Wang 2025 — Mast cells and estrogen-induced pain sensitization (endometriosis bridge to FM)

One-paragraph summary

Narrative review on the role of mast cells in estrogen-driven pain sensitization in endometriosis. Not FM-direct, but mechanistically pivotal for explaining FM's striking female predominance (3:1 to 9:1 F:M) through the H2 chain. Three specific molecular claims: (1) Estrogen directly activates mast cells within affected tissue via estrogen receptors. (2) Activated mast cells release histamine and fibroblast growth factor 2 (FGF2) as key pain-sensitization mediators. (3) These mediators enhance peripheral pain signalling AND drive central sensitization through elevated dorsal horn neuron responsiveness and increased neurotransmitter release in the spinal dorsal horn — establishing a direct molecular bridge from H2 (mast cells) to H3 (central sensitization) at the neurotransmitter/spinal-cord level. The endometriosis context provides a "positive feedback loop" model: estrogen drives lesion growth, lesions activate MCs, MCs sensitize nociceptors, sensitized nociceptors amplify pain perception. Direct relevance to FM: if MC-active FM is partly an estrogen-driven phenomenon, the female predominance has a mechanistic explanation, and cyclic FM symptom variation with menstrual cycle would be predicted (and is anecdotally reported by patients).

Claims as triples

• estrogen — causes → mast_cell [evidence: estrogen receptor activation of MCs in endometriosis lesions; confidence: emerging]
• estrogen — bridges → widespread_pain [evidence: endometriosis pain literature; confidence: bridging]
• mast_cell — modulates → central_sensitization [evidence: MC mediators → dorsal horn hyperresponsiveness; confidence: emerging]
• histamine — modulates → central_sensitization [via dorsal horn; confidence: emerging]
• FGF2 — modulates → central_sensitization [evidence: dorsal horn neuron sensitization; confidence: emerging]

Methods note

Narrative review of endometriosis pain literature with mast-cell mechanistic focus. Authors: Chinese gynecology/pain group. Reviews preclinical and clinical data; not a primary research paper.

Limitations

• Endometriosis, not FM. Direct extrapolation requires that the estrogen-MC-pain mechanism operates in FM tissue (probably DRG, peripheral nerves, possibly skin) similarly to how it operates in endometriotic lesions. Plausible but not tested directly.
• Narrative review — selection bias possible.
• Doesn't address whether MC-active FM patients show menstrual-cyclic symptom patterns predicted by the estrogen-MC mechanism.

Open questions raised

• Q37 (NEW): Does FM symptom severity show menstrual-cycle correlation in MC-active FM patients? If yes, the estrogen-MC mechanism is operating; if no, FM-MC may be estrogen-independent.
• Does menopause / ovariectomy reduce FM symptoms in MC-active patients? (Test of necessity of ongoing estrogen for the mechanism.)
• Do hormonal contraceptives (continuous progesterone-only? GnRH agonists?) modulate FM severity in MC-active patients? — Could be a candidate intervention with established gynecologic safety profiles.
• Does histamine/FGF2 measurement in cerebrospinal fluid distinguish MC-active from MC-inactive FM?

Triangulation notes

• Direct mechanistic bridge from H2 to H3: previously the chain mast_cell → CS was descriptive; this paper specifies the molecular intermediates (histamine, FGF2) and the anatomical site (spinal dorsal horn). The H2-to-H3 link is now load-bearing rather than just inferential.
• Female predominance gets a candidate mechanism: most existing FM literature explains the 3:1-9:1 F:M ratio with vague "hormonal influences" hand-waving. The estrogen-MC mechanism is testable.
• Pairs with Christoforou 2026 (ingested concurrently): if estrogen drives MC activation in MC-active FM, then high-dose cromolyn (Christoforou) interrupts the chain at the MC level. Combination with hormonal modulation (e.g., progesterone-only or GnRH agonist) could be additive.
• Connects to Q24 (anti-SGC IgG vs MC overlap): the estrogen-MC mechanism predicts that MC-active FM patients should be enriched for female sex and reproductive-age, while anti-SGC IgG positive may not show the same demographic skew. Comparing demographics across the H1×H2 cells would test this prediction.

Bridges

• NEW B9 candidate: Endometriosis ↔ FM via estrogen-MC-pain axis. Endometriosis has well-established estrogen-MC literature; if FM-MC-active subset shows similar mechanism, the conditions share a substrate explaining their high comorbidity (endometriosis-FM comorbidity is documented in clinical literature). Worth promoting if Q37 confirms menstrual-cycle correlation in MC-active FM.
• B6 (post-infectious nociplastic) framing complicated: if estrogen-MC drives MC-active FM, the H2 chain has both post-viral trigger AND endocrine substrate. Bigger picture: H2 may need to split into "post-viral H2" and "endocrine-MC H2" sub-axes.