A Molecular Classification of Human Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSC) are widely used, isolated from a variety of tissues and increasingly adopted for cell therapy, but the identity of these cells is poorly defined and commonalities between MSC from different tissues sources is controversial. Here we undertook a comprehensive review of all public MSC expression studies to assess whether cells derived from different sources shared any common molecular attributes. In doing so, we discovered an over-arching transcriptional phenotype shared by a wide variety of MSC, freshly isolated or cultured cells, and under a variety of growth conditions. We developed a modified variable selection protocol that included cross platform normalisation, and assessment of the selected gene stability and informativeness. A 16-gene signature classified MSC with >97% accuracy, discriminating these from fibroblasts, other adult stem/progenitor cell types and differentiated cells. The genes form part of a protein-interaction network, and mutations in more than 65% of this network were associated with Mendelian disorders of skeletal growth or metabolism. The signature and accompanying datasets are provided as a community resource at www.stemformatics.org resource, and the method is available from the CRAN repository.