The study, led by Roksana Gozdowska and Marek Kuch together with colleagues at the Medical University of Warsaw and collaborating institutions, focused on circulating microRNAs, tiny fragments of non-coding RNA that drift through the bloodstream inside membrane-wrapped vesicles or bound to carrier proteins. MicroRNAs are short molecules, roughly 18 to 25 nucleotides long, that never get translated into proteins. Instead, they act as fine-tuners of gene expression: each microRNA can bind to matching sequences on messenger RNA transcripts and suppress their translation or trigger their degradation. Because a single microRNA can regulate dozens of target genes, and because their levels change in response to tissue injury, inflammation and stress, they have become prime suspects in the search for biomarkers that capture complex biological processes such as cardiac healing.

To find out whether these molecules could flag patients destined for recovery, the researchers enrolled 39 patients who had just experienced their first myocardial infarction. Everyone in the cohort completed a structured cardiac rehabilitation program, the standard supervised combination of exercise training and lifestyle support given after a heart attack. The team then applied strict echocardiographic criteria to define who had achieved reverse remodeling by the eight-week follow-up: either an absolute increase in left ventricular ejection fraction of at least 10 percentage points, or a reduction in left ventricular end-systolic volume of at least 15 percent. Ejection fraction measures the proportion of blood the ventricle ejects with each beat, while end-systolic volume reflects how much blood remains in the chamber after contraction, so together they capture both the pumping strength and the size of the recovering ventricle.

From the original cohort, ten patients who met the reverse remodeling criteria were matched with ten patients whose left ventricular status remained stable over the same period. The twenty analyzed patients had a mean age of 57 years, with a standard deviation of nine years. At baseline, before rehabilitation began, the two groups looked meaningfully different on standard imaging: the stable group started with a significantly higher ejection fraction of 53 percent, compared with 44 percent in the group that would go on to recover, a difference that reached statistical significance with a p-value of 0.013. That starting gap makes the subsequent recovery all the more notable, because the patients who improved began from a weaker position.

The echocardiographic follow-up added a second layer of evidence. Regional contractility impairment, meaning localized areas of the ventricular wall that move abnormally because of infarct damage, was present in all of the patients who later achieved reverse remodeling. By the eight-week mark, 70 percent of those patients had reversed this regional dysfunction, their previously stunned or hibernating heart muscle segments regaining movement. This pattern suggests that a substantial share of early post-infarction dysfunction is not permanent cell death but recoverable injury, and that the patients who recover are those whose hearts successfully re-activate this dormant tissue during rehabilitation.

The molecular heart of the study lay in the blood samples. Using quantitative reverse transcription polymerase chain reaction, a technique that amplifies and measures specific RNA sequences with high sensitivity, the team quantified 375 circulating microRNAs in each patient at baseline. They then searched for molecules that were more abundant in the patients who would later recover, reasoning that a higher starting level of a recovery-associated microRNA might act as an early signal of a heart poised to heal. This screen yielded fourteen candidate biomarkers: miR-15b-5p, miR-24-3p, miR-29c-3p, miR-99b-5p, miR-127-3p, miR-146a-5p, miR-199a-3p, miR-361-5p, miR-502-5p, miR-625-5p, miR-376c-3p, miR-18b-5p, miR-342-5p and miR-429. Several of these, including miR-502-5p, miR-376c-3p and miR-18b-5p, had not previously been implicated in human cardiac reverse remodeling, making them genuinely novel candidates.

Identifying the microRNAs was only the first step; the researchers also wanted to know what these molecules might actually be doing. Because individual microRNAs repress many target genes, the team performed enrichment analysis, a computational method that asks whether the genes targeted by a set of microRNAs cluster within particular biological pathways more often than chance would predict. The analysis pointed squarely at four major signaling networks: the PI3K-Akt pathway, the MAPK cascade, FoxO signaling and HIF-1 signaling. These are not obscure corners of cell biology. PI3K-Akt is a central pro-survival route that protects heart muscle cells from programmed death and drives growth and metabolism; MAPK pathways transmit stress and growth signals from the cell surface to the nucleus; FoxO transcription factors govern cell survival, autophagy and oxidative stress responses; and HIF-1 is the master regulator of the cellular response to low oxygen, a condition the infarcted heart knows intimately.

The convergence of the fourteen candidate microRNAs on these pathways paints a coherent biological picture. A heart recovering from an infarction must simultaneously limit further cell death, clear damaged tissue, stimulate repair, and re-vascularize oxygen-starved regions, and each of the enriched pathways contributes to one or more of those tasks. Circulating microRNAs, in this framing, are not merely passive debris shed from injured tissue; they are potentially active participants in intercellular communication, capable of being delivered to recipient cells and shifting gene expression programs there. If baseline microRNA profiles genuinely reflect the heart’s reparative capacity, a simple blood draw taken days after a heart attack could eventually help clinicians identify which patients are most likely to benefit from intensive rehabilitation and which need closer surveillance or additional therapies.

The authors are careful to frame the work as a bridge between laboratory findings and clinical practice rather than a definitive answer. Preclinical studies in cell cultures and animal models have long implicated microRNAs in cardiac remodeling, but translating those findings to patients has been difficult, partly because human heart attack patients are heterogeneous in age, infarct size, medication and comorbidities. By measuring microRNAs directly in patients and linking them to objectively defined echocardiographic outcomes, the study connects preclinical biology to real clinical settings. At the same time, the sample size is small, with only twenty patients in the final matched analysis, and the candidate biomarkers were identified in a pooled discovery design. The authors themselves emphasize that validation in larger, independent, non-pooled cohorts is essential before any of these molecules could move toward clinical use as a diagnostic or prognostic test.

Even with those caveats, the study adds an appealing piece to one of cardiology’s most consequential puzzles. Reverse remodeling after a heart attack represents the heart’s innate capacity for self-repair, a capacity that varies dramatically between patients for reasons that remain poorly understood. If a panel of fourteen circulating microRNAs, measured from a routine blood sample, can flag that capacity early, it could reshape how patients are triaged after infarction, personalize rehabilitation programs, and even identify candidates for emerging regenerative therapies. It would also reinforce a broader shift in medicine toward liquid biopsies, in which molecular signals circulating in blood replace or complement invasive and imaging-based assessments. For now, the fourteen microRNAs remain candidates rather than validated tools, but they offer a molecular fingerprint of cardiac recovery and a concrete starting point for the larger studies that will determine whether that fingerprint can be read reliably at the bedside.

Subject of Research: Circulating microRNAs as candidate biomarkers of left ventricular reverse remodeling after myocardial infarction

Article Title: Circulating microRNAs as potential candidate biomarkers of left ventricular reverse remodeling after myocardial infarction: A pilot study

Article References: Gozdowska, R., Konopka, M., Hojka-Osińska, A., Jas, G., Czarzasta, K., Cudnoch-Jędrzejewska, A., Braksator, W., Klimczak-Tomaniak, D., & Kuch, M. (2026). Circulating microRNAs as potential candidate biomarkers of left ventricular reverse remodeling after myocardial infarction: A pilot study. PLOS One, 21(10), e0360414. https://doi.org/10.1371/journal.pone.0360414

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360414

Keywords: microRNAs, myocardial infarction, left ventricular reverse remodeling, biomarkers, cardiac rehabilitation, echocardiography, ejection fraction, PI3K-Akt pathway, MAPK, FoxO signaling, HIF-1, non-coding RNA