PROTON NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY UNAMBIGUOUSLY IDENTIFIES DIFFERENT NEURAL CELL-TYPES

Proton nuclear magnetic resonance (H-1 NMR) spectroscopy is a noninvasive technique that can provide information on a wide range of metabolites. Marked abnormalities of H-1 NMR brain spectra have been reported in patients with neurological disorders, but their neurochemical implications may be difficult to appreciate because NMR data are obtained from heterogeneous tissue regions composed of several cell populations. The purpose of this study was to examine the H-1 NMR profile of major neural cell types. This information may be helpful in understanding the metabolic abnormalities detected by H-1 NMR spectroscopy. Extracts of cultured cerebellar granule neurons, cortical astrocytes, oligodendrocyte-type 2 astrocyte (O-2A) progenitor cells, oligodendrocytes, and meningeal cells were analyzed. The purity of the cultured cells was > 95% with all the cell lineages, except for neurons (approximately 90%). Although several constituents (creatine, choline-containing compounds, lactate, acetate, succinate, alanine, glutamate) were ubiquitously detectable with H-1 NMR, each cell type had distinctive qualitative and/or quantitative features. Our most unexpected finding was a large amount of N-acetyl-aspartate (NAA) in O-2A progenitors. This compound, consistently detected by H-1 NMR in vivo, was previously thought to ne present only in neurons. The finding that meningeal cells have an alanine:creatine ratio three to four times higher than astrocytes, neurons, or oligodendrocytes is in agreement with observations that meningiomas express a higher alanine:creatine ratio than gliomas. The data suggest that each individual cell type has a characteristic metabolic pattern that can be discriminated by H-1 NMR, even by looking at only a few metabolites (e.g., NAA, glycine, beta-hydroxybutyrate). Some of these features may be useful in interpreting H-1 NMR observations, for example,those of patients with brain tumors where there are marked changes in cell population, and in cases where selective neuronal loss or abnormal development can be expected.