Mitogenic and protein synthetic activity of tissue repair cells: Control by the postsurgical macrophage

It is well known that fibroblasts are a main source of extracellular matrix synthesis necessary for tissue repair. In addition, macrophage s secrete products that are known to modulate synthesis of extracellular matrix. Accordingly, we studied the incorporation of [³H]thymidine, [³H]proline, and [³⁵S]sulfate into macromolecules produced by fibroblasts recovered from the site of peritoneal tissue repair cultured with and without spent media from postsurgical peritoneal macrophages. Rabbits underwent resection and re-anastomosis of their small intestines. Peritoneal exudative cells (PEC) were then collected on postsurgical day 5 and day 10 as well as from nonsurgical controls, separated by discontinuous Percoll gradient centrifugation, and cultured for 48 h. A second group of rabbits underwent peritoneal wall abrasion from which fibroblast tissue repair cells (TRC) were collected from the site of injury at postsurgical day 7 and maintained in culture for varying times. Incorporation of radiolabeled precursors into DNA, collagen, and sulfated proteoglycans was determined. Incorporation of [³H]thymidine and [³H]proline into untreated TRC gradually decreased with culture duration. Conversely, [³⁵S]sulfate incorporation gradually increased during prolonged culture. Macrophage spent media increased the levels of [³H]thymidine incorporation by the TRC. [³H]Proline and [³⁵S]sulfate incorporation into TRC were also stimulated by macrophage spent media. However, this stimulation may be due to the enhanced proliferation of TRC by macrophage spent media. In conclusion, tissue repair fibroblasts are activated for postsurgical repair at the site of injury by many factors including secretory products from postsurgical macrophages.