Cardiac scarring cells
When muscle is lost, the body fills the gap with fibrous tissue. Signaling molecules released during the acute phase switch these cells on, and other cell types are recruited to become them. Scar is not muscle — it does not contract, and once it is laid down it stays. This is the step that decides whether function returns or a permanent deficit remains.
In depth
The cells that lay down scar where muscle used to be.
What drives it
Heart muscle inflammation increases it.
10.1016/j.bbrep.2025.102344 — Phase three — where a recoverable illness becomes a permanent one. 'profibrotic cytokines and mediators released during acute myocarditis in susceptible individuals activate fibroblasts and recruit new fibroblast differentiation via endothelial mesenchymal transition leading to cardiac remodeling and dilated cardiomyopathy' (Mayo/Elsevier chapter — Viral Myocarditis and Dilated Cardiomyopathy: Mechanisms of Cardiac Injury, Inflammation, and Fibrosis). Scar is not muscle. It does not contract, and once laid down it stays. This is the step that decides whether the heart recovers its function OR keeps a permanent deficit. doi 10.1016/j.bbrep.2025.102344
Reduces scarring increases it.
10.3390/cells10071716 — phase three — where a recoverable illness becomes a permanent one. 'profibrotic cytokines and mediators released during acute myocarditis in susceptible individuals activate fibroblasts and recruit new fibroblast differentiation via endothelial mesenchymal transition leading to cardiac remodeling and dilated cardiomyopathy' (Mayo/Elsevier chapter — Viral Myocarditis and Dilated Cardiomyopathy: Mechanisms of Cardiac Injury, Inflammation, and Fibrosis). Scar is not muscle. It does not contract, and once laid down it stays. This is the step that decides whether the heart recovers its function OR keeps a permanent deficit. doi 10.3390/cells10071716
Cell migration switch increases it.
10.1038/nm1613 — phase three — where a recoverable illness becomes a permanent one. 'profibrotic cytokines and mediators released during acute myocarditis in susceptible individuals activate fibroblasts and recruit new fibroblast differentiation via endothelial mesenchymal transition leading to cardiac remodeling and dilated cardiomyopathy' (Mayo/Elsevier chapter — Viral Myocarditis and Dilated Cardiomyopathy: Mechanisms of Cardiac Injury, Inflammation, and Fibrosis). Scar is not muscle. It does not contract, and once laid down it stays. This is the step that decides whether the heart recovers its function OR keeps a permanent deficit. doi 10.1038/nm1613
Coxsackievirus B3 increases it.
The cell that makes the scar is also the cell the virus prefers — and that reframes the whole illness. 'We found that in addition to cardiomyocytes cardiac fibroblasts were infected by CVB3 and displayed a higher virus replication (132-fold increase) compared to cardiomyocytes (14-fold increase) between 6 and 24 hours after infection' (pmc4211177 — Cardiac Fibroblasts Aggravate Viral Myocarditis: Cell Specific Coxsackievirus B3 Replication). And they shout louder too: 'the expression of TNF-α, IL-6, MCP-1, and IFN-β was significantly increased in cardiac fibroblasts compared to cardiomyocytes OR macrophages'. ⇒ nearly ten times the viral output of the muscle cell, and more inflammatory signal. The same cell then lays down the scar that replaces the muscle the virus destroyed. It is not a late-stage bystander — it is there from the first day, amplifying the infection it will later paper over.
What it drives
It increases Tissue remodeling.
10.3390/cells10071716 — phase three — where a recoverable illness becomes a permanent one. 'profibrotic cytokines and mediators released during acute myocarditis in susceptible individuals activate fibroblasts and recruit new fibroblast differentiation via endothelial mesenchymal transition leading to cardiac remodeling and dilated cardiomyopathy' (Mayo/Elsevier chapter — Viral Myocarditis and Dilated Cardiomyopathy: Mechanisms of Cardiac Injury, Inflammation, and Fibrosis). Scar is not muscle. It does not contract, and once laid down it stays. This is the step that decides whether the heart recovers its function OR keeps a permanent deficit. doi 10.3390/cells10071716
It increases Supports heart function.
10.1038/nrcardio.2017.57 — phase three — where a recoverable illness becomes a permanent one. 'profibrotic cytokines and mediators released during acute myocarditis in susceptible individuals activate fibroblasts and recruit new fibroblast differentiation via endothelial mesenchymal transition leading to cardiac remodeling and dilated cardiomyopathy' (Mayo/Elsevier chapter — Viral Myocarditis and Dilated Cardiomyopathy: Mechanisms of Cardiac Injury, Inflammation, and Fibrosis). Scar is not muscle. It does not contract, and once laid down it stays. This is the step that decides whether the heart recovers its function OR keeps a permanent deficit. doi 10.1038/nrcardio.2017.57
It increases Coxsackievirus B3.
The cell that makes the scar is also the cell the virus prefers — and that reframes the whole illness. 'We found that in addition to cardiomyocytes cardiac fibroblasts were infected by CVB3 and displayed a higher virus replication (132-fold increase) compared to cardiomyocytes (14-fold increase) between 6 and 24 hours after infection' (pmc4211177 — Cardiac Fibroblasts Aggravate Viral Myocarditis: Cell Specific Coxsackievirus B3 Replication). And they shout louder too: 'the expression of TNF-α, IL-6, MCP-1, and IFN-β was significantly increased in cardiac fibroblasts compared to cardiomyocytes OR macrophages'. ⇒ nearly ten times the viral output of the muscle cell, and more inflammatory signal. The same cell then lays down the scar that replaces the muscle the virus destroyed. It is not a late-stage bystander — it is there from the first day, amplifying the infection it will later paper over.
It increases Monocyte recruitment.
The signal that calls in the reinforcements — and the scar cell shouts it loudest. Myricetin ameliorates the disease 'by modulating immune response and inhibiting MCP-1 expression' (doi 10.1016/j.ejphar.2023.175551 — Myricetin ameliorates experimental autoimmune myocarditis in mice by modulating immune response and inhibiting mcp-1 expression). And the source matters: 'the expression of TNF-α, IL-6, MCP-1, and IFN-β was significantly increased in cardiac fibroblasts compared to cardiomyocytes or macrophages' (pmc4211177 — Cardiac Fibroblasts Aggravate Viral Myocarditis: Cell Specific Coxsackievirus B3 Replication). ⇒ the cell that will later lay down the scar is also the loudest caller-in of inflammation. doi 10.1016/j.ejphar.2023.175551
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.