Galectin-1 expression in human MSCs. (A) Reverse transcription PCR of galectin family members in MSCs analyzed by agarose gel electrophoresis. mRNA of galectin-1 to galectin-4, galectin-7 to galectin-9, and galectin-12 were detected, whereas mRNA of galectin-10, galectin-13, and galectin-14 were not detectable. (B) Comparison of the galectin expression by qPCR in MSCs. Besides the abundant expression of galectin-1, galectin-3 and galectin-8 were also highly expressed. The relative expression level was normalized to expression of 18S RNA. The qPCR data are representative of 3 independent experiments representing 3 different MSC donors (mean ± SD). (C) Flow cytometric analysis of galectin-1 by intracellular and cell-surface staining of MSCs. (D) Detection of galectin-1 in the supernatant of MSCs by ELISA. MSCs released galectin-1 in high amounts into the supernatant in a cell-number–dependent manner. The correlation between cell number and galectin-1 release was not linear, as evidenced by the significant difference in the galectin-1 concentration between 6 hours and 48 hours of incubation, when 30 000 MSCs were seeded (confluent cell layer). However, there was no significant difference, when only 7500 (subconfluent layer) were seeded. This suggests a cell-contact–dependent increase in the confluent culture (30 000 cells per 96-well plate). Data are shown as means (± SD) of triplicates (n = 3); n.s., not significant.