Oriented growth of octacalcium phosphate on and inside the collagenous matrix in vitro

To investigate the factors which regulate the growth of apatite in a collagenous matrix, a calcification experiment was carried out in a model system, where Ca2+ and PO43- ions diffused into a slice of Achilles tendon from mutually opposite grew on the Ca-side of the collagenous matrix, while small plate-like OCP crystals (< 1 micron) grew inside the matrix. The major part of crystals grew with the c-axis parallel to the collagen fibers. Others grew with the c-axis parallel to the collagen bands or perpendicular to the fibrils. Crystals grew with orientation on collagen fibrils from the beginning. It was concluded that collagen fibrils and property of the collagenous matrix played a regulatory role in the deposition and growth of OCP in the collagenous matrix.