1. Introduction
Chronic rhinosinusitis (CRS) is a disease characterized by symptomatic inflammation of the sinus mucosa lasting >12 weeks, as confirmed by endoscopy and/or imaging. CRS is classified into two types: type 2, mainly associated with a Th2 immune response, and non-type 2, characterized by a prevalence of type 1 and type 3 inflammation [
1,
2,
3,
4,
5]. Eosinophilic chronic rhinosinusitis (ECRS) constitutes a subgroup of chronic rhinosinusitis with nasal polyps (CRSwNP) and is characterized by severe eosinophil infiltration. Pathological analyses of ECRS revealed a predominance of type 2 inflammation (3, 6, 7).
Oncostatin M (OSM) is a member of the interleukin (IL)-6 family of cytokines, which includes IL-11, IL-31, and leukemia inhibitory factor (LIF) [
8]. OSM has been shown to be expressed by many cell types of the hematopoietic lineage, including T cells, neutrophils, macrophages, and eosinophils [
9]. OSM is not known to be expressed by epithelium, fibroblasts, or smooth muscle, all of which express the two forms of the OSM receptor (OSMR) [
10]. Individuals with CRS have been reported to have elevated levels of OSM in nasal polyp tissue, and OSM was shown to reduce the barrier function of the nasal mucosa [
11]. Higher concentrations of OSM in sputum have been described in asthmatic patients with irreversible airflow obstruction [
12,
13]. In lung tissue, OSM has been found to increase airway hyper-responsiveness and cause eosinophilia [
14]. It is not yet clear how OSM is involved in the development of CRS, however.
We conducted the present study to determine whether OSM is involved in the pathogenesis of CRS. We focused on the association between OSM and cytokines, specifically examining the relationship between OSM and type 1 and type 2 inflammatory cytokines. The role of OSM in the pathogenesis of CRS is also discussed.
4. Discussion
Chronic rhinosinusitis (CRS) is a prevalent condition characterized by symptomatic inflammation of the sinonasal mucosa persisting for >12 weeks, as confirmed by endoscopic examination and/or imaging studies. CRS is categorized into type 2 CRS, which is primarily associated with the Th2 immune response, and non-type 2 CRS, characterized by the prevalence of type 1 and type 3 inflammation [
1,
2,
3,
4,
5]. Type 2 CRS involves crucial contributions from Th2 cytokines such as IL-4, IL-5, and IL-13, which are produced by Th2 cells, ILC2 cells, and mast cells. Conversely, non-type 2 CRS is marked by elevated levels of IFN-γ, IL-1β, IL-6, IL-8, and IL-17, along with the accumulation of Th1 and Th17 cells.
Eosinophilic chronic rhinosinusitis (ECRS) constitutes a subgroup within chronic rhinosinusitis with nasal polyps (CRSwNP) and is characterized by severe eosinophilic infiltration. This condition poses a significant challenge, as demonstrated by the findings of the JESREC Study [
7]. Pathological analyses of ECRS revealed a predominant type 2 inflammation [
3,
6]. In contrast to non-ECRS patients, individuals with ECRS typically exhibit a poor response to both medical and surgical treatments.
OSM (oncostatin M) is a member of the IL-6 family of cytokines, and it exerts potent effects on stromal cell behavior in various tissues and organs. It is expressed and produced by multiple cell types within the hematopoietic lineage, including T cells, neutrophils, mast cells, macrophages, and eosinophils [
9,
18].
Human OSM signaling occurs through two receptors. The type I receptor is a heterodimer consisting of leukemia inhibitory factor receptor (LIFR) and gp130, and the type II receptor is a heterodimer composed of OSM receptor beta (OSMRβ) and gp130 [
19]. In both scenarios, OSM initially binds to gp130 with low affinity, but effective signaling requires the subsequent recruitment of LIFR or OSMR, leading to the formation of high-affinity competent trimers [
10]. In adult tissues, LIFR is expressed at low levels in a variety of epithelial, hematopoietic, and mesenchymal cell types and is not typically associated with pathological processes. In contrast, type II OSMR is highly expressed in numerous non-hematopoietic mesenchymal cells, including fibroblasts, endothelial cells, smooth muscle cells, osteoblasts, and adipocytes. OSMR is also present in hepatocytes, mesothelial cells, glial cells, and epithelial cells in various organs [
20,
21]. Due to the fact that the expression of LIFR is not commonly linked with pathological processes, studies of OSM often emphasize the crucial roles played by OSMR, rather than LIFR, in mediating OSM biology.
Increased OSM expression has been associated with inflammatory processes leading to barrier dysfunction in dermal and mucosal organs such as the skin, lungs, and intestines. Elevated levels of OSM in nasal polyp tissues of patients with CRS have been encountered, and OSM has been reported to diminish the barrier function of the nasal mucosa [
11]. Therapeutic interventions aimed at preventing barrier dysfunction or restoring the barrier once it is compromised could thus potentially be effective in treating inflammatory diseases in human airways, including asthma, CRS, and allergic rhinitis. Targeting OSM may prove beneficial in both non-ECRS and ECRS cases, where barrier dysfunction is sensitive to immune responses. The present study was designed to investigate whether controlling the activation of OSM could be a strategy to enhance and restore polarized and organized epithelial function. As of this writing, no published study has explored the interplay between OSM function and the development of CRS with varying phenotypes in a Japanese population.
Our present analyses revealed that the levels of both OSM and OSMR-β were elevated in surgical specimens obtained from CRS patients. When categorized by the disease groups, the OSMR-β level was predominantly increased in the non-ECRS group, and the OSM level was predominantly increased in the ECRS group. Consistent with earlier findings, both OSM and OSMR-β were found to be heightened in the paranasal sinus mucosa of the present patients diagnosed with CRS. A significant correlation was also observed between each cytokine and OSM as well as OSMR-β. Specifically, the OSM level was correlated with IL-1β and IL-13, while OSMR-β was correlated with TNF-α.
An earlier study revealed that in the context of type 1 inflammation, OSM enhances the expression of OSMR and IL-1R1 in synovial fibroblasts, thereby amplifying the pathological effects of both OSM and IL-1 in rheumatoid arthritis (RA) [
22]. In patients with RA, in line with these in vitro discoveries, it was reported that an intra-articular overexpression of OSM along with TNF-α or OSM and IL-1β leads to more extensive joint destruction compared to the impact of any single cytokine alone [
23]. Regarding type 2 inflammation, earlier studies have documented heightened levels of OSM in sinus tissue from patients with allergic rhinitis and in the sputum of asthmatic individuals who exhibited irreversible airflow obstruction [
12,
13]. Additionally, elevated levels of OSM have been observed in nasal polyps from CRS patients, as well as in tissue biopsies and induced sputum from asthmatic patients. Biopsies from patients with eosinophilic esophagitis (EoE) showed increased OSM levels compared to controls [
11,
24]. In a mouse model, an intratracheal administration of adenovirus that expressed OSM was shown to be sufficient to induce robust type 2 inflammation in the lungs, even without a specific antigen challenge [
25].
Those findings indicated that OSM is involved in both type 1 and type 2 inflammation. In our present study, OSM showed correlations with cytokines related to both type 1 and type 2 inflammation. Moreover, we explored the impact of OSM on airway epithelial cells under inflammatory conditions in humans, such as CRS. When BEAS-2B cells were stimulated with OSM and subjected to a gene expression analysis by RT-PCR, notable and temporal increases in the expression levels of IL-13RA1, IL-4Rα, and IL-1R1 were observed.
In summary, our results suggest that OSM levels are increased in the nasal mucosa of CRS patients and are associated with both type 1 and type 2 inflammation OSM was also reported to disrupt nasal mucosal barrier function [
11]. Notably, the anti-OSMR-β antibody vixarelimab (KPL-716) is currently undergoing clinical trials as a treatment for nodular prurigo (ClinicalTrials.gov Identifier: NCT03816891) [
26]. As our understanding of OSM's role in the pathogenesis of CRS deepens, there is optimism for the development of new therapeutic options for this prevalent disorder.
Author Contributions
Conceptualization, C.I. and S.T.; methodology, S.T.; validation, T.H. and T.U.; formal analysis, C.I. and S.T.; investigation, C.I., Y.O., T.K. (Takashi Kakimoto), T.K. (Tomohiro Kawasumi) K.T. and M.N.; resources, S.T. and T.I.; data curation, T.I.; writing—original draft, C.I. and Y.O.; writing—review and editing, S.T., T.H., and T.U.; visualization, C.I.; supervision, S.T. and A.T.; project administration, S.T.; funding acquisition, C.I. and S.T. All authors have read and agreed to the published version of the manuscript.