AN IN-VITRO MODEL OF FIBROBLAST ACTIVITY AND ADHESION FORMATION DURING FLEXOR TENDON HEALING

We studied fibroblast activity during tendon healing with an in vitro tendon culture model. Tendons were embedded in a translucent collagen gel matrix whose porous nature permitted free nutrient diffusion, fibr oblast migration out of the tendon, and microphotographic documentatio n of fibroblast activity. Experiments were performed using one or more tendons cultured in the same collagen gel. We identified three zones of fibroblast activity in the gel. Zone I was an area of randomly disp ersed cells directly adjacent to the tendon where collagen synthesis a nd remodeling were probably taking place. In zone II, spindle-shaped f ibroblasts were aligned pointing away from the cut tendon end forming a sunburst-like aggregate of cells. Zone II fibroblasts were responsib le for formation of migration trails by exerting a mechanical force on the collagen matrix, which was evident as a local gel contraction. Zo ne Ill was the leading edge of the sunburst populated by the fastest m oving fibroblasts, which responded to guidance by other cut tendon end s. We speculate that the collagen gel used in the culture system may h elp maintain a chemotactic concentration gradient that allows fibrobla sts to locate other distal cut tendon surfaces also embedded in the co llagen gel.