NASA Technical Reports Server (NTRS) 20170000835: Responses of Cardiac Tissue to Simulated Weightlessness

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by  NASA Technical Reports Server (NTRS)

Responses of cardiac tissue to simulated weightlessness
Candice Tahimic1,2, Sonette Steczina1,3, Masahiro Terada1, Yasaman Shirazi-Fard1,2, Ann-Sofie Schreurs1,4,
David Goukassian5, Ruth K. Globus1
1Space Biosciences Division, NASA Ames Research Center, 2Wyle Laboratories, 3Blue Marble Sciences, 4NASA Academic
Mission Services, 5Temple University
INTRODUCTION HYPOTHESES MILESTONES
Long duration simulated weightlessness and Validation of RNA extraction protocol and
Risk of adverse cardiovascular changes during and
subsequent recovery causes select and persistent assessment of RNA quality from frozen hearts
after spaceflight
changes in gene expression and oxidative defense- received to date (completed)
related pathways.
• Space travel causes both rapid and delayed effects
• RNA yield and concentration are optimal for all
on the cardiovascular system.
assays
EXPERIMENT PLAN
• Exposure to microgravity causes a cephalad shift of
• RNA quality is acceptable for RNAseq assays (RIN >
body fluids leading to increased heart stroke volume
9 as assessed by Bioanalyzer)
Groups and treatments
and a rise in left ventricular end diastolic dimensions.
• Fisher rats: Three month old (Young) males and
Fluid shifts can diminish the ability of the heart to cope
Validation of heart tissue quality for
females; nine month old (Aged) males
with gravitational stress immediately after returning to
immunohistochemisty applications (completed)
• Treatment: Hindlimb unloading (HU) for 7, 14, 21 and
earth, leading to orthostatic intolerance (syncope)
90 days with corresponding ambulatory (no HU)
• Sample quality is satisfactory for immunohistological
observed in some astronauts.
controls; or HU followed by re-ambulation via release
assessment of cardiomyocyte size and fibrosis
• Earth-based models of prolonged exposure to
from tail suspension (Recovery groups) with
microgravity (long-duration hindlimb unloading in
corresponding ambulatory controls (no HU)
Mason Trichrome Staining to
mice) causes cardiac enlargement, depressed
assess fibrosis in rat heart.
contractility, and increased susceptibility to
Pericardium (black arrow) and
Sample collection and processing
fibrotic structures stain blue.
arrhythmias.
• Hearts are being collected from an ongoing HHC
Nuclei appear as dark punctate
Tissue Sharing initiative
structures.
Spaceflight effects on oxidative stress-related genes • After euthanasia, hearts are bisected into ventral
in the heart (fixed) and dorsal (flash frozen) halves
Measurement of cardiomyocyte
• Collected samples are transported from UC Davis to
size in rat heart. White arrows
NASA Ames Research Center for further processing
show a single cardiomyocyte
with boundary delineated by
and analysis
immunoreactivity to anti-wheat
germ agglutinin (WGA). Blue
Assays
signals (DAPI stain) are from
• RNAseq and qPCR analysis for differential expression
nuclei.
of genes involved in cardiac disease, cardiac
UPCOMING ACTIVITIES
remodeling, stress responses, apoptosis,
inflammation, macrophage activity, cell cycle and
• Immunohistological assessment of cardiomyocyte
growth
size, macrophage infiltration and fibrosis
• Oxidative damage assays (8-hydroxyguanosine,
• RNAseq
malondialdehyde, nitro-tyrosine)
• Assessment of oxidative damage via measurement of
• Histology and immunohistochemistry to assess
Figure 1. Spaceflight induces expression or redox-
8-hydroxyguanosine immunoreactivity
macrophage infiltration, fibrosis and cardiomyocyte
related genes. Hearts from rodents flown in STS-131
ACKNOWLEDGEMENTS
size
were examined for expression of genes regulating redox
balance using a real time PCR array of 84 genes related
This work is supported by the NASA Human Research
Questions being addressed by this study
to oxidative metabolism. Of the 84 genes analyzed, 15
Program through the Human Health and
• Which cardiac changes occur at the molecular level in
genes were up-regulated and three were down-
Countermeasures (PI: R. Globus). M. Terada is
response to the fluid shifts, musculoskeletal disuse
regulated in flight samples (p<0.05).
supported by a Space Biology/NASA Space Biology
and the relative inactivity that occur during long
Postdoctoral Fellowship Award. We thank Dr. Chuck
duration weightlessness?
Fuller (UC Davis) and his team for providing rat heart
PURPOSE OF THE STUDY
• Are these changes reversible, and do the animal data
tissues. We are grateful to Drs. April Ronca, Laura
suggest a significant risk to astronaut health?
Lewis and Sungshin Choi and the rest of the dissection
Determine the time course and persistence of simulated
• Are females as vulnerable as males to the adverse
team for facilitating sample collection at UC Davis. We
weightlessness-induced changes in the heart, as well as
effects of long duration weightlessness?
thank Samantha Torres and Sheenah Bryant for their
the contributions of sex and age to the observed
• Does age affect the ability of cardiac tissue to adapt to
assistance in experiments.
responses.
and recover from long duration weightlessness?