Vascular access complications associated with resuscitative endovascular balloon occlusion of the aorta in adult trauma patients: A systematic review and meta-analysis.

BACKGROUND: Resuscitative endovascular balloon occlusion of the aorta (REBOA) is gaining popularity worldwide for managing hypotensive trauma patients. Vascular access complications related to REBOA placement have been reported, with some cases resulting in permanent morbidity. We aim to capitalize on the increase in literature to further describe and estimate the incidence of REBOA-associated vascular access complications in adult trauma patients. METHODS: We searched Medline, EMBASE, Scopus, and CINAHL for studies reporting vascular access complications of REBOA in adult trauma patients from inception to October 14, 2021. Studies reporting data from adult trauma patients who underwent REBOA insertion were eligible. Exclusion criteria included patients 15 years and younger, nontrauma patients, non-REBOA use, non-vascular access complications and patient duplication. Study data was abstracted using the PRISMA checklist and verified independently by three reviewers. Meta-analysis of proportions was performed using a random effects model with Freeman-Turkey double-arcsine transformation. Post hoc meta-regression by year of publication, sheath-size, and geographic region was also performed. The incidence of vascular access complications from REBOA insertion was the primary outcome of interest. Subgroup analysis was performed by degree of bias, sheath size, technique of vascular access, provider specialty, geographical region, and publication year. RESULTS: Twenty-four articles were included in the systematic review and the meta-analysis, for a total of 675 trauma patients who underwent REBOA insertion. The incidence of vascular access complications was 8% (95% confidence interval, 5%-13%). In post hoc meta-regression adjusting for year of publication and geographic region, the use of a smaller (7-Fr) sheath was associated with a decreased incidence of vascular access complications (odds ratio, 0.87; 95% confidence interval, 0.75-0.99; p = 0.046; R 2 = 35%; I 2 = 48%). CONCLUSION: This study provides a benchmark for quality of care in terms of vascular access complications related to REBOA insertion in adult trauma patients. Smaller sheath size may be associated with a decrease in vascular access complications. LEVEL OF EVIDENCE: Systematic Review and Meta-Analysis; Level III.

Distal perfusion cannulae reduce extracorporeal membrane oxygenation-related limb ischemia.

BACKGROUND: Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a means of providing cardiopulmonary support that is being increasingly used in patients with acute heart failure. When ECMO cannulae are placed peripherally, their large diameters pose a risk of limb ischemia. Distal perfusion cannulae (DPC) have been proposed as means to reduce risk, but their use is not recommended by the most recent ECMO guidelines. We sought to establish their utility at our institution. METHODS: We performed a retrospective review of of all patients treated with peripheral VA-ECMO at our institution from 2013-2018. During the first 2 years, DPC were not routinely placed, whereas in the final 4 years, DPC were recommended as part of the ECMO cannulation routine. RESULTS: One hundred and one patients were treated with peripheral VA-ECMO, with an overall mortality of 61%. By univariate analysis, obesity (47% vs. 75%, P<0.01) and limb ischemia (57% vs. 83%, P<0.05) were associated with increased mortality. DPC were placed prophylactically in 49% of patients. Prophylactic placement of a DPC at the time of cannulation significantly reduced the incidence of limb ischemia (2% vs. 32%, P<0.05), but did not impact mortality (53% vs. 69%, P=0.0953). In patients who did not have a DPC placed during ECMO cannulation and subsequently developed limb ischemia, late DPC placement for limb salvage did not impact mortality. CONCLUSIONS: Limb ischemia portends a poor outcome in VA-ECMO patients, and prophylactic DPC placement significantly reduces the risk of limb ischemia. We propose prophylactic DPC placement be considered in patients requiring peripheral VA-ECMO.

Safety and feasibility of endovascular aortic aneurysm repair as day surgery.

OBJECTIVE: The adoption of endovascular aneurysm repair (EVAR) during the past two decades has led to significantly shorter length of stay as well as lower hospital resource use. Currently, most patients are admitted to the hospital after EVAR; however, there are no standard observation periods, and timing of discharge is based on clinical judgment. The aim of this study was to confirm the safety and feasibility of performing EVAR as outpatient surgery. METHODS: We developed criteria to identify patients for potential same-day discharge (infrarenal aneurysm, low perioperative risk, to be accompanied for first 24 hours). We then implemented a prospective trial that observed patients planned for same-day discharge and compared them with a historical control group (patients who had undergone EVAR during the previous 2 years and met same-day discharge criteria). Basic demographic and operative data as well as length of stay, inpatient and perioperative complications, emergency department visits, readmissions, reinterventions, and deaths were collected. The primary outcome was the 30-day complication rate, and the study was powered to assess noninferiority. RESULTS: Prospectively, we assessed 266 patients and planned 110 (41%) for outpatient EVAR (62% of historical controls met outpatient criteria). Demographic characteristics were similar between planned outpatients and historical controls. In planned outpatients, hospital stay was significantly shorter (0.7 ± 2.6 days vs 2.5 ± 6.9 days; P < .01), and 79% were discharged the same day of surgery. The 30-day follow-up was available for all study patients and 94% of control patients; there were no differences in complication (11% vs 9%), readmission (2% vs 4%), reintervention (4% vs 4%), or mortality (1% vs 1%) rates, but study patients had significantly more emergency department visits (15% vs 6%; P < .05). Unsuccessful same-day discharge was associated with longer operative times, increased blood loss, and use of general anesthesia. CONCLUSIONS: In selected patients undergoing elective EVAR, same-day discharge is feasible without increasing complication rates. Health resource utilization remains a challenge in transitioning to an outpatient model.

Sheath-shunt technique for avoiding lower limb ischemia during complex endovascular aneurysm repair.

Complex aortic aneurysms are now being repaired by endovascular techniques, albeit with a potentially increased risk of lower limb ischemia-reperfusion injury. We report a simple technique to maintain perfusion to the lower limb during endovascular repair, using one additional introducer sheath placed antegrade, distal to the stent graft introduction site, and connected to the side arm of the working sheath in the contralateral artery. This allows continuous perfusion of the limb distal to the main stent graft introduction site. In our initial experience with 12 cases, with confirmed occlusion of the native arterial system by the stent graft introducer sheath, arterial occlusion time was 165 ± 84 minutes. Use of the sheath-shunt technique resulted in pulsatile flow in all cases, with an average flow of 42.2 ± 13.2 mL/min, and actual ischemia time was reduced to 14 ± 11 minutes. There were no complications related to the use of this technique. Given the limited risk of this technique coupled with a potential benefit, we propose its consideration in patients undergoing complex endovascular repair.

Randomized controlled trial comparing outcomes of video capsule endoscopy with push enteroscopy in obscure gastrointestinal bleeding.

BACKGROUND: Optimal management of obscure gastrointestinal bleeding (OGIB) remains unclear. OBJECTIVE: To evaluate diagnostic yields and downstream clinical outcomes comparing video capsule endoscopy (VCE) with push enteroscopy (PE). METHODS: Patients with OGIB and negative esophagogastroduodenoscopies and colonoscopies were randomly assigned to VCE or PE and followed for 12 months. End points included diagnostic yield, acute or chronic bleeding, health resource utilization and crossovers. RESULTS: Data from 79 patients were analyzed (VCE n=40; PE n=39; 82.3% overt OGIB). VCE had greater diagnostic yield (72.5% versus 48.7%; P<0.05), especially in the distal small bowel (58% versus 13%; P<0.01). More VCE-identified lesions were rated possible or certain causes of bleeding (79.3% versus 35.0%; P<0.05). During follow-up, there were no differences in the rates of ongoing bleeding (acute [40.0% versus 38.5%; P not significant], chronic [32.5% versus 45.6%; P not significant]), nor in health resource utilization. Fewer VCE-first patients crossed over due to ongoing bleeding (22.5% versus 48.7%; P<0.05). CONCLUSIONS: A VCE-first approach had a significant diagnostic advantage over PE-first in patients with OGIB, especially with regard to detecting small bowel lesions, affecting clinical certainty and subsequent further small bowel investigations, with no subsequent differences in bleeding or resource utilization outcomes in follow-up. These findings question the clinical relevance of many of the discovered endoscopic lesions or the ability to treat most of these effectively over time. Improved prognostication of both patient characteristics and endoscopic lesion appearance with regard to bleeding behaviour, coupled with the impact of therapeutic deep enteroscopy, is now required using adapted, high-quality study methodologies.

Epidermal growth factor induces adult human islet cell dedifferentiation.

Given the inherent therapeutic potential of the morphogenetic plasticity of adult human islets, the identification of factors controlling their cellular differentiation is of interest. The epidermal growth factor (EGF) family has been identified previously in the context of pancreatic organogenesis. We examined the role of EGF in an in vitro model whereby adult human islets are embedded in a collagen gel and dedifferentiated into duct-like epithelial structures (DLS). We demonstrated that DLS formation was EGF dependent, while residual DLS formation in the absence of added EGF was abrogated by EGF receptor inhibitor treatment. With respect to signaling, EGF administration led to an increase in c-Jun NH2-terminal kinase (JNK) phosphorylation early in DLS formation and in AKT and extracellular signal-regulated kinase (ERK) phosphorylation late in the process of DLS formation, concomitant with the increased proliferation of dedifferentiated cells. In the absence of EGF, these phosphorylation changes are not seen and the typical increase in DLS epithelial cell proliferation seen after 10 days in culture is attenuated. Thus, in our model, EGF is necessary for islet cell dedifferentiation, playing an important role in both the onset of DLS formation (through JNK) and in the proliferation of these dedifferentiated cells (through AKT and ERK).

Estimating the risk of prolonged air leak after pulmonary resection using a simple scoring system.

BACKGROUND: The high rate of prolonged air leak (PAL) after pulmonary resection has prompted interest in surgical adjuncts designed to prevent this complication. However, these adjuncts are costly and might not be beneficial if used routinely. Identification of patients at highest risk might allow for more effective use of these adjuncts. Therefore, we sought to develop a simple scoring system to predict PAL. STUDY DESIGN: A derivation set of 580 patients was identified from a prospectively entered database of consecutive pulmonary resections at a single institution from 2002 to 2007. Patient and operative characteristics were compared using Student's t-test and chi-square tests. Significant variables on univariate analysis were entered into a stepwise logistic regression to establish a simple predictive model to estimate the risk of PAL. This scoring system was then validated in a consecutive set of 381 patients operated at the same institution from 2007 to 2009. RESULTS: The rate of PAL was 14% in the derivation set and 18% in the validation set. Poor pulmonary function (forced expiratory volume in 1 second and carbon monoxide diffusing capacity, percent predicted) and pleural adhesions were significantly associated with PAL in the derivation set. A weighted scoring system was devised using pleural adhesions (+2 points), forced expiratory volume in 1 second (+1 per 10% below 100%), and carbon monoxide diffusing capacity (+1 per 20% below 100%). Total number of points estimated the probability of PAL. Hosmer-Lemeshow goodness-of-fit test confirmed validity (p > 0.2) of this scoring system in the validation set. CONCLUSIONS: We have devised and validated a simple scoring system to predict the probability of PAL after pulmonary resection.

{beta}-Cell mass dynamics and islet cell plasticity in human type 2 diabetes.

Studies of long-standing type 2 diabetes (T2D) report a deficit in beta-cell mass due to increased apoptosis, whereas neogenesis and replication are unaffected. It is unclear whether these changes are a cause or a consequence of T2D. Moreover, whereas islet morphogenetic plasticity has been demonstrated in vitro, the in situ plasticity of islets, as well as the effect of T2D on endocrine differentiation, is unknown. We compared beta-cell volume, neogenesis, replication, and apoptosis in pancreata from lean and obese (body mass index > or = 27 kg/m(2)) diabetic (5 +/- 2 yr since diagnosis) and nondiabetic cadaveric donors. We also subjected isolated islets from diabetic (3 +/- 1 yr since diagnosis) and nondiabetic donors to an established in vitro model of islet plasticity. Differences in beta-cell volume between diabetic and nondiabetic donors were consistently less pronounced than those reported in long-standing T2D. A compensatory increase in beta-cell neogenesis appeared to mediate this effect. Studies of induced plasticity indicated that islets from diabetic donors were capable of epithelial dedifferentiation but did not demonstrate regenerative potential, as was seen in islets from nondiabetic donors. This deficiency was associated with the overexpression of Notch signaling molecules and a decreased neurogenin-3(+) cell frequency. One interpretation of these results would be that decreased beta-cell volume is a consequence, not a cause, of T2D, mediated by increased apoptosis and attenuated beta-cell (re)generation. However, other explanations are also possible. It remains to be seen whether the morphogenetic plasticity of human islets, deficient in vitro in islets from diabetic donors, is a component of normal beta-cell mass dynamics.

Production and characterization of the recombinant Islet Neogenesis Associated Protein (rINGAP).

Islet Neogenesis Associated Protein (INGAP) is implicated in pancreatic islet neogenesis. INGAP peptide, a pentadecapeptide comprising amino acids 104-118, reverses diabetes in rodents and improves glucose homeostasis in patients with diabetes. The mechanism of INGAP action is unknown, but such studies would benefit from the availability of the full-length recombinant protein (rINGAP). Here we report the production of rINGAP from 293-SF cells following lentiviral transduction, and its characterization by MALDI-TOF and Q-TOF Mass Spectrometry, and HPLC. Importantly, we show that rINGAP exhibits 100x the bioactivity of INGAP peptide on a molar basis in an in vitro assay of human islet regeneration.

Pancreatic ß-Cell Mass as a Pharmacologic Target in Diabetes.

While the prevalence of maternal While the prevalence of diabetes mellitus reaches epidemic proportions, most available treatments still focus on the symptoms of the disease, rather than the underlying pathology. Types 1 and 2 diabetes have in common a deficit in ß-cell mass. In type 1 diabetes, auto-immune ß-cell destruction leads to an absolute deficit in ß-cells, while in type 2 diabetes, insulin resistance and ß-cell dysfunction cause a functional deficit. More recently, however, it has been suggested that type 2 diabetes is also marked by an absolute deficit in ß-cell mass, although a causal relationship has not yet been established. Overall ß-cell mass reflects the balance between the dynamic processes of ß-cell expansion, through proliferation and neogenesis, and ß-cell loss via apoptosis. Given that ß-cell mass can be modified significantly by altering the rate of any of these mechanisms, therapies that modulate ß-cell expansion and loss have garnered recent interest. We review herein the current therapeutics under investigation as modulators of ß-cell mass dynamics, and the basic research that supports these novel therapeutic targets.

Islet-derived progenitors as a source of in vitro islet regeneration.

Current therapies do not prevent the complications of diabetes. Furthermore, these therapies do not address the underlying pathology; the lack of functional beta-cell mass that occurs in both types 1 and 2 diabetes. While pancreas and islet transplantation do serve to increase beta-cell mass, a lack of donor organs limits the therapeutic potential of these treatments. As such, expansion of beta-cell mass from endogenous sources, either in vivo or in vitro, represents an area of increasing interest. One potential source of islet progenitors is the islet proper, via the dedifferentiation, proliferation, and redifferentiation of facultative progenitors residing within the islet. We have developed a tissue culture platform whereby isolated adult human pancreatic islets form proliferative duct-like structures expressing ductal and progenitor markers. Short-term treatment with a peptide fragment of islet neogenesis-associated protein (INGAP) induces these structures to reform islet-like structures that resemble freshly isolated islets with respect to the frequency and distribution of the four endocrine cell types, islet gene expression and hormone production, insulin content, and glucose-responsive insulin secretion. As such, the plasticity of adult human islets has significant implications for islet regeneration.

Cellular origins of adult human islet in vitro dedifferentiation.

Cultured human islets can be dedifferentiated to duct-like structures composed mainly of cytokeratin+ and nestin+ cells. Given that these structures possess the potential to redifferentiate into islet-like structures, we sought to elucidate their specific cellular origins. Adenoviral vectors were engineered for beta-, alpha-, delta- or PP-cell-specific GFP expression. A double-stranded system was designed whereby cultures were infected with two vectors: one expressed GFP behind the cumate-inducible promoter sequence, and the other expressed the requisite transactivator behind the human insulin, glucagon, somatostatin or pancreatic polypeptide promoter. This system labels hormone+ cells in the islet in a cell-specific manner, allowing these cells to be tracked during the course of transformation from islet to duct-like structure. Post-infection, islets were cultured to induce dedifferentiation. Fluorescence microscopy demonstrated that alpha-, delta- and PP-cells contributed equally to the cytokeratin+ population, with minimal beta-cell contribution, whereas the converse was true for nestin+ cells. Complementary targeted cell ablation studies, using streptozotocin or similar adenoviral expression of the Bax (Bcl2-associated X protein) toxigene, validated these findings and suggested a redundancy between alpha-, delta- and PP-cells with respect to cytokeratin+ cell derivation. These results call into question the traditional understanding of islet cells as being terminally differentiated and provide support for the concept of adult islet morphogenetic plasticity.

Donor and isolation variables predicting human islet isolation success.

BACKGROUND: Recent advances in the fields of islet transplantation and in vitro islet cell expansion place a renewed emphasis on the optimization of islet isolation from cadaveric human donor organs. We retrospectively analyzed 171 islet isolations to identify variables that predict islet yield and isolation success. METHODS: Cadaveric human donor pancreata were procured and processed according to established protocols. Donor-, procurement-, and isolation-related variables were analyzed for correlation with islet yield and isolation success (> or =250,000 islet equivalents). RESULTS: Univariate analysis suggested correlations between islet yield and donor age (P<0.005), body surface area (P<0.005), duration of enzymatic digestion (P<0.001), and pancreatic beta-cell volume (P<0.05). Donor sex (P<0.01), procurement team (P<0.05), and peridigestion serine protease inhibition (P<0.05) affected islet yield, whereas enzyme lot (P<0.01) and pancreatic fatty infiltration (P<0.05) influenced isolation success. By logistic regression, donor sex and age, and duration of enzymatic digestion could predict a successful isolation with 72% accuracy. The use of Liberase CI improved islet yield (P<0.05) in young donors (< or =25 years). CONCLUSIONS: While donor-related variables are useful in predicting islet yield, these are likely surrogates for pancreatic beta-cell volume. Enzyme lot, and the associated duration of enzymatic digestion (P<0.05), appears to be key determinants of isolation success.

The role of islet neogenesis-associated protein (INGAP) in islet neogenesis.

Islet Neogenesis-Associated Protein (INGAP) is a member of the Reg family of proteins implicated in various settings of endogenous pancreatic regeneration. The expression of INGAP and other RegIII proteins has also been linked temporally and spatially with the induction of islet neogenesis in animal models of disease and regeneration. Furthermore, administration of a peptide fragment of INGAP (INGAP peptide) has been demonstrated to reverse chemically induced diabetes as well as improve glycemic control and survival in an animal model of type 1 diabetes. Cultured human pancreatic tissue has also been shown to be responsive to INGAP peptide, producing islet-like structures with function, architecture and gene expression matching that of freshly isolated islets. Likewise, studies in normoglycemic animals show evidence of islet neogenesis. Finally, recent clinical studies suggest an effect of INGAP peptide to improve insulin production in type 1 diabetes and glycemic control in type 2 diabetes.

Transforming growth factor beta is a critical regulator of adult human islet plasticity.

Tissue plasticity is well documented in the context of pancreatic regeneration and carcinogenesis, with recent reports implicating dedifferentiated islet cells both as endocrine progenitors and as the cell(s) of origin in pancreatic adenocarcinoma. Accordingly, it is noteworthy that accumulating evidence suggests that TGFbeta signaling is essential to pancreatic endocrine development and maintenance, whereas its loss is associated with the progression to pancreatic adenocarcinoma. The aim of this study was to examine the role of TGFbeta in an in vitro model of islet morphogenetic plasticity. Human islets were embedded in a collagen gel and cultured under conditions that induced transformation into duct-like epithelial structures (DLS). Addition of TGFbeta caused a dose-dependent decrease in DLS formation. Although it was demonstrated that collagen-embedded islets secrete low levels of TGFbeta, antibody-mediated neutralization of this endogenously released TGFbeta improved DLS formation rates, suggesting local TGFbeta concentrations may in fact be higher. Time course studies indicated that TGFbeta signaling was associated with an increase in ERK and p38 MAPK phosphorylation, although inhibitor-based studies were consistent with an islet endocrine-stabilizing effect mediated by p38 alone. Localization of TGFbeta signaling molecules suggested that the action of TGFbeta is directly on the beta-cell to inhibit apoptosis and thus stabilize endocrine phenotype.

Design and analysis of a long-term live-cell imaging chamber for tracking cellular dynamics within cultured human islets of Langerhans.

A means of expanding islet cell mass is urgently needed to supplement the limited availability of donor islets of Langerhans for transplant. Live cell imaging of human islets in culture has the potential to identify the specific cells and processes involved in islet expansion. A novel imaging chamber was developed to facilitate long-term three-dimensional imaging of human islets during transformation. Islets have been induced to transform into duct-like epithelial cystic structures and revert back to glucose responsive endocrine cells under appropriate conditions (Jamal et al. Cell Death Differ. 2005 12:702-712). Here we aim to further our understanding by characterizing the process at a single cell level over time-essentially constructing a high resolution recorded history of each cell and its progeny during transformation and reversion. The imaging chamber enables high resolution imaging of three-dimensional islets while maintaining the structure of the islet cells and intercellular matrix components. A mathematical model was developed to validate the imaging chamber design by determining the required chamber dimensions to avoid introduction of oxygen and nutrient transport limitations. Human islets were embedded in collagen in the imaging chamber and differential interference contrast time course images were obtained at 3 min intervals. Immunofluorescent imaging confirmed that islet phenotype was maintained for at least 5 days during imaging. Analysis of the time courses confirms our ability to identify and track individual cells over time and to observe cell death and phenotype transformation in isolated human islets.

Tumor necrosis factor-alpha production by human islets leads to postisolation cell death.

BACKGROUND: Recent successes in islet transplantation highlight the importance of islet isolation by experienced centers and minimization of cell injury as crucial to the achievement of insulin independence. Islet injury may manifest as cell death by apoptosis, shorter graft survival, and the need for retransplantation. Although an inflammatory cytokine response at the graft site is known to inhibit engraftment, recent evidence indicates that islet cells may contribute to this response. METHODS: Isolated human islets were cultured for up to one week in serum-free CMRL-1066 with 25 microM of tumor necrosis factor (TNF)alpha inhibitor RDP58. Gene expression was measured by reverse transcriptase polymerase chain reaction, apoptosis and TNFalpha secretion by enzyme-linked immunosorbent assay and enzyme-linked immunospot, and islet function by stimulated insulin secretion. RESULTS: Isolation induced a twofold increase in TNFalpha expression between days one and three (P<0.05), while TNFalpha secretion peaked at day one. RDP58 reduced TNFalpha secretion by 70.6% (P<0.02), though TNFalpha gene expression was unaffected. RDP58 reduced the frequency of TNFalpha-secreting islets by 64.4% (P<0.05) and reduced apoptotic levels by 26.4% within 24 hr postisolation (P<0.05). The reduction in apoptosis was maintained throughout the week (P<0.01), while apoptosis increased in control cultures. Finally, RDP58-treated islets displayed increased insulin secretion in response to both elevated glucose (1915.0+/-396.6 vs. 825.3+/-261.1 mU/L, P<0.01) and secretagogues (2294.3+/-529.5 vs. 939.8+/-333.7 mU/L, P<0.02). CONCLUSIONS: These data demonstrate that intraislet cytokine production should be considered as a factor leading to islet cell death postisolation and postengraftment, and strategies aimed at countering islet cytokine production represent a novel target for improving islet viability and function.

Islet neogenesis: a potential therapeutic tool in type 1 diabetes.

Current therapies for type 1 diabetes, including fastidious blood glucose monitoring and multiple daily insulin injections, are not sufficient to prevent complications of the disease. Though pancreas and possibly islet transplantation can prevent the progression of complications, the scarcity of donor organs limits widespread application of these approaches. Understanding the mechanisms of beta-cell mass expansion as well as the means to exploit these pathways has enabled researchers to develop new strategies to expand and maintain islet cell mass. Potential new therapeutic avenues include ex vivo islet expansion and improved viability of islets prior to implantation, as well as the endogenous expansion of beta-cell mass within the diabetic patient. Islet neogenesis, through stem cell activation and/or transdifferentiation of mature fully differentiated cells, has been proposed as a means of beta-cell mass expansion. Finally, any successful new therapy for type 1 diabetes via beta-cell mass expansion will require prevention of beta-cell death and maintenance of long-term endocrine function.

Islet neogenesis: a potential therapeutic tool in type 1 diabetes.

Current therapies for type 1 diabetes, including fastidious blood glucose monitoring and multiple daily insulin injections, are not sufficient to prevent complications of the disease. Though pancreas and possibly islet transplantation can prevent the progression of complications, the scarcity of donor organs limits widespread application of these approaches. Understanding the mechanisms of beta-cell mass expansion as well as the means to exploit these pathways has enabled researchers to develop new strategies to expand and maintain islet cell mass. Potential new therapeutic avenues include ex vivo islet expansion and improved viability of islets prior to implantation, as well as the endogenous expansion of beta-cell mass within the diabetic patient. Islet neogenesis, through stem cell activation and/or transdifferentiation of mature fully differentiated cells, has been proposed as a means of beta-cell mass expansion. Finally, any successful new therapy for type 1 diabetes via beta-cell mass expansion will require prevention of beta-cell death and maintenance of long-term endocrine function.