Recurrent Mild Acute Rejections and Donor-specific Antibodies as Risk Factors for Cardiac Allograft Vasculopathy in a National Pediatric Heart Transplant Cohort.

Background: Immune-mediated factors such as acute cellular rejections and donor-specific antibodies (DSAs) are risk factors for cardiac allograft vasculopathy (CAV). We studied a national cohort with a unified setting and thorough protocol endomyocardial biopsy (EMB) data for an association between cellular rejections, especially when mild and recurrent, and DSAs with CAV in pediatric heart transplant (HTx) patients. Methods: This is a retrospective, national cohort study of 94 pediatric HTxs performed between 1991 and 2019 and followed until December 31, 2020. Diagnosis of CAV was based on reevaluation of angiographies. Protocol and indication EMB findings with other patient data were collected from medical records. Associations between nonimmune and immune-mediated factors and CAV were analyzed with univariable and multivariable Cox regression analyses. Results: Angiographies performed on 76 patients revealed CAV in 23 patients (30%). Altogether 1138 EMBs (92% protocol biopsies) were performed on 78 patients (83%). During the first posttransplant year, grade 1 rejection (G1R) appeared in 45 patients (58%), and recurrent (≥2) G1R findings in 14 patients (18%). Pretransplant DSAs occurred in 13 patients (17%) and posttransplant DSAs in 37 patients (39%). In univariable analysis, pretransplant DSAs, appearance and recurrence of G1R findings, and total rejection score during the first posttransplant year, as well as recurrent G1R during follow-up, were all associated with CAV. In multivariable analysis, pretransplant DSAs and recurrent G1R during the first posttransplant year were found to be associated with CAV. Conclusions: Our results indicate that pretransplant DSA and recurrent G1R findings, especially during the first posttransplant year, are associated with CAV after pediatric HTx.

Liver and serum expression of matrix metalloproteinases in asymptomatic pediatric liver transplant recipients.

We related hepatic gene and serum expression of matrix metalloproteinases (MMP) and their tissue inhibitors (TIMP) to liver histology in pediatric LT recipients. Liver biopsies and serum samples were obtained from 52 patients 10.6 years post-LT and age-matched controls for analyses of MMPs and TIMPs. Patients with fibrosis had significantly higher hepatic gene expression of MMP-2, MMP-9, MMP-14, TIMP-1, and TIMP-2 than patients without. Expression of these genes correlated with graft Metavir fibrosis stage (r = 0.494-0.684, P ≤ 0.006 for all). Gene expression of MMP-1, MMP-3, MMP-8, TIMP-3, and TIMP-4 was undetectable in both patients and controls. Portal inflammation and cytokeratin 7 correlated positively with gene expression of TIMP-1. Gene expression of MMP-2, MMP-9, and TIMP-2 correlated negatively with the time of low-dose cortisone usage (r = -0.448 to -0.422, P < 0.05 for all). Serum concentrations of MMP-8 and TIMP-1 were significantly increased and MMP-9 decreased among patients compared with controls, but no correlations to graft histology or gene expression were observed. Hepatic gene expression of certain MMPs and TIMPs is increased in stable pediatric LT recipients displaying graft fibrosis, but this did not reflect to their serum concentrations. Increased hepatic gene expression of TIMP-1 correlated with graft fibrosis stage, inflammation, and chronic cholestasis.