# Behavior of Astrocytes Derived from Human Neural Stem Cells Flown onto Space and Their Progenies
## 4 Discussion
While with the data analyzed so far, we cannot assert that there is an increased division of these cells in comparison to1G NSCs derived astrocytes, we found preliminary evidence that SPC-flown NSCs generate younger-like astrocytes and radial-glial cells evocative of neural development where radial glial cells are an abundant progenitor population in particular for cortical expansion. [26; 27]. Our analysis will continue when the pandemic allows us to go back to the laboratory to complete this ongoing study. Nonetheless, one could hypothesize that these glial cells may play a role in the intracranial hypertension, or pressure inside the skull, that has been observed during human spaceflight. On one hand, our data confirmed the moderate contribution that one could expect from astrocytes generating new astrocytes in non-injury conditions. On the other hand, four questions come to mind: (1) Are astrocytes in the brain of astronauts increasing in number, even if slowly, and therefore contributing to intracranial hypertension? (2) Are space flown NSCs giving rise to radial-glia in addition to astrocytes? (3) Are space-flown-NSCs transmitting their proliferative potential to cells that are specified to the astrocyte phenotype in 1G? And (4) are these newly specified astrocytes in a state of \"inherited stress\" resulting from the space flight, or the return of their mother NSCs re-entry and splash down? Currently, we do not have answers to these important questions. A subsequent space flight would be necessary to generate enough material to pursue studies aimed at answering them. Moreover, studies in samples containing other cell types, such as organotypic cultures or animal work where the entire CNS experiences space microgravity are of the essence to understand if the regulation of proliferation in space differs when cells are in homogeneous cultures as opposed to the entire brain. The following are available online at [[https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)]([https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)) 7/11/41/s1, Figure S1: Comparison of the morphological features and general aspect of astrocytes derive from naive-1G NSCs vs. astrocytes derive from SPC-flown NSCs 50 days after being in DF-10% FCS. (A) Astrocytes derived from hiPS-NSCs grown solely in 1G display their typical flat morphology. (B) Astrocytes derived from hiPS-derived NSCs flow into space displayed a less flat morphology, presented elongated cell processes, and some preserved the bipolar elongated radial glia-like morphology frequently observed during CNS development (inset). Bar = 50 \(\upmu\)m). S.S., N.C. and V.T., performed extensive image analysis of time-lapse files, consolidated the data for graphs and statistics, contributed to manuscript preparation; [PERSON] designed the entire study, chose the hardware, performed experimental verification tests, as well as the work at Kennedy Space Center for flight integration. She harvested all cells from the space hardware upon their return to Earth and performed image acquisition of live cells and thereafter performed immunocyt, analysis of the data and prepared the manuscript. All authors have read and agreed to the published version of the manuscript. We thank NASA Space Biology for Grant: NNX15 AB43G; The IDDRC Cell Culture Core is supported by NIH/NICHD grant number U54 HD087101-05. The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials  
We are grateful to [PERSON] and the entire Zeiss team for their support with the microscopy needs for this study, without their support this study would not have been possible. We also thank [PERSON] for support with her microscope system as well. [PERSON]. [PERSON], and [PERSON] for their help with the implementation of the study. The NASA Space Biology Project team at Ames Research Center [PERSON], [PERSON], [PERSON], ARC Space BiologyProject Manager and the support personnel at the Space Station Processing Facility at Kennedy Space Center.