[Beyond the placebo effect: exploring the mast cell-dependent analgesic effect of shallow needling control]

Based on the distribution characteristics of mast cells and existing mechanistic evidence, the study explores the potential biological effects of shallow needling control (sham-acupuncture). Regarding cellular distribution, mast cells exhibit a physiological characteristic of dense distribution in both the dermis and subcutaneous tissue, predominantly in the distal regions, and show a higher density in acupoint areas compared with non-acupoint areas. At the puncture site, shallow needling primarily targets the dermis and the superficial subcutaneous tissue, with these two layers overlapping anatomically. Regarding its mechanism of action, acupuncture can induce local mast cell degranulation through mechanical stimulation, thereby releasing bioactive substances that subsequently activate relevant signaling pathways to produce analgesic effect. The study proposes that the shallow needling control at the same acupoint or non-acupoint not merely obtains placebo effect, but also involves potential biological mechanism associated with mast cells, aiming to provide new insights for future clinical trial design and research on the underlying mechanism of acupuncture and sham-acupuncture.