The pericardium is a biological tissue widely used as a biomaterial for tissue engineering applications, including the construction of a variety of bio prostheses such as vascular grafts, patches for abdominal or vaginal wall reparation and, more frequently, heart valves. However, despite significant advances, some drawbacks have been found in these bio prostheses such as biological matrix deterioration and tissue degeneration associated with calcifications, even though xenopericardium or glutaraldehyde-treated autologous pericardium were used. In non-autologous pericardial processing, the pericardium must be decellularized in order to remove cellular antigens and procalcific remnants while preserving extracellular matrix integrity.

 A large variety of cellularization protocols exist, such as chemical, physical or enzymatic methods. Additional cross-linking processing must be carried out to render the tissue non-antigenic and mechanically strong. So far, almost all bio prosthetic materials made of pericardium, and used in clinical practice, are glutaraldehyde-treated bovine or porcine xenopericardium. However, long-term reports are raising issues concerning their durability, especially highlighting the high risk of calcification. Regarding heart valves, calcification currently represents the major drawback leading to potential failure of the bio prosthesis. The aim of this review is to present current issues, challenges, outcomes and future prospects of pericardial processing, including decellularization and cross-linking steps. Understanding current issues and improving pericardial processing will allow refining bio prosthesis conception and patients’ safety.

The pericardium is composed of a simple squamous epithelium and connective tissue. It is a collagen-rich biological tissue containing mostly type I collagen, as well as glycoproteins and glycosaminoglycan’s (GAGs) in addition to its constitutive cells. Collagen is structured into different levels of organization ranging from fibrils to laminates, fibers and fiber bundles. This organization determines the mechanical properties of the pericardial tissue and provides an anisotropic and non-linear mechanical behaviour. Interestingly, depending on the location on the pericardium, the thickness and mechanical properties vary. Thus, the location of the sample that will be harvested should be carefully selected when designing a tissue engineering protocol. Human autologous pericardium is thus an interesting option, presenting several advantages over allografts since it is free of donor-derived pathogens and does not induce any immune response, is easily available, easily handled and of low cost.

 Ultimately, these characteristics allow for shorter and less aggressive pericardial processing before implantation of the bio prosthesis. However, because of intermittent reports of its tendency to retract or become aneurysmal, the general opinion has been negative. For cusp tissue replacement or valve tissue replacement, stabilization of pericardium is performed with a solution of 0,2% to 0,6% glutaraldehyde in order to prevent secondary shrinkage. As allografts have been the main source for pericardial bio prostheses currently in use, significant processing steps have to be performed prior to clinical use. In particular, as xenogeneic cellular antigens induce an immune response or an immune-mediated rejection of the tissue, decellularization protocols are widely used to reduce the host tissue response Once decellularized, the free-cell pericardial tissue is composed of extracellular matrix proteins which are generally conserved among species, and thus can be easily used as a scaffold for the host cell attachment, migration and proliferation.

Thanks & Regards,
Nicola B
Editorial Team
Journal of Biochemistry & Biotechnology