High-efficiency lentiviral transduction of primary human CD34⁺ hematopoietic cells with low-dose viral inocula

Macrophage depletion overcomes human hematopoietic cell engraftment failure in zebrafish embryo

Zebrafish is widely adopted as a grafting model for studying human development and diseases. Current zebrafish xenotransplantations are performed using embryo recipients, as the adaptive immune system, responsible for host versus graft rejection, only reaches maturity at juvenile stage. However, transplanted primary human hematopoietic stem/progenitor cells (HSC) rapidly disappear even in zebrafish embryos, suggesting that another barrier to transplantation exists before the onset of adaptive immunity. Here, using a labelled macrophage zebrafish line, we demonstrated that engraftment of human HSC induces a massive recruitment of macrophages which rapidly phagocyte transplanted cells. Macrophages depletion, by chemical or pharmacological treatments, significantly improved the uptake and survival of transplanted cells, demonstrating the crucial implication of these innate immune cells for the successful engraftment of human cells in zebrafish. Beyond identifying the reasons for human hematopoietic cell engraftment failure, this work images the fate of human cells in real time over several days in macrophage-depleted zebrafish embryos.

Mesenchymal stromal cell mitochondrial transfer to human induced T-regulatory cells mediates FOXP3 stability

The key obstacle to clinical application of human inducible regulatory T cells (iTreg) as an adoptive cell therapy in autoimmune disorders is loss of FOXP3 expression in an inflammatory milieu. Here we report human iTreg co-cultured with bone marrow-derived mesenchymal stromal cells (MSCs) during short-term ex vivo expansion enhances the stability of iTreg FOXP3 expression and suppressive function in vitro and in vivo, and further that a key mechanism of action is MSC mitochondrial (mt) transfer via tunneling nanotubules (TNT). MSC mt transfer is driven by mitochondrial metabolic function (CD39/CD73 signaling) in proliferating iTreg and promotes iTreg expression of FOXP3 stabilizing factors BACH2 and SENP3. These results elucidate cellular and molecular mechanisms underlying human MSC mt transfer to proliferating cells. MSC mt transfer stabilizes FOXP3 expression in iTregs, thereby enhancing and sustaining their suppressive function in inflammatory conditions in vitro and in vivo.

Efficient CRISPR/Cas9 genome editing in a salmonid fish cell line using a lentivirus delivery system

BACKGROUND

Genome editing is transforming bioscience research, but its application to non-model organisms, such as farmed animal species, requires optimisation. Salmonids are the most important aquaculture species by value, and improving genetic resistance to infectious disease is a major goal. However, use of genome editing to evaluate putative disease resistance genes in cell lines, and the use of genome-wide CRISPR screens is currently limited by a lack of available tools and techniques.

RESULTS

In the current study, we developed an optimised protocol using lentivirus transduction for efficient integration of constructs into the genome of a Chinook salmon (Oncorhynchus tshwaytcha) cell line (CHSE-214). As proof-of-principle, two target genes were edited with high efficiency in an EGFP-Cas9 stable CHSE cell line; specifically, the exogenous, integrated EGFP and the endogenous RIG-I locus. Finally, the effective use of antibiotic selection to enrich the successfully edited targeted population was demonstrated.

CONCLUSIONS

The optimised lentiviral-mediated CRISPR method reported here increases possibilities for efficient genome editing in salmonid cells, in particular for future applications of genome-wide CRISPR screens for disease resistance.

Improvement of K562 Cell Line Transduction by FBS Mediated Attachment to the Cell Culture Plate

Lentiviral vectors have been used for gene therapy in the clinical phase in recent years. These vectors provide a tool for gene insertion, deletion, or modification in organisms. The K562 human cell line has been used extensively in hematopoietic research. Despite its broad application, it is hard-to-transfection and transduction. So, this study presents a simple method to increase the transduction efficiency of K562 cells with a low multiplicity of infection (MOI) of the virus particle. For this purpose, 24-well plate was coated by 300 μl fetal bovine serum (FBS) before seeding. Then 2×10⁴ K562 cells were seeded in each FBS coated plate. After 24h, K562 cells were attached and doubled. Different amount of lentivirus-based GFP vector according to MOI (5, 10, 15, and 20) along with 8 μg polybrene was added to the attached K562 cells and after 6h cells and viral particle complex were spinfected. Then cells were returned to the plate and incubated in 37°C overnight. After 48h transduction efficiency was established by measuring the GFP-expressing cells by flow cytometry. Flow cytometry analysis showed that, after plate treatment by FBS, 64.5% transduction rate in K562 cells was achieved at MOI=20. Therefore, this method can be an effective and simple way to increase the lentiviral transduction rate for suspended cells such as K562.

Foxp3 expression in induced T regulatory cells derived from human umbilical cord blood vs. adult peripheral blood

Foxp3 is essential for T regulatory cell (Treg) function. Broad complex-Tramtrack-Bric-a-brac domain (BTB) and Cap'n'collar (CNC) homology 1, transcription factor 2 (BACH2) stabilizes Treg immune homeostasis in murine studies. However, little is known regarding what role, if any, BACH2 may have in Foxp3 regulation in human-induced Treg (iTreg). We examined Foxp3 expression and regulation comparing iTreg differentiated from umbilical cord blood (UCB) vs. adult blood (AB) naive CD4⁺ T-cells. Foxp3 expression was higher in UCB vs. AB-derived iTreg, and was sustained during 21-day expansion in vitro. The number of Foxp3⁺ iTreg generated from UCB vs. AB naive CD4⁺ T-cells was higher in iTreg differentiation conditions. In addition, UCB iTreg were more potent in suppressing T-cell proliferation compared to AB iTreg. Naive UCB CD4⁺ T-cells highly expressed BACH2 protein compared to AB. Putative transcriptional BACH2 binding sites were identified at the Foxp3 promoter, using BACH2 consensus sequence. Cross-linking chromatin immunoprecipitation (ChIP) showed that BACH2 binds to the Foxp3 proximal promoter in UCB iTreg, but not AB iTreg. BACH2 was transcriptionally active, as shRNA-mediated BACH2 knockdown resulted in reduction of Foxp3 gene transcription in UCB CD4⁺ T-cells. In summary, BACH2 serves to stabilize robust Foxp3 expression in UCB CD4⁺ T-cell-derived iTreg.

Stem cell-based therapies for HIV/AIDS

One of the current focuses in HIV/AIDS research is to develop a novel therapeutic strategy that can provide a life-long remission of HIV/AIDS without daily drug treatment and, ultimately, a cure for HIV/AIDS. Hematopoietic stem cell-based anti-HIV gene therapy aims to reconstitute the patient immune system by transplantation of genetically engineered hematopoietic stem cells with anti-HIV genes. Hematopoietic stem cells can self-renew, proliferate and differentiate into mature immune cells. In theory, anti-HIV gene-modified hematopoietic stem cells can continuously provide HIV-resistant immune cells throughout the life of a patient. Therefore, hematopoietic stem cell-based anti-HIV gene therapy has a great potential to provide a life-long remission of HIV/AIDS by a single treatment. Here, we provide a comprehensive review of the recent progress of developing anti-HIV genes, genetic modification of hematopoietic stem progenitor cells, engraftment and reconstitution of anti-HIV gene-modified immune cells, HIV inhibition in in vitro and in vivo animal models, and in human clinical trials.

Plate in situ hybridization (PISH) as a time and cost effective RNA expression assay to study phenotypic heterogeneity in a population of cultured murine cells at single cell resolution

OBJECTIVES

Regenerative medicine approaches using reprogrammed or transdifferentiated cells require efficient single cell expression profiling to analyze culture homogeneity for quality control and recipients' safety.

RESULTS

While antigen-antibody based systems have been developed for several proteins, probing at the mRNA level allows for more flexibility, faster adaption to the ever increasing new data from next generation sequencing and increased specificity, especially for genes of conserved gene families.

CONCLUSIONS

We developed a time and cost effective expression profiling assay for monolayer cell culture in 96-well plates based on RNA in situ hybridization, termed PISH, at single cell resolution.