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

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.

Cell Type-specific Knockout with Gli1-mediated Cre Recombination in the Developing Cerebellum

The inducible Cre-loxP system provides a useful tool for inducing the selective deletion of genes that are essential for proper development and enables the study of gene functions in properly developed animals. Here, we show that inducible Cre-loxP driven by the Gli1-promoter can induce cell-type-specific deletion of target genes in cerebellar cortical neurons. We used reporter mice containing the YFP (yellow fluorescence protein) gene at the Gt(ROSA)26Sor locus with a loxP -flanked transcriptional stop sequence, in which successful Cre-mediated excision of the stop sequence is indicated by YFP expression in Cre-expressing cells. Administration of tamoxifen during early postnatal days (P4~7) induces Cre-dependent excision of stop sequences and allows YFP expression in proliferating neuronal progenitor cells in the external granule layer and Bergmann glia in the Purkinje cell layer. A substantial number of YFP-positive progenitor cells in the external granule layer migrated to the internal granule cell layer and became granule cell neurons. By comparison, injection of tamoxifen during late postnatal days (P19~22) induces YFP expression only in Bergmann glia, and most granule cell neurons were devoid of YFP expression. The results indicate that the Gli1 promoter is temporarily active in progenitor cells in the external granule layer during the early postnatal period but constitutively active in Bergmann glia. We propose that the Gli1-mediated CreER system can be applied for the conditional deletion of genes of interest from cerebellar granule cell neurons and/or Bergmann glia.

Cell Type-specific Knockout with Gli1-mediated Cre Recombination in the Developing Cerebellum

The inducible Cre-loxP system provides a useful tool for inducing the selective deletion of genes that are essential for proper development and enables the study of gene functions in properly developed animals. Here, we show that inducible Cre-loxP driven by the Gli1-promoter can induce cell-type-specific deletion of target genes in cerebellar cortical neurons. We used reporter mice containing the YFP (yellow fluorescence protein) gene at the Gt(ROSA)26Sor locus with a loxP -flanked transcriptional stop sequence, in which successful Cre-mediated excision of the stop sequence is indicated by YFP expression in Cre-expressing cells. Administration of tamoxifen during early postnatal days (P4~7) induces Cre-dependent excision of stop sequences and allows YFP expression in proliferating neuronal progenitor cells in the external granule layer and Bergmann glia in the Purkinje cell layer. A substantial number of YFP-positive progenitor cells in the external granule layer migrated to the internal granule cell layer and became granule cell neurons. By comparison, injection of tamoxifen during late postnatal days (P19~22) induces YFP expression only in Bergmann glia, and most granule cell neurons were devoid of YFP expression. The results indicate that the Gli1 promoter is temporarily active in progenitor cells in the external granule layer during the early postnatal period but constitutively active in Bergmann glia. We propose that the Gli1-mediated CreER system can be applied for the conditional deletion of genes of interest from cerebellar granule cell neurons and/or Bergmann glia.

Spatiotemporal Protein Atlas of Cell Death-Related Molecules in the Rat MCAO Stroke Model

Ischemic stroke and cerebral infarction triggered by the blockage of blood supply can cause damage to the brain via a complex series of pathological changes. Recently, diverse therapies have emerged as promising candidates for the treatment of stroke. These treatments exert therapeutic effects by acting on diverse target molecules and cells in different time windows from the acute to chronic phases. Here, using immunohistochemistry, we show pathophysiological changes in the brain microenvironment at the hyperacute (within 6 h), acute (1~3 days), subacute (7 days), and chronic (1 month) phases following ischemic injury. Ischemic injury in rats was induced by occluding the middle cerebral artery and was validated by magnetic resonance imaging. The progression of damage to the brain was evaluated by immunohistochemistry for NeuN⁺ neurons, GFAP⁺ astrocytes, and Iba1⁺ microglia, and by the emergence of the cell death-related molecules such as AIF, FAF1, and activated caspase-3. Our data regarding the spatial and temporal information on pathophysiological changes may warrant the investigation of the timing of administration of therapeutic treatments in preclinical studies with an animal model of stroke.

Gene Expression of NeuroD/BETA2 during Development of the Mouse Central Nervous System / 대한해부학회지

NeuroD/BETA2, a basic helix-loop-helix transcription factor, has been known to play a role in terminal differentia-tion during neurogenesis. To gain further insight into the function of NeuroD/BETA2 in the nervous system devel-opment, we examined the expression pattern of NeuroD/BETA2 during embryonic and postnatal development by in situ hybridization. Dynamic changes of NeuroD/BETA2 expression were observed in the developing nervous system. Gene expression of the NeuroD/BETA2 in developing cerebellum and hippocampus increased during the embryonic stages and persisted throughout postnatal development and remained at a stable level in the adult brain. NeuroD/ BETA2 expression was detected in postmitotic cells in the subventricular zone of the cerebrum during embryogenesis. This observation confirms that NeuroD/BETA2 may have a role in terminal differentiation during neurogenesis.