The effect of burn on serum concentrations of sclerostin and FGF23

Severe burn results in acute bone resorption followed by an adynamic state, most likely due to changes brought about by the inflammatory and glucocorticoid responses to the injury. There is a consequent increase in annual extrapolated fracture incidence in children. While osteoblasts have been reported to disappear from the bone surface and stem cell differentiation into osteoblasts is impaired, the effect of burns on osteocyte function is unknown. We measured serum concentrations of two osteocyte proteins, sclerostin and fibroblast growth factor (FGF)-23 between 6 and 60 days post-burn in pediatric patients, ages 5-18 years who had participated in a randomized controlled double-blind study of acute administration of pamidronate to prevent the resorptive bone loss. While FGF-23 was undetectable in all samples, the plot of sclerostin concentration versus time post-burn yielded a statistically significant difference between slopes, -2.5 in the placebo control group and +3.5 in the group receiving pamidronate, p = 0.016 by ANCOVA. The FGF23 data suggest that osteocytes may be apoptotic, although the sclerostin data may indicate partial preservation of osteocyte function in subjects receiving pamidronate or an ectopic source of sclerostin.