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Abstract
AimThe aim of this work was the development of successful cell therapy techniques for cartilage engineering. This will depend on the ability to monitor non-invasively transplanted cells, especially mesenchymal stem cells (MSCs) that are promising candidates to regenerate damaged tissues.MethodsMSCs were labeled with superparamagnetic iron oxide particles (SPIO). We examined the effects of long-term labeling, possible toxicological consequences and the possible influence of progressive concentrations of SPIO on chondrogenic differentiation capacity.ResultsNo influence of various SPIO concentrations was noted on human bone marow MSC viability or proliferation. We demonstrated long-term (4 weeks) in vitro retention of SPIO by human bone marrow MSCs seeded in collagenic sponges under TGF-β1 chondrogenic conditions, detectable by Magnetic Resonance Imaging (MRI) and histology. Chondrogenic differentiation was demonstrated by molecular and histological analysis of labeled and unlabeled cells. Chondrogenic gene expression (COL2A2, ACAN, SOX9, COL10, COMP) was significantly altered in a dose-dependent manner in labeled cells, as were GAG and type II collagen staining. As expected, SPIO induced a dramatic decrease of MRI T2 values of sponges at 7T and 3T, even at low concentrations.ConclusionsThis study clearly demonstrates (1) long-term in vitro MSC traceability using SPIO and MRI and (2) a deleterious dose-dependence of SPIO on TGF-β1 driven chondrogenesis in collagen sponges. Low concentrations (12.5–25 µg Fe/mL) seem the best compromise to optimize both chondrogenesis and MRI labeling.
Highlights
Because of their differentiation potentialities, mesenchymal stem cells (MSCs) provide a promising avenue to regenerate damaged tissues in articular diseases
MSC labeling was initiated by the addition of medium that contained superparamagnetic iron oxide (SPIO) (Endorem, Guerbet S.A., Paris, France) and Poly-L-Lysine mixture (375 ng/mL, PLL Mw: 70,000–150,000, Sigma) and incubation was at 37uC/5% CO2 for 24 hours
After 24 hours of exposure to SPIO, NO production significantly increased to the highest concentrations of 400 to 1600 mg Fe/ml with or without PLL (9 to 12 fold without PLL and about 4 to 7 fold with PLL higher compared to 0 mg Fe/ ml, p,0.05)
Summary
Because of their differentiation potentialities, mesenchymal stem cells (MSCs) provide a promising avenue to regenerate damaged tissues in articular diseases. To assess the effects of MSC implantation, a non-invasive imaging technique was developed [3]. This allowed analysis of the bio-integration and biofunctionality of the engineered tissues and tracking of the labeled MSCs within the joint. Several studies have addressed the topic of visualization and tracking of non-invasively transplanted cells by the use of MRI with superparamagnetic iron oxide (SPIO) particles as a contrast agent [5,6,7,8]. A transfection agent (TA) such as poly-L-Lysine (PLL), which enhances cell adhesion to the surface of a culture dish during in vitro cell cultivation, could be used as a vehicle for iron particle transport into cells. PLL does not lead to cytotoxity as has been demonstrated by numerous studies [12,13]
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