Toll like Receptor 3 & 4 Responses of Human Turbinate Derived Mesenchymal Stem Cells: Stimulation by Double Stranded RNA and Lipopolysaccharide

Abstract

Background and objectivesMultipotent mesenchymal stromal cells (MSCs) represent a promising cell-based therapy for a number of inflammatory or autoimmune diseases. Herein, Toll like receptor (TLR) expression by MSCs and their immune regulatory roles are investigated. In this study, we investigated the influence of TLR on the immune response, proliferation, and differentiation potential of human turbinated MSC (hTMSC) cultures in vitro.Subjects and MethodsAfter isolating hTMSCs from discarded inferior turbinate tissue, FACS analysis was used to assess the expression of TLRs such as TLR2, TLR3, TLR4, and TLR5 in hTMSCs and cell proliferation was assessed using a cell counting kit (CCK)-8. Cytokine and chemokine secretions were analyzed with multiplex immunoassays for IL-1α, IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12, IP-10 (CXCL10), RANTES (CCL5), TNF-a, GM-CSF, and IFN-γ. The differentiation potential of hTMSCs was evaluated in the osteogenic, chondogenic, and adipogeinc media and analyzed by histology and gene expression related to differentiation.ResultsFACS analysis revealed that TLR3 and TLR4 expression consisted of a relatively high percentage of the surface proteins expressed by hTMSCs. The proliferation of hTMSCs was influenced and significantly increased by the presence of TLR4 agonists. In particular, hTMSCs produced a set of cytokines and chemokines and the expression of IL-6, IL-8, IL-12, IP-10 (CXCL10), RANTES (CCL5), TNF-α, and GM-CSF were up-regulated in response to the TLR4 agonist LPS. The osteogenic and adipogeinc differentiation potential of hTMSCs was not affected by TLR agonists.ConclusionsWe conclude that TLR4 stimulation affects TLR expression, proliferation, and the immunomodulation potential of hTMSCs. Understanding the mechanism behind TLR's influence on hTMSCs and their immunomodulating properties would be useful for providing a novel target to exploit in the improvement of stem cell-based therapeutic strategies.

Controversial Role of Toll-like Receptor 4 in Adult Stem Cells

“…Similar pro-proliferative effects have been observed after stimulation of adult human bone marrow MSCs with 1 μg/ml LPS from E. coli (O55:B5) for 48 h [72]. Besides bone marrow MSCs, LPS may also have proliferation inducing effect in peripheral MSCs isolated from human turbinate tissue [18]. Remarkably, exposure of this MSC-population to 10 ng/ml LPS (1 h) has only weak pro-proliferative effect which could only be observed 48 h after the treatment.…”

“…Similarly, LPS treatment of human adipose tissuederived MSCs seems to increase their osteogenic potential [74]. In contrast to these studies, short-term exposure (1 h) to LPS had no significant effects on osteogenic and adipogenic differentiation of human turbinate-derived MSCs [18]. Notably, in mice lacking TLR4, neither osteogenic nor adipogenic differentiation were significantly changed compared to MSCs from control animals [76].…”

“…In addition to terminally differentiated cell types, TLR4 is known to be expressed in stem and progenitor cells in various tissues. Its expression has been verified in hematopoietic stem cells (HSCs) [15], endothelial progenitor cells (EPCs) [16], peripheral and cord blood mesenchymal stem cells (or mesenchymal stromal cells -MSCs) [17][18][19], dental pulp stem cells [20], retinal progenitor cell [21], neuronal progenitor cells (NPCs) [22] and neural stem cells (NSCs) [13,22]. This broad spectrum of expression suggests a function not limited to immune response.…”

Activation, homing, and role of the mesenchymal stem cells in the inflammatory environment

“…Explanation of these different outcomes may be based on the findings that TLR3 and TLR4 activate MSCs in different ways. Activation through TLR4 with LPS induced the pro-inflammatory phenotype of MSCs where secretion of IL-6, IL-8, and TGF-β was intensified by co-stimulation with IFN-γ 77–79. On the other hand, activation through TLR3 with polyinosinic:polycytidylic acid (poly I:C) induced anti-inflammatory phenotype of MSCs where production of IDO, PGE-2, IL-4, and IL-1RA was detected 77,79.…”

Growth Inhibition of Mesenchymal Stem Cells by Laminarin: Impact on Chondrocyte Differentiation

“…Thus, influencing MSCs phenotype and modulating MSCs responses remain an important task in research related to tissue repair. Various studies have shown that activation of Toll-like receptors (TLR) pathway, scavenger receptor pathway or growth factor pathway can influence the capacity of these cells to differentiate into bone, fat or cartilage by increasing or decreasing their capacity [44][45][46][47]. Therefore understanding how different agonists of these pathways may influence the MSCs responses could help to identify new molecules with a beneficial impact on MSCs, which can be used in the repair of tissues.…”