Developmental massage therapy (DMT) during early postnatal life: effect on bone growth, mineralization, and strength in juvenile and young rats

The purpose of the current study was to nvestigate the effects of developmental massage therapy (DMT) during early postnatal life on growth, body composition, and skeletal development in juvenile and young adult rats. Twenty-four rat pups received a daily session of DMT (10 minutes/day) from D6 to D10 of postnatal life and were compared to matched controls (CTL, n=24). Body composition, soft tissue lean mass, fat mass, bone mineral density (BMD), bone mineral content (BMC), and bone area (BA) were measured by peripheral dual energy X-ray absorptiometry (pDXA); bone strength (Peak Load) and intrinsic stiffness on femur shaft were tested by three-point bending (MTS); cortical and cancellous bone histomorphometric measurements were performed on the tibia shaft and metaphysis. Food and water intake were monitored and did not differ among groups between weaning (D21) and D60. Body weight, body length and soft tissue lean mass at D21 were significantly greater in the DMT cohort; at D60 soft tissue lean mass was still greater in DMT groups but no differences were detected in body weight and body length. Moderate to strong correlations were found between body weight and soft tissue lean mass and measured bone outcome variables. BMD by DXA was significantly higher in D21 DMT rats and BA was only greater in D60 DMT males. Femur diameter and length were significantly greater in D60 DMT males. Bone strength and the endosteal percent mineral surface were significantly increased in D60 DMT females compared to CTL. In addition, DMT treatment improved the cancellous bone mineral surface, mineral apposition rate and bone formation rate on the trabecular bone surface area in D21 female rats. Treatment and sex interactions were found for BMC and BA at D60. In summary, DMT during early postnatal life elicited anabolic effects on muscle-bone relationships in juvenile (D21) and young adult (D60) rats. These findings were confirmed histologically by increased percent mineral surface and mineral apposition rates. It is speculated that the positive skeletal outcomes were, in part, due to a modulation of stress by DMT resulting in an improved balance of the neuroendocrine system and regulation of the muscle-bone unit. The absence of biochemical markers as well as body composition and bone studies in older animals suggest a need for future studies to verify whether early life DMT has a prolonged positive impact on lifelong skeletal health.