Figure 2.

Inflammatory response contribution to acute pain resolution based on the results from transcriptomics-wide profiling of a prospective cohort of patients with acute low back pain (based on Parisien et al).⁵⁸ Human patients incur tissue damage eliciting back pain. After an acute pain period, pain in some patients resolves, the “resolved pain” group (left, green), whereas for others, the pain persists, the “persistent pain” group (right, red). Evidence from transcriptomics studies indicates different time trajectories for the inflammatory response in the 2 groups (bottom row). During the acute pain stage, the inflammatory response in the resolved pain group is stronger than for the persistent pain group. With time, the inflammatory response substantially lessened in patients with resolved pain (left). In patients with persistent pain, the inflammatory response is already elevated at the time of injury but does not rise during the acute pain stage; however, it transitions to a low-grade inflammatory state over time (right). The inflammatory response seems to coincide with neutrophil count and activation. Together, the acute-to-chronic pain transition features the absence of active processes of upregulation and subsequent resolution of inflammation.