At the same time point of the bone biopsies [at day 0 (pre-transplant) and nearly at month 12] serum levels of FGF23, and its cofactor Klotho, and sclerostin will be measured in the immunology lab of our hospital, according to the manufacturer's instructions. C-terminal FGF23 will be measured by sandwich ELISA (Immunotopics, San Clement, CA). Alfa-klotho will be measured by ELISA (IBL America, MN, USA). Sclerostin will be assessed by TECO Sclerostin EIA kit, which is a 96-well immune-capture ELISA (Sissach, Switzerland).