Humoral Nature of Osteogenic Activity of Transitional Epithelium

Abstract

THE osteogenic activity of transitional epithelium was discovered in the course of ligation of the renal artery¹ and bladder mucosa transplantation². In both cases bone is induced in connective tissue along the line of contact with invading cells of hyperplastic transitional epithelium³. The question arises whether direct physical contact is required for induction, or whether transitional epithelium contains some diffusible substance with osteogenic activity which may act as an inductor well away from epithelium. All efforts to induce osteogenesis with cell-free extracts and homogenates of bladder mucosa have until now been unsuccessful. The same applies to the products of transitional epithelium secretion which occurs under the experimental conditions. In such experiments only extramedullar mielogenesis was induced⁴.