Follicular helper T cell signature of replicative exhaustion, apoptosis, and senescence in common variable immunodeficiency.

Common variable immunodeficiency (CVID) is the most frequent primary antibody deficiency whereby follicular helper T (Tfh) cells fail to establish productive responses with B cells in germinal centers. Here, we analyzed the frequency, phenotype, transcriptome, and function of circulating Tfh (cTfh) cells in CVID patients displaying autoimmunity as an additional phenotype. A group of patients showed a high frequency of cTfh1 cells and a prominent expression of PD-1 and ICOS as well as a cTfh mRNA signature consistent with highly activated, but exhausted, senescent, and apoptotic cells. Plasmatic CXCL13 levels were elevated in this group and positively correlated with cTfh1 cell frequency and PD-1 levels. Monoallelic variants in RTEL1, a telomere length- and DNA repair-related gene, were identified in four patients belonging to this group. Their blood lymphocytes showed shortened telomeres, while their cTfh were more prone to apoptosis. These data point toward a novel pathogenetic mechanism in CVID, whereby alterations in DNA repair and telomere elongation might predispose to antibody deficiency. A Th1, highly activated but exhausted and apoptotic cTfh phenotype was associated with this form of CVID.

Antibody response to multiple antigens of SARS-CoV-2 in patients with diabetes: an observational cohort study.

AIMS/HYPOTHESIS: The aim of the study was to characterise the humoral response against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients with diabetes. Demonstrating the ability to mount an appropriate antibody response in the presence of hyperglycaemia is relevant for the comprehension of mechanisms related to the observed worse clinical outcome of coronavirus disease 2019 (COVID-19) pneumonia in patients with diabetes and for the development of any future vaccination campaign to prevent SARS-CoV-2 infection. METHODS: Using a highly specific and sensitive measurement of antibodies by fluid-phase luciferase immunoprecipitation assays, we characterised the IgG, IgM and IgA response against multiple antigens of SARS-CoV-2 in a cohort of 509 patients with documented diagnosis of COVID-19, prospectively followed at our institution. We analysed clinical outcomes and antibody titres according to the presence of hyperglycaemia, i.e., either diagnosed or undiagnosed diabetes, at the time of, or during, hospitalisation. RESULTS: Among patients with confirmed COVID-19, 139 (27.3%) had diabetes: 90 (17.7%) had diabetes diagnosed prior to the hospital admission (comorbid diabetes) while 49 (9.6%) had diabetes diagnosed at the time of admission (newly diagnosed). Diabetes was associated with increased levels of inflammatory biomarkers and hypercoagulopathy, as well as leucocytosis and neutrophilia. Diabetes was independently associated with risk of death (HR 2.32 [95% CI 1.44, 3.75], p = 0.001), even after adjustment for age, sex and other relevant comorbidities. Moreover, a strong association between higher glucose levels and risk of death was documented irrespective of diabetes diagnosis (HR 1.14 × 1.1 mmol/l [95% CI 1.08, 1.21], p < 0.001). The humoral response against SARS-CoV-2 in patients with diabetes was present and superimposable, as for timing and antibody titres, to that of non-diabetic patients, with marginal differences, and was not influenced by glucose levels. Of the measured antibody responses, positivity for IgG against the SARS-CoV-2 spike receptor-binding domain (RBD) was predictive of survival rate, both in the presence or absence of diabetes. CONCLUSIONS/INTERPRETATION: The observed increased severity and mortality risk of COVID-19 pneumonia in patients with hyperglycaemia was not the result of an impaired humoral response against SARS-CoV-2. RBD IgG positivity was associated with a remarkable protective effect, allowing for a cautious optimism about the efficacy of future vaccines against SARs-COV-2 in people with diabetes. Graphical abstract.

Diabetes-free survival after extended distal pancreatectomy and islet auto transplantation for benign or borderline/malignant lesions of the pancreas.

Islet autotransplant is particularly attractive to prevent diabetes after extended pancreatectomy for benign or borderline/malignant pancreas disease. Between 2008 and 2018, 25 patients underwent left extended pancreatectomy (>60%) and islet autotransplant for a neoplasm located in the pancreatic neck or proximal body. Overall, disease-free and diabetes-free survivals were estimated and compared with those observed in 68 nondiabetic patients who underwent distal pancreatectomy for pancreatic neoplasms without islet autotransplant. Median follow-up was 4 years. We observed no deaths and a low morbidity (nonserious procedure-related complications in 2 of 25 patients). Patient and insulin-independent survival rates at 4 years were 100% and 96%, respectively. Glucose homeostasis remained within a nondiabetic range at all times for 19 (73%) of 25 patients. Preoperative glycemic level and insulin resistance were major predictors of diabetes development in these patients. Patients undergoing islet autotransplant had a longer diabetes-free survival than did patients without islet autotransplant (P = .04). In conclusion, islet autotransplant after extended pancreatic resection for neoplasms is a safe and successful procedure for preventing diabetes.

The allocation of pancreas allografts on donor age and duration of intensive care unit stay: the experience of the North Italy Transplant program.

Starting in 2011, the North Italy Transplant program (NITp) has based on the allocation of pancreas allografts on donor age and duration of intensive care unit (ICU) stay, but not on donor weight or BMI. We analyzed the detailed allocation protocols of all NITp pancreas donors (2011-2012; n = 433). Outcome measures included donor characteristics and pancreas loss reasons during the allocation process. Twenty-three percent of the 433 pancreases offered for allocation were transplanted. Younger age, shorter ICU stay, traumatic brain death, and higher eGFR were predictors of pancreas transplant, either as vascularized organ or as islets. Among pancreas allografts offered to vascularized organ programs, 35% were indeed transplanted, and younger donor age was the only predictor of transplant. The most common reasons for pancreas withdrawal from the allocation process were donor-related factors. Among pancreas offered to islet programs, 48% were processed, but only 14.2% were indeed transplanted, with unsuccessful isolation being the most common reason for pancreas loss. Younger donor age and higher BMI were predictors of islet allograft transplant. The current allocation strategy has allowed an equal distribution of pancreas allografts between programs for either vascularized organ or islet transplant. The high rate of discarded organs remained an unresolved issue.

Rapamycin unbalances the polarization of human macrophages to M1.

Plasticity is a hallmark of macrophages, and in response to environmental signals these cells undergo different forms of polarized activation, the extremes of which are called classic (M1) and alternative (M2). Rapamycin (RAPA) is crucial for survival and functions of myeloid phagocytes, but its effects on macrophage polarization are not yet studied. To address this issue, human macrophages obtained from six normal blood donors were polarized to M1 or M2 in vitro by lipopolysaccharide plus interferon-γ or interleukin-4 (IL-4), respectively. The presence of RAPA (10 ng/ml) induced macrophage apoptosis in M2 but not in M1. Beyond the impact on survival in M2, RAPA reduced CXCR4, CD206 and CD209 expression and stem cell growth factor-ß, CCL18 and CCL13 release. In contrast, in M1 RAPA increased CD86 and CCR7 expression and IL-6, tumour necrosis factor-α and IL-1ß release but reduced CD206 and CD209 expression and IL-10, vascular endothelial growth factor and CCL18 release. In view of the in vitro data, we examined the in vivo effect of RAPA monotherapy (0·1 mg/kg/day) in 12 patients who were treated for at least 1 month before islet transplant. Cytokine release by Toll-like receptor 4-stimulated peripheral blood mononuclear cells showed a clear shift to an M1-like profile. Moreover, macrophage polarization 21 days after treatment showed a significant quantitative shift to M1. These results suggest a role of mammalian target of rapamycin (mTOR) into the molecular mechanisms of macrophage polarization and propose new therapeutic strategies for human M2-related diseases through mTOR inhibitor treatment.

Extending indications for islet autotransplantation in pancreatic surgery.

OBJECTIVE: To assess metabolic and oncologic outcomes of islet autotransplantation (IAT) in patients undergoing pancreatic surgery for either benign or malignant disease. BACKGROUND: IAT is performed to improve glycemic control after extended pancreatectomy, almost exclusively in patients with chronic pancreatitis. Limited experience is available for other indications or in patients with pancreatic malignancy. METHODS: In addition to chronic pancreatitis, indications for IAT were grade C pancreatic fistula (treated with completion or left pancreatectomy, as indicated); total pancreatectomy as an alternative to high-risk anastomosis during pancreaticoduodenectomy; and distal pancreatectomy for benign/borderline neoplasm of pancreatic body-neck. Malignancy was not an exclusion criterion. Metabolic and oncologic follow-up is presented. RESULTS: From November 2008 to June 2012, 41 patients were candidates to IAT (accounting for 7.5% of all pancreatic resections). Seven of 41 did not receive transplantation for inadequate islet mass (4 pts), patient instability (2 pts), or contamination of islet culture (1 pt). IAT-related complications occurred in 8 pts (23.5%): 4 bleeding, 3 portal thromboses (1 complete, 2 partial), and 1 sepsis. Median follow-up was 546 days. Fifteen of 34 patients (44%) reached insulin independence, 16 patients (47%) had partial graft function, 2 patients (6%) had primary graft nonfunction, and 1 patient (3%) had early graft loss. Seventeen IAT recipients had malignancy (pancreatic or periampullary adenocarcinoma in 14). Two of them had already liver metastases at surgery, 13 were disease-free at last follow-up, and none of 2 patients with tumor recurrence developed metastases in the transplantation site. CONCLUSIONS: Although larger data are needed to definitely exclude the risk of disease dissemination, the present study suggests that IAT indications can be extended to selected patients with neoplasm.

Post hoc analysis of a randomized, double-blind, prospective trial evaluating a CXCR1/2 inhibitor in new-onset type 1 diabetes: endo-metabolic features at baseline identify a subgroup of responders.

Aim: In a recent randomized, multicenter trial (NCT02814838) a short-term anti-inflammatory treatment with ladarixin (LDX; an inhibitor of the CXCR1/2 chemokine receptors) did not show benefit on preserving residual beta cell function in new-onset type 1 diabetes. We present a post hoc analysis of trial patients in the predefined subgroup analysis developed according to baseline daily insulin requirement (DIR) tertiles. Method: A double-blind, randomized (2:1), placebo-controlled study was conducted in 45 men and 31 women (aged 18-46 years) within 100 days of the first insulin administration. Patients received LDX (400 mg twice daily) for three cycles of 14 days on/14 days off, or placebo. The primary endpoint was the area under the curve for C-peptide [AUC (0-120 min)] in response to a 2-h mixed meal tolerance test (MMTT) at week 13 ± 1. Seventy-five patients completed the week 13 MMTT and were divided into three groups according to the DIR tertiles: lower, ≤ 0.23U/kg/die (n = 25); middle, 0.24-0.40 U/kg/die (n = 24); upper, ≥ 0.41 U/kg/die (n = 26). Results: When considering the patients in the upper tertile (HIGH-DIR), C-peptide AUC (0-120 min) at 13 weeks was higher in the LDX group (n = 16) than in the placebo (n = 10) group [difference: 0.72 nmol/L (95% CI 0.9-1.34), p = 0.027]. This difference reduced over time (0.71 nmol/L at 26 weeks, p = 0.04; 0.42 nmol/L at 52 weeks, p = 0.29), while it has never been significant at any time in patients in the lower and/or middle tertile (LOW-DIR). We characterized at baseline the HIGH-DIR and found that endo-metabolic (HOMA-B, adiponectin, and glucagon-to-C-peptide ratio) and immunologic (chemokine (C-C motif) ligand 2 (CCL2)/monocyte chemoattractant protein 1 (MCP1) and Vascular Endothelial Growth Factor (VEGF)) features distinguished this group from LOW-DIR. Conclusion: While LDX did not prevent the progressive loss of beta-cell function in the majority of treated subjects, the post hoc analysis suggests that it could work in subjects with HIGH-DIR at baseline. As we found differences in endo-metabolic and immunologic parameters within this subgroup, this generates the hypothesis that the interactions between host factors and drug action can contribute to its efficacy. Further research is needed to evaluate this hypothesis.

No Evidence of Long-Term Disruption of Glycometabolic Control After SARS-CoV-2 Infection.

PURPOSE: To assess whether dysglycemia diagnosed during severe acute respiratory syndrome coronavirus 2 pneumonia may become a potential public health problem after resolution of the infection. In an adult cohort with suspected coronavirus disease 2019 (COVID-19) pneumonia, we integrated glucose data upon hospital admission with fasting blood glucose (FBG) in the year prior to COVID-19 and during postdischarge follow-up. METHODS: From February 25 to May 15, 2020, 660 adults with suspected COVID-19 pneumonia were admitted to the San Raffaele Hospital (Milan, Italy). Through structured interviews/ medical record reviews, we collected demographics, clinical features, and laboratory tests upon admission and additional data during hospitalization or after discharge and in the previous year. Upon admission, we classified participants according to American Diabetes Association criteria as having (1) preexisting diabetes, (2) newly diagnosed diabetes, (3) hyperglycemia not in the diabetes range, or (4) normoglycemia. FBG prior to admission and during follow-up were classified as normal or impaired fasting glucose and fasting glucose in the diabetes range. RESULTS: In patients with confirmed COVID (n = 589), the proportion with preexisting or newly diagnosed diabetes, hyperglycemia not in the diabetes range and normoglycemia was 19.6%, 6.7%, 43.7%, and 30.0%, respectively. Patients with dysglycemia associated to COVID-19 had increased markers of inflammation and organs' injury and poorer clinical outcome compared to those with normoglycemia. After the infection resolved, the prevalence of dysglycemia reverted to preadmission frequency. CONCLUSIONS: COVID-19-associated dysglycemia is unlikely to become a lasting public health problem. Alarmist claims on the diabetes risk after COVID-19 pneumonia should be interpreted with caution.

Bone marrow as an alternative site for islet transplantation.

The liver is the current site for pancreatic islet transplantation, but has many drawbacks due to immunologic and nonimmunologic factors. We asked whether pancreatic islets could be engrafted in the bone marrow (BM), an easily accessible and widely distributed transplant site that may lack the limitations seen in the liver. Syngeneic islets engrafted efficiently in the BM of C57BL/6 mice rendered diabetic by streptozocin treatment. For more than 1 year after transplantation, these animals showed parameters of glucose metabolism that were similar to those of nondiabetic mice. Islets in BM had a higher probability to reach euglycemia than islets in liver (2.4-fold increase, P = .02), showed a compact morphology with a conserved ratio between alpha and beta cells, and affected bone structure only very marginally. Islets in BM did not compromise hematopoietic activity, even when it was strongly induced in response to a BM aplasia-inducing infection with lymphocytic choriomeningitis virus. In conclusion, BM is an attractive and safe alternative site for pancreatic islet transplantation. The results of our study open a research line with potentially significant clinical impact, not only for the treatment of diabetes, but also for other diseases amenable to treatment with cellular transplantation.

Mesenchymal cells appearing in pancreatic tissue culture are bone marrow-derived stem cells with the capacity to improve transplanted islet function.

Adherent fibroblast-like cells have been reported to appear in cultures of human endocrine or exocrine pancreatic tissue during attempts to differentiate human beta cells from pancreatic precursors. A thorough characterization of these mesenchymal cells has not yet been completed, and there are no conclusive data about their origin.We demonstrated that the human mesenchymal cells outgrowing from cultured human pancreatic endocrine or exocrine tissue are pancreatic mesenchymal stem cells (pMSC) that propagate from contaminating pMSC. The origin of pMSC is partly extrapancreatic both in humans and mice, and by using green fluorescent protein (GFP(+)) bone marrow transplantation in the mouse model, we were able to demonstrate that these cells derive from the CD45(+) component of bone marrow. The pMSC express negligible levels of islet-specific genes both in basal conditions and after serum deprivation or exogenous growth factor exposure, and might not represent optimal candidates for generation of physiologically competent beta-cells. On the other hand, when cotransplanted with a minimal pancreatic islet mass, pMSC facilitate the restoration of normoglycemia and the neovascularization of the graft. These results suggest that pMSCs could exert an indirect role of "helper" cells in tissue repair processes.

Pre-Existing Diabetes and COVID-Associated Hyperglycaemia in Patients with COVID-19 Pneumonia.

AIM: The aim of the current study was to compare clinical characteristics, laboratory findings, and major outcomes of patients hospitalized for COVID-19 pneumonia with COVID-associated hyperglycaemia or pre-existing diabetes. METHODS: A cohort of 176 adult patients with a diagnosis of pre-existing diabetes (n = 112) or COVID-associated hyperglycaemia (n = 55) was studied. RESULTS: Patients with COVID-associated hyperglycaemia had lower BMI, significantly less comorbidities, and higher levels of inflammatory markers and indicators of multi-organ injury than those with pre-existing diabetes. No differences between pre-existing diabetes and COVID-associated hyperglycaemia were evident for symptoms at admission, the humoral response against SARS-CoV-2, or autoantibodies to glutamic acid decarboxylase or interferon alpha-4. COVID-associated hyperglycaemia was independently associated with the risk of adverse clinical outcome, which was defined as ICU admission or death (HR 2.11, 95% CI 1.34-3.31; p = 0.001), even after adjustment for age, sex, and other selected variables associated with COVID-19 severity. Furthermore, at the same time, we documented a negative association (HR 0.661, 95% CI 0.43-1.02; p = 0.063) between COVID-associated hyperglycaemia to swab negativization. CONCLUSIONS: Recognizing hyperglycaemia as a specific clinical entity associated with COVID-19 pneumonia is relevant for early and appropriate patient management and close monitoring for the progression of disease severity.

Islets for Research: Nothing Is Perfect, but We Can Do Better.

In December 2018, Diabetes and Diabetologia began requiring authors of papers reporting data obtained from studies on human islets to report critical characteristics of the human islets used for research. The islet community was asked to provide feedback on it. Here is the contribution by the European Consortium for Islet Transplantation.

Islet Allotransplantation in the Bone Marrow of Patients With Type 1 Diabetes: A Pilot Randomized Trial.

BACKGROUND: Results in murine and nonhuman primate suggested that the bone marrow (BM) might be an alternative site for pancreatic islet transplantation. METHODS: We report the results of 2 clinical studies in patients with type 1 diabetes receiving an intra-BM allogeneic islet transplantation: a feasibility study in patients with hepatic contraindications for liver islet allotransplantation receiving a single intra-BM islet infusion (n = 4) and a pilot randomized trial (1:1 allocation using blocks of size 6) in which patients were randomized to receive islets into either the liver (n = 6) or BM (n = 3) to evaluate islet transplant function and survival. RESULTS: We observed no adverse events related to the intrabone injection procedure or the presence of islets in the BM. None of the recipient of an intra-BM allogeneic islet transplantation had a primary nonfunction, as shown by measurable posttransplantation C-peptide levels and histopathological evidence of insulin-producing cells or molecular markers of endocrine tissue in BM biopsy samples collected during follow-up. All patients receiving islets in the BM except 1 lost islet function during the first 4 months after infusion (2 with an early graft loss). Based on biopsies and immunomonitoring, we concluded that the islet loss was primarily caused by the recurrence of autoimmunity. CONCLUSIONS: Bone marrow is not a suitable alternative site for pancreatic islet allotransplantation in patients with type 1 diabetes.

Relevance of hyperglycemia on the timing of functional loss of allogeneic islet transplants: implication for mouse model.

BACKGROUND: The role of recipient hyperglycemia on timing of allograft survival is unknown. In this study, we investigated if and how variation in recipient glycemia affects the ability to achieve and maintain normoglycemia after transplant of C57BL/6 islets into diabetic BALB/c mice. METHODS AND RESULTS: 85 diabetic BALB/c mice with non-fasting glycaemia ranging between 275 and 600 mg/dL were transplanted with 400 C57BL/6 islets. The time of rejection inversely correlated with the pre-transplant blood glucose concentration (P=0.004). All the 13 mice with normoglycemia beyond 50 days had pretransplant glycemia <450 mg/dL and the presence of autologous beta cell function was demonstrated in 8 (>100 days function) by the persistence of normoglycemia after allograft removal. The presence of immunosuppression (rapamycin plus FK506 plus anti-IL-2Ra chain mAbs, n=31; rapamycin plus IL-10; n=29) removed the influence of pretransplant hyperglycemia but after treatment withdrawn the timing and the probability of graft loss correlate with the pretransplant hyperglycemia. Pretransplant glycemia was inversely correlated with HOMA-B and serum insulin showing that a significant residual beta cell mass was present in mice with glycemia <450 mg/dL. CONCLUSION: This study demonstrates that the timing of functional loss of islets allotransplantation depends on the degree of recipient hyperglycemia. This potential bias should be kept in count in experimental results and a threshold that excludes moderate diabetes should be used in defining recipient's eligibility.

miR-204 is associated with an endocrine phenotype in human pancreatic islets but does not regulate the insulin mRNA through MAFA.

miR-204 has been proposed to modulate insulin expression in human pancreatic islets by regulating the expression of the MAFA transcript, and in turn insulin transcription. We investigated miR-204 expression in pancreatic endocrine tumors (PET), a panel of human tissues, tissues derived from pancreatic islet purification, and in induced pluripotent stem cells (iPSCs) differentiated towards a pancreatic endocrine phenotype by quantitative real time RT-PCR or droplet digital PCR (ddPCR). In addition, we evaluated the effect of miR-204 up- or down-regulation in purified human islets and in the EndoC-ßH1 cell line, as an experimental model of human pancreatic ß cells. Our results confirm that miR-204 was enriched in insulin producing PET, in ß cells within healthy pancreatic islets, and highly expressed in EndoC-ßH1 cells. Moreover, in iPSCs miR-204 increased stepwise upon stimulated differentiation to insulin producing cells. However, up- or down-regulation of miR-204 in human islets and in EndoC-ßH1 cells resulted in modest and not significant changes of the MAFA and INS mRNAs measured by ddPCR or c-peptide release. Our data confirm the association of miR-204 with a ß cell endocrine phenotype in human pancreatic islets, but do not support its direct role in regulating the levels of insulin mRNA through MAFA.

Transplant Site Influences the Immune Response After Islet Transplantation: Bone Marrow Versus Liver.

BACKGROUND: The aim of this study was to characterize the immune response against intrabone marrow (BM-Tx) or intraliver (liver-Tx) transplanted islets in the presence or in the absence of immunosuppression. METHODS: Less (C57BL/6 in Balb/c) and highly (Balb/c in C57BL/6) stringent major histocompatibility complex fully mismatched mouse models were used to evaluate the alloimmune response. Single antigen-mismatched mouse model (C57BL/6 RIP-GP in C57BL/6) was used to evaluate the antigen-specific immune response. Mice received tacrolimus (FK-506, 0.1 mg/kg per day)/mycophenolate mofetil (MMF, 60 mg/kg per day), and anti-CD3 (50 µg/day) either alone or in combination. RESULTS: Transplant site did not impact the timing nor the kinetics of the alloimmune and single antigen-specific memory T cell responses in the absence of immunosuppression or in the presence of MMF/FK-506 combination. On the other hand, the median time to graft rejection was 28 ± 5.2 days and 16 ± 2.6 days (P = 0.14) in the presence of anti-CD3 treatment, 50 ± 12.5 days and 10 ± 1.3 days (P = 0.003) in the presence of anti-CD3/MMF/FK-506 treatment for liver-Tx and BM-Tx, respectively. Anti-CD3 did not differentially reach BM and liver tissues but was more effective in reducing graft associated T cell responses in liver-Tx than in BM-Tx. CONCLUSIONS: Islets infused in the BM appear less protected from the adaptive immune response in the presence of the anti-CD3 treatment. This result raises some concerns over the potential of the BM as a site for islet allotransplantation.

Islet Volume and Indexes of ß-Cell Function in Humans.

Islet volume and endocrine pancreas architecture (islet size distribution) may be independent determinants of ß-cell function. Furthermore, the accuracy of homeostatic model assessment (HOMA) indexes in predicting ß-cell mass has never been assessed. Here we investigated the relationships between islet volume, islet density, and islet size distribution, estimated after pancreatic tissue digestion, with established indexes of ß-cell function in humans. We included in this study 42 patients who were candidates for islet autotransplantation and had well-characterized glucose metabolism. Indexes of insulin secretion were calculated and compared with the islet volume, as a surrogate of ß-cell mass, obtained after digestion of pancreas. Islet counting analysis showed considerable interindividual variation in islet density and size. Islet volume, but not density nor size, was the only independent determinant of ß-cell function assessed by insulin HOMA ß-cell. Islet volume was significantly reduced in the patients with overt hyperglycemia, but not in patients with impaired fasting glucose. Insulin HOMA ß-cell predicted islet volume better than other measures of fasting insulin secretion. In conclusion, the present study documented a close direct relationship between indexes of ß-cell function and islet volume in humans. The insulin HOMA ß-cell provides a more reliable estimate of pancreatic islet volume than fasting glucose before islet isolation.

Human pancreatic islets produce and secrete MCP-1/CCL2: relevance in human islet transplantation.

We investigated the capacity of human islets to produce monocyte chemoattractant protein-1 (MCP-1). Primary cultures of pancreatic islets expressed and secreted MCP-1, as determined by Northern blot, immunohistochemistry, in situ hybridization, and enzyme-linked immunosorbent assay. The produced MCP-1 was biologically active as it attracted monocytes in chemotaxis assay, and chemotactic activity was almost abrogated by a neutralizing anti-MCP-1 monoclonal antibody. Expression of MCP-1 was increased by primary inflammatory cytokines (interleukin-1 beta, tumor necrosis factor-alpha) and lipopolysaccharide at both the mRNA and protein levels but not by glucose. However, MCP-1 did not modulate insulin secretion. MCP-1 secreted by pancreatic islets plays a relevant role in the clinical outcome of islet transplant in patients with type 1 diabetes. In fact, low MCP-1 secretion resulted as the most relevant factor for long-lasting insulin independence. This finding opens new approaches in the management of human islet transplantation. Finally, the finding that MCP-1 appears constitutively present in normal human islet beta-cells (immunohistochemistry and in situ hybridization), in the absence of an inflammatory infiltrate, suggests that this chemokine could have functions other than monocyte recruitment and opens a new link between the endocrine and immune systems.

Human induced pluripotent stem cells differentiate into insulin-producing cells able to engraft in vivo.

AIMS: New sources of insulin-secreting cells are strongly required for the cure of diabetes. Recent successes in differentiating embryonic stem cells, in combination with the discovery that it is possible to derive human induced pluripotent stem cells (iPSCs) from somatic cells, have raised the possibility that patient-specific beta cells might be derived from patients through cell reprogramming and differentiation. In this study, we aimed to obtain insulin-producing cells from human iPSCs and test their ability to secrete insulin in vivo. METHODS: Human iPSCs, derived from both fetal and adult fibroblasts, were differentiated in vitro into pancreas-committed cells and then transplanted into immunodeficient mice at two different stages of differentiation (posterior foregut and endocrine cells). RESULTS: IPSCs were shown to differentiate in insulin-producing cells in vitro, following the stages of pancreatic organogenesis. At the end of the differentiation, the production of INSULIN mRNA was highly increased and 5 ± 2.9 % of the cell population became insulin-positive. Terminally differentiated cells also produced C-peptide in vitro in both basal and stimulated conditions. In vivo, mice transplanted with pancreatic cells secreted human C-peptide in response to glucose stimulus, but transplanted cells were observed to lose insulin secretion capacity during the time. At histological evaluation, the grafts resulted to be composed of a mixed population of cells containing mature pancreatic cells, but also pluripotent and some neuronal cells. CONCLUSION: These data overall suggest that human iPSCs have the potential to generate insulin-producing cells and that these differentiated cells can engraft and secrete insulin in vivo.