Research
This laboratory develops and explores Magnetic Resonance (MR) visible nanoparticle to tag intracellular gene transcription activator proteins and gene transcripts for non-invasive MR imaging. Molecular biological assays have advanced our understanding of human neurological disorders but are not performed in human brains, except in late tumor cases. With the recent translation of stem cell therapy for neurological degenerative diseases, bone marrow regenerative cells can be recruited to repair brain damage. However, biopsy sampling defeats the benefits of stem cell therapy.
We are currently using two rodent models to validate our work before applications in humans.
Effect of Amphetamine abuse: Drug addiction is a major health problem that severely hampers the productivity of many members of society. While research indicates that drug addiction results from the combined influence of genes and environment, recent studies suggest that epigenetic modifications of gene transcription factors may play an important role in the development of addiction in humans.
Angiogenesis during Brain Repair: Approximately 250,000 Americans die each year as a result of cardiac arrest. Fewer than 10% of those who suffer cardiac arrest survive more than 6 months, and those who do survive can develop residual neurological deficits. Several mesenchymal- and hematopoietic-lineage cells have been used to validate localized angiogenesis; these cell types include neuronal, glial, and endothelial biomarkers such as proteins RNA and DNA (Fig 1). However, such regenerative cells have only been detected by unique antibodies in biopsy or postmortem samples, and these do not benefit the regeneration purposes of stem cells. The challenge is to adapt these top-notch molecular assays to in vivo conditions for future clinical application.
Currently, MRI and positron emission tomography are the only non-invasive tools available for identifying the location of damaged brain tissue and the important process of tissue repair, including therapy using stem cells and the formation of cerebral neo-vascularization (angiogenesis). We have developed a nanotechnology to detect molecular events in the living brain. We have now demonstrated a noninvasive technique to detect Nestin mRNA in endogenous bone marrow regenerative stem cells, by delivering dual targeting agents to the same mice (Fig 2). We detected a repair patch of new blood vessels after cerebral ischemia in mice, achieving a resolution of 0.06 mm3 using an MR contrast agent of 5-30 nm (dia) to identify angiogenesis. Such multipotent regenerative cells can be differentiated as either new pericytes in microvessels, or muscle cells in larger vessels.
The bases of nanotechnology for gene tagging in the living rodent brain for mechanistic research imaging are illustrated in Fig 3. There are three unique components in the specially made MR contrast agent (panel A): a carrier (phosphorothioate-modified micro DNA, or sODN) for endocytosis (Beltinger et al., 1995), a DNA sequence for tagging mRNA of interest by hybridization in specific cells, and a contrast agent cargo compound (MR-visible contrast agents) for MRI. These are unconventional and exceptionally innovative in their application: (1) to utilize a short DNA to carry large SPION (~30 nm in diameter) into cells in the living brain with a stable NA and biotin linkage to survive in body fluids; (2) to validate specific cell tagging by TEM and (3) compare sensitivity with RT-PCR or TaqMan analysis; (4) to image mRNA activities with an optimal concentration of MR contrast agent in a cell for imaging using a high field strength (9.4Tesla) MR system with (5) a low dose of sODN (3 pmol per mouse), effecting specific binding according to Watson and Crick base-pairing without a measurable gene knockdown effect, and (6) clearing out from the cell within a few hours so longitudinal and repeating MRI is possible. This nanotechnology has future application in clinical trials in the live brain to identify gene action and especially for cell mapping.
Projects
Imaging Markers of Damage and Repair Processes after Cerebral Ischemia
Imaging Drug Addiction Markers in Brains
Progress Report (2011)
Christina H. Liu, Jia Q Ren, Zerong You,Jinsheng Yang, Charngming Liu, Ratika Uppal, and Philip K. Liu. Neural Progenitor Identification in Living Brains by Dual Gene Transcript-Targeted MRI; the FASEB Journal, 11/27/2011.
Liu, PK, and Christina H. Liu. Gene Targeting MRI: Nucleic Acid-Based Imaging and Applications (Ch. 18). (Michel Modo & Jeff W.M. Bulte, eds), Springer Science+Business Media. 2011
Shizuka Minamishima, Kotaro Kida, Patrick Y. Sips, Huifang Wang, Kentaro Tokuda, Shizuko Kosug, Joseph B. Mandeville, Emmanuel S. Buys, Peter Brouckaert, Philip K. Liu, Kenneth D. Bloch, Fumito Ichinose. Inhaled Nitric Oxide Improves Long-term Outcome After Successful Cardiopulmonary Resuscitation in Mice. Circulation, 124(15), 1645-53, 2011. PMCID 3199136.
Renhua Wu, Charng-Ming Liu, Philip K Liu, and Phillip Zhe Sun. Improved measurement of labile proton concentration-weighted chemical exchange rate (kws) with experimental factor-compensated and T1-normalized quantitative chemical exchange saturation transfer (CEST) MRI, Contrast Media and Molecular Imaging, accepted Dec, 27. 2011.
Ongoing Research Support
1R01DA026108-03 (PI: PK Liu)
06/15/2009-05/30/2012 (NCE)
Title: In vivo Profiling of Glial and Neuronal Activities in Psychostimulant Abuse. We will detect altered gene expression in neurons and glia of live animal affected by addictive drugs, using a novel Magnetic Resonance Imaging (MRI) technique that we have developed.
1R01DA029889-01 (PI: PK Liu)
07/01/2010–06/30/2014
Title: Aptamer Imaging: A Theranostic Strategy for Substance Abuse, (Exceptional, Unconventional Research Enabling Knowledge Acceleration or EUREKA Award). This proposed project aims to tag intracellular activator protein of the live animal brain for non-invasive MRI
1R01EB013768-01A1 (PI: PK Liu)
07/01/2011-06/30/2015
Title: DNA-Based MR Probes for Imaging mRNA Transcripts in vivo. We will study and compare mRNA targeted by phosphorothioate-modified DNA- and RNA-based contrast agents to improve the utility of ggene transcript-targeted MRI.
Am Heart Association 09GRNT2060416 (PI: PKLiu)
07/01/2009 – 06/30/2012
Title: In vivo MR Assessment of altered gene Expression after transitent global cerebral ischemia.
Completed (most current , four of ten)
NIH R21DA024235 (PI: Philip K Liu)
09/01/2007-08/31/2010
Title: MR Assessment of Altered Gene Expression after Amphetamine Exposure
NIH R21NS057556 (PI: Philip K. Liu)
06/16/2007-05/30/2010
Title: Neurovascular Mechanisms of Brain Function and Diseases
NIH R01NS045845 (PI: Philip K. Liu)
05/01/2003-06/30/2009
Title: Gene Repair in Signal Transduction after CNS Injury
NIH R01NS034810 (PI: Philip K. Liu)
09/01/1996-8/31/2001
Title: Hydroxyl Radical Biology by Cerebral Ischemia
