Proteoglycan biosynthesis in relation to differentiation of cord blood monocytes in vitro

Human monocytes were obtained from umbilical cord blood and cultured in vitro. By morphological criteria, the neonatal monocytes developed into macrophage-like cells in the course of 3–5 days in culture. The cells were exposed to [³⁵S]sulphate for 24 h, either from day 0–1 or day 9–10 in vitro. The ³⁵S-labelled macromolecules recovered were mainly associated with the medium fraction (approximately 75%) in both day 1 and day 10 cultures. These secretory macromolecules were demonstrated by the use of chondroitinase ABC-digestions to contain predominately chondroitin sulphate proteoglycan (CSPG). [³⁵S]galactosaminoglycan chains from day 10 cultures were more highly sulphated than the corresponding day 1 species due to the appearance of (glucuronosyl-4,6-diS-N-acetylgalactosamine) disulphated disaccharide units. The galactosaminoglycan chains in neonatal CSPG were found to increase in M_r during cultivation in vitro; from mean M_r of 20 400 to 30 200 (n = 5) in day 1 and day 10 medium proteoglycans, respectively. The corresponding M_r values for adult monocyte [³⁵S]galactosaminoglycan chains were 21 300 and 22 800. On the basis of the concomitant changes in cellular morphology and glycosaminoglycan structure, it is concluded that neonatal monocytes, like monocytes from adults, differentiate into macrophage-like cells in vitro.