Quantifying cell division with deuterated water and multi-isotope imaging mass spectrometry (MIMS)

Cell division is commonly quantified by the administration of nucleotide labels that are incorporated by the nucleotide salvage pathway. A new approach uses precursors of the de novo nucleotide synthesis pathway, such as labeled water or glucose. Because such precursors are not specific for DNA synthesis, studies utilizing this approach have analyzed isolated genomic DNA to exclude nonspecific background labeling. We hypothesized that pulse-chase administration of stable isotope labeled water would result in sufficient nuclear labeling to enable discrimination of recently divided cells by quantitative ion microscopy. We administered deuterated (D)-water and ¹⁵N-thymidine to mice concurrently, guided by the rationale that ¹⁵N-thymidine incorporation would serve as a "gold standard" to identify dividing cells. We show both qualitatively and quantitatively that dividing cells in the small intestine (¹⁵N-labeled) demonstrate a discernable D-signal in the nucleus not observed in undivided cells (¹⁵N-unlabled). Correlation with ³¹P^- and ¹²C¹⁵N^-:¹²C¹⁴N^- images demonstrate preferential localization of ²H labeling in regions of the nucleus with high DNA content as expected of labeling being incorporated during DNA synthesis and cell division. These data support the concept that stable isotope tagged precursors of the de novo nucleotide synthesis pathway can be used in concert with NanoSIMS to study cell division in vivo. A major implication of this study then is the possibility of using stable isotope tagged water and MIMS to study human cell turnover.