TGFB1 and systemic sclerosis: At present, TGF-β1 is the most in-depth and important cytokine in the cytokine network involved in SSc-ILD, which regulates the expression of matrix metalloproteinases (MMP) and extracellular matrix (ECM) by activating EMT-related transcription factors to promote epithelial cell apoptosis, migration, and conversion to mesenchymal cells [29, 30].