Application and Best Practices of Liver Biopsy in Non-Rodents

The liver is a vital organ responsible for metabolism and detoxification, involved in the metabolism of sugars, fats, vitamins, hormones, and drugs. It also plays a vital role in secreting and excreting bile and producing clotting factors. With the rapid development of new modalities, particularly oligonucleotide drugs that target the liver, direct research on drug exposure in liver can provide better assessments of their dose-response relationships. This blog discusses liver biopsy techniques in non-rodents, their applications, challenges, and best practices.

What is liver biopsy?

A liver biopsy involves using a biopsy needle to extract a small amount of liver tissue while the animal is under anesthesia. This procedure allows for multiple biopsies in large animals, enabling researchers to study drug exposure in liver tissues. In animal studies, liver biopsy is a cost-effective and animal-saving method for assessing liver tissue distribution, aligning with the principles of the 3Rs—Reduce, Replace, and Refine. In addition, this approach allows for repeated sample collection from the same animal, ensuring the reliability and consistency of data.

Applications of liver biopsy in non-rodents

By analyzing liver tissue samples obtained from liver biopsy, scientists can gain a comprehensive understanding of drug metabolism pathways, enzymatic activity, and their impact on drug efficacy and safety. This also allows for an understanding of their maximum concentrations, duration of efficacy, and interactions with receptors and transporters, which influence the pharmacokinetics and the pharmacological characteristics of drugs. Furthermore, liver biopsy techniques contribute to the evaluation of drug-induced hepatotoxicity and the identification of potential safety concerns by investigating pathological changes in the liver tissue.

Oligonucleotide drugs are known for their ability to target specific tissues, and the liver is a common target due to its high blood flow and metabolic activity. Both commonly used delivery systems GalNAc and ASGPR have high affinity with liver cells, facilitating the delivery of oligonucleotides to liver. Another strategy involves using nanoliposomes that bind to apolipoprotein E (ApoE), allowing entry into hepatocytes via the low-density lipoprotein receptor (LDL-R). Both approaches aim to improve the specificity and efficiency of oligonucleotide delivery to liver cells. Figure 1 shows the mean plasma and liver concentrations, and PK parameters of a GalNAC-modified siRNA after a single subcutaneous injection in cynomolgus monkeys. Plasma concentrations dropped below the detective limit of quantification (BLQ) at 16 hours after administration, while liver concentrations remained above the detective limit of quantification until 57 days after administration.

Figure 1. Mean (n=6) plasma and liver concentration of a GalNAC-modified siRNA after a single subcutaneous injection in cynomolgus monkeys

Challenges and best practices of liver biopsy

Conducting liver biopsies in preclinical experiments presents various challenges, particularly concerning technical skills, experimental design, and animal selection considerations.

#1 Optimizing techniques and equipment

Inexperienced operators and low-resolution equipment can significantly hinder experimental success. Our extensive experience across numerous projects has led to the development of standardized biopsy procedures and protocols, enhancing the reliability of results. Figure 2 shows an ultrasound-guided biopsy monitor display.

Figure 2. Ultrasound-guided biopsy monitor display with a biopsy needle

#2 Designing experimental protocols

Each project requires tailored experimental parameters, including anesthesia, biopsy frequency, and tissue volume collected. It is essential to prolong the intervals between biopsies to allow adequate recovery time for the animals while meeting experimental needs.

#3 Animal selection and welfare

Selecting animals without coagulation disorders, anemia, or ascites is crucial, and heavier animals are preferred (≥ 3 kg). Ensuring animal welfare is a fundamental aspect. This involves health assessments, appropriate anesthetic administration, and analgesics to minimize pain. Monitoring physiological indicators and offering additional foods are also critical for maintaining the well-being of the animals.

Concluding remarks

Liver biopsy techniques have broad clinical applications and play a vital role in the development of new drugs. Currently, liver biopsies are widely used in new drug research for dynamic monitoring of disease models, assessing tissue drug concentration distribution, and measuring target genes. WuXi AppTec DMPK has over ten years of experience in liver biopsies, continually refining techniques and upgrading equipment. This dedication has fostered the development of a highly skilled professional team committed to supporting clients and advancing new drug research.

Authors: Liping Tang, Huayu Li, Hang Zhao, Zhihai Li, Shoutao Liu

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