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

Mesenchymal stem cells as therapeutic vehicles for glioma

Glioma is a disease with a poor prognosis despite the availability of multimodality treatments, and the development of novel therapies is urgently needed. Challenges in glioma treatment include the difficulty for drugs to cross the blood-brain barrier when administered systemically and poor drug diffusion when administered locally. Mesenchymal stem cells exhibit advantages for glioma therapy because of their ability to pass through the blood-brain barrier and migrate to tumor cells and their tolerance to the immune system. Therefore, mesenchymal stem cells have been explored as vehicles for various therapeutic agents for glioma treatment. Mesenchymal stem cells loaded with chemotherapeutic drugs show improved penetration and tumor accumulation. For gene therapy, mesenchymal stem cells can be used as vehicles for suicide genes, the so-called gene-directed enzyme prodrug therapy. Mesenchymal stem cell-based oncolytic viral therapies have been attempted in recent years to enhance the efficacy of infection against the tumor, viral replication, and distribution of viral particles. Many uncertainties remain regarding the function and behavior of mesenchymal stem cells in gliomas. However, strategies to increase mesenchymal stem cell migration to gliomas may improve the delivery of therapeutic agents and enhance their anti-tumor effects, representing promising potential for patient treatment.

Mesenchymal-Stem-Cell-Based Therapy against Gliomas

Glioblastoma is the most aggressive, malignant, and lethal brain tumor of the central nervous system. Its poor prognosis lies in its inefficient response to currently available treatments that consist of surgical resection, radiotherapy, and chemotherapy. Recently, the use of mesenchymal stem cells (MSCs) as a possible kind of cell therapy against glioblastoma is gaining great interest due to their immunomodulatory properties, tumor tropism, and differentiation into other cell types. However, MSCs seem to present both antitumor and pro-tumor properties depending on the tissue from which they come. In this work, the possibility of using MSCs to deliver therapeutic genes, oncolytic viruses, and miRNA is presented, as well as strategies that can improve their therapeutic efficacy against glioblastoma, such as CAR-T cells, nanoparticles, and exosomes.

Beneath the radar: immune-evasive cell sources for stroke therapy

Stem cell therapy is an emerging treatment paradigm for stroke patients with remaining neurological deficits. While allogeneic cell transplants overcome the manufacturing constraints of autologous grafts, they can be rejected by the recipient's immune system, which identifies foreign cells through the human leukocyte antigen (HLA) system. The heterogeneity of HLA molecules in the human population would require a very high number of cell lines, which may still be inadequate for patients with rare genetic HLAs. Here, we outline key progress in genetic HLA engineering in pluripotent stem and derived cells to evade the host's immune system, reducing the number of allogeneic cell lines required, and examine safety measures explored in both preclinical studies and upcoming clinical trials.

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

AIMS

The current evidence demonstrates that mesenchymal stem cells (MSCs) hold therapeutic potential for ischemic stroke. However, it remains unclear how changes in the secretion of MSC cytokines following the overexpression of heme oxygenase-1 (HO-1) impact excessive inflammatory activation in a mouse ischemic stroke model. This study investigated this aspect and provided further insights.

METHODS

The middle cerebral artery occlusion (MCAO) mouse model was established, and subsequent injections of MSC, MSCHO-1 , or PBS solutions of equal volume were administered via the mice's tail vein. Histopathological analysis was conducted on Days 3 and 28 post-MCAO to observe morphological changes in brain slices. mRNA expression levels of various factors, including IL-1β, IL-6, IL-17, TNF-α, IL-1Ra, IL-4, IL-10, TGF-β, were quantified. The effects of MSCHO-1 treatment on neurons, microglia, and astrocytes were observed using immunofluorescence after transplantation. The polarization direction of macrophages/microglia was also detected using flow cytometry.

RESULTS

The results showed that the expression of anti-inflammatory factors in the MSCHO-1 group increased while that of pro-inflammatory factors decreased. Small animal fluorescence studies and immunofluorescence assays showed that the homing function of MSCsHO-1 was unaffected, leading to a substantial accumulation of MSCsHO-1 in the cerebral ischemic region within 24 h. Neurons were less damaged, activation and proliferation of microglia were reduced, and polarization of microglia to the M2 type increased after MSCHO-1 transplantation. Furthermore, after transplantation of MSCsHO-1 , the mortality of mice decreased, and motor function improved significantly.

CONCLUSION

The findings indicate that MSCs overexpressing HO-1 exhibited significant therapeutic effects against hyper-inflammatory injury after stroke in mice, ultimately promoting recovery after ischemic stroke.

Assessment of Risks and Benefits of Using Antibiotics Resistance Genes in Mesenchymal Stem Cell-Based Ex-Vivo Therapy

Recently, ex-vivo gene therapy has emerged as a promising approach to enhance the therapeutic potential of mesenchymal stem cells (MSCs) by introducing functional genes in vitro. Here, we explored the need of using selection markers to increase the gene delivery efficiency and evaluated the potential risks associated with their use in the manufacturing process. We used MSCs/CD that carry the cytosine deaminase gene (CD) as a therapeutic gene and a puromycin resistance gene (PuroR) as a selection marker. We evaluated the correlation between the therapeutic efficacy and the purity of therapeutic MSCs/CD by examining their anti-cancer effect on co-cultured U87/GFP cells. To simulate in vivo horizontal transfer of the PuroR gene in vivo, we generated a puromycin-resistant E. coli (E. coli/PuroR) by introducing the PuroR gene and assessed its responsiveness to various antibiotics. We found that the anti-cancer effect of MSCs/CD was directly proportional to their purity, suggesting the crucial role of the PuroR gene in eliminating impure unmodified MSCs and enhancing the purity of MSCs/CD during the manufacturing process. Additionally, we found that clinically available antibiotics were effective in inhibiting the growth of hypothetical microorganism, E. coli/PuroR. In summary, our study highlights the potential benefits of using the PuroR gene as a selection marker to enhance the purity and efficacy of therapeutic cells in MSC-based gene therapy. Furthermore, our study suggests that the potential risk of horizontal transfer of antibiotics resistance genes in vivo can be effectively managed by clinically available antibiotics.

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

Therapeutic efficacy of mesenchymal stem cells (MSCs) is determined by biodistribution and engraftment in vivo. Compared to intravenous infusion, biodistribution of locally transplanted MSCs are partially understood. Here, we performed a pharmacokinetics (PK) study of MSCs after local transplantation. We grafted human MSCs into the brains of immune-compromised nude mice. Then we extracted genomic DNA from brains, lungs, and livers after transplantation over a month. Using quantitative polymerase chain reaction with human Alu-specific primers, we analyzed biodistribution of the transplanted cells. To evaluate the role of residual immune response in the brain, MSCs expressing a cytosine deaminase (MSCs/CD) were used to ablate resident immune cells at the injection site. The majority of the Alu signals mostly remained at the injection site and decreased over a week, finally becoming undetectable after one month. Negligible signals were transiently detected in the lung and liver during the first week. Suppression of Iba1-positive microglia in the vicinity of the injection site using MSCs/CD prolonged the presence of the Alu signals. After local transplantation in xenograft animal models, human MSCs remain predominantly near the injection site for limited time without disseminating to other organs. Transplantation of human MSCs can locally elicit an immune response in immune compromised animals, and suppressing resident immune cells can prolong the presence of transplanted cells. Our study provides valuable insights into the in vivo fate of locally transplanted stem cells and a local delivery is effective to achieve desired dosages for neurological diseases.