Jinghan Li (Alex)_SURF2025_Evaluation of CRISPR/Cas9-Based Gene Fragment Deletion in Primary Human Chondrocytes using the Pregnancy-Associated Plasma Protein A (PAPPA) Gene as Target

Osteoarthritis (OA) is the most common joint disorder, impacting more than 500 million people worldwide, and has become increasingly prominent in the past two decades. It can lead to serious health and economic burden, while there is currently no curative treatment for OA because its disease development is complex. Genetic factors are the top contributing factors of OA, and it is imperative to understand the genetic basis of OA. Pregnancy-associated plasma protein A (PAPPA) is a novel gene identified to be involved in OA development with support of genome-wide association studies (GWAS), expression quantitative trait loci (eQTL), and high-throughput chromatin conformation capture (Hi-C) data. This study used primary human chondrocytes as the model system and employed ribonucleoprotein transfection-based CRISPR/Cas9 delivery to create two double-stranded breaks in the exon 2 of the PAPPA gene in these cells. Screening of the population following transfection showed that a significant number of cells have undergone a deletion in the exon 2 of PAPPA, which will putatively generate a knock-out (KO) of the PAPPA gene. Single colonies were then isolated and expanded from the transfected population, and multiple colonies of cells with homozygous deletion of a region in PAPPA exon 2 were identified. These colonies of cells are highly valuable for functional follow-up experiments on changes in gene expression and phenotypes of chondrocytes with PAPPA KO, which will be performed subsequently. In summary, this study further verified the feasibility of generating gene fragment deletions using CRISPR/Cas9 in chondrocytes and has laid the basis for the functional studies of PAPPA as a potential key mediator of OA.