Bone cell behavior on Matrigel-coated Ca/P coatings of varying crystallinities

Rat calvarial cell mitogenic behavior was investigated on various biomaterials coated with Matrigel, a basement membrane matrix containing growth factors. Low (20-40%) and high (70-90%) crystallinity hydroxyapatite (rHA and cHA), rough titanium (Ti), and tissue culture polystyrene (TP) surfaces were compared. Surface chemistry and calcium resorption of HA coatings, alkaline phosphatase activity (APA), and growth of cells were measured for Matrigel-coated and uncoated surfaces at 2, 7, and 14 days. Gene expression for four noncollagenous bone-related proteins (osteonectin, osteopontin, alkaline phosphatase, and osteocalcin) was also investigated by reverse transcription and polymerase chain reaction up to 28 days. Ca concentration in incubating solutions increased with time for the two types of HA coatings and was always greater for rHA than cHA. Surface chemistry and coating dissolution rates were not affected by the presence of Matrigel or cells throughout the study. APA of cells on the two HA-coated surfaces was comparably enhanced in the presence of Matrigel and was greater than on Ti surfaces. Only HA surfaces showed an increased APA of cells with time in the presence of Matrigel. Cell growth peaked at 7 days and was greatest for cells on the two HA surfaces and without Matrigel. At 14 days, cell growth was comparable on the four surfaces. The presence of HA and Matrigel enhanced cell-specific APA at 14 days. Gene expression for all four proteins investigated showed no differences between surfaces after 7 days. At 2 and 7 days, gene expression was indicative of proliferation for Ti, and of proliferation, differentiation, and mineralization for HA and TP more so without Matrigel. The addition of this matrix significantly enhanced mitogenicity of calvarial cells on HA only after 14 days. Matrigel eliminated differences seen between the two HA coatings. Gene expression was not enhanced or inhibited by the presence of Matrigel.