Fibrosis

What causes fibrosis?

Fibrosis occurs in response to injury of parenchymal tissue. The injury may be caused by a variety of insults including, infection, autoimmune reactions, mechanical injury, and toxins. Damage and apoptosis of the epithelial cells of the tissue that release inflammatory mediators lead to an increase in inflammatory cells that function to remove cellular debris. In addition to these cells, myofibroblasts are also increased locally through the upregulation of cytokines and fibroblast growth factors. 

In the normal healing process, the myofibroblasts secrete components of the extracellular matrix (ECM), and undergo apoptosis once the injury is repaired. In fibrosis, there is an unregulated activation and failure of apoptosis of myofibroblasts, leading to deposition of excessive extracellular matrix components. Chronic inflammation is one factor implicated in the dysregulation of wound healing. 

What are the clinical consequences of fibrosis?

The abnormal amounts of fibrotic tissue created by the excess interrupt the parenchymal tissue and the flow of oxygen, causing further damage to the cells of the organ and impairing function. Fibrosis can occur in several organ systems and may lead to organ failure and death. Examples of fibrotic diseases include:

• Liver cirrhosis
• Idiopathic pulmonary fibrosis
• Systemic sclerosis
• Interstitial fibrosis