Ceramide-1-phosphate (C1P), like its related derivative sphingosine-1-phosphate (S1P), is derived from sphingolipids, which are important components of cell membranes. In contrast to S1P, which is secreted as a signaling molecule from intact cells, C1P is released from cells that are damaged and “leaky”. Unlike ceramide (which is often pro-apoptotic), C1P is anti-apoptotic and, as we have demonstrated, does not impair the clonogenicity of hematopoietic progenitors (Leukemia 2011, doi: 10.1038/leu.2011.185) and promotes their migration through an unknown receptor-initiated signaling pathway that is pertussis toxin-sensitive and therefore likely to involve a Gai protein-coupled seven-transmembrane-spanning receptor. Hypothesis: Taking into consideration the anti-apoptotic effects of C1P and the fact that it is released in damaged tissues, we have hypothesized that C1P plays an important and under-appreciated role in tissue/organ regeneration. Materials and Methods: To better address the potential role of C1P in this process we i) employed the Transwell system and FACS analysis to evaluate chemotactic responsiveness of stem cells involved in tissue and organ regeneration, including CD31+CD45−Lin− mesenchymal stroma cells (MSCs), Sca-1+CD51+CD45-Lin−CD31− endothelial progenitor cells (EPCs) and Sca-1+Lin−CD45− very small embryonic-like stem cells (VSELs), ii) measured the C1P level in damaged tissues (BM conditioned for transplantation, myocardium after heart infarct, and chemically damaged liver), iii) studied the activation of intracellular signaling pathways related to cell migration/adhesion (MAPKp42/44, AKT, and p38) in bone marrow stromal cells and umbilical cord blood-derived endothelial cells (HUVECs) in response to C1P stimulation, iv) evaluated the effect of C1P on adhesion and migration of stromal fibroblasts and endothelial cells, v) evaluated the influence of C1P on tube formation by HUVECs, and v) evaluated the effect of C1P stimulation on secretion of cytokines and chemokines by bone marrow stromal cells. All these effects were studied in parallel in comparison to other bioactive lipids (S1P, lysophosphatidic acid [LPA], and lysophosphatidylocholine [LPC]), as well as directly compared to the effects of known chemottractants of stem cells, bone marrow (BM)-derived fibroblasts, and endothelial cells (SDF-1, HGF, VEGF, and FGF-2). Results: We observed that C1P is upregulated in damaged tissues and strongly chemoattracts stem cells from BM that are potentially involved in tissue/organ regeneration (VSELs, MSCs, and EPCs). In chemotactic assays performed on expanded BM-derived fibroblasts and HUVECs, C1P had a similar strong chemotactic effect as S1P, but stronger than other bioactive lipids (LPA and LPC). C1P strongly stimulated phosphorylation of MAPKp42/44 and AKT in HUVECs and MAPKp42/44 in BM-derived fibroblasts. Interestingly, compared to all bioactive lipids tested in this study, C1P most strongly stimulated tube formation by HUVECs and stimulated secretion from BM-derived fibroblasts of several cytokines and chemokines, including stromal derived factor-1 (SDF-1). Conclusions: Our data demonstrate, for the first time, that C1P is a, potent bioactive lipid released from damaged cells that plays an important novel role not only in homing of HSPCs to BM, as we demonstrated recently, (Leukemia 2011, doi: 10.1038/leu.2011.185) but also directs migration and activates stem cells that are involved in repair of other damaged organs and tissues. We also envision that modulation of C1P signaling may turn out to be a viable strategy for tissue/organ repair and this is currently tested in our laboratory.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.