Umbilical Cord Blood Mononuclear Cells for Ex-Vivo Gene Therapy
Authors: Bashirov Farid V. , Salafutdinov Ilnur I. , Sokolov Michail E. , Izmailov Andrew A. , Markosyan Vage A. , Fadeev Filip O. , Rizvanov Albert , Islamov Rustem I. 
Published: October 2019

Abstract
Cell-mediated (ex-vivo) gene therapy for the treatment of adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID) had started in 1990 and nowadays it is the first marketing approval of an ex vivo gene therapy in Europe. The method based on ex-vivo transduction of peripheral blood lymphocytes with retroviral vector carrying the functional ADA gene in 2002 have been improved to use hematopoietic stem cell (HSC) for ex-vivo transduction with 100% survival and the evidence of safety and efficacy. Remarkably, umbilical cord blood mononuclear cells (UCB-MC) were successfully used for treatment of ADA deficiency in neonates as well. Meanwhile SCID is a very rare congenital disorder of the immune system although the option to use peripheral blood lymphocytes as cell carriers of the therapeutic genes for regenerative medicine is highly attractive. In our studies to overcome the neural cells death and stimulate neuroregeneration at neurodegenerative diseases (ALS), spinal cord injury (SCI), and stroke in animal models we employed ex-vivo triple gene therapy based on human UCB-MC transduced with adenoviral vectors carrying vascular endothelial growth factor (VEGF), glial cell-derived neurotrophic factor (GDNF) and neural cell adhesion molecule (NCAM). The reason for clinical application of UCB-MC is based on their availability, ease of preparation and potential for long term storage, as well as legislative, ethical and religious benefits for the transplantation. In our gene-cell construct NCAM was used for homing and survival of UCB-MC at the site of neurodegeneration. VEGF and GDNF are the molecules with well-known neuroprotective function. Moreover VEGF is useful in restoring of the microcirculation as well.
The positive results in treatment of ALS mice (Islamov et al, 2016), SCI (Izmailov et al, 2017) and stroke in rats (Sokolov et al, 2018) let us to propose the rationality to use of UCB-MC as cell carriers for the therapeutic genes based on:(1) suitability for both auto- and allotransplantation; (2) low immunogenicity; (3) high level of transduction; (4) high capability of synthetic and secretory activity for production of recombinant therapeutic molecules as well as endogenous growth and neurotrophic factors, cytokines and chemokines; (5) the action of therapeutic molecules on target cells via the paracrine or endocrine mechanism; (6) duration of recombinant molecule production limited by adenoviral vector half-life; (7) elimination of UCB-MC in 1-2 month after administration and possible multiple transplantation. Important, cell-mediated gene delivery makes the viral antigens inside the ex-vivo transduced UCB-MC invisible to the recipient immune system and it is easy to control production of recombinant molecules via the level of cell transduction or the number of transplanted cells. Thus, the cord blood mononuclear cells can serve as powerful tools for address delivery of recombinant genes encoding therapeutic molecules for regenerative medicine. This study was supported by the grant of Russian Science Foundation No 16-15-00010. Kazan Federal University was supported by the Russian Government Program of Competitive Growth.

Disclosures
No relevant conflicts of interest to declare.