Exploration of the mechanism of NORAD activation of TGF-ß1/Smad3 through miR-136-5p and promotion of tacrolimus-induced renal fibrosis.

BACKGROUND: Tacrolimus is a potent immunosuppressant, but has various side effects, with nephrotoxicity being the most common. Renal fibrosis is an important process of tacrolimus nephrotoxicity. Therefore, it is important to identify the factors that contribute to renal fibrosis after tacrolimus nephrotoxicity, and control its development. METHODS: The present study aims to determine whether tacrolimus may speed up the course of renal fibrosis by upregulating noncoding RNA activated by DNA damage (NORAD) to compete with miR-136-5p, and activating the TGF-ß1/Smad3 pathway. Furthermore, in vivo rat models and in vitro cell models were established. Then, the expression levels of NORAD and miR-136-5p were determined by RT-qPCR, while the expression of the TGF-ß1/Smad3 pathway was determined by western blot and RT-qPCR. In order to investigate the interaction between NORAD and miR-136-5p, as well as miR-136-5p and SYK, two luciferase reporters were employed. The renal fibrosis of mice was observed using Masson and PAS staining. The expression of inflammatory factors IL-1, IL-6, MCP-1 and TNF-α was detected by ELISA. RESULTS: In the in vitro experiments, NORAD was upregulated, while miR-136-5p was downregulated after tacrolimus induction. The expression of the TGF-ß1/Smad3 pathway correspondingly changed after the induction by tacrolimus. In the in vivo experiments, the expression of NORAD and miR-136-5p, and the trend for renal fibrosis were consistent with the results in the in vitro experiments. Furthermore, the inflammatory factors correspondingly changed with the severity of renal fibrosis. Moreover, the expression trend of the TGF-ß1/Smad3 pathway in tacrolimus-induced rats was consistent with that in the in vitro experiments. CONCLUSION: Through in vitro and in vivo experiments, the present study was able to successfully prove that tacrolimus upregulates NORAD to compete with miR-136-5p, resulting in a decrease in miR-136-5p expression, which in turn activates the TGF-ß1/smad3 pathway, and finally induces the aggravation of renal fibrosis.

Clinical characteristics of 15 cases of renal transplantation with pre-exsiting donor-specific antibody. / 15ä¾‹é¢„å­˜ä¾›è€ ç‰¹å¼‚æ€§æŠ—ä½“é˜³æ€§è‚¾ç§»æ¤çš„ä¸´åºŠç‰¹å¾.

OBJECTIVES: Currently, patients with pre-exsiting donor-specific antibody (DSA) are prone to antibody-mediated rejection (AMR) after surgery and are at a relatively high risk of postoperative complications and graft failure. The risk of postoperative complications and graft failure is relatively high. This study aims to discuss the clinical outcome of DSA-positive kidney transplantation and analyze the role and safety of preoperative pretreatment in DSA-positive kidney transplantation, providing single-center treatment experience for DSA-positive kidney transplantation. METHODS: We retrospectively analyzed the clinical data of 15 DSA-positive kidney transplants in the Department of Renal Transplantation of First Affiliated Hospital of Zhengzhou University from August 2017 to July 2022. Eight cases were organ donation after citizen's death (DCD) kidney transplant recipients, of which 3 cases in the early stage were not treated with preoperative desensitisation therapy (DCD untreated group, n=3), and 5 recipients were treated with preoperative rituximab desensitisation (DCD preprocessing group, n=5). The remaining 7 cases were living related donors recipients (LRD) who received preoperative desensitisation treatment with rituximab and plasma exchange (LRD preprocessing group, n=7). We observed and recorded the incidence of complications with changes in renal function and DSA levels in the recipients and the survival of the recipients and transplanted kidneys at 1, 3 and 5 years, and to compare the differences in recovery and postoperative complications between 3 groups. RESULTS: All 15 recipients were positive for preoperative panel reactive antibody (PRA) and DSA and were treated with methylprednisolone+rabbit anti-human thymocyte immunoglobulin induction before kidney transplantation. DCD untreated group all suffered from DSA level rebound, delayed renal graft function (DGF) and rejection reaction after surgery. After the combined treatment, DSA level was reduced and the graft renal function returned to normal. The DCD preprocessing group were all without antibody rebound, 1 recipient developed DGF and the renal function returned to normal after plasmapheresis, and the remaining 4 recipients recovered their renal function to normal within 2 weeks after the operation. In the LRD preprocessing group, 2 cases had antibody rebound and 1 case had rejection, but all of them recovered to normal after treatment, and DSA was maintained at a low level or even disappeared. The incidence of DGF and rejection in the DCD untreated group were significantly higher than that in the DCD preprocessing group and the LRD preprocessing group; and there were no significant difference in the incidence of postoperative haematuria, proteinuria, bacterial and fungal infections, and BK virus infection between the 3 groups (all P>0.05). A total of 11 of the 15 recipients were followed up for more than 1 year, 6 for more than 3 years, and 1 for more than 5 years, and the survival rates of both the recipients and the transplanted kidneys were 100%. CONCLUSIONS: Effective preoperative pretreatment with desensitization therapy can effectively prevent antibody rebound in DSA-positive kidney transplantation and reduce perioperative complications.

Transplantation of a single kidney from pediatric donors less than 10 kg to children with poor access to transplantation: a two-year outcome analysis.

BACKGROUND: Access to kidney transplantation by uremic children is very limited due to the lack of donors in many countries. We sought to explore small pediatric kidney donors as a strategy to provide transplant opportunities for uremic children. METHODS: A total of 56 cases of single pediatric kidney transplantation and 26 cases of en bloc kidney transplantation from pediatric donors with body weight (BW) less than 10 kg were performed in two transplant centers in China and the transplant outcomes were retrospectively analyzed. RESULTS: The 1-year and 2-year death-censored graft survival in the en bloc kidney transplantation (KTx) group was inferior to that in the single KTx group. Subgroup analysis of the single KTx group found that the 1-year and 2-year death-censored graft survival in the group where the donor BW was between 5 and 10 kg was 97.7 and 90.0%, respectively. However, graft survival was significantly decreased when donor BW was ≤5 kg (p < 0.01), mainly because of the higher rate of thrombosis (p = 0.035). In the single KTx group, the graft length was increased from 6.7 cm at day 7 to 10.5 cm at 36 months posttransplant. The estimated glomerular filtration rate increased up to 24 months posttransplant. Delayed graft function and urethral complications were more common in the group with BW was ≤5 kg. CONCLUSIONS: Our study suggests that single kidney transplantation from donors weighing over 5 kg to pediatric recipients is a feasible option for children with poor access to transplantation.

miR-136 improves renal fibrosis in diabetic rats by targeting down-regulation of tyrosine kinase SYK and inhibition of TGF-ß1/Smad3 signaling pathway.

Objective: To investigate the way that miR-136 regulated spleen tyrosine kinase (SYK) and transforming growth factor-ß1 (TGF-ß1)/Smad3 signaling pathways on renal fibrosis.Methods: 100 male SD (Sprague-Dawley) rats were randomly divided into diabetic nephropathy (DN) group, normal control (NC) group, miR-136 mimics group, and control group. The renal fibrosis model of diabetic rats was established by streptozotocin (STZ) method. NRK-52E cells were transfected into six groups: HG group, HG + miR-136 group, HG + miR-NC group, miR-136 + SYK group, miR-136 + NC group, and control group. Histopathological examination, the expressions of miR-136 and SYK mRNA, the expression of mTOR, blood glucose, urine protein, body weight, creatinine level, blood urea nitrogen (BUN), and KW/BW were detected in each group. Transfection efficiency, the targeted binding, and regulation between miR-136 and SYK, as well as the expression level of related inflammatory factors, the expression levels of SYK, E-Cad (E-cadherin), Vimentin, Collagen I, α-smooth muscle actin (α-SMA), and vascular endothelial growth factor A (VEGFA) were detected.Results: It was shown that the expression level of miR-136 in DN group significantly decreased. The blood glucose and urine protein concentrations in the DN group and miR-136 mimics group significantly increased and the body weight was decreased, but the blood glucose concentration in the miR-136 mimics group increased with time. The prolongation of the decline significantly decreased, and the growth rate of urinary protein reduced. Creatinine, BUN, and the kidney weight to body weight ratio (KW/BW) in DN group increased significantly. Cell culture results showed that SYK was a target gene of miR-136 and miR-136/SYK-mediated renal fibrosis by activating TGF-ß1/Smad3 signal.Conclusion: SYK activates TGF-ß1/Smad3 signaling, while miR-136 inhibits TGF-ß1/Smad3 signaling mediating tubular epithelial cell fibrosis by down-regulating SYK.

Elevated Circulating IL-10 Producing Breg, but Not Regulatory B Cell Levels, Restrain Antibody-Mediated Rejection After Kidney Transplantation.

Background: Antibody-mediated rejection (AMR) occupies a major position for chronic rejection after kidney transplantation. Regulatory B cell (Breg) has been reported to have an inhibitory immune function, which contributes to the resistance for AMR. Methods: A nested case-control study for nine healthy donors, 25 stable (ST) patients, and 18 AMR patients was performed to determine the type of Breg in maintaining immune tolerance and preventing AMR. Results: Compared to the ST group, circulating interleukin (IL)-10+ Bregs, but not Bregs, significantly decreased. The receiver operating characteristic (ROC) curve analysis revealed that rather than the circulating Bregs, decreased circulating IL-10+ Breg levels were positively associated with AMR. However, kidney B cell and IL-10 infiltration was significantly increased in the AMR group with high expression of C-X-C motif chemokine 13 (CXCL13). In addition, circulating IL-10+ Bregs, rather than Bregs, remained higher than those at pre-operation, during the 90-day post-operation in immune homeostasis. Conclusion: The circulating IL-10+ Breg levels are more appropriate measures for assessing the resistance of AMR after kidney transplantation.

Immature dendritic cells derived exosomes promotes immune tolerance by regulating T cell differentiation in renal transplantation.

OBJECTIVE: To investigate the mechanism of immature dendritic cells-derived exosomes (imDECs) in the regulation of T cell differentiation and immune tolerance in renal allograft model mice. RESULTS: imDECs significantly improved the percent of survival, relieved inflammatory response, and reduced CD4+T cell infiltration. In addition, imDECs reduced the rejection associated cytokines in allograft mice, and increased the percentage of Foxp3+CD4+T cells in spleen and kidney tissues. imDECs suppressed the IL17+CD4+T cells and promoted the Foxp3+CD4+T cells under Th17 polarization condition. Moreover, miR-682 was found to be highly expressed in imDECs which suppressed the IL17+CD4+T cells and promoted the Foxp3+CD4+T cells. Luciferase reporter assay showed ROCK2 was a target of miR-682, and ROCK mRNA level was negative correlated with miR-682 mRNA level. CONCLUSION: miR-682 was highly expressed in imDECs, and imDECs-secreted miR-682 promoted Treg cell differentiation by negatively regulating ROCK2 to promote immune tolerance in renal allograft model mice. METHODS: Renal allograft model mice were established, and imDECs or mature dendritic cells-derived exosomes (mDECs) were injected into model mice. Rejection associated cytokines IFN-γ, IL-2, IL-17 levels in plasma were detected by ELISA. IL-17A, Foxp3, miR-682, ROCK2, p-STAT3, p-STAT5 expressions were measured by qRT-PCR or western blot.

Bortezomib ameliorates acute allograft rejection after renal transplant by inhibiting Tfh cell proliferation and differentiation via miR-15b/IRF4 axis.

OBJECTIVE: The present study aimed to investigate the functional role of bortezomib in the development of acute allograft rejection (AR) after renal transplant. METHODS: The mouse model of AR was established by allograft kidney transplant followed by the treatment of bortezomib. The serum cytokines, renal function, and the percentage of T follicular helper (Tfh) cells in CD4+ T cells were measured. The effect of miR-15b and interferon-regulatory factor 4 (IRF4) on Tfh cell proliferation and differentiation was assessed by cell transfection technology and CCK-8 assay. The interaction between miR-15b and IRF4 was assessed by luciferase reporter assay. RESULTS: Bortezomib relieved acute AR after renal transplant by suppressing Tfh cell proliferation and differentiation. Meanwhile, bortezomib treatment markedly increased miR-15b expression in AR renal tissues. The upregulation of miR-15b inhibited Tfh cell proliferation and differentiation by reducing IRF4. In addition, bortezomib ameliorated AR by suppressing Tfh cell proliferation and differentiation through miR-15b/IRF4 axis in vitro and in vivo. CONCLUSION: Our findings indicated the mechanism underlying the bortezomib in treating acute AR after renal transplant, and suggested the critical role of miR-15b in Tfh cell proliferation and differentiation, which provided a therapeutic target in attenuating acute AR.

Inhibition of lncRNA MEG3 protects renal tubular from hypoxia-induced kidney injury in acute renal allografts by regulating miR-181b/TNF-α signaling pathway.

Early damage to transplanted organs initiates excess inflammation that deteriorates existing injury, which is a leading cause of graft loss. Long noncoding RNAs (lncRNAs) are recently thought to play a significant role in cellular homeostasis during pathological process of kidney diseases. The aim of this study was to assess the function and mechanism of lncRNA, maternally expressed gene 3 (MEG3), on early renal allografts pathogenesis. Real-time polymerase chain reaction (RT-PCR) analysis found that the levels of MEG3 and miR-181b-5p were increased and decreased respectively in grafted kidney. The Western blot assay showed that TNF-alpha was upregulated in the kidney and in HK-2 cells. Administering MEG3-specific small interfering RNA (siRNA) in mice silenced MEG3 expression and protected kidney renal allograft from injury. Bioinformatical analysis and luciferase assay indicated that MEG3 is a target of miR-181b-5p. MEG3 inhibition and overexpression promoted and suppressed miR-181b-5p levels respectively. In addition, Western blot and immunohistochemical staining suggested that decreased TNF-alpha expression was observed in the kidney. In contrary to MEG3, miR181b overexpression attenuated hypoxia-induced HK-2 cell apoptosis, as well as suppressed hypoxia-induced TNF-alpha upregulation. In luciferase reporter assay, we confirmed that miR-181b directly bound to the 3'-untranslated region (3'-UTR) of TNF-alpha, thereby negatively regulating the TNF-alpha expression. Our data suggested that MEG3 functions as a competing endogenous RNA for miR-181b to regulate the TNF-alpha expression in hypoxia-induced kidney injury in acute renal allografts.

Long non-coding RNA GAS5 sensitizes renal cell carcinoma to sorafenib via miR-21/SOX5 pathway.

Although the use of sorafenib appears to increase the survival rate of renal cell carcinoma (RCC) patients, there is also a proportion of patients who exhibit a poor primary response to sorafenib treatment. Therefore, it is critical to elucidate the mechanisms underlying sorafenib resistance and find representative biomarkers for sorafenib treatment in RCC patients. Herein, we identified that a long noncoding RNA GAS5 was downregulated in sorafenib nonresponsive RCCs. GAS5 overexpression conferred sorafenib sensitive to nonresponsive RCC cells, whereas knockdown of GAS5 promoted responsive RCC cells resistant to sorafenib treatment in vitro and in vivo. Mechanistically, GAS5 functioned as competing endogenous RNA to repress miR-21, which controlled its down-stream target SOX5. We proposed that GAS5 was responsible for sorafenib resistance in RCC cells and GAS5 exerted its function through the miR-21/ SOX5 axis. Our findings suggested that GAS5 downregulation may be a new marker of poor response to sorafenib and GAS5 could be a potential therapeutic target for sorafenib treatment in RCC.

Over-expressed microRNA-181a reduces glomerular sclerosis and renal tubular epithelial injury in rats with chronic kidney disease via down-regulation of the TLR/NF-κB pathway by binding to CRY1.

BACKGROUND: MicroRNAs (miRNAs) contribute to the progression of chronic kidney disease (CKD) by regulating renal homeostasis. This study explored the effects of miR-181a on CKD through the Toll-like receptor (TLR)/nuclear factor-kappa B (NF-κB) pathway by binding to CRY1. METHODS: Seventy male rats were selected and assigned into specific groups: miR-181a mimic, miR-181a inhibitor, and siRNA against CRY1, with each group undergoing different treatments to investigate many different outcomes. First, 24-h urinary protein was measured. ELISA was used to determine the serum levels of SOD, ROS, MDA, IL-1ß, IL-6, and TNF-α. Biochemical tests for renal function were performed to measure albumin, uric acid, and urea in urine and urea nitrogen and creatinine in serum. The glomerulosclerosis index (GSI) and renal tubular epithelial (RTE) cell apoptosis were detected using PASM staining and TUNEL staining, respectively. Finally, RT-qPCR and western blot were done to determine miR-181a, CRY1, TLR2, TLR4, and NF-κB expression. RESULTS: CRY1 is the target gene of miR-181a, according to a target prediction program and luciferase assay. Rats diagnosed with CKD presented increases in 24-h urinary protein; GSI; RTE cell apoptosis rate; serum ROS, MDA, IL-1ß, IL-6, and TNF-α; and CRY1, TLR2, TLR4, and NF-κB expression, as well as decreases in SOD level and miR-181a expression. Following transfection with either the miR-181a mimic or si-CRY1, 24-h urinary protein, renal damage, GSI, and cell apoptosis rate were all decreased. In addition, the overexpression of miR-181a or inhibition of CRY1 alleviated the degree of kidney injury through suppression of the TLR/NF-κB pathway. CONCLUSION: miR-181a alleviates both GS and RTE injury in CKD via the down-regulation of the CRY1 gene and the TLR/NF-κB pathway.

Experimental studies on islets isolation, purification and function in rats.

To develop a simple and effective method of islet isolation and purification in rats. Collagenase P was injected into pancreatic duct followed by incubation in water bath to digest the pancreas and isolate islet, then discontinuous gravity gradient purification was used to purify the islet. The purified islets were identified by dithizone staining. The viability of islets was assessed by fluorescence staining of acridine orange (AO) and propidium iodide (PI). The function of purified islets was determined by glucose-stimulated insulin release test and transplantation of rat with streptozocin-induced diabetes. 738±193 islets were recovered after purification. The average purity was 77±13%, the viability of islets was more than 95%. When inspected by glucose stimulation, the secreted insulin concentration was 24.31±5.47 mIU/L when stimulated by low concentration glucose and 37.62±4.29 mIU/L by high concentration glucose. There was significant difference between the two phases (P<0.05). The blood sugar concentration recovered to normal level after two days in the animals with islet transplantation. In conclusion, islets can be procured with good function and shape by using the method of injecting collagenase into pancreatic duct followed by incubation in water bath and purification using discontinuous gravity gradient.

Kidney transplantation from pediatric donors in a single Chinese center.

To report clinical outcomes of kidney transplantation from pediatric brain and cardiac death donors (DBCD) in a single Chinese center and to investigate its feasibility to expand organ donor pool. 18 recipients, transplanted between August 2011 and October 2013 in the First Affiliated Hospital of Zhengzhou University, receive a single graft from DBCD donors age ranged from 1.5 to 13 years old. Renal function expressed as serum creatinine, blood urea nitrogen as well as eGFR values at 1, 2 weeks as well as 1-, 3-, 6-, and 12-months post-transplantation was evaluated. Graft size was also monitored at the same time by ultrasonography. In addition, delayed graft function, acute rejection, surgical complication as well as patient and graft survival were also assessed. The primary causes of DBCD donors included six cases of severe brain trauma and three cases of cerebral hemorrhage. The mean age of DBCD donors was (7.2 ± 3.4) years (range 1.5-13). The mean weight of DBCD donors was (29.8 ± 15.3) kilogram (range 13-67). The mean height of DBCD donors was (118.3 ± 27.8) centimeter (range 70-173). ECMO was applied to DBCD donors to avoid warm ischemia time and the applicating time was (79.8 ± 44.5) (range 32-180) minutes.There were seven males and 11 females recipients. Among which, 16 recipients were pediatrics and two recipients were adults. The mean age of the recipients was (14.6 ± 9.7) years (range 4-47). The mean weight of recipients was (31.9 ± 12.4) kilogram (range 11-54). The mean height of recipients was (138.0 ± 23.7) centimeter (range 84-172). Renal function recovered to normal within the first-week post-operation except one recipient which occurred acute rejection. Two cases of renal artery stenosis were found 2-week and 3-month post-transplantation, respectively. They subsequently underwent ballon angioplasty and followed up for 8 and 12 months, respectively, and no recurrence was found. One recipient developed ureteral leak. Five weeks later, the ureter leak healed after adequate drainage and prolongation of indwelling catheter. Graft size significantly and continuously increased during the first year, especially in the first 3-month post-transplantation. All the 18 recipients are alive at the last follow-up. Among which, 16 recipients are followed up for 12 months and 1-year recipient/graft survival rate is 100 %. The use of single kidney graft from pediatric DBCD could yield good short-term results.

Reduced ATG-F dosage for induction in pediatric renal transplantation: a single-center experience.

Rabbit antithymocyte globulin (ATG-F) is an extensively used induction agent. To our knowledge, no study to date has assessed reduced ATG-F dosage in children undergoing renal transplantation. This was a retrospective analysis of pediatric renal recipients in the Department of Kidney Transplantation, The First Affiliated Hospital of Zhengzhou University, from May 2007 to February 2013. Thirty-nine children underwent renal transplantation including 25 living related and 14 cardiac deceased donor transplantation. Each recipient received ATG-F 1.5 mg/kg/d once daily for 4 days. Of the 39 recipients, five (12.8%) showed delayed graft function, including one of 25 recipients (4%) of living donor and four of 14 recipients (28.6%) of deceased donor transplantation (p < 0.05). Six of the 39 recipients (15.4%) showed acute rejection on renal biopsy. Follow-up in these children ranged from 6 to 87 months. The one-, three-, and five-yr recipients and grafts survival rates postoperation were each 94.9% and 97.3%, 97.3%, and 94.6%, respectively. The incidence of postoperative infection was 35.9% (14/39), and did not differ significantly in the living related and deceased donor groups (p > 0.05). Low-dose ATG-F can be safely used as an immune induction agent in pediatric renal transplantation.

Panel-reactive antibody levels and renal transplantation rates in sensitized patients after desensitization and human leucocyte antigen amino acid residue matching.

OBJECTIVE: To determine whether a new desensitization protocol (mycophenolate mofetil [MMF], plasmapheresis and antithymocyte globulin [ATG], complemented with human leucocyte antigen [HLA] amino acid residue matching) could reduce panel-reactive antibody (PRA) levels in sensitized patients, to facilitate successful renal transplantation. METHODS: Patients awaiting transplantation with PRA levels >10% received treatment with MMF; those with PRA levels >30% were also treated with plasmapheresis. Patients whose PRA level was <20% after desensitization were eligible for transplantation. When a donor became available, traditional HLA matching and HLA amino acid residue matching were performed. All patients received ATG induction therapy postoperatively. RESULTS: Thirty-two sensitized patients were enrolled. Desensitization produced a significant decrease in PRA levels; 27 patients (84.4%) became eligible for transplantation and 26 (81.2%) subsequently underwent successful transplantation. Residue matching improved the proportion with a mismatch number of 0-1 from 7.7% to 65.4%, compared with traditional HLA matching. Postoperatively, all patients showed immediate graft function. Acute rejection occurred in three patients (11.5%) and infections in seven patients (25.9%); all were treated successfully. CONCLUSION: The combination of a desensitization protocol (MMF, plasmapheresis and ATG) and residue matching appears to be an effective strategy for sensitized patients awaiting renal transplantation.

[Co-culture of cryopreserved rat islets with small intestinal submucosa].

OBJECTIVE: To investigate the feasibility and benefits of co-culture of cryopreserved islets with small intestinal submucosa (SIS). METHODS: Purified rat islets cryopreserved for one month were divided into SIS group and control group, and after culture in standard islet culture media RPMI1640 for 1 week, the morphology and function of the islets were assessed. RESULTS: The SIS protects the fragile islets from damage by cryopreservation, and increased the recovery from (60.6-/+3.3)% to (91.7-/+1.8) % (P<0.05). Compared with the control group, incubation of the islets of the SIS group in high-glucose (16.7 mmol/L) solution resulted in significantly enhanced insulin secretion (23.7-/+1.6 vs 12.5-/+1.1 mU/L, P<0.05). When the islets were incubated in high-glucose solution containing theophylline, the calculated stimulation index of SIS group was about 3-fold higher than that of the control group. CONCLUSION: Co-culture of cryopreserved rat islets with SIS can increase the recovery of islet cells and improve their function.

[Cryopreservation of microencapsulated rat islets].

OBJECTIVE: To investigate the role of alginate-polylysine-alginate (APA) microcapsules in protecting rat islet cells in cryopreservation. METHOD: Purified rat islet cells microencapsulated with APA and free islet cells were cryopreserved for one month and then thawed for culture in RPMI 1640 overnight. The morphology of the cells was observed and their function assessed by stimulated insulin release test. RESULT: APA microcapsulation protected the fragile islets from freezing damage by increasing the recovery rate of the cells from 68.6%+/-2.9% to 94.7%+/-1.4% (P<0.05). After incubation with high glucose (16.7 mmol/L) solution, the insulin release from the encapsulated cells after cryopreservation significantly increased in comparison with that of the nonencapsulated cells (22.6+/-1.8 mU/L vs 11.7+/-1.5 mU/L, P<0.05). In high glucose solution containing theophylline, the calculated stimulation index of the encapsulated cells was about 3 times that of the nonencapsulated cells. CONCLUSION: APA microencapsulation may significantly increase the post-thaw recovery and improve the function for cryopreserved rat islets.

Effect of small intestinal submucosa on islet recovery and function in vitro culture.

BACKGROUND: The ability to maintain isolated human islet preparation in tissue culture has recently been adopted by most islet transplant centers to improve the safety and practicality of islet transplantation. However, maintaining islet viability and recovery remains a challenge in clinical setting. Extracellular matrix (ECM) is one of the most important components of islet microenvironment. The reconstruction of the cell-matrix relationship seems to be effective in improving the loss of differentiated islet structure and function. Small intestinal submucosa (SIS), a naturally occurring ECM, has been investigated to be able to promote wound healing, tissue remodeling, and cell growth. The purpose of this study was to evaluate the recovery and function of isolated rat pancreatic islets after in vitro culture with SIS. METHODS: Pancreatic islets were isolated from Wistar rats by using standard surgical procurement followed by intraductal collagenase distension, mechanical dissociation, and EuroFicoll purification. Groups of purified islets were cultured in plates which were coated with multilayer SIS (SIS-treated group) or without (standard cultured group) for 7 days and 14 days in standard islet culture conditions of RPMI 1640 tissue culture media in humidified atmosphere containing 95% air and 5% CO2 at 37 degree centigrade. The mean recovery of islets after the culture period was determined by sizing duplicate counts of a known volume and their viability was assessed by static incubation with low glucose (2.7 mmol), high glucose (16.7 mmol) and high glucose solution supplemented with 50 mum 3-isobutyl-1-methylxanthine (IBMX) solution. RESULTS: After 7 days and 14 days of in vitro tissue culture, the SIS-treated group showed a significantly higher recovery compared with those cultured under standard conditions. The recovery in the SIS-treated group was about two times of the control group cultured in standard conditions after 14 days culture. In the SIS-treated group, there was no statistically difference between the short and long periods of culture(95.8+/-1.0% vs. 90.8+/-1.5%, P>0.05). During incubation in high glucose (16.7 mmol) solution, there was a 2-3 fold increase in insulin secretion from both groups,but the SIS-treated group showed a higher increase than the standard cultured group after 14-day culture (20.7+/-1.1 mU/L vs. 11.8+/-1.1 mU/L, P<0.05). When islets were placed in the high glucose solution supplemented with IBMX, the stimulated insulin response in the SIS-treated group was higher than that in the standard cultured group in spite of the duration of the culture. The stimulation index of the SIS-treated group was about 2-3 times of the standard cultured group. In addition, after a long period of culture, the stimulation index of the SIS-treated group was statistically equivalent with that of the short period of culture (9.5+/-0.2 vs. 10.2+/-1.2, P>0.05). CONCLUSIONS: The co-culture of isolated rat islets with native sheet-like SIS can provide an excellent extracellular matrix, possible biotrophic and growth factors that promote the recovery and subsequent function of islets after in vitro tissue culture. In view of results of this study and rapid degradation of SIS in vitro, future studies will investigate the extended duration of culture and the effect of SIS on islets in vitro.

Small intestinal submucosa improves islet survival and function during in vitro culture.

AIM: To evaluate the recovery and function of isolated rat pancreatic islets during in vitro culture with small intestinal submucosa (SIS). METHODS: Pancreatic islets were isolated from Wistar rats by standard surgical procurement followed by intraductal collagenase distension, mechanical dissociation and Euroficoll purification. Purified islets were cultured in plates coated with multilayer SIS (SIS-treated group) or without multilayer SIS (standard cultured group) for 7 and 14 d in standard islet culture media of RPMI 1640. After isolation and culture, islets from both experimental groups were stained with dithizone and counted. Recovery of islets was determined by the ratio of counts after the culture to the yield of islets immediately following islet isolation. Viability of islets after the culture was assessed by the glucose challenge test with low (2.7 mmol/L) and high glucose (16.7 mmol/L) solution supplemented with 50 mmol/L 3-isobutyl-1-methylxanthine (IBMX) solution. Apoptosis of islet cells after the culture was measured by relative quantification of histone-complexed DNA fragments using ELISA. RESULTS: After 7 or 14 d of in vitro tissue culture, the recovery of islets in SIS-treated group was significantly higher than that cultured in plates without SIS coating. The recovery of islets in SIS-treated group was about twice more than that of in the control group. In SIS-treated group, there was no significant difference in the recovery of islets between short- and long-term periods of culture (95.8+/-1.0% vs 90.8+/-1.5%, P>0.05). When incubated with high glucose (16.7 mmol/L) solution, insulin secretion in SIS-treated group showed a higher increase than that in control group after 14 d of culture (20.7+/-1.1 mU/L vs 11.8+/-1.1 mU/L, P<0.05). When islets were placed in high glucose solution containing IBMX, stimulated insulin secretion was higher in SIS-treated group than in control group. Calculated stimulation index of SIS-treated group was about 23 times of control group. In addition, the stimulation index of SIS-treated group remained constant regardless of short- and long-term periods of culture (9.5+/-0.2 vs 10.2+/-1.2, P>0.05). Much less apoptosis of islet cells occurred in SIS-treated group than in control group after the culture. CONCLUSION: Co-culture of isolated rat islets with native sheet-like SIS might build an extracellular matrix for islets and provide possible biotrophic and growth factors that promote the recovery and subsequent function of islets.