Faculty Bibliography

Extracorporeal liver cross-circulation (ELC) using gene-edited porcine liver xenografts offers a potential bridge therapy for liver failure. We previously performed five ELC procedures in four brain-dead human decedents, during which the recipients developed severe thrombocytopenia. The porcine liver xenografts maintained their parenchymal structure, with immune cell infiltration and detectable IgM deposition on endothelial cells. Here, to investigate the underlying host-xenograft interactions, we performed longitudinal proteomic, lipidomic and metabolomic profiling of 64 blood samples, alongside spatial transcriptomics and histology of 25 porcine liver xenograft and 3 native human liver biopsies. Spatial transcriptomic analysis revealed progressive infiltration of human immune cells (predominantly inflammatory macrophages and neutrophils) in the xenografts, concurrent with the loss of porcine Kupffer-like macrophages and T cells. Distinct human and porcine complement dynamics were observed, with suppressed human but elevated porcine complement levels, accompanied by increased levels of porcine acute-phase proteins and coagulation factors. Moreover, multiomics analyses identified candidate cellular and molecular factors associated with thrombocytopenia. Human platelets colocalized with activated porcine endothelial cells, which showed increasing porcine vWF expression over time, as well as with immune cells (primarily macrophages and neutrophils) and hepatocytes in the xenografts. Integrative analyses indicated that ELC procedures provided hepatic support for apolipoprotein synthesis, bilirubin clearance, energy metabolism and detoxification, although circulating lipid levels remained low under anhepatic conditions. Collectively, these findings yield insights into the complex interplay between human and xenograft systems during ELC and inform strategies to improve liver xenograft biocompatibility for clinical translation.

BACKGROUND:The gut microbiota (GM) plays an important role in chronic kidney disease (CKD) progression, and dialysis modalities can differentially impact the GM composition and function. There is also limited information on the GM in Arab populations. AIM/OBJECTIVE:To investigate the distinct microbial profiles and functional alterations associated with hemodialysis (HD) and peritoneal dialysis (PD) in a Saudi Arabian cohort. METHODS:We performed whole-genome metagenomic sequencing on fecal samples from 189 participants (controls and CKD, HD, and PD patients). RESULTS:interactions. Conversely, the HD group showed partial recovery of microbial balance and beneficial metabolic functions, including increased short-chain fatty acid metabolism and reduced lipopolysaccharide biosynthesis. CONCLUSION/CONCLUSIONS:The findings of this study highlight the potential of the microbial profile as a robust biomarker for CKD classification and underscore the differential impacts of different dialysis modalities.

BACKGROUND:Ischemic stroke in Saudi Arabia arises in a highly consanguineous population with a distinctive genetic architecture, likely enriching rare coding variants that influence stroke risk. Yet the contribution of these variants to stroke susceptibility, age at onset, and subtype patterns in this setting remains incompletely defined. METHODS:We analyzed whole-exome sequencing data from 514 stroke patients in a case only study design. Gene-based rare variant burden analyses was performed using SAIGE-GENE+ burden and SKAT-O tests across predefined phenotype contrasts within the cohort, stroke severity (modified Rankin Scale, mild < 3 vs. severe ≥ 3 ,), age at onset (early-onset < 25 years vs. late-onset > 45 years; mid-life onset < 45 vs. > 45), etiological subtypes (TOAST classification), and vascular imaging patterns (intracranial vs. extracranial).Post-association functional annotations included GTEx expression, gnomAD constraint metrics, and draggability insights. RESULTS:Gene-level associations at a suggestive threshold (p < 0.005) identified several candidates including HSP90AB1, PRR23A, and LRRC42 (severity and age-at-onset); POGZ and SMIM34 (age-at-onset); and COL9A3, DCP1B, and ADGRV1 (imaging and etiology subtypes). The highlighted genes showed varying expression across brain and vascular tissues and intolerance to loss-of-function variation. Notably, HSP90AB1, a molecular chaperone highly expressed in the brain and vasculature, has small-molecule inhibitors, supporting its potential relevance to stroke biology. CONCLUSIONS:Our findings identify exploratory candidate gene-level signals across clinically defined ischemic stroke phenotypes based on case-only within-cohort comparisons, in underrepresented population. These results should be considered hypothesis-generating and require replication and functional validation before biological or clinical inferences can be made.

Plasma circular RNAs (circRNAs) are stable RNA molecules found in blood, which makes them potential noninvasive biomarkers for acute myocardial infarction (MI). The aim of this study was to describe the plasma circRNA profile in patients with acute MI and to identify circRNA markers that may help detect heart injury and reflect the biological processes involved. We compared plasma samples from patients with acute MI and healthy controls using total RNA sequencing with unique molecular identifiers (UMIs). After sequencing, reads were processed through quality control, alignment, duplicate removal, and circRNA detection. Differential expression was analyzed after adjusting for age, sex, smoking, and technical factors. Several circRNAs were significantly different between MI cases and controls and were able to separate the two groups in principal component and receiver operating characteristic analyses. Among the most increased circRNAs were hsa-PASK_0004, hsa-STXBP3_0002, hsa-RCAN3_0002, and hsa-RANBP9_0044, while hsa-HIF1A_0002, hsa-SUZ12_0049, hsa-PNRC1_0001, and hsa-RAB2A_0002 were decreased. Several candidates showed AUC values above 0.7. Pathway analysis linked the host genes of these circRNAs to inflammation, platelet activation, coagulation, and cardiomyocyte stress responses. Overall, these findings suggest that circulating circRNAs may serve as useful blood-based markers of MI and provide insight into the molecular changes that accompany acute MI.

The inaugural Richard Slayman Clinical Xenotransplantation Workshop convened >140 participants from North America, Europe, and Asia to discuss emerging advances and challenges in translating xenotransplantation from bench to bedside. This report summarized key discussions spanning kidney, heart, and liver xenotransplantation, with an emphasis on clinical readiness and future directions. Core themes included the importance of patient selection, the role of genetic editing to reduce immune incompatibility, adaptive immunosuppressive strategies, novel molecular tools for immune and infectious surveillance, and the growing recognition of innate immune activation as a barrier to long-term graft survival. The workshop highlighted decedent models as a translational bridge, the use of machine perfusion in liver xenograft applications, and progress in living recipients. Notably, 1 patient achieved 9 mo of kidney xenograft function, underscoring the feasibility of extended survival in carefully selected candidates. Perspectives from patients and families, including a reflection honoring Richard Slayman, the first living recipient of a genetically edited pig kidney, framed the scientific dialogue within the broader human impact of this emerging field. The workshop marked a pivotal moment in aligning scientific, ethical, and regulatory efforts to advance safe and equitable access to xenotransplantation.

Xenotransplantation of genetically-modified pig kidneys offers a solution to the scarcity of organs for end-stage renal disease patients.¹ We performed a 61-day alpha-Gal knock-out pig kidney and thymic autograft transplant into a nephrectomized brain-dead human using clinically approved immunosuppression, without CD40 blockade or additional genetic modification. Hemodynamic and electrolyte stability and dialysis independence were achieved. Post-operative day (POD) 10 biopsies revealed glomerular IgM and IgA deposition, activation of early complement components and mesangiolysis with stable renal function without proteinuria, a phenotype not seen in allotransplantation. On POD 33, an abrupt increase in serum creatinine was associated with antibody-mediated rejection and increased donor-specific IgG. Plasma exchange, C3/C3b inhibition and rabbit anti-thymocyte globulin (rATG), completely reversed xenograft rejection. Pre-existing donor-reactive T cell clones expanded progressively in the circulation post-transplant, acquired an effector transcriptional profile and were detected in the POD 33 rejecting xenograft prior to rATG treatment. This study provides the first long-term physiologic, immunologic, and infectious disease monitoring of a pig-to-human kidney xenotransplant and indicates that pre-existing xenoreactive T cells and induced antibodies to unknown epitope(s) present a major challenge, despite significant immunosuppression. It also demonstrates that a minimally gene-edited pig kidney can support long-term life-sustaining physiologic functions in a human.

Organ shortage remains a major challenge in transplantation, and gene-edited pig organs offer a promising solution^1-3. Despite gene-editing, the immune reactions following xenotransplantation can still cause transplant failure⁴. To understand the immunological response of a pig-to-human kidney xenotransplantation, we conducted large-scale multi-omics profiling of the xenograft and the host's blood over a 61-day procedure in a brain-dead human (decedent) recipient. Blood plasmablasts, natural killer (NK) cells, and dendritic cells increased between postoperative day (POD)10 and 28, concordant with expansion of IgG/IgA B-cell clonotypes, and subsequent biopsy-confirmed antibody-mediated rejection (AbMR) at POD33. Human T-cell frequencies increased from POD21 and peaked between POD33-49 in the blood and xenograft, coinciding with T-cell receptor diversification, expansion of a restricted TRBV2/J1 clonotype and histological evidence of a combined AbMR and cell-mediated rejection at POD49. At POD33, the most abundant human immune population in the graft was CXCL9+ macrophages, aligning with IFN-γ-driven inflammation and a Type I immune response. In addition, we see evidence of interactions between activated pig-resident macrophages and infiltrating human immune cells. Xenograft tissue showed pro-fibrotic tubular and interstitial injury, marked by S100A6⁵, SPP1⁶ (Osteopontin), and COLEC11⁷, at POD21-POD33. Proteomics profiling revealed human and pig complement activation, with decreased human component after AbMR therapy with complement inhibition. Collectively, these data delineate the molecular orchestration of human immune responses to a porcine kidney, revealing potential immunomodulatory targets for improving xenograft survival.

BACKGROUND:The genetic architecture of chronic kidney disease (CKD) is complex, including monogenic and polygenic contributions. CKD progression to kidney failure is influenced by factors including male sex, baseline estimated glomerular filtration rate (eGFR), hypertension, diabetes, proteinuria, and the underlying kidney disease. These traits all have strong genetic components, which can be partially quantified using polygenic risk scores. This paper examines the association between polygenic risk scores for CKD-related traits and age at kidney failure development. METHODS:Genome-wide genotype data from 10,586 patients with kidney failure were compiled from 12 cohorts. Polygenic risk scores for hypertension, albuminuria, rapid decline in eGFR, decreased total kidney volume, and decreased eGFR were calculated using weights from published independent population-scale genome-wide association studies. The association between each polygenic risk score and age at kidney failure was investigated using logistic regression models. The association between polygenic risk score and age at kidney failure was also investigated separately for each primary kidney disease. RESULTS:Individuals in the highest 10% of polygenic risk score for decreased eGFR developed kidney failure 2 years earlier than those in the bottom 90% (49.9 years and 47.9 years, P = 5e-5). A standard deviation increase in decreased eGFR polygenic risk score was associated with increased odds of developing kidney failure before the age of 60 years (Odds ratio (OR) = 1.05; 95% CI 1.01-1.10; P = 0.01), as was high decreased eGFR polygenic risk score (OR = 1.26; 95% CI 1.08-1.46; P = 0.003). CONCLUSIONS:We conclude that decreased eGFR polygenic risk score explains a portion of the variation in age at development of kidney failure.