Functional intestinal disorders constitute major, potentially lethal health problems in humans. Consequently, research focuses on elucidating the underlying pathobiological mechanisms and establishing therapeutic strategies. In this context, intestinal organoids have emerged as a potent in vitro model as they faithfully recapitulate the structure and function of the intestinal segment they represent. Interestingly, human-like intestinal diseases also affect dogs, making canine intestinal organoids a promising tool for canine and comparative research. Therefore, we generated organoids from canine duodenum, jejunum and colon, and focused on simultaneous long-term expansion and cell differentiation to maximize applicability. Following their establishment, canine intestinal organoids were grown under various culture conditions and then analyzed with respect to cell viability/apoptosis and multi-lineage differentiation by transcription profiling, proliferation assay, cell staining, and transmission electron microscopy. Standard expansion medium supported long-term expansion of organoids irrespective of their origin, but inhibited cell differentiation. Conversely, transfer of organoids to differentiation medium promoted goblet cell and enteroendocrine cell development, but simultaneously induced apoptosis. Unimpeded stem cell renewal and concurrent differentiation was achieved by culturing organoids in the presence of tyrosine kinase ligands. Our findings unambiguously highlight the characteristic cellular diversity of canine duodenum, jejunum and colon as fundamental prerequisite for accurate in vitro modelling.

Alimentary lymphomas arising from T cells are rare and aggressive malignancies in humans. In comparison, they represent the most common anatomical form of lymphoma in cats. Due to the low prevalence in humans, the underlying pathomechanism for these diseases is poorly characterised, limiting experimental analysis and therapeutic exploration. To date, activating mutations of the JAK/STAT core cancer pathway and particularly the STAT5B oncoprotein have been identified in human enteropathy-associated T cell lymphoma. Here, we describe a high homology of human and feline STAT3 and STAT5B proteins and strong conservation at the genomic level. Analysis of 42 samples of feline T cell alimentary lymphoma reveals broad activation of STAT3 and STAT5B. Screening for known activating mutations in STAT3 or STAT5B identifies the presence of the STAT5B^N642H driver mutation in feline enteropathy-associated T cell lymphoma in 7 out of 42 (16.67%) samples in total. Regarding lymphoma subtypes, the majority of mutations with 5 out of 17 (29.41%) cases were found in feline enteropathy-associated lymphoma type II (EATL II). This identification of an oncogenic STAT5B driver mutation in felines recapitulates the genetic situation in the corresponding human disease, thereby establishing the cat as a potential new model for a rare and incurable human T cell disease.

The use of transgenic mouse models has revolutionized the study of many human diseases. However, murine models are limited in their representation of spontaneously arising tumors and often lack key clinical signs and pathological changes. Thus, a closer representation of complex human diseases is of high therapeutic relevance. Given the high failure rate of drugs at the clinical trial phase (i.e., around 90%), there is a critical need for additional clinically relevant animal models. Companion animals like cats and dogs display chronic inflammatory or neoplastic diseases that closely resemble the human counterpart. Cat and dog patients can also be treated with clinically approved inhibitors or, if ethics and drug safety studies allow, pilot studies can be conducted using, e.g., inhibitors of the evolutionary conserved JAK-STAT pathway. The incidence by which different types of cancers occur in companion animals as well as mechanisms of disease are unique between humans and companion animals, where one can learn from each other. Taking advantage of this situation, existing inhibitors of known oncogenic STAT3/5 or JAK kinase signaling pathways can be studied in the context of rare human diseases, benefitting both, the development of drugs for human use and their application in veterinary medicine.