| Bone marrow-derived mesenchymal stem cells ( BMSCs ) differentiate readily into chondrocytes, adipocytes, osteocytes, and they can support hematopoietic stem cells in culture. Evidence suggests BMSCs can also express phenotypic characteristics of endothelial, smooth muscle, skeletal myoblasts, and cardiac myocyte cells. BMSCs have shown promise as cellular therapy in cardiac repair after myocardial infarction. However, poor viability of transplanted BMSCs in the infarcted heart has limited the therapeutic efficacy. Lysophosphatidic acid (LPA) is a simple and natural lipid which has emerged as a potent mediator with a broad range of cellular actions, mediated via five G-protein-coupled receptors (GPCRs) referred to as LPA 1 -5. The aim of this study is to investigate the effects of LPA on the apoptosis of BMSCs. In this study BMSCs were preincubated with LPA for 1 hour prior to exposure to hypoxia/SD for 6 hours in the continued presence (LPA 1 h+6 h) or absence (LPA 1 h) of LPA. In other groups, LPA was added to cells at the point of exposure to hypoxia/SD and was maintained in the medium throughout the latter phase (LPA 6 h). BMSCs cultured in complete medium under non-hypoxic conditions were used as the non-apoptotic controls and cells exposed to hypoxia/SD alone without any prior or sustained exposure to LPA (No LPA) represents the apoptotic controls. The apoptosis was detected by Hoechst33342 staining and Annexin V/PI dual-color flow cytometry, and the expression of signaling proteins was evaluated by Western blot analysis. In the condition of hypoxia and serum deprivation (hypoxia/SD), a significant apoptosis occurred in BMSCs. The groups of LPA 6 h (12.86±3.93) orLPA1+6h (12.57±0.94), but not LPA 1 h(23.17±5.15), significantly decreased the apoptosis induced by hypoxia/SD (24.2±3.12) (p<0.05).The apoptosis between LPA 6 h and LPA 1+6 h has no significant. The effect of LPA on the intracellular signal pathways was also examined. Akt was activated, while ERK1/2 was depressed by LPA under hypoxia/SD conditions. These results suggest LPA could decrease the apoptosis of BMSCs induced by hypoxia/SD, and increase the survival of BMSCs. Lysophosphatidic acid (LPA) is a bioactive phospholipid mediator with diverse physiological and pathological actions on many types of cells, including Ca2+ mobilization, modulation of adenylyl cyclase, and mitogen-activated protein kinase (MAPK) activation, neurogenesis, myelinatoin, angiogenesis, wound healing, and cancer progression. LPA has been widely considered to elicit its biological functions through five types of G protein-coupled receptors, LPA1/Edg-2/vzg-l,Edg-4/LPA2, and Edg-7/LPA3, LPA4/Gpr23/p2y9,LPA5/Gpr92. The LPA1-3 receptors are belong to Edg family (endothelial differentiation gene family, Edg family). However, LPA4 shares only 20-24% amino acid with LPA1-3, and LPA5 has 35% amino acid identity with the LPA4 receptor. The phylogenetic analysis also shows that LPA4 and LPA5 are far distant from the Edg family. In this study, we first time found bone marrow-derived mesenchymal stem cells( BMSCs) expressed the LPA4 and LPA5 receptors. Sequence analyses of rat GPR23/LPA4 have 87% or 95% nucleotide identity with human or mouse derived LPA4.And rat GPR92/LPA5 shares 86% or 89% nucleotide identity with human or mouse derived LPA5. And in the progress of apoptosis induced by the condition of hypoxia and serum deprivation (hypoxia/SD) in BMSCs, LPA4 mRNA increased deeply while LPA5 mRNA depressed significantly in Real Time PCR. These results support the LPA4 and LPA5 receptors may involve in the apoptosis of BMSCs induced by hypoxia/SD. |
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