In vitro molecular magnetic resonance imaging detection and measurement of apoptosis using superparamagnetic iron oxide + antibody as ligands for nucleosomes.
Recent research in cell biology as well as oncology research has focused on apoptosis or programmed cell death as a means of quantifying the induced effects of treatment. A hallmark of late-stage apoptosis is nuclear fragmentation in which DNA is degraded to release nucleosomes with their associated histones. In this work, a method was developed for detecting and measuring nucleosome concentration in vitro with magnetic resonance imaging (MRI). The indirect procedure used a commercially available secondary antibody-superparamagnetic iron oxide (SPIO) particle complex as a contrast agent that bound to primary antibodies against nucleosomal histones H4, H2A and H2B. Using a multiple-echo spin-echo sequence on a 1.5 T clinical MRI scanner, significant T₂ relaxation enhancement as a function of in vitro nucleosomal concentration was measured. In addition, clustering or aggregation of the contrast agent was demonstrated with its associated enhancement in T₂ effects. The T₂ clustering enhancement showed a complex dependence on relative concentrations of nucleosomes, primary antibody and secondary antibody + SPIO. The technique supports the feasibility of using MRI measurements of nucleosome concentration in blood as a diagnostic, prognostic and predictive tool in the management of cancer.
Thunder Bay Regional Health Sciences Centre, Thunder Bay, Ontario P7B 6V4, Canada. rapleyp@tbh.net
P L
PL
Rapley
C
C
Witiw
K
K
Rich
S
S
Niccoli
M L
ML
Tassotto
J
J
Th'ng
D000906:Antibodies / Q000276:immunology*; D017209:Apoptosis; D001775:Blood Circulation; D005240:Feasibility Studies; D005290:Ferric Compounds / Q000737:chemistry* / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D008024:Ligands; D008279:Magnetic Resonance Imaging / Q000379:methods*; D059346:Magnets / Q000737:chemistry*; D008863:Microspheres; D009707:Nucleosomes / Q000378:metabolism*; D011379:Prognosis; D015203:Reproducibility of Results
D000906:Antibodies; D005290:Ferric Compounds; D008024:Ligands; D009707:Nucleosomes; C000499:ferric oxide