Comparative study of splenic wound healing in young and adult rats

Nonoperative management (NOM) of splenic injuries is a common practice in stable trauma patients. Nevertheless, age-related differences in the success rate of NOM have prompted inclusion of age among the criteria of patient selection. Elucidation of the cellular mechanism of splenic wound healing in the young versus that of adults may explain why age can be related to the success of NOM in splenic injuries.

A laceration was made in the splenic antihilar surface of 40 young and 40 adult male rats. Postoperatively, at specified intervals extending until day 21, spleens were removed, fixed, and examined by routine histopathology. In addition, sections were stained histochemically for collagen fibers and immunohistochemically for myofibroblast histomorphometry.

The intense local hemorrhage was resorbed within 48 hours in the young rats, and within 7 days in the adults. Disappearance of germinal centers and other splenic alterations started on the first day in both groups, but regeneration of splenic parenchyma was accomplished after 14 days in the young, whereas in the adults, on day 21 it was still incomplete. Maximal myofibroblast accumulation at the laceration site was seen after two days in the young, whereas in adults only on day 4 (p < 0.0001). Collagen scars were not present in either group. Thickening of the damaged capsule, composed of collagen fibers with yellowish-green polarization colors, was observed only in adult rats.

Splenic wounds heal by regeneration and not by collagen scarring. In the young, myofibroblasts accumulate in the site of injury faster than in adults. These cells may enhance contraction and increase the rate of wound healing until parenchymatic regeneration is completed. Our results may indirectly explain the higher success rate of NOM of splenic injury in young patients.