Objectives: This study investigated the efficacy of Montmorency tart cherry (TC) alone and in combination with exercise on improving bone quality in young growing animals and the underlying mechanisms of action.

Methods: Six-week-old female C57BL/6 mice were randomly assigned to 4 groups (n=12 mice/group) in a 2x2 factorial design: control AIN-93G diet (CON), CON+exercise, TC (10% w/w), or TC+exercise. The exercise consisted of treadmill running for 30 min, 5 d/wk at 12 m/min and a 5 degree incline. Body weights were recorded weekly. After 8 wks of treatment, mesenchymal stem cells (MSC) in the tibial bone marrow were quantified via flow cytometry fluorescent activated cell sorting (FACS). Trabecular and cortical bone microarchitecture in the femur and lumbar vertebrae was assessed using micro-computed tomography. Biomechanical testing was performed using finite element analysis (FEA). The relative abundance of RNA for genes involved in osteoblast and osteoclast differentiation and activity was determined using RT-PCR. Data were analyzed using a 2-way ANOVA with TC and exercise as factors.

Results: At the end of the study, no differences in body weight were observed. Trabecular bone volume in the femur and spine was increased with exercise and TC (p<0.05), but there was no interaction. Cortical bone thickness in the vertebra was also increased by TC and exercise (p<0.001), but not in the femur. Trabecular bone strength and stiffness were increased in the vertebra in response to TC and exercise, but only in response to TC in the femur (P<0.001). An increase in bone marrow MSCs occurred in response to exercise (p<0.01), but not TC. However, the combination of TC and exercise reduced nuclear factor of activated T-cells 1 (Nfatc1) femur gene expression, a key regulator of osteoclastogenesis (p<0.05). TC also increased bone morphogenetic protein (BMP)2 gene expression, a regulator of osteoblastogenesis.

Conclusion: Our data indicate that TC and exercise alone had positive effects on bone quality by suppressing regulators of osteoclastogenesis and increasing regulators of osteoblastogenesis. Even though the effects of TC and exercise were not synergistic, the effects of TC alone on bone were similar to and in some cases greater than exercise alone.