Pre-conditioning of Equine Bone Marrow-Derived Mesenchymal Stromal Cells Increases Their Immunomodulatory Capacity

Abstract

Mesenchymal stem/stromal cells (MSCs) are increasingly explored for the treatment of degenerative and inflammatory diseases in human and veterinary medicine. One of the key characteristics of MSCs is that they modulate inflammation mainly through the secretion of soluble mediators. However, despite widespread clinical use, knowledge regarding the effector mechanisms of equine MSCs, and consequently their effectiveness in the treatment of diseases, is still unknown. The objectives of this study were to determine the mechanisms underlying inhibition of lymphocyte proliferation by equine bone marrow-derived MSCs, and to evaluate the effect of pre-conditioning of equine MSCs with different pro-inflammatory cytokines on inhibition of lymphocyte proliferation. We determined that inhibition of lymphocyte proliferation by equine MSCs depends on activity of prostaglandin-endoperoxide synthase 2 and indoleamine 2,3-dioxygenase. Additionally, pre-conditioning of MSCs with TNF-α, IFN-γ or their combination significantly increased the expression of prostaglandin-endoperoxide synthase 2, indoleamine 2,3-dioxygenase, iNOS and IL-6. This upregulation correlated with an increased inhibitory effect of MSCs on lymphocyte proliferation. In conclusion, pre-conditioning of bone marrow-derived MSC increases their inhibitory effect on lymphocyte proliferation in horses.

Bone Marrow MSC Secretome Increases Equine Articular Chondrocyte Collagen Accumulation and Their Migratory Capacities

“…Tumor necrosis factor-alpha (TNF-α) priming led to an upregulation of immunoregulatory factors. The priming of MSCs with several inflammatory cytokines may have additional effects, as shown with the combination of IFN-γ and TNF-α in a recent study [ 42 ]. Human MSCs stimulated with interleukin (IL)-1β, IL-6, and IL-23 produced higher levels of transforming growth factor-beta (TGF-β) than the unstimulated MSCs [ 43 ].…”

The immunomodulation–immunogenicity balance of equine Mesenchymal Stem Cells (MSCs) is differentially affected by the immune cell response depending on inflammatory licensing and major histocompatibility complex (MHC) compatibility

“…Equine studies have reported different results regarding iNOS2 participation. Carrade et al ( 4 ) described that NO production by equine MSCs varies from different tissue sources, and subsequent studies have shown that iNOS2 inhibition does not change the inhibitory effect of equine MSCs on lymphocyte proliferation ( 26 , 30 , 42 ). IDO1 activity does not seem to be involved in the capacity of equine MSCs to inhibit allogeneic lymphocyte proliferation ( 26 ) but may participate in maintaining this suppressive effect ( 42 ).…”

“…Carrade et al ( 4 ) described that NO production by equine MSCs varies from different tissue sources, and subsequent studies have shown that iNOS2 inhibition does not change the inhibitory effect of equine MSCs on lymphocyte proliferation ( 26 , 30 , 42 ). IDO1 activity does not seem to be involved in the capacity of equine MSCs to inhibit allogeneic lymphocyte proliferation ( 26 ) but may participate in maintaining this suppressive effect ( 42 ). In addition to soluble mediators, cell–cell interactions between MSCs and lymphocytes via adhesion molecules may increase the effectiveness of the MSC immunomodulation ( 43 ).…”

The Effect of Inflammatory Priming on the Therapeutic Potential of Mesenchymal Stromal Cells for Spinal Cord Repair

“…Typically, untreated MSC are transplanted in the spinal cord, which could cause sudden environmental shock for the cells. Other MSC priming methods (i.e., cytokines, hypoxia, antioxidants, chemical drugs) have been used to increase their therapeutic efficacy in a variety of tissues, resulting in enhanced repair [20,[68][69][70][71]. However, the effect of those priming methods on transplant survival are varied or not always presented.…”

“…However, the effect of those priming methods on transplant survival are varied or not always presented. A culture of MSC with IFNγ and TNFα added to the medium increases MSC immunomodulatory activity [21,23,68,72]. Pre-treatment of MSC with antioxidants, such as melatonin or all-trans retinoic acid, results in upregulation of the survival gene, bcl2, and increased MSC proliferation and wound healing efficacy, respectively [69,70].…”