Rate of tendon gap closure in an in vitro collagen gel matrix

Tendon gap closure was examined in a tissue culture model and found to have a similar time course as skin wound closure. Foot tendons from White Rock chickens were mounted in a collagen gel matrix and maintained with the use of Dulbecco's modified Eagle medium, containing fetal calf serum and antibiotics, for 4 weeks at 37 degrees C in an incubator. Gap distances between tendons were measured every 1 to 3 days and plotted against time as the contraction curve. After an initial lag period of 4 to 8 days, gap distance showed a progressive decrease. Gap closure rate was defined as the slope of the contraction curve, and it was found to be a function of initial gap distance (r = 0.643, p 0.045). The time necessary to reduce the initial gap distance by half had a significant correlation with the initial gap distance (r = 0.986, p < 0.001). Fibroblast migration began on days 2 to 3 after a 1- to 2-day lag period. Fibroblasts were visible in the tendon gap region before the start of collagen gel contraction. At this time, the fibroblast migration rate was 0.33 mm/day. A critical density of fibroblasts was necessary to start collagen gel contraction. Once the gap distance began to diminish, fibroblast migration measurements were hampered because the measurable area was decreasing. Collagen gel contraction reduced the measurable fibroblast migration rate by nearly half to 0.18 mm/day. A linear correlation was found between fibroblast distance traveled and time in culture during both the gel lag and gel contraction time periods. This tendon culture model may be potentially useful for wound healing studies because it allows for studies of fibroblast activity in the early lag phase when the cells populate the collagen lattice but before contraction of the gel occurs.