Lentiviral Vector-mediated Gene Therapy of Hepatocytes Ex Vivo for Autologous Transplantation in Swine

Summary

This protocol is intended to describe porcine hepatocyte isolation and ex vivo gene delivery to cure models of metabolic diseases via autologous cell transplantation. Although this particular model enjoys unique advantages that favor successful therapy, the application is a relevant foundation to address additional diseases and indications.

Abstract

Gene therapy is an ideal choice to cure many inborn errors of metabolism of the liver. Ex-vivo, lentiviral vectors have been used successfully in the treatment of many hematopoietic diseases in humans, as their use offers stable transgene expression due to the vector's ability to integrate into the host genome. This method demonstrates the application of ex vivo gene therapy of hepatocytes to a large animal model of hereditary tyrosinemia type I. This process consists of 1) isolation of primary hepatocytes from the autologous donor/recipient animal, 2) ex vivo gene delivery via hepatocyte transduction with a lentiviral vector, and 3) autologous transplant of corrected hepatocytes via portal vein injection. Success of the method generally relies upon efficient and sterile removal of the liver resection, careful handling of the excised specimen for isolation of viable hepatocytes sufficient for re-engrafting, high-percentage transduction of the isolated cells, and aseptic surgical procedures throughout to prevent infection. Technical failure at any of these steps will result in low yield of viable transduced hepatocytes for autologous transplant or infection of the donor/recipient animal. The pig model of human type 1 hereditary tyrosinemia (HT-1) chosen for this approach is uniquely amenable to such a method, as even a small percentage of engraftment of corrected cells will lead to repopulation of the liver with healthy cells based on a powerful selective advantage over native-diseased hepatocytes. Although this growth selection will not be true for all indications, this approach is a foundation for expansion into other indications and allows for manipulation of this environment to address additional diseases, both within the liver and beyond, while controlling for exposure to viral vector and opportunity for off-target toxicity and tumorigenicity.

Introduction

Inborn errors of metabolism of the liver are a family of genetic diseases that collectively affect as many as 1 in 800 live births¹. Many of these diseases are single gene defects² and can be functionally cured by introducing a single corrected copy of the affected gene into a sufficient number of hepatocytes³. The actual percentage of hepatocytes that needs to be corrected varies by the disease⁴ and is largely dependent on the nature of the protein it encodes, for example, excreted proteins versus cytoplasmic. In most cases, efficacy of any treatment for metabolic disease ....

Protocol

All animal procedures were performed in accordance with institutional guidelines and were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) prior to study conduct. Procedures described here were performed on male and female large white farm pigs (50% Landrace/50% Large White genetic background) up to 3 months of age that are deemed healthy and suitable for surgery.  Animals are socially housed unless considered incompatible by institutional veterinary care staff.  Animals are fed appropriate levels of chow twice daily and observed for clinical signs by care staff at least once daily.

1. Preparation for....

Results

The liver resection and autologous transplantation are represented schematically in Figure 1. In a representative cohort of 5 pigs that underwent hepatic resection, most had yields of >1 x 10⁹ hepatocytes with approximately 80% viability (Table 2), providing plenty of cells for any type of desired manipulations, including gene therapy. Subsequent culture of the non-transplanted portion of prepared hepatocytes from each of those .......

Discussion

This report describes an ex vivo autologous gene therapy approach to cure a porcine model of HT-1. It involves a partial hepatectomy, followed by ex vivo hepatocyte isolation and transduction of isolated hepatocytes with lenti virus carrying the corrective transgene. Corrected autologous hepatocytes are then transplanted back to the FAH deficient animal through the portal vein⁸. Although the method described is applicable to all large animal models with some modification, the FAH.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC)	Yecuris	20-0027
12 mm Trocar	Covidien	B12STS
5 mm Trocar	Covidien	B5SHF
Endo Surgical Stapler 60	Covidien	EGIA60AMT
Endo Surgical Stapler 45	Covidien	EGIA45AVM
Endo Surgical Stapler 30	Covidien	SIG30AVM
Endo catch bag	Covidien	173050G
0 PDS	Ethicon	Z340H
2-0 Vicryl	Ethicon	J459H
4-0 Vicryl	Ethicon	J426H
Dermabond	Ethicon	DNX12	Sterile Dressing
Williams’-E Powder	Gibco	ME16060P1
NaHCO3	Sigma Aldrich	S8875-1KG
HEPES	Fisher	BP310-1
Pen/Strep	Gibco	15140-122
Fetal Bovine Serum	Corning	35-011-CV
NaCl (g/L)	Sigma Aldrich	S1679-1KG
KCl (g/L)	Sigma Aldrich	P3911-500G
EGTA (g/L)	Oakwood Chemical	45172
N-acetyl-L-cysteine	Oakwood Chemical	3631
(N-A-C, g/L)	Sigma Aldrich	A9165-100G
CaCl2 2H2O (g/L)	Sigma Aldrich	223506-500G
Collagenase D (mg/mL)	Crescent Chemical	17456.2
Dulbecco's modified eagle medium (DMEM)	Corning	15-013-CV
Dexamethasone	Fresenius Kabi	NDC6337
Epidermal Growth Factor	Gibco	PHG0314