Recovery From Heart Failure: Microvascular Mechanisms

25 Mar 20264 min read0 viewsJournal Feed

GIST

Circulation, Ahead of Print. BACKGROUND:Heart failure (HF) is a significant global health problem.

Left ventricular assist device (LVAD) implantation serves as a bridge for patients awaiting heart transplantation. Intriguingly, LVAD support often improves cardiac histology and function, sometimes enough to avoid transplantation after LVAD removal.

However, the cellular programs underlying this recovery remain unclear.METHODS:Myocardial tissues were obtained from patients with HF at the time of LVAD implantation (pre LVAD) and explantation (post LVAD) for histological analysis and single-nucleus RNA sequencing. A murine model of HF recovery, combined with lineage tracing studies, was employed to define cellular sources of vascular repair.

Cardiac function, fibrosis, and vascular density were assessed using echocardiography, histology, and fluorescent microsphere perfusion. A patient-derived cardiac nonmyocyte culture system was established to interrogate mechanisms of cell fate regulation.RESULTS:Post-LVAD myocardial tissues exhibited reduced fibrosis and increased capillary density compared with pre-LVAD samples.

Across samples, fibroblast abundance was inversely correlated with endothelial cell abundance, consistent with enhanced angiogenesis during recovery. Single-nucleus RNA sequencing identified a fibroblast subset predisposed to undergo mesenchymal-to-endothelial transition, acquiring an endothelial cell identity.

Clinical Editorial

Context and aims

The report investigates cellular programs underpinning heart failure (HF) recovery observed with left ventricular assist device (LVAD) support, including instances where recovery permits removal of the device and avoidance of transplantation.
The study combines human tissue analysis, a murine HF recovery model with lineage tracing, and patient-derived nonmyocyte cultures to explore vascular repair and cell fate dynamics.

Study design and methods

Human myocardium: samples obtained at LVAD implantation (pre-LVAD) and explantation (post-LVAD) for histology and single-nucleus RNA sequencing.
Functional and structural assessments: echocardiography, histology, and fluorescent microsphere perfusion measured cardiac function, fibrosis, and vascular density.
Experimental systems: a mouse model recapitulating HF recovery with lineage tracing; patient-derived nonmyocyte cultures used to probe mechanisms of cell fate regulation.
Analytic focus: correlations between fibroblast and endothelial cell abundances; identification of fibroblast subsets with mesenchymal-to-endothelial transition potential.

Key histologic and cellular signals

Post-LVAD samples show less fibrosis and higher capillary density versus pre-LVAD tissues.
An inverse relationship emerged across samples between fibroblast and endothelial cell populations, consistent with augmented angiogenesis during recovery.
Single-nucleus RNA sequencing revealed a fibroblast subset with propensity to undergo mesenchymal-to-endothelial transition, acquiring endothelial identity.

Functional reprogramming and lineage evidence

Patient-derived nonmyocytes from pre-LVAD hearts exhibited limited proliferation and poor vascular structure formation.
Nonmyocytes from post-LVAD hearts demonstrated enhanced proliferation, angiogenic ability, and the formation of vessel-like structures, supporting an angiogenic reprogramming theme in HF recovery.
Mechanistic modulation linked to c-Myc: siRNA knockdown in post-LVAD cells yielded a shift toward a pre-LVAD–like state; conversely, c-Myc overexpression in pre-LVAD cells induced a post-LVAD–like phenotype, suggesting c-Myc as a driver of this fate switch.

In vivo concordance and implications

The murine model paralleled human findings, showing histological and functional restoration with increased microvascular perfusion and a fibroblast-to-endothelial transition supported by lineage tracing.

Limitations and open questions

Not all mechanistic details are defined, and the extent to which these findings translate to broader HF populations remains uncertain.
The exact regulatory networks beyond c-Myc that govern the fibroblast-to-endothelial transition warrant further study.