These tissues are rich in collagen and thus provide the strong scaffolding matrix needed for surgery. of mesh available, how they are processed, and examine these characteristics in terms of their strengths and weaknesses in application to surgical technique. Keywords:biologic mesh, cross-linking, xenograft, ventral hernia CME Objectives:Upon completion of this article, the reader should be able to summarize the various sources used for biologic mesh and the goals of mesh processing. The use of biologic mesh has increased dramatically in the past 10 years. In the field of abdominal wall reconstruction, biologic mesh has offered solutions to some of the difficult problems with synthetic mesh repair. Synthetic mesh repair can be complicated by chronic inflammation, enteric erosion, contraction, pain, loss of compliance, and bacterial colonization. The theory behind biologics is to provide a graft material that not only affords strength toward the surgical repair but also integrates over time into the host tissue by way of angiogenesis, cellular infiltration, and collagen deposition.1These attributes allow its use in contaminated fields with less fear of mesh infection. In this section, we will look at some of the characteristics of biologic meshes and their manufacturing techniques in an effort to gain a better understanding of their strengths and weaknesses in application to surgical technique.Table 1provides a summary of various biologic meshes and selected characteristics. == Table 1. Types and charateristics of biologic meshes. == Abbreviation: HMDI, hexamethylene diisocyanate. Based on data from Deeken C, Eliason B. Differentiation of biologic scaffold materials through physicomechanical, thermal, and enzymatic degradation techniques. Ann Surg 2012;255(3):595604. > 20 N accepted threshold for hernia repair. 10 to 30% tissue strain AMG-925 when subjected to 16 N/cm of force is the accepted threshold for hernia repair. == Xenografts versus Homografts == Biologic meshes are available as xenografts (porcine AMG-925 or bovine) or homografts (human cadaver). Biologic meshes are heavily processed to decellularize, sterilize, and strengthen the product. These various processing techniques employed by mesh manufacturers are proprietary and thus differ widely between products. It is believed that the processing technique, and not the tissue of origin, is the basis for the induced tissue reaction of the host.2 Both the innate and acquired host immune system will respond to foreign cellular protein and can lead to a reaction anywhere from mild inflammation to acute rejection. Components of the extracellular matrix (ECM) are generally conserved among species and thus well tolerated.3A key component to biologic mesh manufacturing is the decellularization process, whereby the donor tissue’s cells are removed leaving behind a collagen matrix scaffold. It has been shown that the greater the amount of cellular debris left behind in the matrix scaffold, the greater the host inflammatory response and adverse remodeling response will be.4The decellularization process varies between products. Decellularization can include processing the tissue with hyper- or hypotonic solutions, acids and bases, detergents, organic solvents, alcohol solvents, proteases, nucleases, chelating agents, and toxins.5Subjecting the tissue to physical forces through freezing and thawing, direct pressure, electroporation, and perfusion are also potential components of the decellularization process. It is impossible to remove all cellular debris, as some will be well incorporated within the acellular collagen matrix.6A delicate balance exists between removing as much cellular debris as possible and preserving the acellular matrix scaffold. This is where proprietary processes come into play and characteristic variation can develop among the products. Standards exist AMG-925 to define the maximum amount of cellular debris allowable in these products and the majority fall well within these guidelines.7 The use of xenograft material presents an obvious concern for host rejection. AMG-925 -Galactosyl (Gal) is a cellular epitope expressed by pigs and other nonprimate mammals.8Humans express large quantities of anti-Gal antibodies due to stimulation from intestinal flora that contain the antigen. Thus, this epitope is one of the major causes of rejection in whole organ xenotransplantation. The decellularization process Rabbit Polyclonal to CRABP2 works to rid the tissue of cellular Gal, but noncell-associated Gal can remain behind integrated into the acellular collagen matrix. In 2000, McPherson et al proved the persistence of small quantities AMG-925 of Gal after decellularization. They also showed minimal host inflammatory response, hypothesizing that the quantity of Gal was inefficient to activate compliment.9Further studies by Daly et al on porcine-derived xenograft confirmed the presence of Gal, documented a diminished host immune response, and further showed no adverse effect on tissue remodeling when compared with an allograft.10 Evidence has strongly shown that the decellularization processes effectively rids the xenograft tissue of clinically relevant quantities of cellular material and truncates the host immune response to a level that prevents rejection and adverse graft remodeling. These data along with the successful transplant of millions of xenografts to date support their safe and efficacious use as biologic meshes.5 == Dermis versus Nondermis == Whether xenogeneic or allogeneic, the anatomic source of the graft tissue can vary from product to product as well. The major.