We recently reported in a rat model of kidney transplantation that the addition of sodium thiosulfate (STS) to organ preservation solution improved renal graft quality and prolonged recipient survival. The present study investigates whether STS pre-treatment would produce a similar effect. In vitro, rat kidney epithelial cells were treated with 150 μM STS before and/or during exposure to hypoxia followed by reoxygenation. In vivo, donor rats were treated with PBS or 2.4 mg/kg STS 30 min before donor kidneys were procured and stored in UW or UW+150 μM STS solution at 4 °C for 24 h. Renal grafts were then transplanted into bilaterally nephrectomised recipient rats which were then sacrificed on post-operative day 3. STS pre-treatment significantly reduced cell death compared to untreated and other treated cells in vitro (p < 0.05), which corresponded with our in vivo result (p < 0.05). However, no significant differences were observed in other parameters of tissue injury. Our results suggest that STS pre-treatment may improve renal graft function after transplantation.

Ischemia-reperfusion injury (IRI) is an inevitable consequence of organ transplant procedure and associated with acute and chronic organ rejection in transplantation. IRI leads to various forms of programmed cell death, which worsens tissue damage and accelerates transplant rejection. We recently demonstrated that necroptosis participates in murine cardiac microvascular endothelial cell (MVEC) death and murine cardiac transplant rejection. However, MVEC death under a more complex IRI model has not been studied. In this study, we found that simulating IRI conditions in vitro by hypoxia, reoxygenation and treatment with inflammatory cytokines induced necroptosis in MVECs. Interestingly, the apoptosis-inducing factor (AIF) translocated to the nucleus during MVEC necroptosis, which is regulated by the mitochondrial permeability molecule cyclophilin D (CypD). Furthermore, CypD deficiency in donor cardiac grafts inhibited AIF translocation and mitigated graft IRI and rejection (n = 7; p = 0.002). Our studies indicate that CypD and AIF play significant roles in MVEC necroptosis and cardiac transplant rejection following IRI. Targeting CypD and its downstream AIF may be a plausible approach to inhibit IRI-caused cardiac damage and improve transplant survival.

The global donor kidney shortage crisis has necessitated the use of suboptimal kidneys from donors-after-cardiac-death (DCD). Using an ex vivo porcine model of DCD kidney transplantation, the present study investigates whether the addition of hydrogen sulfide donor, AP39, to University of Wisconsin (UW) solution improves graft quality. Renal pedicles of male pigs were clamped in situ for 30 min and the ureters and arteries were cannulated to mimic DCD. Next, both donor kidneys were nephrectomized and preserved by static cold storage in UW solution with or without AP39 (200 nM) at 4 °C for 4 h followed by reperfusion with stressed autologous blood for 4 h at 37 °C using ex vivo pulsatile perfusion apparatus. Urine and arterial blood samples were collected hourly during reperfusion. After 4 h of reperfusion, kidneys were collected for histopathological analysis. Compared to the UW-only group, UW+AP39 group showed significantly higher pO₂ (p < 0.01) and tissue oxygenation (p < 0.05). Also, there were significant increases in urine production and blood flow rate, and reduced levels of urine protein, serum creatinine, blood urea nitrogen, plasma Na⁺ and K⁺, as well as reduced intrarenal resistance in the UW+AP39 group compared to the UW-only group. Histologically, AP39 preserved renal structure by reducing the apoptosis of renal tubular cells and immune cell infiltration. Our finding could lay the foundation for improved graft preservation and reduce the increasingly poor outcomes associated with DCD kidney transplantation.

Organ transplantation is associated with various forms of programmed cell death which can accelerate transplant injury and rejection. Targeting cell death in donor organs may represent a novel strategy for preventing allograft injury. We have previously demonstrated that necroptosis plays a key role in promoting transplant injury. Recently, we have found that mitochondria function is linked to necroptosis. However, it remains unknown how necroptosis signaling pathways regulate mitochondrial function during necroptosis. In this study, we investigated the receptor-interacting protein kinase 3 (RIPK3) mediated mitochondrial dysfunction and necroptosis. We demonstrate that the calmodulin-dependent protein kinase (CaMK) family members CaMK1, 2, and 4 form a complex with RIPK3 in mouse cardiac endothelial cells, to promote trans-phosphorylation during necroptosis. CaMK1 and 4 directly activated the dynamin-related protein-1 (Drp1), while CaMK2 indirectly activated Drp1 via the phosphoglycerate mutase 5 (PGAM5). The inhibition of CaMKs restored mitochondrial function and effectively prevented endothelial cell death. CaMKs inhibition inhibited activation of CaMKs and Drp1, and cell death and heart tissue injury (n = 6/group, p < 0.01) in a murine model of cardiac transplantation. Importantly, the inhibition of CaMKs greatly prolonged heart graft survival (n = 8/group, p < 0.01). In conclusion, CaMK family members orchestrate cell death in two different pathways and may be potential therapeutic targets in preventing cell death and transplant injury.

Background: Frostbite injury is a thermal injury where ice crystals form in skin tissues and subsequently lead to damage due to prolonged exposure to cold temperatures below 0 °C. The extremities are mostly affected, leading to potential amputation. As there is no pharmacological treatment of frostbite injury, we recently reported that non-clinically viable hydrogen sulfide (H₂S) donors promote frostbite wound healing in mice. In this study, we investigated whether commonly used cosmetic creams supplemented with sodium thiosulfate (STS), a clinically viable H₂S donor drug, also promote healing of frostbite wounds. Methods: Frozen magnets (−80 °C) were placed on the dorsal skin of 40 C57BL/6 mice for 3 min to induce frostbite injury. Next, commercially available cosmetic creams (Aveeno, Dove, Neutrogena, and Nivea) were topically applied on frostbite wounds daily for 14 days with or without 150 µM of STS supplementation. The mice were sacrificed on day 15 after induction of frostbite injury, and samples of the injured dorsal skin tissue were collected for analysis. Results: Addition of STS enhanced frostbite wound healing, as evidenced by progressive and significantly reduced wound area by about 50% and inflammation (p < 0.05), and markedly increased granulation tissue formation by >45%, fibroblast maturation by >28%, and re-epithelialization by >63% compared to control groups (p < 0.05), with Nivea producing a superior wound-healing effect. Also, STS supplementation significantly upregulated the expression of CD31 (by >25%), KI-67 (by >25%), CD163 (by >20%), fibronectin (by >14%), and cytokeratin (by >50%) in frostbite wounds compared to control groups, with Aveeno and Nivea producing a better wound-healing effect than Dove and Neutrogena creams. Conclusions: In conclusion, STS accelerated healing of frostbite wounds. Therefore, it could be considered as a novel pharmacological treatment of clinical frostbite.

Despite their reduced viability, kidneys from donors-after-circulatory-death (DCD) increase the pool of transplantable kidneys. Molecular hydrogen (H₂) is emerging as a gas with therapeutic potential against graft injury. We investigated the effect of H₂ in an ex vivo porcine model of DCD kidney transplantation. Renal arteries of male Yorkshire pigs (n = 6) were clamped in situ for 60 min to induce ischemia, and ureters and arteries were cannulated to mimic DCD kidney injury. Upon nephrectomy, kidneys were flushed with UW solution or H₂-saturated UW solution and then preserved by machine perfusion at 4 °C for 4 h followed by a 4-h reperfusion period with warm autologous blood. Urine and arterial blood samples were collected hourly. H₂ preserved renal architecture, evidenced by significantly reduced tubular necrosis and renal expression of damage markers, which corresponded with the downregulated renal expression of pro-inflammatory genes compared to the UW-only group (p < 0.05). H₂ also markedly reduced levels of serum creatinine, BUN and intrarenal resistance, while flow rate, creatinine clearance and urine output were significantly higher, which positively correlated with Trx-1 and HO-1 expression in comparison with UW only group (p < 0.05). Improvement in renal graft quality and function is associated with Trx-1/HO-1 activation, suggesting preliminary clinical trials in kidney transplantation.