Bone Abstracts

Objectives: CKD in children is associated with suppressed body growth. Physical activity has been previously shown to increase expression of IGF1 signaling in muscles of rats with CKD, but the effects of this intervention on bone tissue have not been investigated yet. The purpose of this study was to examine the effects of aerobic exercise on CKD related bone disease.

Methods: Twenty-day old/50 g male rats underwent a two step subtotal nephrectomy (Nx) or sham surgeries. The animals were divided into two running groups: control (Cr) and CKD (CKDr) (treadmill running, 20 m/min, 0.5 h/day, 5 days/week) and two non running groups: control (C) and CKD. Food delivery was equal for all groups. The intervention lasted 4 weeks. We monitored somatic growth levels, kidney function and proximal tibiae epiphyseal growth plate (EGP) histomorphometry.

Results: Growth retardation (both longitudinal and weight gain) was well noticed in CKD vs C. Exercise caused an increase in longitudinal growth and tibial length in Cr Vs C rats. However, CKDr rats did not grow better than CKD. CKDr rats consumed less food than CKD but grew to the same extent, hinting for better food efficiency. The EGP hypertrophic zone was wider and vascularization at the primary ossification center was decreased in CKD vs C. EGP immunostainable IGF1 and VEGF as well as VEGF mRNA were reduced in CKD. However, total EGP width (both proliferative and hypertrophic zones) was increased in CKDr vs CKD.

Conclusions: CKD induces growth retardation irrespective of food intake, associated with widened EGP hypertrophic zone but less vacularization, hinting for a chondrocyte maturation arrest. Endurance training did not rescue CKD somatic growth retardation, but longitudinal bone formation (as reflected by EGP histomorphometry) was better organized.