Social structure influences effects of pair-housing on wound healing

Chronic stress or noxious stimuli delay wound healing in humans and rodents. The effects of stress on wound healing appear to be mediated by the hypothalamic-pituitary-adrenal (HPA) axis and, in particular, increases in corticosteroids. As previously shown, positive social interaction faciltiates wound healing through suppression of corticosteroids. In the present study, we investigated the effects of pair-housing on wound healing and corticosteroid concentrations in three mouse species, the monogamous Peromyscus californicus, the facultative-monogamous Peromyscus eremicus, and the polygynous Peromyscus leucopus. Pair-housed P. californicus and P. eremicus had significantly smaller wounds than socially isolated cohorts. However, wound healing in P. leucopus was not affected by housing condition. P. californicus and P. eremicus mice that were pair-housed for 2 weeks, then separated from their partners 48h prior to wounding also had wounds comparable to socially isolated mice. The benefits of social housing diminished when P. californicus and P. eremicus pairs were prevented from interacting physically via a double screen barrier. Two hours of daily restraint did not affect basal corticosterone concentrations or wound healing in either P. californicus or P. eremicus. In contrast, restraint facilitated wound healing in P. leucopus. Taken together, these data suggest that social contact facilitates wound healing in two monogamous, but not a polygynous, mouse species.