TIMP1 shapes the fibrotic and hypertrophic response to tac-induced pressure overload

The cardiac extracellular matrix (ECM) regulates mechanical stability, signaling and remodeling. Pressure overload, as seen in aortic stenosis, disrupts ECM turnover and triggers fibroblast ativation, inflammation, and fibrosis, driving maladaptive hypertrophy and heart failure[1]. ECM homeostasis is controlled by matrix metalloproteinases (MMPs) and their inhibitors, including tissue inhibitor of metalloprotease 1 (TIMP1)[2]. Beyond MMP inhibition, TIMP1 signals through CD63 an integrin β1 to activate Smad2/3 and β-catenin pathways, promoting collagen synthesis and myofibroblast differentiation[3].

This study investigates the role of TIMP1 in pressure-overload–induced cardiac remodeling by comparing wild-type and TIMP1-deficient mice subjected to transverse aortic constriction (TAC). We aimed to determine how TIMP1 influences hypertrophic growth, ECM turnover, fibrotic and myofibroblast activation, inflammatory signaling, and apoptosis, and whether it serves as a key regulator of maladaptive remodeling under biomechanical stress.

Eight-week-old Timp1⁰/⁻ (KO) and Timp1⁺/⁺ (WT) mice underwent TAC or sham surgery and were evaluated at 2 or 6 weeks. Stenosis was assessed using trans-stenotic pressure gradients and cardiac hypertrophy was proven by increased heart weights. RNA-Seq and MS-based proteomic was performed on LV tissue to examine gene and protein expression especially for genes associated with hypertrophic, fibrotic, ECM-related and inflammatory markers. Histological analyses included Picrosirius Red staining for collagen deposition and α-smooth muscle actin (SMA) immunostaining to assess myofibroblast conversion.

Echocardiography confirmed successful aortic constriction, with trans-stenotic pressure gradients ≥40mmHg as inclusion criteria. TAC-induced cardiac enlargement in both genotypes, most pronounced at 6 weeks (WT: p=0.02; KO: p<0.0001). Only Timp1⁺/⁺ samples showed a significant correlation between gradients and biventricular weights, indicating attenuated hypertrophy in Timp1⁰/⁻ mice. Further, hypertrophic markers were upregulated in both genotypes, but fold-changes (FC) were higher in hearts of Timp1⁺/⁺ mice (e.g. Nppa: FC2w=5.2, FC6w=9.1). At 2 weeks, Timp1⁺/⁺ mice exhibited enhanced fibrotic remodeling, with increased Acta2 (FC=1.6) and Ctgf (FC=2.9) expression, abundant collagen deposition, and widespread α-SMA-positive myofibroblast activation. Timp1⁰/⁻ animals showed a trend toward lower Mmp9 expression. Inflammatory and apoptotic genes (Il6, Bcl2) were strongly induced in Timp1⁺/⁺ mice but only modestly increased in Timp1⁰/⁻ animals.

TIMP1 deficiency reduces hypertrophy, fibrotic remodeling and inflammatory activation in response to biomechanical stress. These findings support a maladaptive role of TIMP1 in ECM remodeling and inflammation during pressure overload, highlighting it as a potential therapeutic target in pressure-overload heart disease.