Effects of centrifuging at 2g on rat long bone metaphyses

Abstract

Hypergravity may be considered as a means of counteracting the deleterious effects of microgravity on bone tissue. The effects of exposure to 4 days of hypergravity provided by centrifuging, on bone tissue were studied using histomorphometry. Young 53-day-old male Sprague Dawley rats were randomly divided into a centrifuged group (2g, n = 10), a rotated group (ROTATE, n = 6) of rats exposed to 1.03 g placed in cages near the centre of rotation of the centrifuge and a stationary control group (CONTROL, n = 10). The body mass of the 2g rats was decreased by this experience by 16% compared to CONTROL. The width of the tibial growth plate of 2g was decreased. In two out of ten 2g rats, the hypertrophic zone was injured. In both the tibial and humeral primary (1 degrees ) spongiosae, a reduced 1 degrees spongiosa width (-35% and -24%, ROTATE versus CONTROL respectively; -37% and -41%, 2g versus CONTROL respectively) associated with bone gain (+27% for tibia and humerus ROTATE versus CONTROL; + 16% and +20%, 2g versus CONTROL respectively) was observed in both ROTATE and 2g. In the tibial secondary (2 degrees) spongiosa, bone mass was increased in the 2g (+13% 2g versus CONTROL) rats due to thicker trabeculae, but was decreased in ROTATE rats (-12% versus CONTROL) due to thinner trabeculae. The parameters of formation and resorption activities were stimulated in the 2g and ROTATE groups, the formation activity being more enhanced in 2g. No structural changes were observed in the humeral 2 degrees spongiosa in any of the groups. Numeral bone formation parameters were decreased in 2g and ROTATE but resorption activity was increased in 2g and decreased in ROTATE compared to CONTROL. In conclusion, as early as the 4th day, 2g hypergravity induced reduced endochondral bone formation and increased cancellous bone mass. Rotation led to mixed results including reduced endochondral bone formation, increased bone volume in the 1 degrees spongiosa and bone loss in the 2 degrees spongiosa.

Histological assessments on the abnormalities of mouse epiphyseal chondrocytes with short term centrifugal loading

“…Meanwhile, the developing cartilage was shown to respond to gravitational changes according to Hert's curve (8,22,23), in which an increased baseline loading reduces cartilage differentiation, while a reduced baseline loading leads to increased differentiation, but only within a range, beyond which lack of differentiation results. This may account for the altered cell shapes seen in our centrifuged cartilages, similar to findings that were previously reported by Vico et al (36) in a study involving excess G loading. At least in our study, the main effects of mechanical stress upon cartilage seem to be changes in extracellular matrix and in cell-to-matrix adhesion.…”

“…Nowadays, mankind's enterprises in space are no longer science fiction, but significant biological, psychological and environmental problems are yet to be addressed (25). The deleterious effects of spaceflights and microgravity upon the musculoskeletal system have been well-documented (13,20), and hypergravity can be considered a valuable means of counteracting those (36).…”

Hypergravity suppresses bone resorption in ovariectomized rats

“…Some studies have reported the effects of hypergravity on the long bones of growing rats (Kohles et al, 1996;Martinez et al, 1998;Smith, 1975;Vico et al, 1999) and growing dogs (Doden et al, 1978;Oyama, 1975). Martinez et al (1998) reported that hypergravity shortened the length of the femurs and reduced the cortical bone area in young growing rats, but the bone density at the femoral mid-diaphysis was unchanged.…”

The turnover of mineralized growth plate cartilage into bone may be regulated by osteocytes

“…This indicates that an increase in body weight is associated with an increase in endochondral bone formation. Similarly, both treadmill exercise and hypergravity (Vico et al, 1999) have been reported to increase the bone volume of the primary spongiosa in growing rats. However, the interpretation of these experiments is not straightforward, since the hypergravity seemed to have an effect apart from the induced change in loading (Vico et al, 1999).…”

“…Similarly, both treadmill exercise and hypergravity (Vico et al, 1999) have been reported to increase the bone volume of the primary spongiosa in growing rats. However, the interpretation of these experiments is not straightforward, since the hypergravity seemed to have an effect apart from the induced change in loading (Vico et al, 1999). In addition, weight loading has been reported to promote growth plate ossification in chicks (Reich et al, 2005), but as the loading also increased vascularization and altered chondrocyte gene expression, this cannot solely be attributed to an osteocyte response.…”