Immunohistochemical evidence of lactoferrin in human embryo-fetal bone and cartilage tissues.

Lf (lactoferrin) is an 80-kDa iron-binding protein, which has been suggested to promote bone growth in murine models. In view of this, we aimed to analyse the immunohistochemical distribution of Lf in human embryonal and fetal bone and cartilaginous tissues at different gestational weeks in order to evaluate whether a role for this protein might be proposed also in human osteogenesis. Bone and cartilaginous specimens were taken at autopsy from 25 fetuses (8-34 weeks of gestation). Ten samples of human adult bone and cartilage were also submitted to the immunohistochemical procedures. Sections, 4-microm thick, were cut from formalin-fixed paraffin-embedded tissue blocks and stained with a monoclonal antibody against human Lf, following antigen retrieval procedures. Lf immunoreactivity was mainly localized in the mesenchymal cells forming the periosteum as well as in chondroblasts at the eighth gestational week; a strong Lf immunoexpression in immature osteocytes and osteoblasts was noted up to the 18th gestation week, with a considerable decrease by the 24th week. No Lf expression was found in any bone area after the 30th and up to the 34th week of gestation. Our data seem to suggest an important role for Lf as a bone growth regulator in the early phases of the human endochondral ossification, with an anabolic action similar to that previously reported in cell culture lines and in animal models.