Oxygenated thawing and rewarming alleviate rewarming injury of cryopreserved pancreatic islets.

BACKGROUND/AIMS: Pancreatic islet transplantation is an effective treatment for Type 1 diabetic patients to eliminate insulin injections; however, a shortage of donor organs hinders the widespread use. Although long-term islet storage, such as cryopreservation, is considered one of the key solutions, transplantation of cryopreserved islets is still not practical due to the extensive loss during the cryopreservation-rewarming process. We have previously reported that culturing islets in a hyperoxic environment is an effective treatment to prevent islet death from the hypoxic injury during culture. In this study, we explored the effectiveness of thawing and rewarming cryopreserved islets in a hyperoxic environment. METHODS: Following cryopreservation of isolated human islets, the thawing solution and culture media were prepared with or without pre-equilibration to 50% oxygen. Thawing/rewarming and the pursuant two-day culture were performed with or without oxygenation. Short-term recovery rate, defined as the volume change during cryopreservation and thawing/rewarming, was assessed. Ischemia-associated and inflammation-associated gene expressions were examined using qPCR after the initial rewarming period. Long-term recovery rate, defined as the volume change during the two-day culture after the thawing/rewarming, was also examined. Islet metabolism and function were assessed by basal oxygen consumption rate and glucose stimulated insulin secretion after long-term recovery. RESULTS: Oxygenated thawing/rewarming did not alter the short-term recovery rate. Inflammation-associated gene expressions were elevated by the conventional thawing/rewarming method and suppressed by the oxygenated thawing/rewarming, whereas ischemia-associated gene expressions did not change between the thawing/rewarming methods. Long-term recovery rate experiments revealed that only the combination therapy of oxygenated thawing/rewarming and oxygenated culture alleviated islet volume loss. These islets showed higher metabolism and better function among the conditions examined. CONCLUSION: Oxygenated thawing/rewarming alleviated islet volume loss, with the help of oxygenated culture.

Isolated human islets require hyperoxia to maintain islet mass, metabolism, and function.

Pancreatic islet transplantation has been recognized as an effective treatment for Type 1 diabetes; however, there is still plenty of room to improve transplantation efficiency. Because islets are metabolically active they require high oxygen to survive; thus hypoxia after transplant is one of the major causes of graft failure. Knowing the optimal oxygen tension for isolated islets would allow a transplant team to provide the best oxygen environment during pre- and post-transplant periods. To address this issue and begin to establish empirically determined guidelines for islet maintenance, we exposed in vitro cultured islets to different partial oxygen pressures (pO2) and assessed changes in islet volume, viability, metabolism, and function. Human islets were cultured for 7 days in different pO2 media corresponding to hypoxia (90 mmHg), normoxia (160 mmHg), and hyerpoxia (270 or 350 mmHg). Compared to normoxia and hypoxia, hyperoxia alleviated the loss of islet volume, maintaining higher islet viability and metabolism as measured by oxygen consumption and glucose-stimulated insulin secretion responses. We predict that maintaining pre- and post-transplanted islets in a hyperoxic environment will alleviate islet volume loss and maintain islet quality thereby improving transplant outcomes.

Evaluation of standard versus reduced dose apixaban for the treatment of venous thromboembolism in patients with severe renal disease (ESRD-VTE).

BACKGROUND: There are no clear dosing recommendations when using apixaban for venous thromboembolism (VTE) treatment in patients with severe or end-stage renal disease; clinical trials excluded patients with a creatinine clearance (CrCl) <25 mL/min or on dialysis. This study compares bleeding rates in patients with severe or end-stage renal disease taking standard versus reduced dose apixaban for VTE treatment. MATERIALS AND METHODS: This was a multicenter, retrospective cohort study using electronic medical records between January 1, 2013, and August 31, 2021. This study included patients 18 years or older who had severe or end-stage renal disease when prescribed apixaban for VTE treatment. Severe or end-stage renal disease was defined as at least one of the following: CrCl <25 mL/min, SCr >2.5 mg/dL, CKD stage 4 or 5, or on dialysis. The primary endpoint was rate of clinically relevant bleeding within six months of starting apixaban. Secondary endpoints were VTE recurrence within six months of starting apixaban, time to clinically relevant bleed, and time to VTE recurrence. RESULTS: A total of 203 patients were included in the final analysis (n = 125 on 5 mg; n = 78 on 2.5 mg). Clinically relevant bleeding rate was significantly higher in the standard dose group (14.4 % vs 3.8 %, p = 0.02). Rates of VTE recurrence appear similar (6.4 % vs 7.7 %, p = 0.21). CONCLUSIONS: A reduced dose of apixaban may be considered when treating VTE in patients with severe or end-stage renal disease.

Iatrogenic Delirium in Patients on Symptom-Triggered Alcohol Withdrawal Protocol: A Case Series.

In this report, we present a case series involving four patients placed on the Clinical Institute Withdrawal Assessment for Alcohol, Revised (CIWA-Ar) protocol for alcohol or sedative-hypnotic withdrawal syndromes, who developed delirium on sustained or increasing symptom-triggered benzodiazepine dosages. In each of the four cases, delirium was not present on admission and resolved in the hospital itself with fixed benzodiazepine tapers. Cases were selected from an electronic medical record database of patients admitted to a United States-based university hospital and placed on CIWA-Ar between 2017 and 2018. This case series illustrates the major limitations of CIWA-Ar including its subjective nature, its susceptibility to inappropriate patient selection, and its requirement for providers to consider alternative etiologies to alcohol and benzodiazepine withdrawal syndromes. These cases demonstrate the necessity of considering other assessment and treatment options such as objective alcohol withdrawal scales, fixed benzodiazepine tapers, and even antiepileptics. An effective systems-based approach to overcoming these challenges may include setting time limits on CIWA-Ar orders within the electronic health record (EHR) system.

Optimizing Temperature and Oxygen Supports Long-term Culture of Human Islets.

Islet transplantation is a promising treatment for type-1 diabetes; however, donor shortage is a concern. Even when a pancreas is available, low islet yield limits the success of transplantation. Islet culture enables pooling of multiple low-yield isolations into an effective islet mass, but isolated islets rapidly deteriorate under conventional culture conditions. Oxygen (O2) depletion in the islet core, which leads to central necrosis and volume loss, is one of the major reasons for this deterioration. METHODS: To promote long-term culture of human islets in PIM-R medium (used for islet research), we adjusted temperature (12°C, 22°C, and 37°C) and O2 concentration (21% and 50%). We simulated the O2 distribution in islets based on islet O2 consumption rate and dissolved O2 in the medium. We determined the optimal conditions for O2 distribution and volume maintenance in a 2-week culture and assessed viability and insulin secretion compared to noncultured islets. In vivo islet engraftment was assessed by transplantation into diabetic nonobese diabetic-severe combined immunodeficiency mouse kidneys. We validated our results using CMRL 1066 medium (used for clinical islet transplantation). RESULTS: Simulation revealed that 12°C of 50% O2 PIM-R culture supplied O2 effectively into the islet core. This condition maintained islet volume at greater than 90% for 2 weeks. There were no significant differences in viability and function in vitro or diabetic reversal rate in vivo between 2-week cultured and noncultured islets. Similar results were obtained using CMRL 1066. CONCLUSIONS: By optimizing temperature and O2 concentration, we cultured human islets for 2 weeks with minimal loss of volume and function.