Table 3.

Summary of proximal tibia and humerus trabecular microarchitecture parameters and tibia and fifth lumbar vertebrae volumetric bone mineral density (BMD) collected from female C57BL/6J mice (77-days-old at euthanasia). Mice were assigned to one of five groups (n=12/group): Baseline, Ground Control (GC) with Vehicle (VEH; phosphate-buffered saline), GC with Osteoprotegerin (OPG-Fc; 20 mg/kg), Spaceflight (SF) with VEH, and SF with OPG-Fc. The duration of microgravity exposure during SF was 12 days.

		Ground Control		Spaceflight
	Baseline	Vehicle	OPG-Fc	Vehicle	OPG-Fc	2-Way ANOVA
Proximal Tibia μCT
BV/TV	5.7 ± 0.4	9.2 ± 0.5	10.5 ± 0.6D	6.8 ± 0.4L	10.6 ± 0.3 D	OPG-Fc>VEH
Conn.D	30 ± 7	88 ± 8	102 ± 10	64 ± 7	113 ± 7 D	OPG-Fc>VEH
SMI	3.08 ± 0.06	2.63 ± 0.07	2.52 ± 0.06	2.79 ± 0.05L	2.46 ± 0.03D	OPG-Fc<VEH
Tb.N	4.07 ± 0.07	4.44 ± 0.1	4.88 ± 0.07D	4.61 ± 0.06	4.80 ± 0.08	OPG-Fc>VEH
Tb.Th	35.9 ± 0.7	40.4 ± 0.4	40.2 ± 0.9	33.9 ± 0.8L	40.1 ± 0.5D	SF<GC; OPG-Fc>VEH
Tb.Sp	247 ± 5	226 ± 6	203 ± 4D	217 ± 3	206 ± 4	OPG-Fc<VEH
Proximal Humerus μCT
BV/TV	10.4 ± 0.5	10.0 ± 0.6	13.4 ± 0.5D	8.9 ± 0.4	12.5 ± 0.04D	SF<GC; OPG-Fc>VEH
Conn.D	80 ± 7	73 ± 9	111 ± 7 D	78 ± 10	109 ± 7D	OPG-Fc>VEH
Proximal Tibia pQCT
Total vBMD	382 ± 5	432 ± 6	528 ± 6LD	383 ± 5L	507 ± 5D	SF<GC; OPG-Fc>VEH
L5 Vertebra pQCT
Total vBMD	298 ± 6	311 ± 5	345 ± 4D	291 ± 5L	331 ± 6LLD	SF<GC; OPG-Fc>VEH

Data are presented at mean ± SEM. 2-way-ANOVA differences are presented in the right-most column. Significant differences within Loading (GC vs. SF) or Drug (VEH vs. OPG-Fc) were tested by a Tukey follow-up test (significance set at P<0.05). Loading (L) indicates a significant difference between SF and GC within VEH or OPG-Fc; Drug (D) indicates a significant difference between OPG-Fc and VEH within GC or SF.