title: Monocyte function is severely impaired by the fluorochrome calcein acetomethylester.
abstract: For rapid chemotaxis quantification, cell prelabelling is often performed with the fluorochrome calcein acetomethylester (calcein AM). We investigated whether calcein AM-prelabelling is reliable for monocyte migration analysis. Human monocytes were either preexposed to calcein AM or unlabelled. Monocyte migration towards the potent chemoattractants transforming growth factor-beta1 (TGF-beta1) and N-formyl-Methionin-Leucin-Phenylalanin (fMLP) was assessed using a 48-well micro-chemotaxis chamber. For quantification, cells were visualized by light microscopy and counted. Surprisingly, random migration of calcein AM-prelabelled cells was significantly impaired compared to the unlabelled control. Accordingly, monocyte chemotaxis towards either TGF-beta1 or fMLP dramatically declined. Adherence of calcein AM-labelled monocytes on plastic was also significantly decreased compared to control cells. As adhesion is regarded as an essential component of monocyte migration, the reduced migration observed in calcein AM-labelled monocytes might be explained by a fluorochrome-induced adhesion defect. Therefore, use of the fluorochrome calcein AM cannot be recommended for functional testing of monocytes.
authors.affiliation: Department of Cardiology, Cardiovascular Research Institute Maastricht, University of Maastricht, P. Debyelaan 25, P.O. Box 5800, 6202 AZ Maastricht, Maastricht, The Netherlands.
authors.forename: Frauke S
authors.initials: FS
authors.lastname: Czepluch
authors.forename: Servé J F
authors.initials: SJ
authors.lastname: Olieslagers
authors.forename: Johannes
authors.initials: J
authors.lastname: Waltenberger
mesh_terms: D002448:Cell Adhesion / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D005452:Fluoresceins / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000494:pharmacology*; D006801:Humans; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D005452:Fluoresceins; D005456:Fluorescent Dyes; C007740:fluorexon