Background: Primary sclerosing cholangitis (PSC) is a rare chronic cholestatic liver disease characterized by multifocal bile duct strictures. To date, underlying molecular mechanisms of PSC remain unclear, and therapeutic options are limited. Methods: We performed cell-free messenger RNA (cf-mRNA) sequencing to characterize the circulating transcriptome of PSC and noninvasively investigate potentially bioactive signals that are associated with PSC. Serum cf-mRNA profiles were compared among 50 individuals with PSC, 20 healthy controls, and 235 individuals with NAFLD. Tissue and cell type-of-origin genes that are dysregulated in subjects with PSC were evaluated. Subsequently, diagnostic classifiers were developed using PSC dysregulated cf-mRNA genes. Results: Differential expression analysis of the cf-mRNA transcriptomes of PSC and healthy controls resulted in identification of 1407 dysregulated genes. Furthermore, differentially expressed genes between PSC and healthy controls or NAFLD shared common genes known to be involved in liver pathophysiology. In particular, genes from liver- and specific cell type-origin, including hepatocyte, HSCs, and KCs, were highly abundant in cf-mRNA of subjects with PSC. Gene cluster analysis revealed that liver-specific genes dysregulated in PSC form a distinct cluster, which corresponded to a subset of the PSC subject population. Finally, we developed a cf-mRNA diagnostic classifier using liver-specific genes that discriminated PSC from healthy control subjects using gene transcripts of liver origin. Conclusions: Blood-based whole-transcriptome cf-mRNA profiling revealed high abundance of liver-specific genes in sera of subjects with PSC, which may be used to diagnose patients with PSC. We identified several unique cf-mRNA profiles of subjects with PSC. These findings may also have utility for noninvasive molecular stratification of subjects with PSC for pharmacotherapy safety and response studies.

BackgroundInflammatory and immune responses are essential and dynamic biological processes that protect the body against acute and chronic adverse stimuli. While conventional protein markers have been used to evaluate systemic inflammatory response, the immunological response to stimulation is complex and involves modulation of a large set of genes and interacting signalling pathways of innate and adaptive immune systems. There is a need for a non-invasive tool that can comprehensively evaluate and monitor molecular dysregulations associated with inflammatory and immune responses in circulation and in inaccessible solid organs.MethodsHere we utilized cell-free messenger RNA (cf-mRNA) RNA-Seq whole transcriptome profiling and computational biology to temporally assess lipopolysaccharide (LPS) induced and JAK inhibitor modulated inflammatory and immune responses in mouse plasma samples.FindingsCf-mRNA profiling displayed a pattern of systemic immune responses elicited by LPS and dysregulation of associated pathways. Moreover, attenuation of several inflammatory pathways, including STAT and interferon pathways, were observed following the treatment of JAK inhibitor. We further identified the dysregulation of liver-specific transcripts in cf-mRNA which reflected changes in the gene-expression pattern in this generally inaccessible biological compartment.InterpretationUsing a preclinical mouse model, we demonstrated the potential of plasma cf-mRNA profiling for systemic and organ-specific characterization of drug-induced molecular alterations that are associated with inflammatory and immune responses.FundingMolecular Stethoscope.

Hepatic fibrosis stage is the most important determinant of outcomes in patients with nonalcoholic fatty liver disease (NAFLD). There is an urgent need for noninvasive tests that can accurately stage fibrosis and determine efficacy of interventions. Here, we describe a novel cell-free (cf)-mRNA sequencing approach that can accurately and reproducibly profile low levels of circulating mRNAs and evaluate the feasibility of developing a cf-mRNA-based NAFLD fibrosis classifier. Using separate discovery and validation cohorts with biopsy-confirmed NAFLD (n = 176 and 59, respectively) and healthy subjects (n = 23), we performed serum cf-mRNA RNA-Seq profiling. Differential expression analysis identified 2,498 dysregulated genes between patients with NAFLD and healthy subjects and 134 fibrosis-associated genes in patients with NAFLD. Comparison between cf-mRNA and liver tissue transcripts revealed significant overlap of fibrosis-associated genes and pathways indicating that the circulating cf-mRNA transcriptome reflects molecular changes in the livers of patients with NAFLD. In particular, metabolic and immune pathways reflective of known underlying steatosis and inflammation were highly dysregulated in the cf-mRNA profile of patients with advanced fibrosis. Finally, we used an elastic net ordinal logistic model to develop a classifier that predicts clinically significant fibrosis (F2-F4). In an independent cohort, the cf-mRNA classifier was able to identify 50% of patients with at least 90% probability of clinically significant fibrosis. We demonstrate a novel and robust cf-mRNA-based RNA-Seq platform for noninvasive identification of diverse hepatic molecular disruptions and for fibrosis staging with promising potential for clinical trials and clinical practice. NEW & NOTEWORTHY This work is the first study, to our knowledge, to utilize circulating cell-free mRNA sequencing to develop an NAFLD diagnostic classifier.

Circulating cell-free mRNA (cf-mRNA) holds great promise as a non-invasive diagnostic biomarker. However, cf-mRNA composition and its potential clinical applications remain largely unexplored. Here we show, using Next Generation Sequencing-based profiling, that cf-mRNA is enriched in transcripts derived from the bone marrow compared to circulating cells. Further, longitudinal studies involving bone marrow ablation followed by hematopoietic stem cell transplantation in multiple myeloma and acute myeloid leukemia patients indicate that cf-mRNA levels reflect the transcriptional activity of bone marrow-resident hematopoietic lineages during bone marrow reconstitution. Mechanistically, stimulation of specific bone marrow cell populations in vivo using growth factor pharmacotherapy show that cf-mRNA reflects dynamic functional changes over time associated with cellular activity. Our results shed light on the biology of the circulating transcriptome and highlight the potential utility of cf-mRNA to non-invasively monitor bone marrow involved pathologies.

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 clinical applications of this technology. Here, we use the bone marrow (BM) and pharmacologic manipulation of its resident cells as a window to study the origin of cf-mRNA. Using NGS-based profiling, we show that cf-mRNA is enriched in transcripts derived from the BM compared to circulating cells. Further, BM ablation experiments followed by hematopoietic stem cell transplants in cancer patients show that cf-mRNA levels reflect the transcriptional activity of BM resident hematopoietic lineages during marrow reconstitution. Finally, by stimulating specific BM cell populations in vivo using growth factor therapeutics (i.e. EPO, G-CSF), we show that cf-mRNA reveals dynamic functional changes in growing cell types, suggesting that, unlike other cell-free nucleic 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 applications in clinical practice.