Understanding Sex Differences in Pain Resolution

Michigan State University researchers report that IL‑10–producing monocytes were observed to interact with pain-sensing neurons in a way that switches off pain. These monocytes are described as being more active in males than in females, aligning with faster pain resolution in the reported models. Lower activity in females was linked to longer-lasting pain and delayed recovery.

The team used high-dimensional spectral flow cytometry to characterize monocytes and identify a subset associated with interleukin-10 (IL-10) signaling to neurons that “shut down” pain.

Higher levels of male sex hormones such as testosterone were associated with the monocyte activity pattern the team reported in males. Females showed less activity of these monocytes, alongside longer pain and delayed recovery in the models discussed. When the researchers blocked male sex hormones in mice, they received the opposite result.

The investigators observed a similar pattern in human patients. The group connected with a University of North Carolina at Chapel Hill collaborator studying outcomes after car accidents, and that those data similarly showed more active IL-10–producing monocytes in men alongside faster pain resolution.