Transforming growth factor-β (TGF-β) isoforms are profibrotic cytokines, par excellence, and
have complex multifunctional effects on many systems, depending on the biologic setting.
Retinoids are vitamin A derivatives that also have diverse effects in development,
physiology, and disease. The interactions between these classes of molecules are, not
surprisingly, highly complex and are dependent on the tissue, cellular, and molecular
settings.