Daniel J. Firl

Recent human decedent model studies^1,2 and compassionate xenograft use³ have explored the promise of porcine organs for human transplantation. To proceed to human studies, a clinically ready porcine donor must be engineered and its xenograft successfully tested in nonhuman primates. Here we describe the design, creation and long-term life-supporting function of kidney grafts from a genetically engineered porcine donor transplanted into a cynomolgus monkey model. The porcine donor was engineered to carry 69 genomic edits, eliminating glycan antigens, overexpressing human transgenes and inactivating porcine endogenous retroviruses. In vitro functional analyses showed that the edited kidney endothelial cells modulated inflammation to an extent that was indistinguishable from that of human endothelial cells, suggesting that these edited cells acquired a high level of human immune compatibility. When transplanted into cynomolgus monkeys, the kidneys with three glycan antigen knockouts alone experienced poor graft survival, whereas those with glycan antigen knockouts and human transgene expression demonstrated significantly longer survival time, suggesting the benefit of human transgene expression in vivo. These results show that preclinical studies of renal xenotransplantation could be successfully conducted in nonhuman primates and bring us closer to clinical trials of genetically engineered porcine renal grafts.

Porcine kidney xenotransplantation is accelerating towards clinical translation. However, despite the demonstrated ability of porcine kidneys to remove metabolic waste products, questions remain about their ability to faithfully recapitulate renal endocrine functions after transplantation. Here we analyze xenograft growth and function of two kidney dependent endocrine pathways in seventeen cynomolgus macaques after kidney xenotransplantation from gene edited Yucatan minipigs. Xenograft growth, the renin-angiotensinogen aldosterone-system, and the calcium-vitamin D-parathyroid hormone axis are assessed using clinical chemistries data, renin activity and beta-C-terminal-telopeptide assays, kidney graft RNA-sequencing and serial ultrasonography. We demonstrate that xenografts transplanted from minipigs show only modest growth and do not substantially contribute to recipient RAAS pathway activity. However, parathyroid hormone-independent hypercalcemia and hypophosphatemia are observed, suggesting a need for close monitoring and timely intervention during human testing. Further study of these phenotypes is warranted in designing prospective clinical trials.

Liver transplantation for hepatocellular carcinoma has proved to be a highly effective cure if the right patient can be selected. Milan criteria has traditionally guided physicians toward appropria...

Globally, hepatocellular carcinoma (HCC) is the sixth most common diagnosed cancer and the fourth most frequent cause of cancer related death¹. Liver transplant (LT) is the optimal treatment for HCC patients with cirrhosis because it is only therapy that can replace the carcinogenic background. In the United States, the Milan criteria (MC) has been the cornerstone for determining liver allocation for patients with HCC².

Objective: Portal vein thrombosis (PVT) does not preclude liver transplantation (LT), but poor portal vein (PV) flow after LT remains a predictor of poor outcomes. Given the physiologic tendency of the hepatic artery (HA) to compensate for low PV flow via vasodilation, we investigated whether adequate HA flow would have a favorable prognostic impact among patients with low PV flow following LT.Methods: This study included 163 patients with PVT who underwent LT between 2004 and 2015. PV and HA flow were categorized into quartiles, and their association with 1‐year graft survival (GS) and biliary complication rates was assessed. For both the HA and the PV, patients at the lowest two quartiles were categorized as having low flow and the remainder as having high flow.Results: The median MELD score was 22 and 1‐year GS was 87.3%. As expected, GS paralleled PV flow with patients at the lowest flow quartile faring the worst. In combination of PV and HA flows, high HA flow was associated with improved 1‐year GS among patients with low PV flow (P = .03). Similar findings were observed with respect to biliary complication rates.Conclusions: Sufficient HA flow may compensate for poor PV flow. Consequently, meticulous HA reconstruction may be central to achieving optimal outcomes in PVT cases.

Prognosticating outcomes in liver transplant (LT) for hepatocellular carcinoma (HCC) continues to challenge the field. Although Milan Criteria (MC) generalized the practice of LT for HCC and improved outcomes, its predictive character has degraded with increasing candidate and oncological heterogeneity. We sought to validate and recalibrate a previously developed, preoperatively calculated, continuous risk score, the Hazard Associated with Liver Transplantation for Hepatocellular Carcinoma (HALTHCC), in an international cohort. From 2002 to 2014, 4,089 patients (both MC in and out [25.2%]) across 16 centers in North America, Europe, and Asia were included. A continuous risk score using pre‐LT levels of alpha‐fetoprotein, Model for End‐Stage Liver Disease Sodium score, and tumor burden score was recalibrated among a randomly selected cohort (n = 1,021) and validated in the remainder (n = 3,068). This study demonstrated significant heterogeneity by site and year, reflecting practice trends over the last decade. On explant pathology, both vascular invasion (VI) and poorly differentiated component (PDC) increased with increasing HALTHCC score. The lowest‐risk patients (HALTHCC 0‐5) had lower rates of VI and PDC than the highest‐risk patients (HALTHCC > 35) (VI, 7.7%[ 1.2‐14.2] vs. 70.6% [48.3‐92.9] and PDC:4.6% [0.1%‐9.8%] vs. 47.1% [22.6‐71.5]; P < 0.0001 for both). This trend was robust to MC status. This international study was used to adjust the coefficients in the HALTHCC score. Before recalibration, HALTHCC had the greatest discriminatory ability for overall survival (OS; C‐index = 0.61) compared to all previously reported scores. Following recalibration, the prognostic utility increased for both recurrence (C‐index = 0.71) and OS (C‐index = 0.63). Conclusion: This large international trial validated and refined the role for the continuous risk metric, HALTHCC, in establishing pre‐LT risk among candidates with HCC worldwide. Prospective trials introducing HALTHCC into clinical practice are warranted.