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In vivo 1 H MRS and 31 P MRSI of the response to cyclocreatine in transgenic mouse liver expressing creatine kinase
Author(s) -
Cui MinHui,
Jayalakshmi Kamaiah,
Liu Laibin,
Guha Chandan,
Branch Craig A.
Publication year - 2015
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3391
Subject(s) - phosphocreatine , in vivo , hepatocyte , creatine kinase , creatine , transplantation , medicine , genetically modified mouse , phosphomonoesters , chemistry , liver transplantation , endocrinology , biochemistry , biology , microbiology and biotechnology , transgene , in vitro , energy metabolism , gene
Hepatocyte transplantation has been explored as a therapeutic alternative to liver transplantation, but a means to monitor the success of the procedure is lacking. Published findings support the use of in vivo 31 P MRSI of creatine kinase (CK)‐expressing hepatocytes to monitor proliferation of implanted hepatocytes. Phosphocreatine tissue level depends upon creatine (Cr) input to the CK enzyme reaction, but Cr measurement by 1 H MRS suffers from low signal‐to‐noise ratio (SNR). We examine the possibility of using the Cr analog cyclocreatine (CCr, a substrate for CK), which is quickly phosphorylated to phosphocyclocreatine (PCCr), as a higher SNR alternative to Cr. 1 H MRS and 31 P MRSI were employed to measure the effect of incremental supplementation of CCr upon PCCr, γ‐ATP, pH and P i /ATP in the liver of transgenic mice expressing the BB isoform of CK (CK BB ) in hepatocytes. Water supplementation with 0.1% CCr led to a peak total PCCr level of 17.15 ± 1.07 mmol/kg wet weight by 6 weeks, while adding 1.0% CCr led to a stable PCCr liver level of 18.12 ± 3.91 mmol/kg by the fourth day of feeding. PCCr was positively correlated with CCr, and ATP concentration and pH declined with increasing PCCr. Feeding with 1% CCr in water induced an apparent saturated level of PCCr, suggesting that CCr quantization may not be necessary for quantifying expression of CK in mice. These findings support the possibility of using 31 P MRS to noninvasively monitor hepatocyte transplant success with CK‐expressing hepatocytes. Copyright © 2015 John Wiley & Sons, Ltd.