Temperature profiles of different cooling methods in porcine pancreas procurement

Sterile Pancreas Inflammation during Preservation and after Transplantation

The pancreas is very susceptible to ischemia-reperfusion injury. Early graft losses due to pancreatitis and thrombosis represent a major issue after pancreas transplantation. Sterile inflammation during organ procurement (during brain death and ischemia-reperfusion) and after transplantation affects organ outcomes. Sterile inflammation of the pancreas linked to ischemia-reperfusion injury involves the activation of innate immune cell subsets such as macrophages and neutrophils, following tissue damage and release of damage-associated molecular patterns and pro-inflammatory cytokines. Macrophages and neutrophils favor tissue invasion by other immune cells, have deleterious effects or functions, and promote tissue fibrosis. However, some innate cell subsets may promote tissue repair. This outburst of sterile inflammation promotes adaptive immunity activation via antigen exposure and activation of antigen-presenting cells. Better controlling sterile inflammation during pancreas preservation and after transplantation is of utmost interest in order to decrease early allograft loss (in particular thrombosis) and increase long-term allograft survival. In this regard, perfusion techniques that are currently being implemented represent a promising tool to decrease global inflammation and modulate the immune response.

Pancreas preservation: clinical practice and future developments

PURPOSE OF REVIEW

To summarize recently published studies of preservation strategies including machine perfusion in pancreas transplantation.

RECENT FINDINGS

The shortage of conventional donors is leading units to use extended criteria donors (ECDs) and donors after cardiac death (DCD). Static cold storage (SCS) is still the standard method of preservation for pancreases and University of Wisconsin remains the gold standard preservation solution. In experimental studies, oxygen delivered during preservation reduced tissue injury and improved islet cell yield and function. Hypothermic machine perfusion of discarded human pancreases has been shown to improve adenosine triphosphate levels without adversely effect histology and oedema compared with SCS. Normothermic machine perfusion of discarded human organs has so far been challenging and led to increasing injury, rather than preservation. There are currently no clinical studies in pancreas transplant with the exception of a small number of pancreases being transplanted following normothermic regional perfusion.

SUMMARY

The storm of new organ preservation methods is now being more widely studied in the pancreas, with some promising results. These new strategies have the potential to allow expansion of the donor pool and greater utilization of ECD and DCD organs.

Composite Tissue Preservation

Composite tissue (CT) preservation is important to outcomes after replant or transplant. Since the first limb replant, the mainstay of preservation has been static cold storage with the amputated part being placed in moistened gauze over ice. Historically, the gold-standard in solid organ preservation has been static cold storage with specialized solution, but this has recently evolved in the last few decades to develop technologies such as machine perfusion and even persufflation. This review explores the impact of cooling and oxygenation on CT, summarizes the work done in the area of CT preservation, discusses lessons learned from our experience in solid organ preservation, and proposes future directions.

Nutrient Regulation by Continuous Feeding for Large-scale Expansion of Mammalian Cells in Spheroids

In this demonstration, spheroids formed from the β-TC6 insulinoma cell line were cultured as a model of manufacturing a mammalian islet cell product to demonstrate how regulating nutrient levels can improve cell yields. In previous studies, bioreactors facilitated increased culture volumes over static cultures, but no increase in cell yields were observed. Limitations in key nutrients such as glucose, which were consumed between batch feedings, can lead to limitations in cell expansion. Large fluctuations in glucose levels were observed, despite the increase in glucose concentrations in the media. The use of continuous feeding systems eliminated fluctuations in glucose levels, and improved cell growth rates when compared with batch fed static and SSB culture methods. Additional increases in growth rates were observed by adjusting the feed rate based on calculated nutrient consumption, which allowed the maintenance of physiological glucose over three weeks in culture. This method can also be adapted for other cell types.

Establishment of a porcine pancreatic stem cell line using T-REx(™) system-inducible Wnt3a expression

OBJECTIVES

Porcine pancreatic stem cells (PSCs) are highly valuable in transplantation applications for type II diabetes. However, there are still many problems to be solved before they can be used in the clinic, such as insufficient cell number availability and low secretion level of insulin. It has been reported that Wnt3a plays pivotal roles during cell proliferation and differentiation. Here, we have aimed to establish an ideal research platform using the T-REx(™) system, to study mechanisms of Wnt3a during PSC proliferation and differentiation.

MATERIALS AND METHODS

Construction of the recombinant plasmid and cell transfection were used for establishment of a porcine PSC line. Related gene expressions were examined using quantitative real-time PCR (QRT-PCR), western blotting, immunostaining and flow cytometry. BrdU incorporation assay and cell cycle analysis were used to investigate Wnt3a roles in PSCs.

RESULTS

Wnt3a-expressing clones regulated by T-REx(™) were successfully obtained. Wnt3a and GFP expression were strictly regulated by Dox in a time- and dose-dependent manner. Furthermore, we found that Wnt3a-expressing porcine PSCs induced by Dox exhibited raised proliferative potential. After Dox stimulation, expression of PCNA, C-MYC and active β-catenin were higher, but were down-regulated after Dkk1 addition.

CONCLUSION

We established a porcine PSC line that dynamically expressed Wnt3a, and we found that Wnt3a promoted PSC proliferative potential. This inducible expression system thus provides an important tool for further study on porcine PSC development and differentiation.