Study identifies ICAM-2 as chimp myocardial fibrosis biomarker: full analysis

A new study in Frontiers in Veterinary Science points to ICAM-2 as a potential blood biomarker for idiopathic myocardial fibrosis in chimpanzees, offering a possible new tool for a disease that has been notoriously hard to diagnose before death. The research team, led by Rachel Jarvis and colleagues, evaluated serum from zoo-housed chimpanzees with postmortem-confirmed cardiac phenotypes and found that ICAM-2 performed best among the candidate markers they tested. In the validation cohort, ICAM-2 stayed significantly elevated in affected animals and met the authors’ definition of a highly specific “rule-in” marker for moderate-to-severe fibrosis. (frontiersin.org)

That matters because myocardial fibrosis has been a persistent concern in captive chimpanzees and other great apes for years. Reviews of great ape cardiovascular disease have described it as one of the leading causes of mortality in zoological collections, with chimpanzees frequently showing myocardial fibrosis at necropsy. Earlier pathology work from the Ape Heart Project also emphasized that idiopathic myocardial fibrosis is a common postmortem finding in zoo-housed chimpanzees, even as the underlying causes remain incompletely understood. (cambridge.org)

In the new paper, the investigators first used a proximity extension assay to screen 92 cardiovascular proteins in 10 chimpanzees. That discovery phase highlighted ICAM-2, AXL, and PECAM-1 as elevated in affected animals. They then moved to ELISA validation in 25 chimpanzees, where only ICAM-2 retained a statistically significant association with disease. Using receiver operating characteristic analysis, the team proposed a cutoff above 1.535 ng/mL, with an AUC of 0.672, 100% specificity, and 100% positive predictive value in this study population. They also reported no significant association between ICAM-2 levels and either age or the interval between blood sampling and death. (frontiersin.org)

The study builds on earlier attempts to find useful circulating markers for chimpanzee heart disease. Previous work on collagen metabolism biomarkers found limitations, including lack of cross-reactivity for some assays and reduced specificity because collagen turnover markers may reflect disease outside the heart. Other reports have noted that commonly used clinical lab measures, including some inflammatory and lipid markers, have not been especially helpful for diagnosing cardiac disease in chimpanzees. Against that backdrop, a marker with strong apparent specificity, even if not yet suited as a broad screening tool, is a meaningful step. (pmc.ncbi.nlm.nih.gov)

Direct outside commentary on this specific paper appears limited so far, but the broader field has been clear about the clinical need. The Great Ape Heart Project, established in 2010 to address cardiovascular disease in great apes, maintains cardiac imaging and medical data resources and advises clinicians that evidence for diagnosis and treatment in these species remains relatively sparse. Its published resources recommend specialist consultation because pharmacology, disease thresholds, and clinical progression are still not well defined in great apes. In that context, the new biomarker paper fits an ongoing push toward earlier, less invasive identification of at-risk animals. (greatapeheartproject.org)

Why it matters: For veterinary professionals, the practical value here is not that ICAM-2 solves chimpanzee cardiology, but that it may help narrow uncertainty. A highly specific marker could be useful when a clinician is deciding whether equivocal clinical signs, imaging changes, or anesthesia planning concerns justify treating a chimpanzee as higher risk for meaningful fibrosis. Because these cases often involve endangered animals, limited handling opportunities, and substantial welfare considerations, even a “rule-in” biomarker with modest overall discrimination may still have operational value if it helps prioritize monitoring, echocardiography, or case review. That said, the AUC reported in the study was moderate, and the sample size was small, so veterinary teams should read the findings as promising rather than practice-changing. (frontiersin.org)

There’s also a conservation and population-management angle. Great ape cardiovascular disease affects not just individual patients, but also breeding recommendations, geriatric care planning, anesthesia protocols, and institutional resource use. A blood test that can be added to routine health assessments would be far easier to deploy across collections than repeated advanced imaging alone, especially if future studies show it performs consistently across sex, age groups, and institutions. (frontiersin.org)

What to watch: The next step is external validation: larger, multi-institution cohorts, clearer performance data in mild disease, and evidence showing how ICAM-2 compares with or complements echocardiography and other cardiac workups. If those studies hold up, this could become part of structured surveillance programs through zoo networks and great ape cardiology collaborations. (frontiersin.org)