The Determination of Inactivated Platelet Lysate Supports the Proliferation and Immunomodulant Characteristics of Mesenchymal Stromal Cells in GMP Culture Conditions

Abstract

Mesenchymal stromal cells (MSCs) isolated from bone marrow (BM-MSCs) are considered advanced therapy medicinal products (ATMPs) and need to be produced according to Good Manufacturing Practices (GMP) for their clinical use. Human Platelet Lysate (HPL) is a good GMP-compliant alternative to animal serum and we have demonstrated that, after pathogen inactivation with psoralen, it was safer and more efficient to use psoralen in the production of MSCs following GMP guidelines. The study objectives were to compare MSCs cultivated in fetal bovine serum (FBS-MSCs) and MSCs with inactivated HPL (iHPL-MSCs) for their immunomodulatory properties. We studied the effects of MSCs on (1) the proliferation of total lymphocytes (Ly) and on naïve T Ly subsets induced to differentiate in Th1 versus Th2 Ly; (2) the immunophenotype of different T-cell subsets; and (3) the cytokine release to verify Th1, Th2, and Th17 polarization. These were analyzed by using an in vitro co-culture system. We observed that iHPL-MSCs showed the same immunomodulatory properties observed in the FBS-MSCs co-cultures. Furthermore, a more efficient effect on the increase of naïve T- cells and in the Th1 cytokine release from iHPL was observed. This study confirms that iHPL, used as a medium supplement, may be considered a good alternative to FBS for a GMP- compliant MSC expansion, and also to preserve their immunomodulatory properties. This study may well open the way for new ambitious projects, which will allow for the identification of new and more advantageous ways to culture MSCs, much safer than those commonly used, in order to create a bio-bank of ready-to-use MSCs for clinical use.