Biology subjects

Rimann, N.

Publications and source records attributed to Rimann, N..

4 recordsLinked to original sources

bioRxiv2024

Therapeutic liver cell transplantation to treat a genetic liver defect

For gene therapy of the liver, in vivo applications based on adeno-associated virus are the most advanced vectors despite limitations, including low efficacy and episomal loss, potential integration and safety issues, and high production costs. Alternative vectors and/or delivery routes are of high interest. The regenerative ability of the liver bears the potential for ex vivo therapy using liver cell transplantation for disease correction if provided with a selective advantage to expand and replace the existing cell mass. Here we present such treatment of a mouse model of human of phenylketonuria (PKU). Primary hepatocytes from wild-type mice were gene modified in vitro (with a lentiviral vector) that carries a gene editing system (CRISPR) to inhibit Cypor. Cypor inactivation confers paracetamol (or acetaminophen) resistance to hepatocytes and thus a growth advantage to eliminate the pre-existing liver cells upon grafting (via the spleen) and exposure to repeated treatment with paracetamol. Grafting Cypor-inactivated wild-type hepatocytes into inbred young adult enu2 (PKU) mice, followed by selective expansion by paracetamol dosing resulted in replacing up to 5% of cell mass, normalization of blood phenylalanine and permanent correction of PKU. Hepatocyte transplantation offers thus an armamentarium of novel therapy options for genetic liver defects.

molecular biology↗

bioRxiv2024

Treatment of a genetic liver disease in mice through transient prime editor expression

Prime editing is a versatile genome editing technology that does not rely on DNA double-strand break formation and homology-directed repair (HDR). This makes it a promising tool for correcting pathogenic mutations in tissues consisting predominantly of postmitotic cells, such as the liver. While recent studies have already demonstrated proof-of-concept for in vivo prime editing, the use of viral delivery vectors resulted in prolonged prime editor (PE) expression, posing challenges for clinical application. Here, we developed an in vivo prime editing approach where we delivered the pegRNA using self-complementary adeno-associated viral (scAAV) vectors and the prime editor using nucleoside-modified mRNA encapsulated in lipid nanoparticles (LNPs). This methodology led to transient expression of the PE for 48h and 26% editing at the Dnmt1 locus using AAV doses of 2.5x1013 vector genomes (vg)/kg and a single dose of 3mg/kg mRNA-LNP. When targeting the pathogenic mutation in the Pahenu2 mouse model of phenylketonuria (PKU), we achieved 4.3% gene correction using an AAV dose of 2.5x1013 vg/kg and three doses of 2 mg/kg mRNA-LNP. Editing was specific to the liver and the intended locus, and was sufficient to reduce blood L-phenylalanine (Phe) levels from over 1500 {micro}mol/l to below the therapeutic threshold of 600 {micro}mol/l. Our study demonstrates the feasibility of in vivo gene correction in the liver with transient PE expression, bringing prime editing closer to clinical application.

bioengineering↗

bioRxiv2023

Safe delivery of AAV vectors to the liver of small weaned pigs by ultrasound guided percutaneous transhepatic portal vein injection

One challenge for liver-directed gene therapy is sufficient vector delivery to the target tissue while minimizing loss of the applied vector dose to other tissues. Infusion via peripheral veins is the least invasive approach; however, it results in systemic diffusion and substantial vector dilution. Here, we describe a safe and minimally invasive method to deliver adeno-associated virus (AAV) vectors to the liver of small weaned pigs by ultrasound-guided percutaneous trans-hepatic portal vein injection. 4-week-old piglets were infused with [~]2.5x1014 vector genomes comprising a dual-rAAV2/9 vector system with a split adenine base editor for in vivo inactivation of PCSK9 to reduce LDL-cholesterol levels. Animals had no signs of discomfort and tolerated the procedure well. However, despite 45% editing of the target site with the applied adenine base editor system in cultivated porcine cells, we only found low amounts of AAV vector genomes and neither detectable transgene-expression nor successful editing in the treated pig livers. We hypothesize that rapid proliferation of pig hepatocytes caused AAV vector dilution, leading to a loss of the vectors from the nucleus, and hence insufficient base editor protein expression for achieving detectable editing rates. Nonetheless, ultrasound-guided percutaneous transhepatic injection to the portal vein is well-tolerated in piglets and has potential for human (neonate) application.

molecular biology↗

bioRxiv2021

Treatment of a metabolic liver disease by in vivo prime editing in mice

Prime editing is a highly versatile CRISPR-based genome editing technology with the potential to correct the vast majority of pathogenic mutations (1). However, correction of a disease phenotype in vivo in somatic tissues has not been demonstrated thus far. Here, we establish proof-of-concept for in vivo prime editing and repair the metabolic liver disease phenylketonuria (PKU) in mice. We first developed a size-reduced SpCas9 prime editor (PE) lacking the RNaseH domain of the reverse transcriptase (PE2{Delta}RnH), and a linker- and NLS-optimized intein-split PE construct (PE2 p.1153) for delivery by adeno-associated virus (AAV) vectors. Systemic dual AAV-mediated delivery of this variant into the liver of neonatal mice enabled installation of a transversion mutation at the Dnmt1 locus with an average efficiency of 15%, and delivery of unsplit PE2{Delta}RnH using human adenoviral vector 5 (AdV5) further increased editing rates to 58%. PE2{Delta}RnH-encoding AdV5 was also used to correct the disease-causing mutation of the phenylalanine hydroxylase (Pah)enu2 allele in phenylketonuria (PKU) mice with an average efficiency of 8% (up to 17.3%), leading to therapeutic reduction of blood phenylalanine (L-Phe) levels. Our study demonstrates in vivo prime editing in the liver with high precision and editing rates sufficient to treat a number of metabolic liver diseases, emphasizing the potential of prime editing for future therapeutic applications. One Sentence SummaryIn vivo prime editing corrects phenylketonuria in mice.

genetics↗