Genetically modified animals are vital for gaining a proper understanding of disease mechanisms. Mice have long been the mainstay of basic research into a wide variety of diseases but are not always the most suitable means of translating basic knowledge into clinical application. The shortcomings of rodent preclinical studies are widely recognised, and regulatory agencies around the world now require preclinical trial data from nonrodent species. Pigs are well suited to biomedical research, sharing many similarities with humans, including body size, anatomical features, physiology and pathophysiology, and they already play an important role in translational studies. This role is set to increase as advanced genetic techniques simplify the generation of pigs with precisely tailored modifications designed to replicate lesions responsible for human disease. This article provides an overview of the most promising and clinically relevant genetically modified porcine models of human disease for translational biomedical research, including cardiovascular diseases, cancers, diabetes mellitus, Alzheimer's disease, cystic fibrosis and Duchenne muscular dystrophy. We briefly summarise the technologies involved and consider the future impact of recent technical advances.

Genetically modified animals continue to provide important insights into the molecular basis of health and disease. Research has focused mostly on genetically modified mice, although other species like pigs resemble the human physiology more closely. In addition, cross-species comparisons with phylogenetically distant species such as chickens provide powerful insights into fundamental biological and biomedical processes. One of the most versatile genetic methods applicable across species is CRISPR-Cas9. Here, we report the generation of transgenic chickens and pigs that constitutively express Cas9 in all organs. These animals are healthy and fertile. Functionality of Cas9 was confirmed in both species for a number of different target genes, for a variety of cell types and in vivo by targeted gene disruption in lymphocytes and the developing brain, and by precise excision of a 12.7-kb DNA fragment in the heart. The Cas9 transgenic animals will provide a powerful resource for in vivo genome editing for both agricultural and translational biomedical research, and will facilitate reverse genetics as well as cross-species comparisons.

We compared gene expression in low and high-grade intraepithelial dysplastic polyps from pigs carrying an APC 1311 truncating mutation orthologous to human APC 1309, analysing whole samples and microdissected dysplastic epithelium. Gene set enrichment analysis revealed differential expression of gene sets similar to human normal mucosa versus T1 stage polyps. Transcriptome analysis of whole samples revealed many differentially-expressed genes reflecting immune infiltration. Analysis of microdissected dysplastic epithelium was markedly different and showed increased expression in high-grade intraepithelial neoplasia of several genes known to be involved in human CRC; and revealed possible new roles for GBP6 and PLXND1. The pig model thus facilitates analysis of CRC pathogenesis.

CCL22 is a key mediator of leukocyte trafficking in inflammatory immune responses, allergy, and cancer. It acts by attracting regulatory T cells and Th2 cells via their receptor CCR type 4 (CCR4). Beyond its role in inflammation, CCL22 is constitutively expressed at high levels in lymphoid organs during homeostasis, where it controls immunity by recruiting regulatory T cells to dendritic cells (DCs). In this study, we aimed to identify the mechanisms responsible for constitutive CCL22 expression. We confirmed that CD11c + DCs are the exclusive producers of CCL22 in secondary lymphatic organs during homeostasis. We show that in vitro both murine splenocytes and human PBMCs secrete CCL22 spontaneously without any further stimulation. Interestingly, isolated DCs alone, however, are unable to produce CCL22, but instead require T cell help. In vitro, only the coculture of DCs with T cells or their supernatants resulted in CCL22 secretion, and we identified T cell-derived GM-CSF as the major inducer of DC-derived CCL22 expression. In vivo, Rag1 2/2 mice, which lack functional T cells, have low CCL22 levels in lymphoid organs, and this can be restored by adoptive transfer of wild-type T cells or administration of GM-CSF. Taken together, we uncover T cell-derived GM-CSF as a key inducer of the chemokine CCL22 and thus, to our knowledge, identify a novel role for this cytokine as a central regulator of immunity in lymphatic organs. This knowledge could contribute to the development of new therapeutic interventions in cancer and autoimmunity.

MicroRNAs are dysregulated in various cancers including colorectal cancer, and are potential useful biomarkers of disease development. We used next generation sequencing to investigate miRNA expression profiles in low- and high-grade intraepithelial dysplastic polyps from pigs carrying a mutation in the adenomatous polyposis coli tumour suppressor (APC1311, orthologous to human APC1309) that model an inherited predisposition to colorectal cancer, familial adenomatous polyposis. We identified several miRNAs and their isomiRs significantly (P < 0.05) differentially expressed between low and high-grade intraepithelial dysplastic polyps. Of these, ssc-let-7e, ssc-miR-98, ssc-miR-146a-5p, ssc-miR-146b, ssc-miR-183 and ssc-miR-196a were expressed at higher level and ssc-miR-126-3p at lower level in high-grade intraepithelial dysplastic polyps. Functional miRNA target analysis revealed significant (P < 0.001) over-representation of cancer-related pathways, including ‘microRNAs in cancer’, ‘proteoglycans in cancer’, ’pathways in cancer’ and ‘colorectal cancer’. This is the first study to reveal miRNAs associated with premalignant transformation of colon polyps.