Ascites formation accompanied by portal vein thrombosis after porcine islet xenotransplantation via the portal vein in Rhesus macaque (Macaca mulatta)

Islet Transplantation in the Lung via Endoscopic Aerosolization: Investigation of Feasibility, Islet Cluster Cell Vitality, and Structural Integrity

Aerosolized drug delivery has recently attracted much attention as a possible new tool for the delivery of complex nanoparticles. This study aims to investigate whether catheter-based aerosolization of islets via endobronchial systems is a feasible option in islet transplantation. Besides investigating the feasibility of islet aerosolization, we also examined cluster cell vitality and structural integrity of the islets following aerosolization. Using an ex vivo postmortem swine model, porcine pancreatic islets were isolated and aerosolized with an endoscopic spray catheter. Following aerosolization, islet cell vitality and function were assessed via Calcein AM and propidium iodide as well as insulin production after glucose exposure. In the final step, the overall feasibility of the procedure and structural integrity of cells were analyzed and evaluated with respect to clinical applicability. No significant difference was detected in the viability of control islets (90.67 ± 2.19) vs aerosolized islets (90.68 ± 1.20). Similarly, there was no significant difference in control islets (1.62 ± 0.086) vs aerosolized islets (1.42 ± 0.11) regarding insulin release after stimulation. Indocyanine green marked islets were transplanted into the lung without major difficulty. Histological analysis confirmed retained structural integrity and predominant location in the alveolar cavity. Our ex vivo data suggest that catheter-based aerosolized islet cell delivery is a promising tool for the application of cell clusters. According to our data, islet cell clusters delivery is feasible from a mechanical and physical perspective. Moreover, cell vitality and structural integrity remain largely unaffected following aerosolization. These preliminary results are encouraging and represent a first step toward endoscopically assisted islet cell implantation in the lung.

Mitomycin C treatment improves pancreatic islet graft longevity in intraportal islet transplantation by suppressing proinflammatory response

The in vitro culture period prior to cell transplantation (i.e. pancreatic islet transplantation) enables cell modification and is thus advantageous. However, the islet preconditioning method has not been fully explored. Here we present a simple approach for islet preconditioning that uses the antibiotic mitomycin C (MMC), which has antitumor activity, to reduce islet immunogenicity and prevent proinflammatory events in an intraportal islet transplantation model. Freshly isolated mice islets were treated for 30 min with 10 μg/mL MMC or not, cultured for 20 h and transplanted into the livers of syngeneic or allogeneic diabetic mouse recipients. In the allogeneic model, MMC preconditioning significantly prolonged graft survival without requiring immunosuppressants. In vitro, MMC treatment suppressed the expression of proinflammatory cytokines in islet allografts, while immunohistochemical studies revealed the suppression of inflammatory cell infiltration into MMC-treated allografts relative to untreated allografts. Furthermore, MMC preconditioning significantly suppressed the mRNA expression of proinflammatory cytokines into the transplant site and induced the differentiation of regulatory T cells with the ability to suppress CD4⁺ T cell-mediated immune responses. In conclusion, islet preconditioning with MMC prolonged graft survival in an intraportal islet transplantation model by suppressing proinflammatory events and inducing potentially regulatory lymphocytes.