Non-invasive characterization of human bone marrow by cell free messenger-RNA reveals response to growth factor stimulation and hematopoietic reconstitution after transplantation

Circulating cell free mRNA (cf-mRNA) holds great promise as a non-invasive diagnostic biomarker.However, the biological origin of cf-mRNA is still not well understood, limiting the clinicalapplications of this technology. Here, we use the bone marrow (BM) and pharmacologicmanipulation of its resident cells as a window to study the origin of cf-mRNA. Using NGS-basedprofiling, we show that cf-mRNA is enriched in transcripts derived from the BM compared tocirculating cells. Further, BM ablation experiments followed by hematopoietic stem celltransplants in cancer patients show that cf-mRNA levels reflect the transcriptional activity of BMresident hematopoietic lineages during marrow reconstitution. Finally, by stimulating specific BMcell populations in vivo using growth factor therapeutics (i.e. EPO, G-CSF), we show that cf-mRNAreveals dynamic functional changes in growing cell types, suggesting that, unlike other cell-freenucleic acids, cf-mRNA is secreted from living cells, rather than exclusively from apoptotic cells.Our results shed new light on the biology of cf-mRNA and demonstrate its potential applicationsin clinical practice.