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.