MicroRNA expression profiles differentiate chronic pain condition subtypes

Abstract

Chronic pain is a significant health care problem, ineffectively treated because of its unclear etiology and heterogeneous clinical presentation. Emerging evidence demonstrates that microRNAs (miRNAs) regulate the expression of pain-relevant genes, yet little is known about their role in chronic pain. Here, we evaluate the relationship among pain, psychological characteristics, plasma cytokines, and whole blood miRNAs in 22 healthy controls (HCs); 33 subjects with chronic pelvic pain (vestibulodynia, VBD); and 23 subjects with VBD and irritable bowel syndrome (VBD + IBS). VBD subjects were similar to HCs in self-reported pain, psychological profiles, and remote bodily pain. VBD + IBS subjects reported decreased health and function; and an increase in headaches, somatization, and remote bodily pain. Furthermore, VBD subjects exhibited a balance in proinflammatory and anti-inflammatory cytokines, whereas VBD + IBS subjects failed to exhibit a compensatory increase in anti-inflammatory cytokines. VBD subjects differed from controls in expression of 10 miRNAs of predicted importance for pain and estrogen signaling. VBD + IBS subjects differed from controls in expression of 11 miRNAs of predicted importance for pain, cell physiology, and insulin signaling. miRNA expression was correlated with pain-relevant phenotypes and cytokine levels. These results suggest that miRNAs represent a valuable tool for differentiating VBD subtypes (localized pain with apparent peripheral neurosensory disruption vs widespread pain with a central sensory contribution) that may require different treatment approaches.

Fig. 1. Pelvic muscle and mucosa pressure pain is enhanced in women with VBD and VBD+IBS, while remote bodily muscle pain and thermal windup is enhanced only in women with VBD+IBS

Women with VBD or VBD+IBS reported greater pain intensity and decreased pain thresholds in the pelvic muscle (A–B) and mucosa (C–D). Women with VBD+IBS demonstrated a trend towards decreased pressure pain thresholds in the trapezius (E) and temporomandibular joint (F) as compared to HC and VBD. (G) For the thermal data, there was a significant interaction between study group and stimulus sequence, although not between study group and the square of stimulus sequence. VBD+IBS women exhibit the greatest degree of pain in response to the windup thermal heat assay. Data are Mean ± SEM. *p<0.05, ***p<0.001, ****p<0.0001 compared to HC; †p<0.05 as compared to HC and VBD.

Fig. 2. Cytokine expression is altered in women with VBD and VBD+IBS

Compared to HC, women with VBD exhibit elevated levels of pro-inflammatory cytokine IL-8 (A) and anti-inflammatory cytokine IL-1ra (B). Women with VBD+IBS exhibit elevated levels of IL-8, but no compensatory increase in IL-1ra. Data are Mean ± SEM. *p<0.05, **p<0.01 compared to HC; †p<0.05 compared to HC and VBD+IBS.

Fig. 3. miRNA expression signatures are altered in women with VBD and VBD+IBS

Compared to HC, women with VBD exhibit significant downregulation of 7 and upregulation of 3 miRNAs (A), while women with VBD+IBS exhibit significant downregulation of 6 and upregulation of 5 miRNAs (B). Red dots represent downregulated miRNAs and blue dots represent upregulated miRNAs compared to HC. Four miRNAs are dysregulated in both VBD and VBD+IBS women. Dysregulated miRNAs are listed with fold change and p values (C).

Fig. 4. miRNA dysregulation affects multiple genes and pathways in women with VBD and VBD+IBS

miRNA dysregulation in women with VBD and VBD+IBS leads to dysregulation of genes involved in pain-relevant pathways including the TGFβ, MAPK, and Wnt signaling pathways (shown in green). Pathways that do not overlap between women with VBD and VBD+IBS represent separate pathways of vulnerability. Pathways unique to VBD (shown in blue) include the dorso-ventral axis formation, GnRH signaling and gap junction pathways. Pathways unique to VBD+IBS (shown in red) include the ECM, DRPLA and insulin resistance pathways. A considerable amount of interaction and communication is demonstrated between genes and across pathways. See Supplemental Content for abbreviations.