Expansion and Secretory Profiles of Human Platelet Lysate Conditioned BM-, UC- and ESC-MSCs for Inflammatory and Immune Therapies

Inflammatory and autoimmune diseases can occur for a number of reasons including the dysregulation of the normal immune response and aggressive inflammation as a result of infection which can affect multiple tissue types, resulting in damage and increased risk of morbidity and/or mortality. Current drug treatment regimens are typically not sufficient to treat moderate to severe cases of inflammatory and autoimmune diseases. Mesenchymal stem cells (MSCs) secrete a cadre of potent immunomodulatory factors and are generally considered to be immunotolerant, thus the ability of MSCs to be manufactured and stored long-term, present a unique opportunity to produce an allogeneic "off-the-shelf" cell therapy for immunomodulation. However, bone marrow (BM)-MSCs are a heterogeneous cell population that have limited expansion capabilities in vitro, additionally, several concerns remain regarding the immunogenicity of xenogeneic cultured MSCs. Recently, culture media supplementation with allogeneic human platelet lysate (hPL) has been demonstrated to promote BM-MSC growth whilst maintaining differentiation potential. However, MSCs derived from earlier developmental stages, including umbilical cord (UC) or embryonic stem cells (ESC), with highly replicative phenotypes may be far superior for generating large numbers of clinical-grade allogeneic MSCs for inflammatory and immune disease treatment.

MSC from BM, UC and ESC were cultured in hPL (10%) or FBS (10%) and doubling time calculated. To determine paracrine factor secretion MSC conditioned media was collected after 24 h under serum free conditions and immunomodulatory factors quantified via ELISA. UC-MSCs secreted the highest levels of immunomodulatory factors PGE2, MCP-1, HGF and IL-6 when compared with ESC-MSCs and BM-MSCs. Notably, UC-MSCs secreted greater than a 2-fold amount of all four factors when compared with ESC-MSCs. Xeno-free hPL culture promoted the expansion of human of both UC-MSCs and ESC-MSCs. The lowest doubling time was achieved with ESC-MSC under hPL conditions (35.4 h ± 1.4), compared to FBS conditions (38.2 ± 1.3). BM-MSCs cultured under FBS conditions demonstrated the highest doubling time (74.7 ± 9.5). BM-MSCs under hPL culture conditions secreted significantly higher levels of cytokines including the immunomodulatory cytokines IL-6 and MCP-1 when compared to FBS culture. Results demonstrate increased proliferation of all MSC types under hPL conditions and potent paracrine secretion from UC-MSCs compared with the other MSC sources. However, greater understanding of MSC source and culture environment on immunomodulatory properties is needed to generate therapeutic allogeneic MSCs for inflammatory and autoimmune diseases. Equally, studying the ability of immature MSCs to suppress the proliferation and cytokine production from specific subsets of immune cells, involved in inflammation and immune disorders, can help to indicate target treatments.