Different types of immune cells are involved in chronic pain in male and female mice, reports a study published online in Nature Neuroscience. If this finding translates to humans, it could indicate a potential need to tailor chronic pain treatments specifically for men or women.
Multiple lines of evidence have established that activation of microglia (a type of immune cell) in the spinal cord is an important step in the development of chronic pain in animal models. Jeffrey Mogil and colleagues confirmed that depletion or inhibition of microglia in mice increases their response thresholds to noxious stimuli after induction of inflammatory pain or pain caused by nerve injury.
However, the researchers also found that the involvement of microglia was sex-specific. While decreasing microglia function in males resulted in the expected pain reduction, it failed to show any effect on pain behavior in female mice. This sex difference was linked to the presence of the male hormone testosterone and additional experiments revealed that instead of microglia, the development of chronic pain in female mice involved different immune cells, called B and T cells. These findings suggest that male mice cannot be used as proxies for females in pain research and could inform clinical trials for analgesics targeting microglia-associated mechanisms.