Unilateral heat accelerates bone elongation and lengthens extremities of growing mice

Abstract

Linear growth failure results from a broad spectrum of systemic and local disorders that can generate chronic musculoskeletal disability. Current bone lengthening protocols involve invasive surgeries or drug regimens, which are only partially effective. Exposure to warm ambient temperature during growth increases limb length, suggesting that targeted heat could noninvasively enhance bone elongation. We tested the hypothesis that daily heat exposure on one side of the body unilaterally increases femoral and tibial lengths. Mice (N ¼ 20) were treated with 40˚C unilateral heat for 40 min/day for 14 days post-weaning. Non-treated mice (N ¼ 6) served as controls. Unilateral increases in ear (8.8%), hindfoot (3.5%), femoral (1.3%), and tibial (1.5%) lengths were obtained. Tibial elongation rate was > 12% greater (15 mm/day) on the heat-treated side. Extremity lengthening correlated with temperature during treatment. Body mass and humeral length were unaffected. To test whether differences persisted in adults, mice were examined 7-weeks post-treatment. Ear area, hindfoot, femoral, and tibial lengths were still significantly increased $6%, 3.5%, 1%, and 1%, respectively, on the heat-treated side. Left-right differences were absent in non-treated controls, ruling out inherent side asymmetry. This model is important for designing noninvasive heat-based therapies to potentially combat a range of debilitating growth impediments in children. ß

Climatic adaptation in human inferior nasal turbinate morphology: Evidence from Arctic and equatorial populations

“…Alternatively, recent research (Holton et al, ) has suggested that nasal components of the chondrocranium, including the turbinates, may influence the development of surrounding intramembranous‐derived nasal structures (e.g., maxillae, premaxillae, nasal bones) during ontogeny. Experimental studies (Serrat, ; Serrat et al, ; Serrat, King, & Lovejoy, ; Serrat, Williams, & Farnum, ) have concurrently demonstrated that environmental temperatures can directly alter cartilage development (and ultimately endochondral bone morphology) via effects on cell proliferation and matrix production. It thus appears conceivable that the temperature of environmental air entering the nasal passages during early postnatal life could potentially impact inferior turbinate morphology via influence on any remaining cartilaginous components.…”

Low temperature decreases bone mass in mice: Implications for humans

“…More recently, Serrat, King, and Lovejoy () and Serrat () found that mice housed at 7 °C had shorter bodies, tails, and limb bones than mice raised at 27 °C, despite higher food intake and no difference in body mass. Importantly, cold exposure reduced blood flow and solute transport to limb bone growth plates in vivo (Serrat et al, ; Serrat, Williams, & Farnum, ), whereas cold‐induced reductions in growth were mitigated by exercise (Serrat, Williams, & Farnum, ) and hindlimb heating (Serrat, ; Serrat et al, ). These studies strongly suggest circulation to the growth plate underlies temperature‐induced differences in limb length, and reduced circulation may contribute to the decreased trabecular bone architecture we observed.…”

Effects of imbalanced muscle loading on hip joint development and maturation

“…Premature, unilateral closure and smaller hips may lead to altered gait and degenerative outcomes . Conversely, asymmetric growth plate expansion of murine long bones of the hindlimb has been shown to be modulated by the delivery of heat, which led to limb length discrepancy and the potential for altered loading patterns between left and right hips . Adaptations to loading during postnatal growth may influence proliferation and differentiation of growth plate cells, particularly of the triradiate cartilage and proximal femur, and future work should explore this further.…”