Division of Oral Reconstruction and Rehabilitation, Kyushu Dental University, Kitakyushu, Fukuoka, Japan.
J Dent Res. 2022 Jul;101(8):942-950. doi: 10.1177/00220345221076071. Epub 2022 Mar 3.
Mucin in saliva plays a critical role in the hydration and lubrication of the oral mucosa by retaining water molecules, and its impaired function may be associated with hyposalivation-independent xerostomia. Age-dependent effects on salivary gland function and rheological properties of secreted saliva are not fully understood as aging is a complex and multifactorial process. We aimed to evaluate age-related changes in the rheological properties of saliva and elucidate the underlying mechanism. We performed ex vivo submandibular gland (SMG) and sublingual gland (SLG) perfusion experiments to collect saliva from isolated glands of young (12 wk old) and aged (27 mo old) female C57BL/6J mice and investigate the rheological properties by determining the spinnbarkeit (viscoelasticity). While fluid secretion was comparable in SMG and SLG of both mice, spinnbarkeit showed a significant decrease in SLG saliva of aged mice than that of young mice. There were no significant differences in GalNAc concentration between young and aged SLG saliva. Liquid chromatography/tandem mass spectrometry analysis of SLG saliva revealed that (Hex) (HexNAc) (NeuAc) at 793.31 was the most abundant O-glycan structure in SLG saliva commonly detected in both mice. Lectin staining of salivary gland tissue showed that SLG stained strongly with lectin II (MAL II) while agglutinin (SNA) stained little, if any, SLG. The messenger RNA expression of 1 that encodes an α-2,3 sialic acid sialyltransferase SIAT4-A showed a decrease in SLG of aged mice, confirmed by a Western blot analysis. Lectin blot analysis in SLG saliva revealed that the relative signal intensity detected by MAL II was significantly lower in aged SLG. Our results suggest that spinnbarkeit decreases in SLG of aging mice due to downregulation of sialic acid linked to α-2,3 sialic acid sialyltransferase expression.
唾液中的黏蛋白通过保留水分子在口腔黏膜的水合和润滑中起着关键作用，其功能受损可能与非唾液分泌减少引起的口干有关。由于衰老过程是一个复杂的多因素过程，因此，年龄对唾液腺功能和分泌唾液流变性的影响尚不完全清楚。我们旨在评估唾液流变性与年龄相关的变化，并阐明其潜在机制。我们进行了下颌下腺（SMG）和舌下腺（SLG）的离体灌注实验，从小鼠（12 周龄）和老年（27 月龄）雌性 C57BL/6J 小鼠的分离腺体中收集唾液，并通过测定纺丝性（粘弹性）来研究唾液的流变性。虽然 SMG 和 SLG 的液体分泌在两种小鼠中相似，但纺丝性显示老年小鼠的 SLG 唾液明显低于年轻小鼠。年轻和老年 SLG 唾液之间的 GalNAc 浓度没有显著差异。SLG 唾液的液相色谱/串联质谱分析显示，（Hex）（HexNAc）（NeuAc）在 793.31 处是 SLG 唾液中最丰富的 O-聚糖结构，在两种小鼠中都普遍存在。唾液腺组织的凝集素染色显示，SLG 强烈染色与 凝集素 II（MAL II），而 凝集素（SNA）染色很少，如果有的话，SLG。编码一种 α-2,3 唾液酸唾液酸转移酶 SIAT4-A 的 1 的信使 RNA 表达在老年小鼠的 SLG 中减少，Western blot 分析证实了这一点。SLG 唾液中的凝集素印迹分析显示，MAL II 检测到的相对信号强度在老年 SLG 中显著降低。我们的结果表明，由于与 α-2,3 唾液酸唾液酸转移酶表达相关的唾液酸连接下调，衰老小鼠的 SLG 纺丝性降低。
