Figure 3. Cyclin expression, cell proliferation, and tenascin expression were up-regulated during fusion of surgically sutured cleft lip. Following surgery to repair cleft lip in the fetuses, the expression of cyclin (a,b,h) and tenascin (e,f,h) was examined. An apparent increase in the number of cyclin-positive cells (b, arrowheads) when compared with control (a) was observed at the site of the operation 1.5 hrs after surgery. Furthermore, a 1.9-fold increase in the relative expression level of cyclin D1 was detected in the sutured group (1.81 + 0.16, N = 5) compared with controls (0.95 + 0.08, N = 5) (h), *p < 0.01. Similarly, 4 hrs after surgery, an increase in tenascin-positive extracellular matrix was observed at the site of the operation in the sutured group (f, arrowheads) when compared with the control (e). A 2.5-fold elevation in the relative expression level of tenascin-C was also detected; control was 5.54 + 1.05 and sutured group was 13.84 + 2.41, N = 5, for both groups (h). We performed BrdU labeling to examine cell proliferation. Sixteen and a half percent of the mesenchymal cells at the site of the operation was positive for BrdU label (d), compared with only 11.4% of the cells in the control group (c). Asterisks indicate oral epithelium. Increased cell proliferation was associated with a significant increase in total mesenchymal cell number (g), with more of these cells positive for cyclin (2.5%; 23.79 + 2.41 cyclin-positive cells compared with 919.19 + 76.77 total cells, N = 5) in the sutured group when compared with the control group (0.5%; 4.07 + 2.34 cyclin-positive cells compared with 727.27 + 30.30 total cells, N = 5), *p < 0.01. Scale bar in (a) for (a-f) is 50 µm.