Introduction: Knowing the repertoire of cell signaling receptors would provide pivotal insight into the\r\ndevelopmental and regenerative capabilities of bone marrow cell (BMC)-derived hematopoietic stem/progenitor\r\ncells (HSPCs) and bone marrow mesenchymal stromal cells (BMMSCs).\r\nMethods: Murine HSPCs were enriched from fluorescence-activated cell sorting (FACS)-sorted Linââ?¬â??c-Kit+Sca-1+\r\nBMCs isolated from the tibia and femoral marrow compartments. Purified BMMSCs (CD73+, CD90+, CD105+, and\r\nCD45ââ?¬â??, CD34ââ?¬â??, CD31ââ?¬â??, c-Kitââ?¬â??) with extensive self-renewal potential and multilineage differentiation capacity\r\n(into different mesodermal cell lineages including osteocytes, chrondrocytes, adipocytes) were derived from\r\nadherent BMC cultures after CD45+ cell depletion. Adherent colony-forming cells were passaged two to three times\r\nand FACS analysis was used to assess cell purity and validate cell-specific surface marker phenotype prior to\r\nexperimentation. Gene transcripts for a number of cell signaling molecules were assessed using a custom\r\nquantitative real-time RT-PCR low-density microarray (94 genes; TaqManÃ?® technology).\r\nResults: We identified 16 mRNA transcripts that were specifically expressed in BMC-derived HSPC (including Ptprc,\r\nc-Kit, Csf3r, Csf2rb2, Ccr4, Cxcr3 and Tie-1), and 14 transcripts specifically expressed in BMMSCs (including Pdgfra,\r\nDdr2, Ngfr, Mst1r, Fgfr2, Epha3, and Ephb3). We also identified 27 transcripts that were specifically upregulated\r\n(=2-fold expression) in BMMSCs relative to HSPCs (Axl, Bmpr1a, Met, Pdgfrb, Fgfr1, Mertk, Cmkor1, Egfr, Epha7, and\r\nEphb4), and 19 transcripts that were specifically upregulated in HSPCs relative to BMMSCs (Ccr1, Csf1r, Csf2ra, Epor,\r\nIL6ra, and IL7r). Eleven transcripts were equally expressed (<2-fold upregulation) in HSPCs and BMMSCs (Flt1, Insr,\r\nKdr, Jak1, Agtrl1, Ccr3, Ednrb, Il3ra, Hoxb4, Tnfrsf1a, and Abcb1b), whilst another seven transcripts (Epha6, Epha8,\r\nMusk, Ntrk2, Ros1, Srms, and Tnk1) were not expressed in either cell population.\r\nConclusions: We demonstrate that besides their unique immunophenotype and functional differences, BMC-derived\r\nHSPCs and BMMSCs have different molecular receptor signaling transcript profiles linked to cell survival, growth, cell\r\ndifferentiation status, growth factor/cytokine production and genes involved in cell migration/trafficking/adhesion that\r\nmay be critical to maintain their pluripotency, plasticity, and stem cell function.
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