Neuropeptides Substance P and Calcitonin Gene Related Peptide Accelerate the Development and Fibrogenesis of Endometriosis

Abstract

Endometriotic lesions are known to be hyperinnervated, especially in lesions of deep endometriosis (DE), which are frequently in close proximity to various nerve plexuses. DE lesions typically have higher fibromuscular content than that of ovarian endometriomas (OE) lesions, but the underlying reason remains elusive. Aside from their traditional role of pain transduction, however, whether or not sensory nerves play any role in the development of endometriosis is unclear. Here, we show that, thorough their respective receptors neurokinin receptor 1 (NK1R), calcitonin receptor like receptor (CRLR), and receptor activity modifying protein 1 (RAMP-1), neuropeptides substance P (SP) and calcitonin gene related peptide (CGRP) induce epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT) and further turn stromal cells into smooth muscle cells (SMCs) in endometriotic lesions, resulting ultimately in fibrosis. We show that SP and CGRP, or the rat dorsal root ganglia (DRG) supernatant, through the induction of NK1R and CGRP/CRLR/RAMP-1 signaling pathways, promoted EMT, FMT and SMM in endometriosis, resulting in increased migratory and invasive propensity, cell contractility, production of collagen, and eventually to fibrosis. Neutralization of NK1R and/or CGRP/CRLR/RAMP-1 abrogated these processes. Extended exposure of endometriotic stromal cells to SP and/or CGRP or the DRG supernatant induced increased expression of α-SMA, desmin, oxytocin receptor, and smooth muscle myosin heavy-chain. Finally, we show that DE lesions had significantly higher nerve fiber density, increased staining levels of α-SMA, NK1R, CRLR, and RAMP-1, concomitant with higher lesional fibrotic content than that of OE lesions. The extent of lesional fibrosis correlated positively with the staining levels of NK1R, CRLR, and RAMP-1, as well as the nerve fiber density in lesions. Thus, this study provides another piece of evidence that sensory nerves play an important role in promoting the development and fibrogenesis of endometriosis. It explains as why DE frequently have higher fibromuscular content than that of OE, highlights the importance of lesional microenvironment in shaping the lesional fate, gives more credence to the idea that ectopic endometrium is fundamentally wounds that go through repeated tissue injury and repair, and should shed much needed light into the pathophysiology of endometriosis.

Platelets induce increased estrogen production through NF-κB and TGF-β1 signaling pathways in endometriotic stromal cells

“…Granted, while almost all past research focus has fixated on endometriotic epithelial and stromal cells nearly exclusively, there are many other cells in its microenvironment. Platelets 21,23 , neutrophils 69 , macrophages 19,24 , and recently nerve fibers 25,26 all have been identified to be accessories to aid and abet the lesional development. Indeed, these cells are known to be irreplaceable partners in a successful wound healing 70 .…”

“…As we showed previously, however, the vast heterogeneity of endometriosis appears to be determined mostly by the lesional microenvironments 80 . Namely, regardless of subtypes, all endometriotic lesions appear to undergo identical molecular processes such as epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT), smooth muscle metaplasia (SMM), and fibrogenesis 25,26,53 , even in adenomyotic lesions 81,82 . Moreoever, increased local production of estrogen is common to all subtypes of endometriosis 83 and even to adenomyosis 84 .…”

“…Rather, its development and the subsequent manifestation of various symptomology require, by necessity, aid and assistance from many aiders and abettors. Indeed, accumulating evidence suggests that endometriotic lesions are essentially wounds undergoing repeated tissue injury and repair (ReTIAR) [19][20][21][22] , and, as such, many non-endometriotic cells in the lesional microenvironment, such as platelets 21,23 , macrophages 19,24 , and now nerve fibers 25,26 , are actively involved in facilitating lesional development.…”

Somatic driver mutations in endometriosis as possible regulators of fibrogenesis (Review)

“…Several elegant reviews have been published focusing on the link between endometriosis and fibrosis thus far. The fibrosis-related factors include TGF-β, neuropeptides substance P (SP), neurokinin receptor 1 (NK1R), calcitonin receptor like receptor (CRLR), calcitonin gene related peptide (CGRP), receptor activity modifying protein 1 (RAMP-1), nuclear receptor subfamily 4 group A member 1 (NR4A1), nuclear factor, erythroid 2 like 2 (NFE2L2, also known as Nrf2), or glutamate cysteine ligase (49,50). Among these fibrosis susceptibility genes, TGF-β is considered to be a key mediator in a number of fibrotic disorders, including endometriosis, and in fibrosis in hepatic, renal, pulmonary and cardiovascular systems (1).…”

“…To date, much has been shown about a complex pathway model for fibrogenesis based on common driver genes. The driver molecules related to the progression of fibrosis are TGF-β, Notch, HIF-1α, PTEN, PIK3CA, PI3K/Akt, KRAS, TP53, NF-κB, BRAF, CDKN2A and ARID1A that can activate myofibrogenesis, resulting in increased ECM production, collagen deposition and fibrosis (11)(12)(13)16,22,25,32,49,50,54). A significant overlap was observed between 2 sets, epigenetic alterations and genetic mutations of the driver genes in endometriosis and the driver molecules related to the progression of fibrosis in the liver, kidney and lung.…”