PDF(Pubmed)
Abstract：
Although SARS-CoV-2 induces mucin hypersecretion in the respiratory tract, hyposalivation/xerostomia has been reported by COVID-19 patients. We evaluate the submandibular gland (SMGs) pathogenesis in SARS-CoV-2-infected K18-hACE2 mice, focusing on the impact of infection on the mucin production and structural integrity of acini, ductal system, myoepithelial cells (MECs) and telocytes. The spike protein, the nucleocapsid protein, hACE2, actin, EGF, TNF-α and IL-1β were detected by immunofluorescence, and the Egfr and Muc5b expression was evaluated. In the infected animals, significant acinar hypertrophy was observed in contrast to ductal atrophy. Nucleocapsid proteins and/or viral particles were detected in the SMG cells, mainly in the nuclear membrane-derived vesicles, confirming the nuclear role in the viral formation. The acinar cells showed intense TNF-α and IL-1β immunoexpression, and the EGF-EGFR signaling increased, together with Muc5b upregulation. This finding explains mucin hypersecretion and acinar hypertrophy, which compress the ducts. Dying MECs and actin reduction were also observed, indicating failure of contraction and acinar support, favoring acinar hypertrophy. Viral assembly was found in the dying telocytes, pointing to these intercommunicating cells as viral transmitters in SMGs. Therefore, EGF-EGFR-induced mucin hypersecretion was triggered by SARS-CoV-2 in acinar cells, likely mediated by cytokines. The damage to telocytes and MECs may have favored the acinar hypertrophy, leading to ductal obstruction, explaining xerostomia in COVID-19 patients. Thus, acinar cells, telocytes and MECs may be viral targets, which favor replication and cell-to-cell viral transmission in the SMG, corroborating the high viral load in saliva of infected individuals.
摘要：
尽管SARS-CoV-2诱导呼吸道粘蛋白分泌过多,COVID-19患者报告了唾液分泌不足/口干症。我们评估了SARS-CoV-2感染的K18-hACE2小鼠的下颌下腺（SMGs）发病机理，重点关注感染对腺泡粘蛋白产生和结构完整性的影响，导管系统,肌上皮细胞（MEC）和端粒细胞。刺突蛋白，核衣壳蛋白，hACE2，肌动蛋白，EGF,免疫荧光法检测TNF-α和IL-1β,并评估Egfr和Muc5b的表达。在受感染的动物中，与导管萎缩相反，观察到明显的腺泡肥大。在SMG细胞中检测到核衣壳蛋白和/或病毒颗粒，主要在核膜来源的囊泡中，确认病毒形成中的核作用。腺泡细胞显示强烈的TNF-α和IL-1β免疫表达,EGF-EGFR信号增强,与Muc5b一起上调。这一发现解释了粘蛋白分泌过多和腺泡肥大，压缩管道。还观察到垂死的MEC和肌动蛋白减少，指示收缩和腺泡支撑的失败，有利于腺泡肥大。在垂死的末端细胞中发现了病毒组装，指出这些相互通信的细胞是SMG中的病毒递质。因此,SARS-CoV-2在腺泡细胞中触发EGF-EGFR诱导的粘蛋白高分泌,可能由细胞因子介导。对末端细胞和MEC的损伤可能有利于腺泡肥大，导致导管阻塞,解释COVID-19患者的口干症。因此，腺泡细胞,端粒细胞和MECs可能是病毒靶标，有利于SMG中的复制和细胞间病毒传播，证实了感染者唾液中的高病毒载量。
