Role of Compensatory miRNA Networks in Cognitive Recovery from Heart Failure

Abstract

Background: Heart failure (HF) is associated with an increased risk of cognitive impairment and hippocampal dysfunction, yet the underlying molecular mechanisms remain poorly understood. This study aims to investigate the role of microRNA (miRNA) networks in hippocampus-dependent memory recovery in a mouse model of HF. Methods: CaMKIIδC transgenic (TG) mice, a model for HF, were used to assess hippocampal function at 3 and 6 months of age. Memory performance was evaluated using hippocampus-dependent behavioral tasks. Small RNA sequencing was performed to analyze hippocampal miRNA expression profiles across both time points. Bioinformatic analyses identified miRNAs that potentially regulate genes previously implicated in HF-induced cognitive impairment. Results: We have previously shown that at 3 months of age, CaMKIIδC TG mice exhibited significant memory deficits associated with dysregulated hippocampal gene expression. In this study, we showed that these impairments, memory impairment and hippocampal gene expression, were no longer detectable at 6 months, despite persistent cardiac dysfunction. However, small RNA sequencing revealed a dynamic shift in hippocampal miRNA expression, identifying 27 miRNAs as "compensatory miRs" that targeted 73% of the transcripts dysregulated at 3 months but reinstated by 6 months. Notably, miR-181a-5p emerged as a central regulatory hub, with its downregulation coinciding with restored memory function. Conclusions: These findings suggest that miRNA networks contribute to the restoration of hippocampal function in HF despite continued cardiac pathology and provide an important compensatory mechanism towards memory impairment. A better understanding of these compensatory miRNA mechanisms may provide novel therapeutic targets for managing HF-related cognitive dysfunction.

Keywords: Alzheimer; MicroRNA; cognitive impairment; heart failure; hippocampal function; memory recovery; transcriptional homeostasis.

Figure 1

Heart Failure in 6 months CamKIIδc TG mice. (A) Significantly decreased ejection fraction (B), cardiac output, and cardiac index (C) in CamkIIδc TG mice (n = 12) compared to control mice (n = 16). (D) Weight ratios of heart to body, (E) left ventricle to body, and (F) lung to body are increased in CamkIIδc TG (n = 12) compared to control (n = 16). (G) No significant difference in speed, path traveled, and time spent in the middle region in the open field test between CamKIIδc TG (n = 11) and control (n = 15) mice. There were no sex-specific differences detected except for the cardiac output in the WT group (p = 0.04) and overall body weight (WT: p =< 0.0.0001; TG p =< 0.0001). Unpaired t-test, two-tailed; *** p < 0.001, **** p < 0.0001; Error bars indicate SEM.

Figure 2

Behavioral analysis of 6-month-old CamKIIδc TG mice. (A) Escape latency during training sessions of the Barnes maze test is not affected in 6 old CamkIIδc TG (n = 11) and control mice (n = 15; two-way ANOVA p = 0.97). (B) Time spent at the target hole during the memory test vs. time spent at other holes is not different in 6-month-old CamkIIδc TG (n = 11) when compared to control mice (n = 15). (C) Time spent in the target quadrant during the memory test in fCamkIIδc TG (n = 11) and control mice (n = 15) during the memory test. (D) Representative images showing the path of mice during the memory test. (E) Distance traveled in the open field in CamkIIδc (n = 11) and control mice (n = 15). (F) Speed during the open field test. (G) Time spent in the center area of the open field is similar in CamkIIδc TG and control mice. (H) Representative images showing the performance during the open field test. There were no sex-specific differences detected. Unpaired t-test, two-tailed; Error bars indicate SEM.

Figure 3

Gene expression changes in 3 and 6-month-old CamKIIδC TG mice. (A) Bar chart showing the number of differentially expressed genes comparing wild-type control to CamKIIδC TG mice (FDR < 0.05) at either 3 or 6 months of age. (log2FC was either < 0.1 or < 0.26). (B) Heatmap showing deregulated genes in 3-month-old mice in WT (n = 5) and CamKIIδC TG (n = 6) and the “rescued” gene expression in 6-month-old CamKIIδC TG mice (n = 11), comparable to 6-month-old WT mice (n = 15). (C) Bar chart showing the number of differentially expressed genes when 3 vs. 6 months old wild type control (WT) or 3 vs. 6 months old CamKIIδC TG mice (TG) were compared (FDR < 0.05; log2FC < 0.26). (D) Volcano plot showing the differentially expressed transcripts when comparing 3 vs. 6 months old wild-type control mice. (E) Volcano plot showing the differentially expressed transcripts when comparing 3 vs. 6 months old CamKIIδC TG mice. In (D,E), the horizontal dotted line indicates the significance threshold for the –log₁₀ P-value (p < 0.05), while the vertical dotted lines indicate the significance thresholds for the log₂ fold change (±0.26).

Figure 4

Changes in miRNA expression in wild-type control and CamKIIδC TG mice between 3 and 6 months of age. (A) Volcano plot showing differentially expressed miRNAs when comparing 3 vs. 6 months old wild type control mice (n = 5, n = 15, respectively). (B) Volcano plot showing differentially expressed miRNAs when comparing 3 vs. 6 months old CamKIIδC TG mice (n = 6, n = 16, respectively). FDR < 0.05, log2 FC < 0.26. In A and B the horizontal dotted line indicates the significance threshold for the –log₁₀ P-value (p < 0.05), while the vertical dotted lines indicate the significance thresholds for the log₂ fold change (±0.26).

Figure 5

A miR RNA network that may act as a compensatory response in heart failure-mediated memory impairment. (A) Schematic illustration of the working hypothesis. (B) Bar graph showing the percentage of “rescued transcripts” targeted by the “compensatory miRNAs”. (C) Bar chart showing the 27 “compensatory miRNAs” (miRs with >= 5 targets) and the number of “rescued transcripts” targeted by each miRNA (blue bars). As a control (black bars), the number of mRNA transcripts upregulated in 3-month-old TG mice is shown. (D) Dot plot showing GO term analysis of the “rescued transcripts” upregulated from 3 to 6 months in CaMKIIδC TG mice. (E) Gene interaction network illustrating the 27 “compensatory miRNAs” (violet; circle size corresponds to the number of target genes regulated by each miRNA) and their relationship with the “rescued transcripts” (blue). This network accounts for 56% of the rescued transcripts.