Impact of the Mk VI SkinSuit on skin microbiota of terrestrial volunteers and an International Space Station-bound astronaut.

Microgravity induces physiological deconditioning due to the absence of gravity loading, resulting in bone mineral density loss, atrophy of lower limb skeletal and postural muscles, and lengthening of the spine. SkinSuit is a lightweight compression suit designed to provide head-to-foot (axial) loading to counteract spinal elongation during spaceflight. As synthetic garments may impact negatively on the skin microbiome, we used 16S ribosomal RNA (rRNA) gene amplicon procedures to define bacterial skin communities at sebaceous and moist body sites of five healthy male volunteers undergoing SkinSuit evaluation. Each volunteer displayed a diverse, distinct bacterial population at each skin site. Short (8 h) periods of dry hyper-buoyancy flotation wearing either gym kit or SkinSuit elicited changes in the composition of the skin microbiota at the genus level but had little or no impact on community structure at the phylum level or the richness and diversity of the bacterial population. We also determined the composition of the skin microbiota of an astronaut during pre-flight training, during an 8-day visit to the International Space Station involving two 6-7 h periods of SkinSuit wear, and for 1 month after return. Changes in composition of bacterial skin communities at five body sites were strongly linked to changes in geographical location. A distinct ISS bacterial microbiota signature was found which reversed to a pre-flight profile on return. No changes in microbiome complexity or diversity were noted, with little evidence for colonisation by potentially pathogenic bacteria; we conclude that short periods of SkinSuit wear induce changes to the composition of the skin microbiota but these are unlikely to compromise the healthy skin microbiome.

Vybrant DyeCycle Violet Stain Discriminates Two Different Subsets of CD34+ Cells.

INTRODUCTION: Studies are needed to understand the role of CD34 expressing cells with regard to efficient engraftment, especially in the adjuvant treatment of cancer. MATERIALS AND METHODS: In this study we have used a modified method in our laboratory for routinely counting CD34+ cells. Unlysed whole blood samples were stained with the DNA-selective and cell membrane-permeant Vibrant DyeCycle Violet stain. RESULTS: CD34+ cells exhibit a consistent and differential Vybrant Dye Cycle Violet staining pattern. Based on their different DCV intensity, we classified these subpopulations as CD34+/DCV(high) and CD34+/DCV(low) cells. In general, DCV(high) cells are about 12-times brighter than DCV(low) cells. CONCLUSION: DCV staining may be used to discriminate subsets of CD34+ cells similarly to other methods which have previously defined different functional properties that can be related to the characterization, resolution, and purification of primitive hematopoietic stem cells in combination with specific useful markers for multicolor flow cytometric measurements.