Engineered Hematopoietic Stem Cells as Therapeutics for Hemophilia A

Comparison of different gene addition strategies to modify placental derived-mesenchymal stromal cells to produce FVIII

Introduction

Placenta-derived mesenchymal cells (PLCs) endogenously produce FVIII, which makes them ideally suited for cell-based fVIII gene delivery. We have previously reported that human PLCs can be efficiently modified with a lentiviral vector encoding a bioengineered, expression/secretion-optimized fVIII transgene (ET3) and durably produce clinically relevant levels of functionally active FVIII. The objective of the present study was to investigate whether CRISPR/Cas9 can be used to achieve location-specific insertion of a fVIII transgene into a genomic safe harbor, thereby eliminating the potential risks arising from the semi-random genomic integration inherent to lentiviral vectors. We hypothesized this approach would improve the safety of the PLC-based gene delivery platform and might also enhance the therapeutic effect by eliminating chromatin-related transgene silencing.

Methods

We used CRISPR/Cas9 to attempt to insert the bioengineered fVIII transgene "lcoET3" into the AAVS1 site of PLCs (CRISPR-lcoET3) and determined their subsequent levels of FVIII production, comparing results with this approach to those achieved using lentivector transduction (LV-lcoET3) and plasmid transfection (Plasmid-lcoET3). In addition, since liver-derived sinusoidal endothelial cells (LSECs) are the native site of FVIII production in the body, we also performed parallel studies in human (h)LSECs).

Results

PLCs and hLSECs can both be transduced (LV-lcoET3) with very high efficiency and produce high levels of biologically active FVIII. Surprisingly, both cell types were largely refractory to CRISPR/Cas9-mediated knockin of the lcoET3 fVIII transgene in the AAVS1 genome locus. However, successful insertion of an RFP reporter into this locus using an identical procedure suggests the failure to achieve knockin of the lcoET3 expression cassette at this site is likely a function of its large size. Importantly, using plasmids, alone or to introduce the CRISPR/Cas9 "machinery", resulted in dramatic upregulation of TLR 3, TLR 7, and BiP in PLCs, compromising their unique immune-inertness.

Discussion

Although we did not achieve our primary objective, our results validate the utility of both PLCs and hLSECs as cell-based delivery vehicles for a fVIII transgene, and they highlight the hurdles that remain to be overcome before primary human cells can be gene-edited with sufficient efficiency for use in cell-based gene therapy to treat HA.

HDAd5/35++ Adenovirus Vector Expressing Anti-CRISPR Peptides Decreases CRISPR/Cas9 Toxicity in Human Hematopoietic Stem Cells

We generated helper-dependent HDAd5/35++ adenovirus vectors expressing CRISPR/Cas9 for potential hematopoietic stem cells (HSCs) gene therapy of β-thalassemia and sickle cell disease through re-activation of fetal γ-globin expression (HDAd-globin-CRISPR). The process of CRISPR/Cas9 gene transfer using these vectors was not associated with death of human CD34+ cells and did not affect their in vitro expansion and erythroid differentiation. However, functional assays for primitive HSCs, e.g., multi-lineage progenitor colony formation and engraftment in irradiated NOD/Shi-scid/interleukin-2 receptor γ (IL-2Rγ) null (NSG) mice, revealed toxicity of HDAd-globin-CRISPR vectors related to the prolonged expression and activity of CRISPR/Cas9. To control the duration of CRISPR/Cas9 activity, we generated an HDAd5/35++ vector that expressed two anti-CRISPR (Acr) peptides (AcrII4 and AcrII2) capable of binding to the CRISPR/Cas9 complex (HDAd-Acr). CD34+ cells that were sequentially infected with HDAd-CRISPR and HDAd-Acr engrafted at a significantly higher rate. Target site disruption frequencies in engrafted human cells were similar to those in pre-transplantation CD34+ cells, indicating that genome-edited primitive HSCs survived. In vitro differentiated HSCs isolated from transplanted mice demonstrated increased γ-globin expression as a result of genome editing. Our data indicate that the HDAd-Acr vector can be used as a tool to reduce HSC cytotoxicity of the CRISPR/Cas9 complex.

The Utilization of Rehabilitation in Patients with Hemophilia A in Taiwan: A Nationwide Population-Based Study

INTRODUCTION

Rehabilitation plays an important role in the physical health of patients with hemophilia. However, comprehensive information regarding the utilization of rehabilitation for such patients remains scarce.

AIM

This population-based study aimed to examine the characteristics, trends, and most important factors affecting rehabilitation usage in patients with hemophilia A using a nationwide database in Taiwan.

METHODS

Data from 777 patients with hemophilia A who were registered in the National Health Insurance Research Database between 1998 and 2008 were analyzed using SAS 9.0.

RESULTS

Musculoskeletal or nervous system-related surgical procedures and clotting factor VIII concentrate costs were identified as factors affecting rehabilitation usage; musculoskeletal or nervous system-related surgical procedures (odds ratio = 3.788; P < 0.001) were the most important predictor of whether a patient with hemophilia A would use rehabilitation services. Joint disorders, arthropathies, bone and cartilage disorders, intracranial hemorrhage, and brain trauma were common diagnoses during rehabilitation use. The costs of physical therapy (physiotherapy) comprised the majority (71.2%) of rehabilitation therapy categories. Increasingly, rehabilitation therapy was performed at physician clinics. The total rehabilitation costs were <0.1% of the total annual medical costs.

CONCLUSION

Musculoskeletal or nervous system-related surgical procedures and increased use of clotting factor VIII concentrate affect the rehabilitation utilization of patients with hemophilia A the most. The findings in this study could help clinicians comprehensively understand the rehabilitation utilization of patients with hemophilia A.