Natural developing process of immunoglobulin G4-related sialadenitis after submandibular gland excision: a retrospective cohort study

IgG4-related disease: an update on pathology and diagnostic criteria with a focus on salivary gland manifestations

Immunoglobulin G4-related disease (IgG4-RD) is a multi-organ disorder characterized by a highly variable clinical presentation depending on the affected organ/s, extent of tumefactive fibroinflammatory lesions, and associated functional impairment. The disease pursues a chronic, relapsing, often asymptomatic course and hence may pose a significant diagnostic challenge. Diagnostic delay can lead to progressive fibrosis and irreversible organ damage resulting into significant morbidity and even mortality. Given its broad clinical spectrum, physicians of all specialties may be the first clinicians facing this diagnostic challenge. Outside the pancreatobiliary system, the head and neck represents the major site of IgG4-RD with variable organ-specific diffuse or mass-forming lesions. In up to 75% of cases, elevated serum IgG4 levels are observed, but this figure possibly underestimates the fraction of seronegative cases, as the disease manifestations may present metachronously with significant intervals. Together with negative serology, this can lead to misdiagnosis of seronegative cases. A standardized nomenclature and diagnostic criteria for IgG4-RD were established in 2012 and revised in 2020 facilitating scientific research and expanding the range of diseases associated with IgG4 abnormalities. In addition to orbital pseudotumor, dacryoadenitis, Riedel thyroiditis, sinonasal manifestations, and rare miscellaneous conditions, IgG4-related sialadenitis is one of the most frequent presentations in the head and neck region. However, controversy still exists regarding the relationship between sialadenitis and IgG4-RD. This review focuses on the clinicopathological features of IgG4-related sialadenitis and its contemporary diagnostic criteria.

[Establishment and application of new techniques for submandibular gland preservation]

The saliva secreted from submandibular gland (SMG) accounts for 60%-65%. It plays an important role in maintaining the human function of swallow, digestion, testing, speech, protection of oral mucosa, and prevention from dental carries. The SMG is frequently resected during the treatment for various kinds of oral and maxillofacial diseases, resulting in xerostomia and decreased quality of life. During the past 15 years, Research Center of Salivary Gland Diseases in Peking University School and Hospital of Stomatology conducted a series of studies on new techniques for preservation of SMG and achieved remarkable results. The clinicopathologic and imaging characteristics of IgG4-related sialadenitis (IgG4-RS) were clarified based on systematic studies. The results of studies on the pathogenesis of IgG4-RS showed that unbalance of inflammatory factors mediated the abnormality of secretion of SMG. IL-4 participates in occurring and development of glandular fibrosis of SMG. Regulation of tumor necrosis factor α (TNF-α) and cleaning of senescent cells might be taken as the targets for treatment of IgG4-RS. The combination of glucocorticoid and steroid-sparing agents showed effective results for treating IgG4-RS, clinical remission was achieved in all the patients, serum IgG4 levels decreased, and salivary gland secretion significantly increased. Sialoendoscopy-assisted sialolithectomy was applied in the treatment of about 1 000 cases with submandibular hilar calculi with a success rate of more than 90%. Transfer of SMG was used for prevention from radiation-induced xerostomia in the patients with head and neck carcinoma. SMG was transferred to the submental region before radiotherapy and was kept away from the ra-diation field. The results of prospective clinical controlled study showed this technique could effectively preserve the function of SMG and prevent from xerostomia. Based on the micro-anatomical study on the blood vessels and ducts of SMG, partial sialoadenectomy was applied for treatment of benign tumors in the SMG. A clinical controlled study confirmed its safety for control of the tumors and its advantage of preservation of SMG function. The studies on the involvement of SMG in oral squamous cell carcinoma (OSCC) provided the anatomical and histopathological basis for preservation of SMG during neck dissection for early cases with OSCC. A innovated surgical modality "four preservations including SMG" was used during the neck dissection for the early cases with OSCC. A prospective randomized clinical controlled study confirmed its safety, feasibility, effectiveness for control of the carcinoma, and advantages of preservation of SMG function.

Interleukin-13 promotes cellular senescence through inducing mitochondrial dysfunction in IgG4-related sialadenitis

Immunoglobulin G4-related sialadenitis (IgG4-RS) is an immune-mediated fibro-inflammatory disease and the pathogenesis is still not fully understood. The aim of this study was to explore the role and mechanism of interleukin-13 (IL-13) in the cellular senescence during the progress of IgG4-RS. We found that the expression of IL-13 and IL-13 receptor α1 (IL-13Rα1) as well as the number of senescent cells were significantly higher in the submandibular glands (SMGs) of IgG4-RS patients. IL-13 directly induced senescence as shown by the elevated activity of senescence-associated β-galactosidase (SA-β-gal), the decreased cell proliferation, and the upregulation of senescence markers (p53 and p16) and senescence-associated secretory phenotype (SASP) factors (IL-1β and IL-6) in SMG-C6 cells. Mechanistically, IL-13 increased the level of phosphorylated signal transducer and activator of transcription 6 (p-STAT6) and mitochondrial-reactive oxygen species (mtROS), while decreased the mitochondrial membrane potential, ATP level, and the expression and activity of superoxide dismutase 2 (SOD2). Notably, the IL-13-induced cellular senescence and mitochondrial dysfunction could be inhibited by pretreatment with either STAT6 inhibitor AS1517499 or mitochondria-targeted ROS scavenger MitoTEMPO. Moreover, IL-13 increased the interaction between p-STAT6 and cAMP-response element binding protein (CREB)-binding protein (CBP) and decreased the transcriptional activity of CREB on SOD2. Taken together, our findings revealed a critical role of IL-13 in the induction of salivary gland epithelial cell senescence through the elevated mitochondrial oxidative stress in a STAT6–CREB–SOD2-dependent pathway in IgG4-RS.

[Studies on newly recognized chronic sialadenitis]

Some kinds of chronic sialadenitis were recognized during the recent years. They have specific pathogenesis, clinical and histopathologic appearances, and require specific treatment. IgG4-related sialadenitis (IgG4-RS) is one of the immune-mediated diseases, characterized by tumefactive lesions. The incidence of IgG4-RS obviously increased during the past 30 years. The study on the potential relationship between occupational exposure to chemical substances and the incidence of IgG4-RS showed that subjects with occupational exposure to agents known to cause IgG4-RD had an increased risk for IgG4-RS. Surgical excision of involved SMG could not control the disease progression, which is not recommended for treatment of IgG4-RS. The combination of glucocorticoid and steroid-sparing agents is effective for treating IgG4-RS, and restores salivary gland function. Radioiodine induced sialadenitis (RAIS) is one of the common complications of postoperative adjuvant treatment of differentiated thyroid cancer by ¹³¹I. The incidence of the disease is related to radiation dosage. Clinically, the patients suffered from swelling and tenderness in the buccal or submandibular regions, especially during the mealtime. Imaging appearances are similar to those of chronic obstructive sialadenitis. Conservative managements, such as gland massage, sialagogues, are the mainstream methods in the treatment of RAIS. Sialendoscopy is feasible for RAIS, but not as effective as conventional obstructive sialadenitis (COS). Therefore the prevention of RAIS is crucial. Eosinophilic sialodochitis (ES) is a new type of chronic inflammatory disease of the salivary gland related to allergy. It has characteristics of swelling of multiple major salivary glands, strip-like gelatinous plugs discharged from the duct orifice of the gland, elevated level of serum IgE and eosinophils in peripheral blood, infiltration of eosinophils and IgE positive plasma cells in the tissues, allergic history, increased expression of allergy-related cytokines, such as IL-4, IL-5, IL-13, and eotaxin, which suggest allergic reactions as a potential pathogenesis of the disease. The clinical, laboratory, histological, and immunohistochemical characteristics of ES are significantly different from conventional obstructive sialadenitis (COS). Therefore, it is suitable to separate ES from COS. Conservative managements, such as self-maintenance therapy and anti- allergic modality are the choices of treatment for ES. Based on the results of our comprehensive studies a new classification of chronic sialadenitis is suggested.