Characterization of the extracellular matrix from human and dog umbilical cords

The extracellular matrix is important for maintaining tissue morphogenesis and homeostasis; it can also be used as a biomaterial for the production of biological scaffolds. Particularly, the umbilical cord has shown potential in the production of scaffolds for small-diameter vessels. This research compared the native extracellular matrix of human and canine umbilical cords to provide data that can contribute to the future application of their scaffolds in Tissue Bioengineering. Thus, samples of human and canine umbilical cords were processed for histology and the slides were stained using hematoxylin and eosin, Masson's trichrome, picrosirius red, and PAS. Indirect immunohistochemistry for metalloproteinases or MMPs (MMP-2, MMP-3, and MMP-14) was also performed. The human umbilical cord had two arteries and a vein surrounded by abundant mucous connective tissue, externally covered by the amnion. Differently, the canine one had an allantois, with very little connective tissue surrounding the blood vessels. There was an abundance of (total) collagen around the vessels, and the distribution of type I and III collagen was similar between species. The MMPs immunostaining patterns were also similar between the cords, with MMP-3 being the most common in humans and MMP-2 being the most common in dogs. PAS revealed the presence of carbohydrates, especially in the endothelium of the vessels and in the amnion. The morphological and structural similarities, as well as its size and diameter, make the canine cord promising for the production of biological scaffolds and application in Tissue Bioengineering.