Heavy Water Labeling of Keratin as a Non-Invasive Biomarker of Skin Turnover In Vivo in Rodents and Humans

Abstract

Measurement of skin turnover has been problematic in humans. Heavy water (2H2O) labeling has recently been developed as a safe, simple method to study in vivo kinetics of many biosynthetic processes, including DNA and protein synthesis. Here, we apply this approach to the measurement of 2H incorporation into skin keratin and show close agreement between keratin and keratinocyte turnover data in the epidermis of rodents. Elevated turnover rates of both keratin and keratinocytes were observed in the epidermis of the flaky skin mouse, although topical treatments effective in human psoriasis had no effect on either turnover rate in these mice. In humans, keratin turnover was monitored non-invasively by serial tape stripping during and after 2H2O labeling. Kinetic data were consistent with previous estimates of epidermal turnover, with a lag time of 18 days before label appeared at the skin surface and a transit time of 4-5 weeks. Variability in skin keratin turnover rates was present among healthy individuals. In summary, 2H2O labeling of skin keratin represents a non-invasive approach for assessing skin turnover dynamics in pre-clinical models and in human subjects.

Regional Cell Proliferation in Microdissected Human Prostate Specimens after Heavy Water Labeling In Vivo: Correlation with Prostate Epithelial Cells Isolated from Seminal Fluid

“…2A, illustrate good compliance with the dosing regimen. The approximately 1% to 2% 2 H 2 O enrichments achieved over the labeling period are consistent with previous studies using similar labeling protocols (17)(18)(19)(20). Blood was collected at week 3 of the study for confirmation of heavy water labeling from enrichments in monocyte DNA, a fully turned over cell population (data not shown), whereas sera was used for determination of PSA levels, which were normal (<2 ng/mL) in all the subjects (Table 1).…”

“…The heavy water-labeling approach has proven to be highly informative for characterizing phenotype in other neoplastic or hyperproliferative conditions, including chronic lymphocytic leukemia (CLL; ref. 17), psoriasis (18), and HIV-1 infection (19,20).…”

Metabolic Labeling Reveals Proteome Dynamics of Mouse Mitochondria

“…Isotope tracers are particularly useful for tracking such continual renewal of the proteome in living systems, because they allow differentiation between preexisting and newly synthesized proteins (5 (11)(12)(13)(14) and peptide analysis in MALDI-TOF MS (15) and LC-MS (16,17). More recently, Price et al described an approach for measuring protein turnover by calculating the theoretical number of 2 H-labeling sites on a peptide sequence (18) and reported the turnover rates of ϳ100 human plasma proteins.…”

Biological Boundaries and Biological Age

“…The distribution of ages of death is concentrated on the [50,100] years interval, if we eliminate perinatal and accidental deaths before 50 years. Let us suppose that for human: -g(C) = 2% of the cells divide at the same time, this residual proliferation being compensated by apoptosis; this percentage is fixed by the turnover of tissue cells or of membranes components: the total cell renewal time is for example equal to 3 weeks for the skin (Lindwall et al 2006), 1.5 day for the intestine (Leblond and Stevens 1948), 4 months for the alveoli (Yanagi et al 2007) and 11 days for mitochondrial inner membrane (Griparic and van der Bliek 2001) in mice and is ruled by an allometric law in mammals (West and Brown 2005). -cells in division inhibit the exit from G 0 of the other cells (e.g.…”