The Novel Role of SERPINB9 in Cytotoxic Protection of Human Mesenchymal Stem Cells

Abstract

Clinical trials using allogeneic mesenchymal stem cells (MSCs) are ongoing for the purpose of providing therapeutic benefit for a variety of human disorders. Pertinent to their clinical use are the accessibility to sufficient quantities of these cells allowing for repetitive administration, as well as a better understanding of the specific mechanisms by which allogeneic MSCs evade host immune responses that in turn influence their life span following administration. In this report, we sought to characterize and compare human peripheral blood MSCs (hPB-MSCs) with bone marrow-derived MSCs. hPB-MSCs met the established criteria to characterize this cellular lineage, including capacity for self-renewal, differentiation into tissues of mesodermal origin, and expression of phenotypic surface markers. In addition, hPB-MSCs suppressed alloreactive proliferation as well as the production of proinflammatory cytokines. Examination of the mechanisms by which allogeneic MSCs evade the host immune response, which is crucial for their therapeutic use, demonstrated that constitutive expression of serine protease inhibitor 9 (PI-9) on hPB-MSCs and bone marrow-derived MSCs is a major defense mechanism against granzyme B-mediated destruction by NK cells. Similarly, MSCs treated with small interfering RNA for PI-9 increased MSC cellular death, whereas expression of transgenic PI-9 following retroviral transduction protected MSCs. These data significantly advance our understanding of the immunomodulatory role for hPB-MSCs as well as the mechanisms by which they evade host immune responses. These findings contribute to the development of MSC-based therapies for diseases.

PI3kα and STAT1 Interplay Regulates Human Mesenchymal Stem Cell Immune Polarization

“…After 24 hours incubation, the cells were harvested, washed three times, and then used in the T‐cell proliferation assay. The anti‐CD3/CD28 proliferation assay was performed as previously described . Isolated peripheral blood mononuclear cells (PBMCs) were reconstituted (at 100,000–200,000 cells/well in a 96‐well‐plate) with RPMI complete medium (RPMI 1640, supplemented with 10% FBS, 1% penicillin‐streptomycin, and 1% l ‐glutamine), stimulated to proliferate with anti‐CD3/CD28 antibodies (6 μg/ml) (eBioscience, San Diego, CA) and cocultured with irradiated (3,000 rad) CB‐MSC for 3 days.…”

An Emerging Role for Serine Protease Inhibitors in T Lymphocyte Immunity and Beyond

“…We have demonstrated that the expression of Spi6 is required for the protection of transplanted MSC from allospecific CTL and subsequent survival and immunosuppressive activity [134]. Expression of transgenic PI9 protected both mouse [134] and human MSC [135] from CTL killing. Importantly, transgenic PI9 improved the survival and function of MSC after transplantation to allo-specific recipient mice [134].…”

Improving the Therapeutic Potential of Human Granzyme B for Targeted Cancer Therapy

“…PI-9 is also expressed in inflammatory cells [121] and in human peripheral blood mesenchymal stem cells [122]. It is also present in cells infected by cytomegalovirus, Epstein-Barr virus and the BK polyomavirus [123][124][125] as well as in endothelial and mesothelial cells [126] and dendritic cells [119].…”

“…The former may be achieved by RNA interference (RNAi) or antisense technology to knock down PI-9 gene expression. The successful use of siRNA to inhibit the expression of PI-9 has been described in stem cells [122] and in breast cancer [84]. However, the development of siRNA-based therapies has fallen out of favor following the Phase III failure of Bevasiranib, which targeted the expression of vascular endothelial growth factor (VEGF) for the treatment of age-related wet macular degeneration.…”