Lysophosphatidic Acid Protects Human Mesenchymal Stromal Cells from Differentiation-Dependent Vulnerability to Apoptosis

Abstract

The survival of transplanted cells and their resulting efficacy in cell-based therapies is markedly impaired due to serum deprivation and hypoxia (SD/H) resulting from poor vascularization within tissue defects. Lysophosphatidic acid (LPA) is a platelet-derived growth factor with pleiotropic effects on many cell types. Mesenchymal stromal cells (MSC) exhibit unique secretory and stimulatory characteristics depending on their differentiation state. In light of the potential of MSC in cell-based therapies, we examined the ability of LPA to abrogate SD/H-induced apoptosis in human MSC at increasing stages of osteogenic differentiation in vitro and assessed MSC survival in vivo. Undifferentiated MSC were rescued from SD/H-induced apoptosis by treatment with both 25 and 100 mM LPA. However, MSC conditioned with osteogenic supplements responded to 25 mM LPA, and cells conditioned with dexamethasone-containing osteogenic media required 100 mM LPA. This rescue was mediated through LPA 1 in all cases. The addition of 25 mM LPA enhanced vascular endothelial growth factor (VEGF) secretion by MSC in all conditions, but VEGF availability was not responsible for protection against apoptosis. We also showed that codelivery of 25 mM LPA with MSC in alginate hydrogels significantly improved the persistence of undifferentiated MSC in vivo over 4 weeks as measured by bioluminescence imaging. Osteogenic differentiation alone was protective of SD/H-induced apoptosis in vitro, and the synergistic delivery of LPA did not enhance persistence of osteogenically induced MSC in vivo. These data demonstrate that the capacity of LPA to inhibit SD/H-induced apoptosis in MSC is dependent on both the differentiation state and dosage. This information will be valuable for optimizing osteogenic conditioning regimens for MSC before in vivo implementation.

Lysophosphatidic Acid and Sphingosine-1-Phosphate: A Concise Review of Biological Function and Applications for Tissue Engineering

“…81 Furthermore, LPA protects MSCs against apoptosis induced by ischemic conditions, likely through a phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/Aktmediated pathway. 4,5,82,83 In mature bone, LPA modulates cytoskeletal organization in osteoblasts and may stimulate extracellular matrix production and organization. 84 Osteoblasts increase ALP production in response to LPA, especially when concomitantly exposed to calcitriol, 7,76 indicating a role in osteoblast maturation.…”

“…Furthermore, osteogenically induced MSCs responded differently to ischemic environments and varying doses of LPA compared with undifferentiated cells. 4 Additional work is required to determine optimal concentrations and retention properties in a range of materials that are suited for distinct therapeutic applications.…”

“…2,14 These lipids have been incorporated into biomaterials for in vivo delivery 4,9,11,15,16 and are several orders of magnitude cheaper than recombinant proteins. 9 Here, the effects of LPA and S1P on both cellular-and tissue-level phenotypes are surveyed, with an eye toward regulating stem/ progenitor cell growth and differentiation.…”

“…Both LPLs signal through the endothelial differentiation gene (EDG) family of receptors and are ligands for the P2Y10 receptor (Table 1). 21,22 Extracellular LPA can affect cellular response through at least six GPCRs (LPA [1][2][3][4][5][6] ), while S1P engages at least five (S1P [1][2][3][4][5] ). These GPCRs are differentially expressed in various tissues, can change with cellular differentiation state, and have separate coupled subunits that trigger distinct intracellular signaling cascades (Fig.…”

“…24,32 The most important biological role of S1P is to serve as a natural ligand for the EDG family of GPCRs. 26 At least five distinct GPCRs, S1P [1][2][3][4][5] , are known to bind S1P with a high affinity (K d of 2-30 nM) and each elicits distinct biological actions of which conflicting results have been reported. 25,33,34 To demonstrate the pleiotropic nature of S1P receptors (S1PRs), S1P 1 activation enhances barrier integrity and vessel maturation whereas S1P 3 conversely promotes vessel permeability and remodeling.…”