An autoradiographic study of 3H-thymidine incorporation and distribution in the dermis of healing skin incisions in the pig.

The dermal response to injury in healing incisional wounds aged from 1 to 24 days was studied by in vitro and in vivo 3H-thymidine (3HT) labelling and the use of colcemid to induce metaphase arrest. In vitro 3HT labelling provided mean numbers (+/- s.e. mean) of labelled dermal cells/section within the incision and in 3 zones in the dermis up to 0.875 mm lateral to the incision. There was a progressive increase in the numbers of DNA-synthesizing cells in the incisions as granulation tissue developed from Day 1 to Day 7, and a sharp decline by Day 9. Immediately adjacent to the incision there was a dramatic increase in the number of labelled cells on Day 2, with reduced numbers laterally. This response, which was largely maintained up to 7 days, paralleled the cellular reaction around blood vessels and skin appendages but also included labelled dermal fibroblasts. The in vivo 3HT study, taken in conjunction with the colcemid and in vitro 3HT studies, supported the idea that during the development of granulation tissue there is a continual recruitment of paraincisional cells, including dermal fibroblasts, either by direct migration or by division and then migration, as well as by continued mitosis of cells already within the incision.