Autophagy-Mediated Immunoregulatory Properties of MIAMI Cells

Nova Southeastern University, Davie, Florida, USA

Mesenchymal stromal cells (MSCs) are frequently used in tissue regeneration as they can be easily isolated and expanded; they maintain progenitor properties, possess a capacity to differentiate into specific cell types, and secrete soluble factors that facilitate regeneration of damaged tissues by multiple mechanisms, including immunomodulation. Immunomodulatory properties of MSCs are associated with their ability to 1) secrete soluble factors upon sensing an inflammatory environment and 2) engage in cell-cell contact with immune cells. Autophagy is a lysosomal-dependent catabolic stress-response mechanism that is upregulated in response to a variety of “stressors” such as starvation, growth factor deprivation, endoplasmic reticulum stress, and/or pathogen infection. Autophagy regulates antigen presentation, cytokine secretion and also secretion of soluble factors. Therefore, we hypothesize that autophagy may be involved in regulating MSCs’ immunomodulatory properties. To test this hypothesis, we utilized a subtype of MSCs called “marrow-isolated adult multilineage inducible” (MIAMI) cells due to their ease of isolation from bone marrow, high differentiation capacity, as well as their immunomodulatory and tissue repair capacities. To enhance MIAMI cells immune-regulatory properties, we pre-treated them with IFN-gamma and, at the same time, treated them with autophagy stimulator or inhibitor drugs. MIAMI cells were exposed to 500U/ml IFN-gamma alone or together with 5µM Tamoxifen (an autophagy stimulator), or 10µM of Chloroquine (an autophagy inhibitor) for 4 days. The cells were subjected to RNA sequencing (RNA-seq) to determine the effects of autophagy modulation on global gene expression. In addition to RNA-seq, we are also evaluating changes in expression of regulatory microRNAs in these cells. Furthermore, preliminary results using co-culture assays suggest that MIAMI cells increase CD4+ T cells regulatory phenotype indicated by the increase in T cell regulatory markers (CD4+CD25+CD127+). Altogether, this project will contribute to development of novel therapeutic approaches where modulation of autophagy may be used to modify therapeutic properties of MIAMI cells.