Title : Mesenchymal Stromal cells and immunoregulatory properties: Concerns and issues utilizing novel stem cell therapy as potential therapeutic strategy
Abstract:
Background: Accumulated evidence has emerged on the role of stem cells in key cellular functions such as their implication in host immune response and tissue regeneration. Currently, Mesenchymal Stromal Cells (MSCs), which are multipotent stem cells, have been used in a great number of clinical trials (> 1300 studies, worldwide), ensuring the safety and tolerability of these cells in several human disorders, such as autoimmune diseases, graft versus host disease (GvHD) and cancer. Lately, well-defined MSCs were used for the toleration of the acute immune response and cytokine release syndrome in severely ill COVID-19 patients. However, significant differences have been reported regarding immune modulation and tissue regeneration exerted by the MSCs. Late evidence has shown that inborn errors of immunity and the presence of different Human Leukocytes Antigens (HLA) may either prevent or promote the beneficial properties of MSCs towards human disorders.
Aim: This study aimed to the evaluation of the immunomodulatory and regenerative properties of MSCs by comprehensively investigating the HLA alleles.
Methods: MSCs derived from the human Wharton's Jelly (WJ) tissue and bone marrow (BM) were isolated, cryopreserved, expanded, and defined according to the criteria outlined by the International Society for Cell and Gene Therapies (ISCT). WJ and BM-MSCs were stimulated with a culture medium containing IFN-γ (50 ng/ μl), 1% penicillin-streptomycin, and 1% L-glutamine for 48 h. The quantification of IL-1Ra, IL-6, IL-10, IL-13, TGF-β1, VEGF-a, FGF, PDGF, and IDO was performed using ELISA kits. The expression of HLA-G1, G5, and G7 was evaluated in WJ and BM-MSCs. The determination of the HLA alleles of the MSCs was performed using the Next Generation Sequencing technology (HLA Holotype 11 loci, Omixon Inc., MiSeq, Illumina). The frequencies of the HLA alleles were estimated using the Arlequin and MEGA X software.
Results: Thawed WJ and BM-MSCs exhibited a spindle-shaped morphology, successfully differentiated to "osteocytes", "adipocytes", and "chondrocytes", and in flow cytometric analysis were characterized by positivity for CD73, CD90, and CD105 (> 95%) and negativity for CD34, CD45, and HLA-DR (< 2%). Moreover, stimulated WJ and BM-MSCs were characterized by increased cytoplasmic granulation, in comparison to unstimulated cells. The HLA-G isoforms (G1, G5, and G7) were successfully expressed by the unstimulated and stimulated WJ-MSCs. On the other hand, only weak expression of HLA-G1 was identified in BM-MSCs. Stimulated MSCs secreted high levels of IL-1Ra, IL-6, IL-10, IL-13, TGF-β1, FGF, VEGF, PDGF, and IDO in comparison to unstimulated cells (P < 0.05) after 12 and 24 h. Finally, macrophages derived from COVID-19 patients successfully adapted the M2 phenotype after co-culturing with stimulated WJ and BM-MSCs. Also, the most frequent HLA alleles were determined, to identify potential correlation with the MSCs? immunomodulatory and regenerative properties.
Conclusion: Specific HLA alleles were correlated positively with the MSCs? immune responses and regenerative properties. In this way, the establishment of a stem cell bank with specific MSCs lines may be performed, in order properly defined MSCs to be used for specific patients, thus bringing precision medicine one step closer to its clinical application.
