Insights from a successful case of intrahepatic islet transplantation into a type 1 diabetic patient

Modulation of Specific Beta Cell Gene (Re)Expression during In Vitro Expansion of Human Pancreatic Islet Cells

The need for transplantable beta cells with a stable phenotype has given rise to several strategies including the expansion of existing pancreatic islets and/or growth of new ones. In vitro studies of beta cell proliferation on extracellular matrices plus growth factors have highlighted a possible cell expansion technique; however, the technique was accompanied with loss of insulin secretion. Herein we showed that human islet cell proliferation was marked by a decreased expression of specific differentiation markers, particularly insulin, insulin promoting factor-1 (IPF-1), and glucokinase. After a 6-day expansion period, we tried to reexpress the beta cell differentiation markers with compounds known for their differentiation and/or insulin-secreting properties. Sodium butyrate was a potent factor of IPF-1, insulin, and glucokinase gene reexpression; it also clearly induced secretion of gastrin, a known neogenic factor. Other compounds, namely TGF-β, calcitriol, GLP-1, and activin A, efficiently enhanced the glucose sensor machinery, particularly Glut-1 and glucokinase, thus triggering glucose responsiveness. Our results indicate that specific beta cell gene expression may be induced after expansion and dedifferentiation. This rekindles interest in human beta cell expansion. The possible stabilization of specialized genes needed by beta cells to fulfill their role as nutrient sensors and metabolic regulators may also be of interest to ensure graft maintenance and efficiency.

Death and dysfunction of transplanted β-cells: lessons learned from type 2 diabetes?

β-Cell replacement by islet transplantation is a potential curative therapy for type 1 diabetes. Despite advancements in islet procurement and immune suppression that have increased islet transplant survival, graft function progressively declines, and many recipients return to insulin dependence within a few years posttransplant. The progressive loss of β-cell function in islet transplants seems unlikely to be explained by allo- and autoimmune-mediated mechanisms alone and in a number of ways resembles β-cell failure in type 2 diabetes. That is, both following transplantation and in type 2 diabetes, islets exhibit decreased first-phase glucose-stimulated insulin secretion, impaired proinsulin processing, inflammation, formation of islet amyloid, signs of oxidative and endoplasmic reticulum stress, and β-cell death. These similarities suggest common mechanisms may underlie loss of insulin production in both type 2 diabetes and islet transplantation and point to the potential for therapeutic approaches used in type 2 diabetes that target the β-cell, such as incretin-based therapies, as adjuncts for immunosuppression in islet transplantation.

Evidence for rapamycin toxicity in pancreatic β-cells and a review of the underlying molecular mechanisms

Rapamycin is used frequently in both transplantation and oncology. Although historically thought to have little diabetogenic effect, there is growing evidence of β-cell toxicity. This Review draws evidence for rapamycin toxicity from clinical studies of islet and renal transplantation, and of rapamycin as an anticancer agent, as well as from experimental studies. Together, these studies provide evidence that rapamycin has significant detrimental effects on β-cell function and survival and peripheral insulin resistance. The mechanism of action of rapamycin is via inhibition of mammalian target of rapamycin (mTOR). This Review describes the complex mTOR signaling pathways, which control vital cellular functions including mRNA translation, cell proliferation, cell growth, differentiation, angiogenesis, and apoptosis, and examines molecular mechanisms for rapamycin toxicity in β-cells. These mechanisms include reductions in β-cell size, mass, proliferation and insulin secretion alongside increases in apoptosis, autophagy, and peripheral insulin resistance. These data bring into question the use of rapamycin as an immunosuppressant in islet transplantation and as a second-line agent in other transplant recipients developing new-onset diabetes after transplantation with calcineurin inhibitors. It also highlights the importance of close monitoring of blood glucose levels in patients taking rapamycin as an anticancer treatment, particularly those with preexisting glucose intolerance.

Islet Engraftment and Revascularization in Clinical and Experimental Transplantation

Proper revascularization after transplantation is assumed to be crucial for appropriate islet graft function. We developed a novel noninvasive imaging method, based on adenoviral transduction of islets with a hypoxia responsive reporter gene, for continuous in vivo monitoring of hypoxia in islet grafts in a mouse model. In addition, morphological data were obtained from a deceased patient previously subject to intraportal transplantation. We detected only transient hypoxia in a minority of the animals transplanted. Importantly, a clear response to hypoxia was observed in vitro after removal of the islet grafts on day 28 after transplantation. Also, the morphological data from the deceased patient demonstrated an extensive revascularization of the transplanted islets. In fact, no differences could be seen between native islets, in pancreas biopsies taken prior to islet isolation, and transplanted islets regarding the number, distribution, and shape of the blood vessels. However, fewer small islets (diameter <39 μm) were found in the liver compared to those found in native pancreases. Notably, an absolute majority of the transplanted islets were found remaining within the venous lumen, in direct contact with the vessel wall. In conclusion, the results presented show less pronounced islet graft hypoxia after subcapsular transplantation than previously reported using more invasive methods. Also, formation of an extensive intraislet capillary network, similar to that seen in native islets in the pancreas, was seen after clinical islet transplantation.

Further evidence for amyloid deposition in clinical pancreatic islet grafts

BACKGROUND

The reasons for the long-term complete or partial loss of islet graft function are unknown, but there are obviously other reasons than just pure allogeneic graft rejection. Earlier studies have shown that deposition of islet amyloid polypeptide amyloid in transplanted islets may indicate a mechanism for loss of β cells.

MATERIALS AND METHODS

Sections from liver material from four deceased islet-bearing recipients have been scrutinized for the presence of amyloid. Clinical data and certain aspects of the islet graft pathology of these patients have been published previously.

RESULT

With this extended histological analysis, we demonstrate the occurrence of amyloid deposits in islets transplanted into the liver in three of four patients with type 1 diabetes.

CONCLUSION

The finding adds evidence to the assumption that aggregation of islet amyloid polypeptide might be an important cause of progressing β-cell dysfunction in clinically transplanted islets.

Impact of islet transplantation on diabetes complications and quality of life

Insulin represents a life-saving therapy for patients with type 1 diabetes but, despite appropriate treatment, it prevents only partially long-term diabetic complications, while generating fatal hypoglycemic episodes. Islet transplantation gained attention because of its safety, effectiveness, and minimal invasiveness; however it remains a procedure reserved for a selected group of patients. The introduction of the Edmonton Protocol in 2000, based on a newly designed steroid-free immunosuppressive protocol, revamped the course of islet transplantation. The main goal of islet transplantation remains insulin independence, although the effect of islet transplantation can be more comprehensively evaluated in terms of frequency of hypoglycemic episodes and impact on diabetic complications and quality of life. Islet transplantation was shown to have positive consequences on cardiovascular, renal, neurologic, and ocular diabetic complications. The proof of concept for cellular replacement therapy in diabetes has been established with islet transplantation, it only needs to be improved and rendered widely available.

Gut microbiota in health and disease

Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual's lifetime and susceptible to both exogenous and endogenous modifications. Recent renewed interest in the structure and function of this "organ" has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond. The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but include elaboration of signaling molecules and recognition of bacterial epitopes by both intestinal epithelial and mucosal immune cells. The advances in modeling and analysis of gut microbiota will further our knowledge of their role in health and disease, allowing customization of existing and future therapeutic and prophylactic modalities.

Histologic graft assessment after clinical islet transplantation

BACKGROUND

An accurate monitoring would help understanding the fate of islet grafts after transplantation.

METHODS

This work assessed the feasibility of needle biopsy monitoring after intraportal islet transplantation (n=16), and islet graft morphology was studied with the addition of autopsy samples (n=2). Pancreas autopsy samples from two nondiabetic individuals were used as control.

RESULTS

Islet tissue was found in five needle samples (31%). Sampling success was related to size (100% sampling for the four biopsies of 1.8 cm in length or higher, P<or=0.01). Mild liver abnormalities included localized steatosis (n=8), mild nodular regenerative hyperplasia and mild portal venopathy (n=3), and hepatocyte swelling (n=2). Endocrine cell composition and distribution were similar between islet grafts and normal islets within the native pancreas. There was no or minimal immune cell infiltrate in patients on and off exogenous insulin, including two patients with ongoing negative metabolic events (increasing HbA1c or insulin requirement). The infiltrate was mainly composed of CD4- and CD8-positive cells.

CONCLUSION

This study demonstrates that needle biopsy is feasible after clinical islet transplantation but with a limited practical value because of its low islet sampling rate using current sampling and analysis methods. Both biopsy and autopsy samples demonstrated the well-preserved islet endocrine composition after transplantation and the presence of focal areas of steatosis. Islet grafts showed no or minimal immune cell infiltration, even in the case of ongoing islet loss. On the basis of the findings, possible reasons for allograft islet loss are discussed.

Islet alone versus islet after kidney transplantation: metabolic outcomes and islet graft survival

BACKGROUND

Isolated islet transplantation with infusions from two to three donor pancreata and Edmonton immunosuppression consistently achieves insulin independence in patients with type 1 diabetes. The success of this protocol has been attributed to a novel combination of immunosuppressive agents and avoidance of steroids; however, the outcome of islet transplantation may differ in kidney transplant recipients who are already immunosuppressed.

METHODS

We compared the metabolic outcomes and graft survival of islet transplantation in our program where nine patients underwent islet transplantation alone treated with Edmonton immunosuppression and eight patients received islet after kidney (IAK) transplants under standard kidney transplant immunosuppression often including steroids.

RESULTS

Transplants in the IAK and islet transplantation alone setting demonstrated similar islet potency (islet equivalents/unit insulin reduction) and recipients from both groups routinely gained insulin independence, functional islet mass, and duration of graft survival, however, seemed superior in the IAK group.

CONCLUSIONS

These results suggest that better islet graft function and survival may be attained using non-Edmonton rather than Edmonton immunosuppression and can include maintenance steroid therapy.

Positron emission tomography in clinical islet transplantation

The fate of islets in clinical transplantation is unclear. To elude on this positron emission tomography combined with computed tomography (PET/CT) was performed for 60 min during islet transplantation in five patients receiving six transplants. A fraction of the islets (23%) were labeled with 18F-fluorodeoxyglucose ([(18)F]FDG) and carefully mixed with unlabeled islets just prior to intraportal transplantation. The peak radioactivity concentration in the liver was found at 19 min after start of islet infusion and corresponded to only 75% of what was expected, indicating that islets are lost during the transplantation procedure. No accumulation of radioactivity was found in the lungs. A nonphysiological peak of C-peptide was found in plasma during and immediately after transplantation in all subjects. Distribution in the liver was heterogeneous with wide variations in location and concentration. Islets found in areas with concentrations of >400 IEQ/cc liver tissue varied between 1% and 32% of the graft in different subjects. No side effects attributed to the PET/CT procedure were found. Clinical outcome in all patients was comparable to that previously observed indicating that the [(18)F]FDG labeling procedure did not harm the islets. The technique has potential to be used to assess approaches to enhance islet survival and engraftment in clinical transplantation.

Impaired proinsulin processing is a characteristic of transplanted islets

We sought to determine whether recipients of islet transplants have defective proinsulin processing. Individuals who had islet allo- or autotransplantation were compared to healthy nondiabetic subjects. Insulin (I), total proinsulin (TP), intact proinsulin and C-peptide (CP) were measured in samples of fasting serum by immunoassay, and the ratios of TP/TP+I and TP/CP were calculated. Islet allotransplant recipients had elevated TP levels relative to nondiabetic controls (16.8 [5.5-28.8] vs. 8.4 [4.0-21.8] pmol/L; p < 0.05) and autologous transplant recipients (7.3 [0.3-82.3] pmol/L; p < 0.05). Islet autotransplant recipients had significantly higher TP/TP+I ratios relative to nondiabetic controls (35.9 +/- 6.4 vs. 13.9 +/- 1.4%; p < 0.001). Islet allotransplant recipients, some of whom were on insulin, tended to have higher TP/TP+I ratios. The TP/CP ratio was significantly higher in both islet autotransplant (8.9 [0.6-105.2]; p < 0.05) and allotransplant recipients (2.4 [0.8-8.8]; p < 0.001) relative to nondiabetic controls (1.4 [0.5-2.6]%). Consistent with these findings, TP/TP+I and TP/CP values in islet autotransplant recipients increased significantly by 1-year posttransplant compared to preoperative levels (TP/CP: 3.8 +/- 0.6 vs. 23.3 +/- 7.9%; p < 0.05). Both allo- and autotransplant subjects who received <10,000 IE/kg had higher TP/CP ratios than those who received >10,000 IE/kg. Islet transplant recipients exhibit defects in the processing of proinsulin similar to that observed in subjects with type 2 diabetes manifest as higher levels of total proinsulin and increased TP/TP+I and TP/CP ratios.

Primary graft function, metabolic control, and graft survival after islet transplantation

OBJECTIVE To investigate the influence of primary graft function (PGF) on graft survival and metabolic control after islet transplantation with the Edmonton protocol. RESEARCH DESIGN AND METHODS A total of 14 consecutive patients with brittle type 1 diabetes were enrolled in this phase 2 study and received median 12,479 islet equivalents per kilogram of body weight (interquartile range 11,072-15,755) in two or three sequential infusions within 67 days (44-95). PGF was estimated 1 month after the last infusion by the beta-score, a previously validated index (range 0-8) based on insulin or oral treatment requirements, plasma C-peptide, blood glucose, and A1C. Primary outcome was graft survival, defined as insulin independence with A1C < or =6.5%. RESULTS All patients gained insulin independence within 12 days (6-23) after the last infusion. PGF was optimal (beta-score > or =7) in nine patients and suboptimal (beta-score < or =6) in five. At last follow-up, 3.3 years (2.8-4.0) after islet transplantation, eight patients (57%) remained insulin independent with A1C < or =6.5%, including seven patients with optimal PGF (78%) and one with suboptimal PGF (20%) (P = 0.01, log-rank test). Graft survival was not significantly influenced by HLA mismatches or by preexisting islet autoantibodies. A1C, mean glucose, glucose variability (assessed with continuous glucose monitoring system), and glucose tolerance (using an oral glucose tolerance test) were markedly improved when compared with baseline values and were significantly lower in patients with optimal PGF than in those with suboptimal PGF. CONCLUSIONS Optimal PGF was associated with prolonged graft survival and better metabolic control after islet transplantation. This early outcome may represent a valuable end point in future clinical trials.

Disproportionate hyperproinsulinemia, beta-cell restricted prohormone convertase 2 deficiency, and cell cycle inhibitors expression by human islets transplanted into athymic nude mice: insights into nonimmune-mediated mechanisms of delayed islet graft failure

To learn more about nonimmune-mediated islet graft failure, we transplanted different preparations (preps) of isolated human islets under the kidney capsule of streptozotocin (STZ)-diabetic nude mice. One month after the implantation of 1,000 or 2,000 islets, grafts were harvested for morphological, immunohistochemical, and ultrastructural analysis. Only a single islet prep cured the diabetes out of all the recipients, while the remaining preps showed only partial function after the implantation of 2,000 islets. Transplanted mice showed high circulating proinsulin levels but, with the exclusion of those bearing curative grafts, relatively low mature insulin levels. Engrafted beta-cells showed positive carboxypeptidase E (CPE) and prohormone convertase 1 (PC1) staining, while prohormone convertase 2 (PC2) was undetectable. In contrast, PC2 was abundantly expressed by engrafted alpha-cells. Moreover, engrafted beta-cells did not show evidence of replication, and preapoptotic beta-cells, with intra- and extracellular amyloid deposition, were detected with electron microscopy. Cell cycle inhibitors p16(INK4), p21(WAF1), and p27(Kip1) were abundantly expressed in the islet grafts and showed a predominant nuclear localization. In conclusion, diabetic nude mice transplanted with human islets showed disproportionate hyperproinsulinemia and graft evidence of beta-cell restricted PC2 depletion, amyloid deposition and beta-cell death, and lack of beta-cell replication with nuclear translocation of p27(Kip1) and p21(WAF1) that together may contribute to delayed graft failure.

Optimising islet engraftment is critical for successful clinical islet transplantation

Clinical islet transplantation is currently being explored as a treatment for persons with type 1 diabetes and hypoglycaemia unawareness. Although 'proof-of-principle' has been established in recent clinical studies, the procedure suffers from low efficacy. At the time of transplantation, the isolated islets are allowed to embolise the liver after injection in the portal vein, a procedure that is unique in the area of transplantation. A novel view on the engraftment of intraportally transplanted islets is presented that could explain the low efficacy of the procedure.

Gliclazide protects human islet beta-cells from apoptosis induced by intermittent high glucose

BACKGROUND

Decreased beta-cell mass, mainly due to apoptosis, is crucial for the development and progression of type 2 diabetes. Chronic exposure to high glucose levels is a probable underlying mechanism, whereas the role of oral anti-diabetic agents (sulphonylureas in particular) is still unsettled.

METHODS

To directly investigate more on such issues, we prepared isolated human islets, which were then cultured for 5 days in continuous normal glucose concentration (NG, 5.5 mmol/L) or normal and high (HG, 16.7 mmol/L) glucose levels (alternating every 24 h), with or without the addition of therapeutical concentration (10 micromol L) of gliclazide or glibenclamide.

RESULTS

Intermittent high glucose caused a significant decrease of glucose-stimulated insulin secretion, which was not further affected by either sulphonylurea. Apoptosis, as assessed by electron microscopy, was also significantly increased by alternating high glucose exposure, which was accompanied by altered mitochondria morphology and density volume, and increased concentrations of nitrotyrosine, a marker of oxidative stress. Gliclazide, but not glibenclamide, was able to significantly reduce high glucose induced apoptosis, mitochondrial alterations, and nitrotyrosine concentration increase.

CONCLUSION

Therefore, gliclazide protected human beta-cells from apoptosis induced by intermittent high glucose, and this effect was likely to be due, at least in part, to the anti-oxidant properties of the molecule.

Morphological and ultrastructural features of human islet grafts performed in diabetic nude mice

Islet transplantation is a new therapeutic approach to type 1 diabetes mellitus. However, in several patients insulin levels are not restored and the glycemic control is inadequate. To clarify the cause of graft failure, the authors investigated with light and electron microscopy some human islet grafts before and after transplantation under the kidney capsule of streptozotocin-induced diabetic nude mice. In isolated islets, both pre- and post-transplantation, the endocrine component was scarcely represented, the beta/alpha cell ratio was reduced, and beta cells showed degenerative aspects such as apoptosis, immature secretory granules, and amylin fibrils deposition. The authors conclude that islet graft failure may be due to an insufficient beta cell mass related to their distress probably caused by anoxia and/or overstimulation.

Islet transplantation is associated with an improvement of cardiovascular function in type 1 diabetic kidney transplant patients

OBJECTIVE

Cardiovascular mortality and morbidity are major problems in type 1 diabetic patients with end-stage renal disease (ESRD). The aim of this study was to determine whether islet transplantation can improve cardiovascular function in these patients.

RESEARCH DESIGN AND METHODS

We assessed various markers of cardiac function at baseline and 3 years later in a population of 42 type 1 diabetic patients with ESRD who received a kidney transplant. Seventeen patients then received an islet transplant that had persistent function as defined by long-term C-peptide secretion (kidney-islet group). Twenty-five patients did not receive a functioning islet transplant (kidney-only group).

RESULTS

GHb levels were similar in the two groups, whereas the exogenous insulin requirement was lower in the kidney-islet group with persistent C-peptide secretion. Overall, cardiovascular parameters improved in the kidney-islet group, but not in the kidney-only group, with an improvement of ejection fraction (from 68.2 +/- 3.5% at baseline to 74.9 +/- 2.1% at 3 years posttransplantation, P < 0.05) and peak filling rate in end-diastolic volume (EDV) per second (from 3.87 +/- 0.25 to 4.20 +/- 0.37 EDV/s, P < 0.05). Time to peak filling rate remained stable in the kidney-islet group but worsened in the kidney-only group (P < 0.05). The kidney-islet group also showed a reduction of both QT dispersion (53.5 +/- 4.9 to 44.6 +/- 2.9 ms, P < 0.05) and corrected QT (QTc) dispersion (67.3 +/- 8.3 to 57.2 +/- 4.6 ms, P < 0.05) with higher erythrocytes Na(+)-K(+)-ATPase activity. In the kidney-islet group only, both atrial natriuretic peptide and brain natriuretic peptide levels decreased during the follow-up, with a stabilization of intima-media thickness.

CONCLUSIONS

Our study showed that type 1 diabetic ESRD patients receiving a kidney transplant and a functioning islet transplant showed an improvement of cardiovascular function for up to 3 years of follow-up compared with the kidney-only group, who experienced an early failure of the islet graft or did not receive an islet graft.

Technique, complications, and therapeutic efficacy of percutaneous transplantation of human pancreatic islet cells in type 1 diabetes: the role of US

PURPOSE

To retrospectively evaluate the role of ultrasonography (US) with regard to the technique, complications, and therapeutic efficacy of percutaneous intrahepatic transplantation of human pancreatic islet cells with combined US and fluoroscopic guidance.

MATERIALS AND METHODS

The institutional review board approved the study, and informed consent was obtained from all patients. After kidney transplantation, 34 uremic diabetic patients (20 men, 14 women; mean age, 40.9 years; age range, 29-61 years) underwent percutaneous intrahepatic transplantation of islet cells. Portal vein patency and liver echotexture were preliminarily assessed with color Doppler US. US also was used to identify early complications and presence (group A patients) or absence (group B patients) of hepatic parenchymal changes. Differences between the two groups in C peptide serum level and range were analyzed (Mann-Whitney test). Therapeutic efficacy of transplantation was assessed with regard to insulin independence period (rate and duration), exogenous insulin requirement, glycated hemoglobin, and C peptide level. A C peptide level of more than 0.5 ng/mL was considered to indicate well-functioning islet cells.

RESULTS

Fifty-eight procedures were technically successful, with a single puncture used in 51 of 58 patients. Complications occurred in three of 58 patients (hemoperitoneum, hemothorax, and thrombosis in one patient each) and were conservatively treated and resolved. Duration of insulin independence in 12 patients was more than 3 months (mean, 21 months). Well-functioning islet cells at 6 years were found in 19 of 34 patients. Hyperechoic parenchymal changes were evident at US in 12 of 34. No statistically significant difference in C peptide level was found between groups (P > .05), but a wider range of values was recorded in group B.

CONCLUSION

Complication rate of transplantation with US and fluoroscopic guidance was low. Well-functioning islet cells were found in about 50% of patients at 6 years of follow-up. Hepatic implantation of islet cells was evident on US images in more than one-third of patients.

Successful islet transplantation: continued insulin reserve provides long-term glycemic control

Clinical islet transplantation is gaining acceptance as a potential therapy, particularly for subjects who have labile diabetes or problems with hypoglycemic awareness. The risks of the procedure and long-term outcomes are still not fully known. We have performed 54 islet transplantation procedures on 30 subjects and have detailed follow-up in 17 consecutive Edmonton protocol-treated subjects who attained insulin independence after transplantation of adequate numbers of islets. Subjects were assessed pretransplant and followed prospectively posttransplant for immediate and long-term complications related to the procedure or immunosuppressive therapy. The 17 patients all became insulin independent after a minimum of 9,000 islets/kg were transplanted. Of 15 consecutive patients with at least 1 year of follow-up after the initial transplant, 12 (80%) were insulin independent at 1 year. In 14 subjects who have maintained demonstrable C-peptide secretion, glucose control has been stable and glycemic lability and problems with hypoglycemic reactions have been corrected. After 2 of the 54 procedures, some thrombosis was detected in the portal vein circulation. Five subjects had bleeding related to the percutaneous portal vein access procedures: three required transfusion alone, and in one subject, who had a partial thrombosis of the portal vein, an expanding intrahepatic and subscapular hemorrhage occurred while on anticoagulation, requiring transfusion and surgery. Elevated liver function test results were found in 46% of subjects but resolved in all. Complications related to the therapy have been hypercholesterolemia requiring statin therapy in 65%; a rise in creatinine in two patients, both of whom had preexisting renal disease; a rise in protein in four, all of whom had preexisting proteinuria; and antihypertensive therapy increased or started in 53%. Three of the 17 patients have required retinal laser photocoagulation. There have been no cases of posttransplant lymphoproliferative disorder or cytomegalovirus infection, and no deaths. The acute insulin response to arginine correlated better with transplanted islet mass than acute insulin response to glucose (AIR(g)) and area under the curve for insulin (AUC(i)), but the AIR(g) and AUC(i) were more closely related to glycemic control. The AUC(i) directly posttransplant was lower in those who eventually became C-peptide deficient. Our results, with a maximum follow-up of 34 months, indicate that prolonged insulin independence can be achieved after islet transplantation. There are some risks associated acutely with the procedure, and hypercholesterolemia and hypertension are treatable concerns on longer-term follow-up. All patients with persisting C-peptide secretion have had a resolution of both glycemic lability and problems with hypoglycemic reactions. Apart from the rise in serum creatinine in two subjects, no serious consequences of immunosuppressive therapy have been encountered. Islet transplantation is a reasonable option in those with severe problems with glycemic lability or hypoglycemia.

Molecular detection of circulating beta-cells after islet transplantation

Islet transplantation is a promising treatment for type 1 diabetes. However, islet grafts are submitted to multiple injuries, including immunosuppressive drug toxicity, hyperglycemia, hypoxia, unspecific inflammatory reactions, as well as allo- and autoimmune destruction. Therapeutic approaches to these damage mechanisms require early detection of islet injury, which is currently not feasible because of the lack of efficient markers. Based on the hypothesis of islet dissociation and release of islet cells into the circulation during islet injury, we designed a highly sensitive and specific molecular assay, able to detect two beta-cells per milliliter of venous blood by RT-PCR of insulin mRNA. We report that circulating beta-cells can be demonstrated up to 10 weeks after intraportal islet transplantation, as assessed after six islet grafts in four type 1 diabetic patients. Furthermore, our results suggest that the time during which circulating islet cells can be detected may depend on the graft environment and the immunosuppressive regimen. This test may allow better estimation of islet cell loss and identification of factors involved in islet graft injury.