucleus by 4-hydroxytamoxifen to make SV40LTAg, hTERT and the Cre-ER gene itself excise without a secondary gene transfer. Our studies suggest that this system is useful to expand rat β cells and may allow for large-scale production due to its simpler manipulation.

Islet transplantation and antioxidant management: A comprehensive review

Islet transplantation as a promising treatment for type 1 diabetes has received widespread attention. Oxidative stress plays an essential role in cell injury during islet isolation and transplantation procedures. Antioxidants have been used in various studies to improve islet transplantation procedures. The present study reviews the role of oxidative stress and the benefits of antioxidants in islet transplantation procedures. The bibliographical databases Pubmed and Scopus were searched up to November 2008. All relevant human and animal in-vivo and in-vitro studies, which investigated antioxidants on islets, were included. Almost all the tested antioxidants used in the in-vitro studies enhanced islet viability and insulin secretion. Better control of blood glucose after transplantation was the major outcome of antioxidant therapy in all in-vivo studies. The data also indicated that antioxidants improved islet transplantation procedures. Although there is still insufficient evidence to draw definitive conclusions about the efficacy of individual supplements, the benefits of antioxidants in islet isolation procedures cannot be ignored.

Innate immunity and heat shock response in islet transplantation

Islet transplantation is an extremely effective therapy for patients with type I diabetes, providing tight control of blood glucose and persistent insulin release. Islet grafts struggle with various stress responses and immunity attacks, which contribute to loss of islet grafts in the long term. In this review we focus upon the innate immunity and heat shock responses, which are closely relevant to the outcome of islet grafts. Potential strategies provided by more comprehensive interventions to control innate immunity and by selective induction of heat shock proteins may ameliorate the outcome of islet transplantation.

Facilitating effects of berberine on rat pancreatic islets through modulating hepatic nuclear factor 4 alpha expression and glucokinase activity

AIM: To observe the effect of berberine on insulin secretion in rat pancreatic islets and to explore its possible molecular mechanism.

METHODS: Primary rat islets were isolated from male Sprague-Dawley rats by collagenase digestion and treated with different concentrations (1, 3, 10 and 30 μmol/L) of berberine or 1 μmol/L Glibenclamide (GB) for 24 h. Glucose-stimulated insulin secretion (GSIS) assay was conducted and insulin was determined by radioimmunoassay. 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate cytotoxicity. The mRNA level of hepatic nuclear factor 4 alpha (HNF4α) was determined by reverse transcription polymerase chain reaction (RT-PCR). Indirect immunofluorescence staining and Western blot analysis were employed to detect protein expression of HNF4α in the islets. Glucokinase (GK) activity was measured by spectrophotometric method.

RESULTS: Berberine enhanced GSIS rather than basal insulin secretion dose-dependently in rat islets and showed no significant cytotoxicity on islet cells at the concentration of 10 μmol/L. Both mRNA and protein expressions of HNF4α were up-regulated by berberine in a dose-dependent manner, and GK activity was also increased accordingly. However, GB demonstrated no regulatory effects on HNF4α expression or GK activity.

CONCLUSION: Berberine can enhance GSIS in rat islets, and probably exerts the insulinotropic effect via a pathway involving HNF4α and GK, which is distinct from sulphonylureas (SUs).

Heme oxygenase-1 and the vascular bed: from molecular mechanisms to therapeutic opportunities

Heme oxygenase-1, an enzyme degrading heme to carbon monoxide, iron, and biliverdin, has been recognized as playing a crucial role in cellular defense against stressful conditions, not only related to heme release. HO-1 protects endothelial cells from apoptosis, is involved in blood-vessel relaxation regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in blood-vessel formation by means of angiogenesis and vasculogenesis. The latter functions link HO-1 not only to cardiovascular ischemia but also to many other conditions that, like development, wound healing, or cancer, are dependent on neovascularization. The aim of this comprehensive review is to address the mechanisms of HO-1 regulation and function in cardiovascular physiology and pathology and to demonstrate some possible applications of the vast knowledge generated so far. Recent data provide powerful evidence for the involvement of HO-1 in the therapeutic effect of drugs used in cardiovascular diseases. Novel studies open the possibilities of application of HO-1 for gene and cell therapy. Therefore, research in forthcoming years should help to elucidate both the real role of HO-1 in the effect of drugs and the clinical feasibility of HO-1-based cell and gene therapy, creating the effective therapeutic avenues for this refined antioxidant system.

Optimization of glucose level to determine the stimulation index of isolated rat islets

OBJECTIVES

Although the stimulation index (SI) is widely used as a parameter that reflects the insulin releasing function of isolated islets, comparison between the outcomes of different institutions is problematic. This basic study was conducted for 2 objectives as we aimed to determine the optimal high glucose level for rat islets and clarify the available evidence in this field.

METHODS

We isolated islets of 3 rat strains (Lewis, Sprague-Dawley, and Wistar--n = 5 per strain) and measured the viability of the islets. We measured the amount of insulin released after high and low glucose stimulation. The SI was calculated as a ratio of the insulin value after high glucose stimulation divided by insulin value after low glucose stimulation. We examined the correlation between SI and viability at the high glucose levels.

RESULTS

Isolated islets released insulin corresponding to the changes of high glucose level. The highest correlation coefficient between SI and viability was seen at a glucose level of 16.5 mmol/L (R2 = 0.546, correlation coefficient = 0.154) followed by 19.3 mmol/L (R2 = 0.541, correlation coefficient = 0.169).

CONCLUSIONS

We could optimize the high glucose level at 16.5 to 19.3 mmol/L (300-350 mg/dL) for isolated rat islets, with evidence acquired from correlation studies between SI and viability.

Genetic modification of cells for transplantation

Progress in gene therapy has produced promising results that translate experimental research into clinical treatment. Gene modification has been extensively employed in cell transplantation. The main barrier is an effective gene delivery system. Several viral vectors were utilized in end-stage differentiated cells. Recently, successful applications were described with adenovirus-associated vectors. As an alternative, embryonic stem cell- and stem cell-like systems were established for generation of tissue-specified gene-modified cells. Owing to the feasibility for genetic manipulations and the self-renewing potency of these cells they can be used in a way enabling large-scale in vitro production. This approach offers the establishment of in vitro cell culture systems that will deliver sufficient amounts of highly purified, immunoautologous cells suitable for application in regenerative medicine. In this review, the current technology of gene delivery systems to cells is recapitulated and the latest developments for cell transplantation are discussed.

Curcumin treatment enhances islet recovery by induction of heat shock response proteins, Hsp70 and heme oxygenase-1, during cryopreservation

Limited recovery of islets post-cryopreservation influences graft survival and transplantation efficiency during diabetes treatment. As curcumin, a potent antioxidant/radical scavenging compound, protects islets against beta cell toxins, we hypothesized that inclusion of curcumin during cryopreservation or during post-thaw culture or both may rescue islets from cryoinjury. To test the effect of curcumin inclusion on islet recovery murine islets were isolated by the collagenase digestion, cultured for 48 h, cryopreserved using dimethylsulphoxide as cryoprotectant -- with or without curcumin (10 microM) -- and then slow cooled to -40 degrees C before immersing them in liquid nitrogen for 7 days. Following rapid thawing with sucrose gradient and 24 h post-thaw culture -- in presence or absence of curcumin (10 microM) -- islet viability and functionality were determined. Islet recovery in curcumin treated groups was significantly higher than in groups where islets were cryopreserved without curcumin. Islets cryopreserved with curcumin also showed more intact islets as well as better morphology as compared to islets cryopreserved without curcumin. Curcumin treated islets also showed significant inhibition of ROS generation as compared to islets cryopreserved without curcumin. Glucose responsiveness and insulin secretion in islets cryopreserved with curcumin was equal to that of the freshly isolated islets as against islets cryopreserved without curcumin. Elevated level of Hsp 70 and HO-1 were observed in islets cryopreserved with curcumin and may contribute to curcumin-induced islet rescue. Hence, we conclude that inclusion of curcumin into cryopreservation medium inhibits ROS generation and corresponding islet damage and dysfunction.

Resveratrol alleviates cardiac dysfunction in streptozotocin-induced diabetes: Role of nitric oxide, thioredoxin, and heme oxygenase

Excessive oxidative stress has been implicated in the pathology and complications of diabetes, which leads to myocardial ischemia reperfusion injury. The present study was designed to examine whether resveratrol (trans-3,5,4'-trihydroxystilbene), a polyphenolic compound present in red wine has a direct cardioprotective effect on diabetic myocardium. Resveratrol (2.5 mg/kg body wt/day) and L-NAME (25 mg/kg body wt/day) were administered orally for 15 days to streptozotocin (65 mg/kg)-induced diabetic rats. Sprague Dawley rats were divided into 5 groups: (i) control, (ii) diabetic, (iii) diabetic+resveratrol, (iv) diabetic+resveratrol+L-NAME (nitric oxide synthase inhibitor), and (v) diabetic+L-NAME. In our present study resveratrol demonstrated significant reduction in glucose level in diabetic rats. After the treatment, the hearts were excised and subjected to 30 min of global ischemia followed by 2 h of reperfusion. Resveratrol-treated diabetic rats demonstrated significant reduction in glucose levels as compared to the nontreated diabetic animals, and improved left ventricular function throughout reperfusion compared to the diabetic or L-NAME-treated animals (dp/dt(max) 1457+/-51 vs 999+/-44 mm Hg/s at 120 min reperfusion). Cardioprotection from ischemic injury in resveratrol-treated diabetic rats showed decreased infarct size (42% vs 51%) and cardiomyocyte apoptosis (35% vs 40%) as compared with diabetic animals. Resveratrol produced significant induction of p-AKT, p-eNOS, Trx-1, HO-1, and VEGF in addition to increased activation of MnSOD activity in diabetic animals compared to nondiabetic animals. However treatment with L-NAME in resveratrol-treated and nontreated diabetic animals demonstrated significant downregulation of the above-noted protein expression profile and MnSOD activity. In the present study we found that the mechanism(s) responsible for the cardioprotective effect of resveratrol in the diabetic myocardium include upregulation of Trx-1, NO/HO-1, and VEGF in addition to increased MnSOD activity and reduced blood glucose level. Thus this study shows a novel mechanism of pharmacological preconditioning with resveratrol in the diabetic myocardium.