The potential of genetically engineered pig heart transplantation in infants with complex congenital heart disease

Treatment of Presumptive Rejection After Orthotopic Pig-to-Baboon Cardiac Xenotransplantation

BACKGROUND

Significant progress has been made in the long-term survival of non-human primates after orthotopic gene-edited pig cardiac xenotransplantation. However, to our knowledge, there are no reports of the successful reversal of an acute rejection episode in such an experiment. We present evidence suggesting that rejection can be reversed with corticosteroids and complement inhibition.

METHODS

Orthotopic transplantation of a pig heart (with 69 gene-edits) was carried out in a baboon. The immunosuppressive regimen was based on CD40/CD154 T cell co-stimulation pathway blockade and rapamycin. Cardiac function remained excellent until Day 162, when there were increases in heart rate, ventricular septal wall thickness, left ventricular end-diastolic pressures (LVEDP), and troponin level, which were associated with a low serum level of rapamycin (<4 ng/mL). Anti-rejection treatment was begun with an increase in rapamycin dosage, steroid bolus therapy, two doses of a C1-esterase inhibitor, and an extra dose of the anti-CD154mAb.

RESULTS

There was a rapid correction of all hemodynamic parameters, and the troponin T level (which had risen to 139 ng/L) returned to pre-rejection levels. Ventricular septal thickness and LVEDP returned to pre-rejection levels after treatment. The baboon remains well with normal graft function. Baseline heart rate remains faster than before the rejection episode.

CONCLUSIONS

As we transition to the clinical application of gene-edited pig cardiac xenotransplantation, the ability to treat rejection is of vital importance. The optimal treatment for rejection remains uncertain but we suggest that systemic complement inhibition is important.

Heart transplantation in adults with congenital heart diseases: A comprehensive meta-analysis on waiting times, operative, and survival outcomes

The rising prevalence of congenital heart disease (CHD) among adults has led to increased heart transplantation (HT) procedures in this population. However, CHD patients face significant challenges including longer waiting times, higher early mortality rates, and increased risks of complications such as renal dysfunction. This systematic review and meta-analysis examined 50 studies to assess waiting times, postoperative outcomes, and survival rates in CHD patients undergoing HT compared to non-CHD patients. Results revealed that CHD patients experience longer HT waiting times (mean difference [MD]: 53.86 days, 95 % CI: [22.00, 85.72], P = 0.0009) and increased ischemic times (MD: 20.01 min, 95 % CI: [10.51, 29.51], P < 0.0001), which may increase waitlist and early postoperative mortality. Regarding complications, renal dysfunction is more prevalent in CHD patients than in non-CHD patients (RR: 2.05, 95 % CI: [1.61, 2.61], P < 0.00001). Despite these challenges, long-term survival rates for CHD patients are comparable to those of non-CHD recipients, with significant improvements noted in recent allocation systems. Our findings emphasize the need for ongoing refinements in HT allocation systems to improve outcomes for CHD patients, particularly in reducing waiting times and managing post-transplant complications.

Trabeculations of the porcine and human cardiac ventricles are different in number but similar in total volume

An intricate meshwork of trabeculations lines the luminal side of cardiac ventricles. Compaction, a developmental process, is thought to reduce trabeculations by adding them to the neighboring compact wall which is then enlarged. When pig, a plausible cardiac donor for xenotransplantation, is compared to human, the ventricular walls appear to have fewer trabeculations. We hypothesized the trabecular volume is proportionally smaller in pig than in human. Macroscopically, we observed in 16 pig hearts that the ventricular walls harbor few but large trabeculations. Close inspection revealed a high number of tiny trabeculations, a few hundred, within the recesses of the large trabeculations. While tiny, these were still larger than embryonic trabeculations and even when considering their number, the total tally of trabeculations in pig was much fewer than in human. Volumetrics based on high-resolution MRI of additional six pig hearts compared to six human hearts, revealed the left ventricles were not significantly differently trabeculated (21.5 versus 22.8%, respectively), and the porcine right ventricles were only slightly less trabeculated (42.1 vs 49.3%, respectively). We then analyzed volumetrically 10 pig embryonic hearts from gestational day 14-35. The trabecular and compact layer always grew, as did the intertrabecular recesses, in contrast to what compaction predicts. The proportions of the trabecular and compact layers changed substantially, nonetheless, due to differences in their growth rate rather than compaction. In conclusion, processes that affect the trabecular morphology do not necessarily affect the proportion of trabecular-to-compact myocardium and they are then distinct from compaction.