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First published online January 31, 2007
Journal of Experimental Biology 210, 602-613 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02675

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Variation in estradiol level affects cortical bone growth in response to mechanical loading in sheep

Maureen J. Devlin^* and Daniel E. Lieberman

Department of Anthropology, Peabody Museum, Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA

View larger version (11K): [in this window] [in a new window]   Fig. 1. Hypothesized mechanism of interaction of E2, ER- and strain in osteoblasts. Left, E2 levels are lower and osteoblasts express fewer ER- receptors, decreasing strain sensitivity. Right, higher E2 upregulates osteoblast expression of ER-, increasing strain sensitivity and causing greater osteogenic response to identical mechanical loading.

View larger version (13K): [in this window] [in a new window]   Fig. 2. Neutral axis (NA) location at 25%, 50% and 75% of stance phase in tibia and metatarsal (after Lieberman et al., 2004). Anterior is at top, lateral to the left. Scale bar, 10 mm. Despite NA rotation, strains remain higher on the anterior and posterior than the medial and lateral cortices, 300–800 µ vs 0–300 µ, respectively.

View larger version (22K): [in this window] [in a new window]   Fig. 3. Regression of bone added (mm2) vs body mass (kg0.66). (A) Femur, (B) tibia, (C) metatarsal.

View larger version (33K): [in this window] [in a new window]   Fig. 4. Residuals of bone added vs body mass. (A) Femur, (B) tibia, (C) metatarsal. Letters indicate significantly different from aHE, bNE group. (P<0.05, ANOVA, post-hoc Fisher's LSD test).

View larger version (25K): [in this window] [in a new window]   Fig. 5. Cross-sectional properties of tibia, relative to body mass and limb length. (A) IN, INy, J. (B) ZNt, ZNc. n.s., not significant.

View larger version (20K): [in this window] [in a new window]   Fig. 6. Linear bone growth of tibia. Anterior and Posterior indicate growth at sites of maximal strain on anterior (cranial) and posterior (caudal) cortices; Medial and Lateral indicate growth at intersection of neutral axis (NA) with medial and lateral cortices. Letters indicate significantly different from aHE or bNE (P<0.05, ANOVA, post-hoc Fisher's LSD test).

View larger version (25K): [in this window] [in a new window]   Fig. 7. Cross-sectional properties of metatarsal, relative to body mass and limb length. (A) IN, INy, J. (B) ZNt, ZNc. Letters indicate significantly different from aHE or bNE (P<0.05, ANOVA, post-hoc Fisher's LSD test).

View larger version (21K): [in this window] [in a new window]   Fig. 8. Linear bone growth of metatarsal. Anterior and Posterior indicate growth at sites of maximal strain on (cranial) and posterior (caudal) cortices; Medial and Lateral indicate growth at intersection of neutral axis (NA) with medial and lateral cortices. Letters indicate significantly different from aHE or bNE (P<0.05, ANOVA, post-hoc Fisher's LSD test).