Table 8.

Changes in gene regulation of bone cells exposed to microgravity conditions.

Cell Type	Gene Regulation	Microgravity	Reference
Mouse Ocy454	Top 5: 2 d upregulated: Cxcl14, Mmp13, C2cd4a, Cdc25c, Gdf7 2 d downregulated: Fabp3, Ptprz1, Sparcl1, Slc12a2, Ogn 4 d upregulated: Scgb1b12, Acan, Taar5, Pappa2, Cfap20dc 4 d downregulated: Slc12a2, Tfrc, Ajuba, Idi1, Dmp1 6 d upregulated: Car9, Egln3, Serping1, Tmem45a, Selenbp1 6 d downregulated: Cth, Ctps, Pinx1, Ddx21, Ostn	r-µg on the ISS for 2, 4, and 6 d	[159]
Human blood-derived stem cells	Methylation at histone H3 sites H3K4me3, H3K27me2/3, H3K79me2/3, and H3K9me2/3 mediates cellular reprogramming that drives gene expression	r-µg on the ISS for 72 h	[160]
Murine osteoblasts and osteoclasts	Downregulation: Atf4, RunX2, Osterix	r-µg on the ISS for 14 d	[26]
Human bone marrow mesenchymal stem cells	Downregulation: CDKN3, MCM5, CCNB1, CDK1, RUNX2, ALPL, BMP2, and COL1A1 Upregulation: RUNX2, ALPL, BMP2, and COL1A1	s-µg on an RPM for 2, 7, and 14 d	[161]
Human fetal osteoblast cells	Differential gene expression of TGFB1, BMP2, SOX9, ACTB, TUBB, VIM, LAMA1, COL1A1, SPP1, and FN1	s-µg on an RPM for 7 and 14 d	[162]
7F2 murine pre-osteoblasts	Downregulation: Alpl, Run, and on after 6 days, no difference between g-levels	s-µg (“full”, 0.16 g (Moon), and 0.38 g (Mars)) on an RPM for 2, 4, and 6 d	[163]
MC3T3-E1 mouse pre-osteoblasts	Identification of 3 core circRNAs (circ_014154, circ_010383, and circ_012460) and six core mRNAs (Alpl, Bg1ap, Col1a1, Omd, Ogn, and Bmp-4) involved in osteogenic differentiation under µg	s-µg on an RCCS for 72 h	[164]

Abbreviations: Days (d); hours (h); random positioning machine (RPM); real microgravity (r-µg); rotating cell culture system (RCCS); simulated microgravity (s-µg).