Mapping of the secretome of primary isolates of mammalian cells, stem cells and derived cell lines.

Within a mammalian organism, the interaction among cells both at short and long distances is mediated by soluble factors released by cells into the extracellular environment. The secreted proteins may involve extracellular matrix proteins, proteinases, growth factors, protein hormones, immunoregulatory cytokines, chemokines or other bioactive molecules that have a direct impact on target cell phenotype. Stem cells of mesenchymal, adipose, neural and embryonic origin, fibroblast feeder cells as well as primary isolates of astrocytes, endothelial and muscle cells have recently become targets of intensive secretome profiling with the search for proteins regulating cell survival, proliferation, differentiation or inflammatory response. Recent advances and challenges of the stem cell and primary cell secretome analysis together with the most relevant results are discussed in this review.