Reticulum-derived extracellular matrix scaffolds

The term “Forestomach Matrix” (abbreviated FM) refers to an extracellular matrix (ECM) scaffold containing the propria-submucosa of the forestomach of a ruminant. The term “propria-submucosa” refers to the tissue structure formed by the blending of the lamina propria and submucosa in the ruminant forestomach. Lamina propria is the luminal portion of the propria-submucosa, which includes a dense layer of ECM. ECM scaffolds can be derived from the rumen, the reticulum, or the omasum of the forestomach. Such ECM scaffolds contain the lamina propria and submucosa (propria-submucosa) layers of the forestomach wall. FM scaffolds are derived from the rumen or from individual laminae within the omasum, in addition to propria-submucosa; FM scaffolds may optionally include intact or partial layers of decellularized epithelium, basement membrane, or tunica muscularis. As a result of the unique structure and function of the forestomach, ECM tissue scaffolds derived from the forestomach have different biochemical, structural, and physical properties relative to previously described scaffolds isolated from glandular stomach, intestine, and bladder. In particular, FM includes a dense band of ECM within the lamina propria. In addition, FM optionally includes an intact or fractured basement membrane. In contrast, a scaffold derived from the glandular stomach submucosa or small intestinal submucosa will include little if any of the lamina propria, because the lamina propria is located mainly between the glands of the mucosa and is consequently removed as the mucosa is delaminated. Importantly, histology shows that the lamina propria is unusually dense, whereas the abluminal side of the FM scaffold is structured as an open reticular matrix. These differences serve an important role in epithelial regeneration, as the dense side acts as a barrier to cell migration, while the less dense side does not present a barrier and therefore allows cell invasion. This structure makes the FM well suited for encouraging epithelial regeneration on the dense luminal side of the matrix, and fibroblast invasion on the less dense abluminal side of the matrix, when used as a medical device for tissue regeneration. In contrast, submucosal tissue grafts derived from the glandular stomach and the urinary bladder have a uniform density. The dense layer of ECM from the lamina propria contributes to the increased thickness and strength of FM scaffolds compared to those derived from other organs. The large surface area of the forestomach and the increased thickness and strength of scaffolds derived from the forestomach allows the isolation of larger ECM scaffolds from the forestomach than is possible from other organs. For example, ECM scaffolds of the forestomach can have a width as large as 10cm or more. Unlike scaffolds obtained from the glandular stomach, FM scaffolds derived from the forestomach can include collagen IV and laminin from the basement membrane on the luminal surface. Surprisingly, these proteins are also present within the dense band of the lamina propria, providing important substrates for epithelial cell adhesion and growth. Glandular stomach scaffolds do not typically include the epithelium or basement membrane, or portions thereof, because these layers are fragile and do not withstand physical delamination. A glandular submucosal scaffold may include remnants of the lamina muscularis mucosa on the luminal side and tunica muscularis on the abluminal side. FM scaffolds have a contoured luminal surface, analogous to the rete ridges of the dermis. In contrast, scaffolds delaminated from small intestine, urinary bladder, and glandular stomach submucosa have a relatively smooth luminal surface. The contoured luminal surface of the FM provides a complex topology, which favors epithelial regeneration. This topology is not present in ECM scaffolds derived from small intestinal submucosa, glandular stomach submucosa, or urinary bladder submucosa.