C57BL/6 Mouse Pancreatic Islets

IMCs Suppressed Macrophage Migration Toward Allogeneic Islets In Vitro

Pancreatic islet transplantation (PITx) offers hope for type 1 diabetes patients, yet faces challenges due to intense post-transplant inflammation and innate immune responses. Previous studies have shown alloantigen-specific immunomodulatory cells (IMCs), grown ex vivo with anti-CD80/CD86 monoclonal antibodies, can induce tolerance post-liver transplantation. Forhioni et al. explored the potential of IMCs in mitigating inflammatory responses and protecting islets during PITx.

To evaluate IMCs' effect on macrophage migration to islets, an in vitro co-culture system mimicking allogeneic PITx was used. C57BL/6 pancreatic islets were paired with RAW264 macrophages, derived from BALB/c mice. The RAW264 cells were placed on a Transwell insert, allowing cell movement, with or without IMCs and C57BL/6 islets. After 24 hours, migrated F4/80+ cells in the lower wells were quantified using flow cytometry. RAW264 cells with only medium showed few macrophages (126.8 ± 123.1). IMCs alone slightly increased migration (1187 ± 605.1), while C57BL/6 islets alone majorly increased it (8212 ± 2157). Adding IMCs with islets notably decreased migration (4285 ± 1418, P < 0.05, Fig. 1B, C).

Fig. 1. Islet-macrophage co-culture with IMCs (Forhioni A, Watanabe M, et al., 2025).

Chemical-Induced ER Stress Upregulates PLIN2 Expression in Pancreatic β Cells

Pancreatic β cell failure is pivotal in the progression from glucose intolerance to diabetes, with endoplasmic reticulum (ER) stress accelerating this process, particularly due to lipotoxicity and excessive insulin demand. ER stress leads to protein misfolding, triggering the unfolded protein response (UPR). Current studies highlight that perilipin 2 (PLIN2) affects lipid balance in the liver and is now identified as a modulator of both UPR and ER stress in pancreatic β cells.

In this study, Chen's team sought to determine the role of PLIN2 in modulating β cell function under ER stress conditions. They treated MIN6 cells with ER stress inducer tunicamycin (TM) and found that the treatment increased PLIN2 expression at both the mRNA and protein levels (Fig. 2A and B). The same treatment also stimulated PLIN2 protein expression (and a trend towards increased Plin2 mRNA expression) in C57BL/6 isolated mouse islets (Fig. 2C and D). In addition to TM, thapsigargin (THAPS), an ER stress inducer that works via different mechanisms25, also stimulated PLIN2 expression in MIN6 cells (Fig. 2E and F). The results suggest that increased ER stress per se is associated with upregulated PLIN2 expression.

Fig. 2. ER stress upregulates PLIN2 expression in MIN6 cells and mouse pancreatic islets (Chen E, Tsai T H, et al., 2017).