title: A molecular MRI probe to detect treatment of cardiac apoptosis in vivo.
abstract: Cell death by apoptosis is critical in myocardial diseases, and noninvasive detection of early, reversible apoptosis might be useful clinically. Exogenous Annexin-V (ANX) protein binds membrane phosphatidylserine, which is externalized in early apoptosis. A molecular MRI probe was constructed with superparamagnetic iron oxide (SPIO) conjugated to recombinant human ANX (ANX-SPIO). Apoptosis was induced with doxorubicin, a cardiotoxic cancer drug, in culture in neonatal rat ventricular myocytes, cardiac fibroblasts, and mesenchymal stem cells, and in vivo in the mouse heart. ANX-SPIO was validated using T2*-weighted 3T MRI. ANX-SPIO produced T2* signal loss, reflecting iron content, that correlated highly with independent apoptosis markers; bound with high affinity to apoptotic myocytes by competition assay (Ki 69 nM); detected apoptosis in culture much earlier than did TUNEL stain; and revealed fibroblast resistance to apoptosis. With apoptosis in vivo, ANX-SPIO produced diffuse myocardial T2* signal loss that correlated with increased iron stain and caspase activity. Treatment with an alpha-1-adrenergic agonist in vivo reversed apoptosis and eliminated the ANX-SPIO MRI signal. It is concluded that cardiac MRI of ANX-SPIO detects early, nonischemic cardiac apoptosis in culture and in vivo, and can identify reversibly injured cardiac cells in diseased hearts, when treatment is still possible.
authors.affiliation: Cardiology Section and Research Service, San Francisco VA Medical Center, San Francisco, California 94121, USA.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Dash
authors.forename: Jaehoon
authors.initials: J
authors.lastname: Chung
authors.forename: Trevor
authors.initials: T
authors.lastname: Chan
authors.forename: Mayumi
authors.initials: M
authors.lastname: Yamada
authors.forename: Joëlle
authors.initials: J
authors.lastname: Barral
authors.forename: Dwight
authors.initials: D
authors.lastname: Nishimura
authors.forename: Phillip C
authors.initials: PC
authors.lastname: Yang
authors.forename: Paul C
authors.initials: PC
authors.lastname: Simpson
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D017304:Annexin A5 / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D003287:Contrast Media / Q000737:chemistry / Q000494:pharmacology; D003911:Dextrans / Q000737:chemistry / Q000494:pharmacology; D004317:Doxorubicin / Q000633:toxicity; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D020287:In Situ Nick-End Labeling; D016014:Linear Models; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D058185:Magnetite Nanoparticles / Q000737:chemistry; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects; D051379:Mice; D009206:Myocardium / Q000166:cytology / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects; D019047:Phantoms, Imaging; D051381:Rats
chemical_list: D000316:Adrenergic alpha-Agonists; D017304:Annexin A5; D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D004317:Doxorubicin; D020169:Caspases; C065507:ferumoxides