Enhancing microbial diversity as well as multi-organ health in hind-limb unloaded mice

During space travel, the gut microbiota is changed which can lead to health-related issues. Previously, we utilized the hind-limb unloaded (HU) mouse, which is an established ground-based in-vivo model of microgravity and observed altered gut microbiota. In this study, we evaluated the beneficial effects of novel bacterial conditioned media in HU mice to understand if they can offset the effects of unloading in the HU mouse model. We aimed to explore the influence of bacterial conditioned media on diversity and quantity of intestinal microbes in HU mice, and investigated the microarchitecture of mice retinas and kidneys to evaluate the potential systemic effects of bacterial conditioned media in HU mice. Four-month-old, male C57/Bl6 mice were separated into groups: including the ground-based control group, the HU group mice fed with vehicle as placebo (HU-placebo mice), and the HU group fed with bacterial conditioned media (HU-CP mice) and kept under controlled environmental conditions for three weeks. Next, mice were sacrificed; gut dissections were conducted, and metagenomic analysis of bacterial species was performed via DNA extraction and 16S rRNA analysis. The results revealed an HU-induced reduction in intestinal microbial diversity, and an increase in pathogenic bacteria dominated by Firmicutes (45%). In contrast, supplementation with bacterial conditioned media for three weeks led to a significant increase in gut microbial diversity with noticeable changes in the OTUs abundance in the HU mice. Additionally, HU-induced muscle weakness and structural abnormalities in the retina and kidney were partially prevented with bacterial conditioned media. Moreover, a greater diversity of several bacteria in the HU-CP was observed including, Bacteriodota, Firmicutes, Proteobacteria, Actionobacteriota, Verrucomicorbiota, Cyanobacteria, Gemmatimonadota, Acidobacteriota, Chloroflexi, Myxococcota, and others. Prospective research involving molecular mechanistic studies are needed to comprehend the systemic effects of bacterial metabolites conditioned media on experimental animal models under chronic stress.