Loss of MGST1 during fibroblast differentiation enhances vulnerability to oxidative stress in human heart failure

Why this research is important

Heart failure is often worsened by oxidative stress, which damages cardiomyocytes, promotes fibroblast activation, and drives fibrosis. While boosting antioxidants has been considered a therapeutic strategy, clinical translation has been limited. Youness and colleagues uncover that fibroblasts, rather than cardiomyocytes, show the greatest loss of antioxidant capacity in heart failure, specifically due to downregulation of the fibroblast-specific enzyme MGST1. By linking MGST1 loss to increased reactive oxygen species (ROS), lipid peroxidation, ferroptosis susceptibility, and fibroblast activation, this work highlights a potential cell-type-specific therapeutic target to protect the heart.

Glossary

• Fibroblast: A structural cell in the heart responsible for producing and remodelling the extracellular matrix. In disease, fibroblasts become “activated,” proliferating and depositing excess collagen, driving fibrosis.
• Cardiomyocyte: The muscle cell of the heart responsible for contraction and pumping blood. Highly energy-demanding and vulnerable to oxidative stress.
• Reactive Oxygen Species: Chemically reactive oxygen-containing molecules (e.g., superoxide, hydrogen peroxide) that can damage proteins, lipids, and DNA when not balanced by antioxidants.
• TGF-β (Transforming Growth Factor-β): A powerful cytokine that activates fibroblasts and promotes fibrosis.

Background

Oxidative stress occurs when reactive oxygen species, ROS, overwhelm the heart’s antioxidant defenses. Excess ROS cause protein and lipid damage, DNA lesions, and dysregulated signaling, collectively contributing to:

• Cardiomyocyte hypertrophy and death,
• Fibrosis and extracellular matrix (ECM) remodelling,
• Progression to heart failure.

Fibroblasts are key players in this process: activated by angiotensin or TGF-β, they proliferate, migrate, and produce ECM. They also protect cardiomyocytes from ferroptosis, a regulated form of iron-dependent cell death. Thus, understanding how fibroblasts handle oxidative stress is critical for identifying new therapeutic strategies.

Key Results

1. Fibroblasts show the strongest loss of antioxidant gene programs in heart failure

Using single-nucleus RNA-seq from 4 non-failing (NF) and 11 failing human hearts (HF), the authors profiled oxidative-stress-related transcriptional changes across major cardiac cell types. Scoring nuclei with a curated Hallmark ROS-responsive gene set revealed that fibroblasts experience the largest reduction in antioxidant/ROS-responsive genes in heart failure as seen in Figure 1. Among the most strongly downregulated genes were MGST1 and GPX3, both key detoxification enzymes with antioxidant activity. MGST1 stood out as both highly expressed in fibroblasts and fibroblast-specific, and its reduction in HF tissue correlated with higher ROS levels in vivo.

2. MGST1 is lost during fibroblast activation

In healthy hearts, MGST1 is enriched in resting fibroblast states. In HF, fibroblasts shift toward activated states and express little to no MGST1. Pseudotime analyses showed a clear anti-correlation between MGST1 and canonical activation markers (POSTN, ACTA2, COL1A1, FAP) indicating that MGST1 loss accompanies and reinforces fibroblast activation. Consistent with this, TGF-β1, the major cytokine driving fibroblast activation, suppressed MGST1 within 24 hours at both RNA and protein levels. Blocking TGF-β receptor I with SD-208 prevented MGST1 loss and even restored expression above baseline, demonstrating that MGST1 downregulation is at least partly TGF-β–dependent.

3. MGST1 loss primes fibroblasts for activation but doesn’t fully activate them

To test functional consequences of altering MGST1 levels, the authors performed siRNA knockdown of MGST1 in fibroblasts. Reducing MGST1 modestly increased fibroblast activation markers but did not trigger the full activation program or alter proliferation, suggesting that MGST1 loss sensitizes fibroblasts to activation but is insufficient to drive it alone.

4. MGST1 is required to protect fibroblasts from ROS and lipid damage

MGST1 silencing compromised fibroblast oxidative resilience:

• ROS accumulated more readily (Figure 2),
• cells were more sensitive to cumene hydroperoxide–induced death,
• and lipid peroxidation increased.

Together, these results highlight MGST1 as a key membrane-protective antioxidant enzyme in cardiac fibroblasts.

5. Heart failure fibroblasts become prone to ferroptosis

Finally, the dataset revealed a broader vulnerability. HF fibroblasts downregulate multiple genes that suppress ferroptosis or handle iron, including FTH1 and FTL. MGST1 expression correlates with ferroptosis-protective pathways, suggesting that its loss contributes to a ferroptosis-prone, oxidation-sensitive state in the failing heart.

Takeaways

Fibroblasts act as antioxidant hubs, shielding themselves and nearby cardiomyocytes from ROS-induced damage, including ferroptosis. MGST1, enriched in resting fibroblasts but lost in activated states that dominate heart failure, is a key mediator of this protection. This study highlights an often-overlooked role of fibroblasts as antioxidant hubs in the heart. By linking MGST1 loss to fibroblast activation, ROS accumulation, and ferroptosis susceptibility, it opens a new angle on HF progression and suggests that boosting endogenous antioxidant defenses, rather than relying on generic ROS scavengers, may be a more effective strategy.

But could targeted delivery of antioxidant enzymes or modulation of TGF-β signalling offer a therapeutic avenue beyond conventional antioxidants? Yet to be determined.

Question to the authors

1. Mechanistic interplay between oxidative stress and activation signals

Since MGST1 loss makes fibroblasts more vulnerable to ROS, and ROS themselves promote TGF-β activation and fibroblast differentiation: Do you envision MGST1 loss as an initiating event, an amplifying event, or both, in the feed-forward loop of fibroblast activation? Could restoring MGST1 break this loop?

2. Therapeutic implications of MGST1 being insufficient to activate fibroblasts

Given that MGST1 loss alone does not drive fibrosis: Does this make MGST1 a safer therapeutic target, since its restoration would dampen activation without risking excessive suppression of normal fibroblast function? Or do you anticipate that restoring MGST1 might interfere with physiological wound healing?

3. Direction for future research

Since your findings position MGST1 as a modifier rather than a primary determinant of fibroblast fate, what do you see as the next step? Is it identifying upstream triggers of MGST1 loss, or defining the downstream pathways by which lowered antioxidant capacity reshapes fibroblast behaviour?

 

Tags: fibroblasts, heartfailure, human health, oxidative stress, therapeutic target

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