High-dose norepinephrine induces disruption of myocardial extracellular matrix and left ventricular dilatation and dysfunction in a novel feline model

Metalloproteinases and Hypertrophic Cardiomyopathy: A Systematic Review

Hypertrophic cardiomyopathy (HCM) is a genetic condition determined by an altered collagen turnover of the extracellular matrix. Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are abnormally released in patients with HCM. The purpose of this systematic review was to thoroughly summarize and discuss the existing knowledge of MMPs profile in patients with HCM. All studies meeting the inclusion criteria (detailed data regarding MMPs in patients with HCM) were selected, after screening the literature from July 1975 to November 2022. Sixteen trials that enrolled a total of 892 participants were included. MMPs-particularly MMP2-levels were found higher in HCM patients compared to healthy subjects. MMPs were used as biomarkers after surgical and percutaneous treatments. Understanding the molecular processes that control the cardiac ECM's collagen turnover allows for a non-invasive evaluation of HCM patients through the monitoring of MMPs and TIMPs.

Acute heart failure with cardiomyocyte atrophy induced in adult mice by ablation of cardiac myosin light chain kinase

AIMS

Under pressure overload, initial adaptive hypertrophy of the heart is followed by cardiomyocyte elongation, reduced contractile force, and failure. The mechanisms governing the transition to failure are not fully understood. Pressure overload reduced cardiac myosin light chain kinase (cMLCK) by ∼80% within 1 week and persists. Knockdown of cMLCK in cardiomyocytes resulted in reduced cardiac contractility and sarcomere disorganization. Thus, we hypothesized that acute reduction of cMLCK may be causative for reduced contractility and cardiomyocyte remodelling during the transition from compensated to decompensated cardiac hypertrophy.

METHODS AND RESULTS

To mimic acute cMLCK reduction in adult hearts, the floxed-Mylk3 gene that encodes cMLCK was inducibly ablated in Mylk3(flox/flox)/merCremer mice (Mylk3-KO), and compared with two control mice (Mylk3(flox/flox) and Mylk3(+/+)/merCremer) following tamoxifen injection (50 mg/kg/day, 2 consecutive days). In Mylk3-KO mice, reduction of cMLCK protein was evident by 4 days, with a decline to below the level of detection by 6 days. By 7 days, these mice exhibited heart failure, with reduction of fractional shortening compared with those in two control groups (19.8 vs. 28.0% and 27.7%). Severely convoluted cardiomyocytes with sarcomeric disorganization, wavy fibres, and cell death were demonstrated in Mylk3-KO mice. The cardiomyocytes were also unable to thicken adaptively to pressure overload.

CONCLUSION

Our results, using a new mouse model mimicking an acute reduction of cMLCK, suggest that cMLCK plays a pivotal role in the transition from compensated to decompensated hypertrophy via sarcomeric disorganization.

Changes in plasma profiles of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs in stress-induced cardiomyopathy

BACKGROUND

Transient changes in the composition of the myocardial extracellular matrix may contribute to the ventricular systolic dysfunction in stress-induced cardiomyopathy (SIC). We examined the changes in plasma matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) that occur early after the clinical presentation of SIC.

METHODS AND RESULTS

Ten patients with SIC were enrolled. Plasma concentrations of the 6 major MMPs (1, 2, 3, 7, 8, and 9) and all 4 TIMPs (1, 2, 3, and 4) were analyzed and compared with data from 15 control subjects. Within 24 hours of the clinical presentation, SIC patients had lower MMP-1 levels (0.41 ± 0.13 vs 0.70 ± 0.13 pg/mL; P = .048) and MMP-8 levels (1.61 ± 0.34 vs 4.84 ± 1.38 pg/mL; P = .001) and higher TIMP-4 levels (3.06 ± 0.40 vs 2.16 ± 0.18 pg/mL; P = .05) compared with control. Seven of 9 SIC patients had elevated LV end-diastolic pressures, and all had normal LV end-diastolic dimensions and volumes.

CONCLUSIONS

Patients afflicted with SIC had MMP and TIMP profiles similar to those described in hypertensive heart disease and diastolic heart failure and different from the profiles following myocardial infarction. Our findings uncovered a unique biomolecular profile in SIC during the first 24 hours of presentation.