Abstract
BackgroundCirculating white blood cells crucially contribute to maintenance and repair of solid organs. Therefore, certain cell populations such as monocytes are attractive targets for use in molecular imaging and cell imaging, e.g. after labelling with radionuclides, as well as for cell therapies. However, the preparation of monocytes may require freezing and thawing to preserve cells for timely and standardised applications. Additional modifications of these cells such as radioisotope labelling are necessary prior to their application in vivo. We therefore tested the hypothesis whether cryopreservation of freshly isolated circulating human monocytes affects their functional phenotype or their suitability for radionuclide labelling.ResultsCD14+CD16− monocytes were isolated from human peripheral blood. They were either directly used for cellular assays and labelling or frozen down using cryoprotectants. In the latter case, cells were thawed prior to further use and analysed for survival, chemotactic responses to various growth factors and adhesion on endothelial cells. In addition, both fresh and cryopreserved monocytes were labelled with radiotracers followed by assessment of survival and chemotactic responses. In all functional assays performed, cryopreserved monocytes did not significantly differ from freshly isolated monocytes with regard to their functionality. Cryopreservation did not affect cell survival. There was no effect on the chemotactic response of monocytes towards different growth factors. Likewise, adhesion properties remained unchanged following cryopreservation. Moreover, the labelling efficiency was similar for freshly isolated and cryopreserved monocytes. Labelling did not negatively affect monocyte survival and function.ConclusionsOur data indicate that cryopreservation of freshly isolated human primary monocytes is feasible and does not negatively affect their functionality when used for labelling and functional assessment.
Highlights
Circulating white blood cells crucially contribute to maintenance and repair of solid organs
Effects of cryopreservation on mononuclear cell viability First, we characterised the effects of cryopreservation on the recovery of cryopreserved CD14++CD16− monocytes
Considering that the cryopreserved cells will be labelled and administrated immediately after thawing for live cell imaging shortly after injection into the recipient, Cryopreservation does not affect monocyte adherence to endothelial cells An important aspect of monocyte function is their adherence to the endothelium, which in turn is the initial step of monocyte recruitment to inflammatory sites, followed by transmigration through the endothelium
Summary
Circulating white blood cells crucially contribute to maintenance and repair of solid organs. The preparation of monocytes may require freezing and thawing to preserve cells for timely and standardised applications. Additional modifications of these cells such as radioisotope labelling are necessary prior to their application in vivo. Monocytes play an important role in inflammation and in host defence as they participate in both innate and adaptive immune responses. They are circulating mononuclear phagocyte-like cells which are derived from a common myeloid precursor in the bone marrow [1]. Monocytes can further differentiate irreversibly into tissue macrophages and/or dendritic cells following stimulation by different factors or induced by inflammation [4, 6]
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