Dural fibroblasts play a potential role in headache pathophysiology

Abstract

Nociceptive signaling from the meninges is proposed to contribute to many forms of headache. However, the events within the meninges that drive afferent activity are not clear. Meningeal fibroblasts are traditionally thought to produce extracellular proteins that constitute the meninges but do not contribute to headache. The purpose of these studies was to determine whether dural fibroblasts release factors that activate/sensitize dural afferents and produce headache-like behavior in rats. Dura mater was removed from male rats and dural fibroblasts were cultured. Fibroblast cultures were stimulated with vehicle or lipopolysaccharide (LPS), washed, and conditioned media was collected. Fibroblast media conditioned with vehicle or LPS was applied to retrogradely-labeled rat dural trigeminal ganglion neurons in vitro. Patch-clamp electrophysiology was performed to determine whether conditioned media activated/sensitized dural afferents. A preclinical behavioral model was used where conditioned media was applied directly to the rat dura to determine the presence of cutaneous facial and hindpaw allodynia. Conditioned media was also tested for interleukin-6 (IL-6) content using an ELISA. Application of LPS-conditioned fibroblast media to dural afferents produced a significant increase in action potential firing as well as cutaneous facial and hindpaw allodynia when this media was applied to the dura. Finally, stimulation of cultured fibroblasts with LPS increased IL-6 levels in the media. These findings demonstrate that fibroblasts stimulated with LPS release factors capable of activating/sensitizing dural afferents. Further, they suggest that fibroblasts play a potential role in the pathophysiology of headache.

Meningeal norepinephrine produces headache behaviors in rats via actions both on dural afferents and fibroblasts

“…We recently showed that the predominant cell type in the dura mater, fibroblasts, can participate in the headache process by releasing pro-inflammatory cytokines in response to stimulation (16). Thus, we investigated whether dural fibroblasts respond to noradrenergic stimulation.…”

“…External solution contained (in mM) 135 NaCl, 2 CaCl 2 , 1 MgCl 2 , 5 KCl, 10 glucose, 10 HEPES, pH 7.4 (adjusted with N-methyl glucamine), and was ~300 mosM. Freshly thawed supernatant (600 μl) was added to the TG culture for 15 minutes and then replaced with bath solution before recording as performed previously (16). Fluoro-Gold-positive neurons were identified and patched immediately after replacement of supernatant with bath.…”

“…Behavioral testing methods were identical to those used previously (16). Rats were acclimated to suspended Plexiglas chambers with a wire mesh bottom.…”

“…Experiments were designed to assess the effects of NE application on excitability of dural afferents in vitro as well as to determine whether direct application of NE to the dura mater produces headache-related behavior in rats. In addition, we recently published that dural fibroblasts may participate in headache as they can release pro-inflammatory cytokines that activate/sensitize dural afferents (16). Experiments described here also examined whether dural fibroblasts respond to NE in a manner that may promote headache.…”

Meningeal Afferent Signaling and the Pathophysiology of Migraine

“…These cells have recently been shown to play a potential role in headache as they release factors that both sensitize dural afferents and cause headache behaviors in rodents when applied to the dura. 63 Among the factors released by these cells is the proinflammatory cytokine interleukin-6 (IL-6). The dura also contains other nonneuronal cell types such as mast cells and macrophages.…”