Improving the Safety of Mesenchymal Stem Cell-Based Ex Vivo Therapy Using Herpes Simplex Virus Thymidine Kinase

Abstract

Human mesenchymal stem cells (MSCs) are multipotent stem cells that have been intensively studied as therapeutic tools for a variety of disorders. To enhance the efficacy of MSCs, therapeutic genes are introduced using retroviral and lentiviral vectors. However, serious adverse events (SAEs) such as tumorigenesis can be induced by insertional mutagenesis. We generated lentiviral vectors encoding the wild-type herpes simplex virus thymidine kinase (HSV-TK) gene and a gene containing a point mutation that results in an alanine to histidine substitution at residue 168 (TK(A168H)) and transduced expression in MSCs (MSC-TK and MSC-TK(A168H)). Transduction of lentiviral vectors encoding the TK(A168H) mutant did not alter the proliferation capacity, mesodermal differentiation potential, or surface antigenicity of MSCs. The MSC-TK(A168H) cells were genetically stable, as shown by karyotyping. MSC-TK(A168H) responded to ganciclovir (GCV) with an half maximal inhibitory concentration (IC 50 ) value 10-fold less than that of MSC-TK. Because MSC-TK(A168H) cells were found to be non-tumorigenic, a U87-TK(A168H) subcutaneous tumor was used as a SAE-like condition and we evaluated the effect of valganciclovir (vGCV), an oral prodrug for GCV. U87-TK(A168H) tumors were more efficiently ablated by 200 mg/kg vGCV than U87-TK tumors. These results indicate that MSC-TK(A168H) cells appear to be pre-clinically safe for therapeutic use. We propose that genetic modification with HSV-TK(A168H) makes allogeneic MSC-based ex vivo therapy safer by eliminating transplanted cells during SAEs such as uncontrolled cell proliferation.

Human umbilical cord derived mesenchymal stem cells overexpressing HO‐1 attenuate neural injury and enhance functional recovery by inhibiting inflammation in stroke mice

“…Histological sections of the paraffin‐embedded heart, liver, spleen, lungs, and kidneys were stained with hematoxylin and eosin (HE) for light microscopy evaluation (Figure 10I). The HE imaging results were all normal, and there was no tumorigenesis (uncontrolled cell proliferation) of the engineered transplanted cells, as mentioned in the literature 25 …”

“…The HE imaging results were all normal, and there was no tumorigenesis (uncontrolled cell proliferation) of the engineered transplanted cells, as mentioned in the literature. 25 …”

Preclinical Study on Biodistribution of Mesenchymal Stem Cells after Local Transplantation into the Brain

“…Mesodermal differentiation was carried out as described previously ( 18 ). Briefly, for adipogenic and osteogenic differentiations, naïve MSCs and MSCs/CD cells were plated at a density of 5×10 4 in a 24-well plate and allowed to grow to confluence.…”

Mesenchymal-Stem-Cell-Based Therapy against Gliomas

“…Another study demonstrated the antitumor effect of MSCs obtained from adipose tissue (AT-MSC) transduced with the HSV-tk gene for the treatment of glioblastoma derived from the U87 cell line [3]. These results show that MSCs, regardless of their origin, are good carriers of suicide genes for glioblastoma gene therapy [55][56][57][58][59].…”