Human placental chorionic villar extracellular matrix. I. Preparation and chemical composition from villar fragments fractionated according to their size

Human placental chorionic villi were obtained by a procedure involving scraping of cotyledons to get a starting population of vascular trees free of large villus trunks and connective tissue. The collected villar vascular trees were disrupted by blending, and fractionated into different size fragments by filtration through a series of nylon sieves of different mesh openings. The resulting four fractions ranged from larger villar branches to the smallest terminal villar microvessels and were characterized by phase contrast and scanning electron microscopy. Extracellular matrix was prepared from these fractions by a procedure involving extensive extraction with Triton X-100 and digestion with deoxyribonuclease to dissolve cellular and membrane proteins and to remove adhering contaminating DNA. The resulting cell-free preparation of chorionic villar extracellular matrix consisted of a network of the villar microvasculature composed of amorphous basement membranes associated with interstitial collagen fibers bounding the vascular spaces, with random patches of amorphous fibrinoid material scattered throughout the preparation. The extracellular matrix derived from all four fractions had similar amino acid and carbohydrate compositions. All fractions were rich in glycine, proline, glutamic and aspartic acids and contained appreciable amounts of 4-hydroxyproline and hydroxylysine, indicating that they were collagenous in nature. Carbohydrate analysis revealed galactose and glucose to be the most abundant sugars, with smaller amounts of mannose and glucosamine, a composition resembling that seen in basement membranes. Both amino acid and carbohydrates compositions indicated a gradual reduction in the collagenous nature of the matrix in processing from the smallest to the larger villar fragments.