Response of the mouse sublingual gland to spaceflight

Abstract

The ultrastructure and immunohistochemistry of secretory proteins of sublingual glands were studied in mice flown on the US space shuttles Discovery [Space Transportation System (STS)-131] and Atlantis (STS-135). No differences in mucous acinar or serous demilune cell structure were observed between sublingual glands of ground (control) and flight mice. In contrast, previous studies showed autophagy and apoptosis of parotid serous acinar cells in flight mice. The expression of parotid secretory protein (PSP) in sublingual demilune cells of STS-131 flight mice was significantly increased compared with ground (control) mice but decreased in STS-135 flight mice. Similarly, expression of mucin (MUC-19) in acinar cells and expression of the type II regulatory subunit of protein kinase A (PKA-RII) in demilune cells were increased in STS-131 flight mice and decreased in STS-135 flight mice, but not significantly. Demilune cell and parotid protein (DCPP) was slightly decreased in mice from both flights, and nuclear PKA-RII was slightly increased. These results indicate that the response of salivary glands to spaceflight conditions varies among the different glands, cell types, and secretory proteins. Additionally, the spaceflight environment, including the effects of microgravity, modifies protein expression. Determining changes in salivary proteins may lead to development of non-invasive methods to assess the physiological status of astronauts.

The effects of spaceflight and fracture healing on distant skeletal sites

“…Here we also examined a longer mission duration (~4 weeks) and observed no significant changes in murine calvaria bone parameters via µCT (Table 3). We also did not see an increase in B.Ar in the mandible even though bone volume (region of interest *B.Ar) was reported to increase during STS-135's 30-day spaceflight mission 38 . We did, however, note a non-significant 15% increase in the cementoenamel junction to alveolar bone crest distance or CEJ-ABC for the Flight + Surgery compared to the Flight + Sham group, suggesting the mandible may experience bone growth.…”

Oral Tissue Responses to Travel in Space

“…PRP, present in acinar cell secretory granules of both sexes, and submandibular gland protein C (SMGC), present in terminal tubule cell secretory granules of female mice, were not significantly different from controls. In the SLG, PSP expression by demilune cells was significantly increased in mice from the space shuttle STS-131 flight, but not in mice from STS-135 [34]. The expression of both PKA-RII in demilune cells, and the acinar cell mucin Muc19, were increased, but not significantly.…”

Effects of spaceflight on the mouse submandibular gland

“…Changes also occur in the expression of several acinar cell secretory proteins. In contrast, the sublingual gland shows few morphological alterations, but changes do occur in serous demilune cell protein expression (Dagdeviren et al, 2018a).…”

“…Thin sections from each mouse of the flight and ground control groups from the three missions were collected on formvar-coated nickel grids. Immunolabeling was carried out overnight at 4°C as described previously (Dagdeviren et al, 2018a), using primary antibodies (Table 1) diluted in phosphate buffered saline containing 1% bovine serum albumin and 5% normal goat serum. Immunolabeling controls included omission of the primary antibody and substitution of non-immune serum or non-immune IgG for the primary antibody.…”

“…Previous studies of animals and humans after travel in space have documented alterations in several tissues and organ systems, including skeletal, immune, cardiovascular, nervous and gastrointestinal (e.g., Borchers et al, 2002;Hargens and Richardson, 2009;Nagaraja and Risin, 2013;Latchney et al, 2014;Porseva et al, 2017;Demontis et al, 2017;Garrett-Bakelman et al, 2019). Early and more recent studies have demonstrated that oral hard and soft tissues, including the mandible (Simmons et al, 1983;Ghosh et al, 2016;Dagdeviren et al, 2018b), teeth (Rosenberg et al, 1984;Dagdeviren et al, 2018b), salivary glands (Groza et al, 1981(Groza et al, , 1983Hand, 1985, 1987;Mednieks et al, 2014Mednieks et al, , 2015Dagdeviren et al, 2018a) and saliva (Brown et al, 1977), are significantly affected by spaceflight.…”