Changes on lysosomal compartment during PMA-induced differentiation of THP-1 monocytic cells: Influence of type I and type IV collagens

In this work, the influence of different substrate adhesion during phorbol-12-myristate-13-acetate (PMA)-induced differentiation of THP-1 monocytic cell line was studied. In particular, by morphocytochemical and cytometric approaches, the influence of type I and type IV collagens in an experimental model representative of three phases (initial, intermediate and terminal) of monocyte–macrophage transition was analyzed. The cells in these three phases of differentiation were obtained by using 6, 30 e 60 nM PMA. In this experimental model, referring to adhesion to glass as control, by using the azo-dye coupling method, we have considered the analysis of Acid Phosphatase (AcP) activity as a marker of differentiated status expression, in relation to the acquisition of macrophagic phenotype. Endosomal/lysosomal system was further characterized by taking in account the uptake of fluorescent probe LysoTracker Red. Fluorochromization in the various experimental conditions was analyzed morphologically (fluorescence microscopy) and quantitatively (static cytometry). Data related to lysosome compartment were integrated, from a cytokinetic point of view, by flow cytometry measurements of DNA/protein content. Our results have indicated that type I and type IV collagens were able to influence, with respect to glass adhesion, various differentiation phases. Type I collagen showed the higher effects in the condition of high differentiation (60 nM PMA), causing an increase in AcP activity and lysosomal system. Type IV collagen, besides determining effects on lysosomal compartment of intermediate and terminally differentiated cells, influenced mainly proliferative activity of cells with initial differentiation level (6 nM PMA).