Comparison of serum levels with bone content and gene expression indicate a contradictory effect of kidney transplantation on sclerostin

In an attempt to clarify the mechanisms of post-transplant bone disease we investigated the bone content and gene expression of several bone-related proteins. After a successful kidney transplant, the content of sclerostin in bone biopsies was found to be increased as measured by immunohistochemistry, multiplex assay, and gene expression despite a concomitant decrease of sclerostin in the serum. The phosphorylation of beta-catenin was increased, confirming Wnt pathway inhibition, an effect accompanied by an increase of the receptor activator of nuclear factor kappa-Β ligand (RANKL) and a decrease of osteoprotegerin protein levels in both serum and bone. Thus, changes in circulating biomarkers after kidney transplantation cannot be easily extrapolated to concomitant changes occurring in the bone. Hence, overall treatment decisions post kidney transplant should not be based on serum biochemistry alone.