The mice in our study were exposed to microgravity for twice as long but since the samples were not fluorochrome-labelled, we cannot confirm whether bone resorption is compromised.
To investigate bone resorption, you could have used TRAP stainning? In femoral metaphysis, resorption is highly increased as previously observed in Gerbaix et al. Sci Rep. 2017 as well as Osterix stainning to investigate osteoblasts number.
Furthermore, fluorochrome-labelled could have help you to investigate bone formation rate but not resorption.
Additional gene expression, proteomic and epigenetic studies of in vivo flight samples are required for a more complete understanding of the major players involved in the altered response of BM-MSCs to microgravity.
To the reviewer point of view, a recent proteomic study investigating BionM1 femur marrow and bone should be considered here :
Analysis of femurs from mice embarked on board BION-M1 biosatellite reveals a decrease in immune cell development, including B cells, after 1 wk of recovery on Earth. Tascher G, Gerbaix M, Maes P, Chazarin B, Ghislin S, Antropova E, Vassilieva G, Ouzren-Zarhloul N, Gauquelin-Koch G, Vico L, Frippiat JP, Bertile F. FASEB J. 2019 Mar;33(3):3772-3783. doi: 10.1096/fj.201801463R. Epub 2018 Dec 6.