The pericardium is a double-walled sac containing the heart and the roots of the large blood vessels. It consists of a superficial sheet, the fibrous pericardium, and a deep sheet, the serous pericardium. The serous pericardium is itself composed of two layers: the parietal layer towards the outside and the visceral layer towards the inside. The latter two layers are separated by a virtual pericardial cavity containing the pericardial fluid.

Pericardial fibroblasts (PcF) are the major cell type of the pericardium. They produce collagens and help form the thin but strong pericardium, which serves as a protective sac for the heart by providing structural support and lubrication, and preventing excessive dilation of the heart. Dysregulated PcF activation and proliferation, collagen and fibrin deposition, chronic inflammation, and scarring have been implicated in constrictive pericarditis, where hardening of the pericardium ultimately prevents the heart from dilating. The associations between fibroblast activation and immunomodulation make PcF cultures a useful tool for studying progressive sclerosing pericarditis.