Augmented murine hematopoietic stem and progenitor cell reconstruction through conventional co-housing

Background and methods: The effects of microbiota toward hematopoietic stem and progenitor cells (HSPCs) were very much complicated based on previous reports. In the current study, normal inbred C57BL6 (B6) mice from the Jackson Laboratory were maintained in the SPF environment for three weeks. Baseline complete blood counts were normal, and animals were then separated into two groups: 1) SPF mice stayed in the SPF facility, and 2) SPF mice being transferred to a conventional facility for co-housing (CVT). At one month of co-housing, we bled and euthanized animals, sorted lineage-CD117+ cells from bone marrow of SPF and CVT mice respectively, and performed single cell RNA sequencing on sorted hematopoietic stem and progenitor cells using 10XGenomics Chromium Single Cell 3' Solution and sequenced with Illumina HiSeq 3000 Systems. Results: We characterized heterogeneity of HSPCs, defined differential gene expression and performed pathway analysis. Proportion of LTHSC was lower and the proportion of GMP was higher from CVT mice than those from SPF mice. Pathway analyses of differentially-expressed genes in HSPCs we found down-regulation of genes related to immune responses and cell proliferation and activation, and up-regulation of genes associated with cellular metabolism, including protein, ribosome, and energy metabolic processes, in cells from CVT mice. Conclusion: Observations from our study demonstrated a positive effect in co-housed CVT mice that promotes HSPC reconstitution through modulation of molecular elements involving multiple signaling pathways. mRNA profiles of single bone marrow hematopoietic stem and progenitor cells of ten B6 mice maintained in a SPF facility and ten B6 mice maintained in conventioanl facility were generated by deep sequencing using quencing using Illumina HiSeq 3000 FACS sorted bone marrow hematopoietic stem and progenitor cells from ten mice maintained in SPF facility were pooled into four samples, and sorted cells from ten mice maintained in conventional facility for one month were pooled into four samples.