We previously reported that alymphoplasia (aly/aly) mice, which have a natural loss-of-function mutation in the Nik gene, which encodes a kinase essential for the processing of p100 to p52 in the alternative nuclear factor-κB (NF-κB) pathway, show mild osteopetrosis with an increase in several parameters of bone formation: bone formation rate, mineral apposition rate, and osteoblast number. We therefore investigated the molecular mechanisms triggered by the alternative NF-κB pathway in the regulation of osteoblast differentiation using primary osteoblasts (POB) prepared from aly/aly mice. Alkaline phosphatase (ALP) activity and mineralization induced by the presence of β-glycerophosphate and ascorbic acid were enhanced in POB from aly/aly compared with wild-type (WT) mice. Furthermore, osteoblastic differentiation induced by bone morphogenetic protein 2 (BMP2), as shown by ALP activity, mRNA expression of osteocalcin, Id1, Osterix and Runx2, and Sma- and Mad-related protein (Smad)1/5/8 phosphorylation, was also enhanced in POB from aly/aly mice. The ectopic bone formation in vivo that was induced by BMP2 was enhanced in aly/aly mice compared with controls. Transfection of a mutant form of p100, p100ΔGRR, which cannot be processed to p52, stimulated ALP activity and Smad phosphorylation. In contrast to p100ΔGRR, overexpression of p52 inhibited these events. Both BMP2-induced ALP activity and Smad phosphorylation were reduced in POB from p100-deficient mice, which carry a homozygous deletion of the COOH-terminal ankyrin repeats of p100 but still express functional p52 protein. p52 and p100ΔGRR interacted with a BMP receptor, ALK2, in overexpressed COS7 cells and changed the ALK2 protein levels in opposite directions: p52 reduced ALK2 and p100 increased it. Thus, the alternative the NF-κB pathway via the processing of p52 from p100 negatively regulates osteoblastic differentiation and bone formation by modifying BMP activity.
CgA levels were high in both groups immediately before surgery, and thus CgA values immediately before surgery may not be a reliable indicator of the need for intravenous sedation. Also, spectral analysis of HRV, especially ΔL/H and ΔCCV(HF), could be useful for assessing tension and anxiety.
Purpose
The effect of microgravity on gingival epithelial cells (GE1) is unknown; thus, we analyzed cell proliferation as well as the gene expression patterns in GE1 cells cultured under simulated microgravity.
Materials and methods
Gingival epithelial cells were seeded and cultured at 10-3 G in a three-dimensional clinostat to simulate microgravity (group CL) or in normal gravity (group C) for 10 days. Cell proliferation was analyzed by counting the numbers of cells. Real-time polymerase chain reaction was performed to amplify the krt 5, krt 13 and involucrin genes. Additionally, total protein was immunoblotted with anti-krt 13 antibody. Statistical analysis (n = 9, three groups repeated three times) was performed (ANOVA, Tukey's test, p < 0.05).
Results
Cell proliferation was significantly upregulated under microgravity based on the average number of cells. Cell proliferation and differentiation marker expression was significantly increased after culture under simulated microgravity. Western blotting showed intense krt 13 staining under simulated microgravity. The simulated microgravity environment had an accelerating effect on GE1 proliferation and differentiation.
Conclusion
These findings suggest that GE1 cells would be affected by the microgravity environment during space flight. Moreover, these findings also suggest that we could promote regeneration of gingival cells using of a simulated microgravity environment.
How to cite this article
Tamura A, Masaki C, Seo Y, Mukai C, Mukaibo T, Kondo Y, Nakamoto T, Hosokawa R. Microgravity might affect Peri-implant Mucosal Epithelial Cells during Space Flight. Int J Prosthodont Restor Dent 2015;5(1):10-16.
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