Diffuse Large B Cell Lymphoma (DLBCL) is the most common lymphoid malignancy in both humans and dogs, characterized by clinical and biological heterogeneity. While standard chemotherapy induces clinical remission in many patients, the majority of them eventually relapse, and effective treatment options for refractory disease are limited. The underlying biological mechanisms driving therapeutic resistance remain poorly defined, in part due to the scarcity of longitudinal samples needed to track disease progression and clonal changes over time. To address this challenge, we leveraged naturally occurring DLBCL in pet dogs, a spontaneousand clinically relevant model that closely mirrors human DLBCL in molecular features, histopathology, treatment response and disease progression. A key advantage of this model is the ability to obtain serial lymph node biopsies as part of standard veterinary care, enabling longitudinal sampling across the disease course. While similar human studies may take more than five years for sample collection due to slower disease kinetics and limited biopsy access, comparable longitudinal data can be collected in dogs within a year. This makes the canine model a uniquely powerful platform for investigating tumor evolution and the emergence of therapy resistance in vivo. Using this approach, we collected matched samples from eight dogs at three clinically relevant timepoints: initial diagnosis, complete remission post-treatment, and relapse. This design allowed us to track the clonal dynamics of tumor subpopulations within the same host, enabling direct insight into how therapy-resistant states develop over time. We performed single cell RNA sequencing on hundreds of thousands of cells from these biopsies and applied a modern analytical pipeline integrating machine learning tools. Specifically, we used scVI for robust batch correction and latent space modeling, CellTypist for precise immune cell annotation, and PySCENIC to infer cell-specific gene regulatory networks. Together, these tools enabled us to build a comprehensive, multidimensional map of the DLBCL tumor microenvironment and its dynamic response to treatment. Our analysis uncovered a transcriptionally distinct population of B cells consistently present across all three disease stages. Although rare at diagnosis and nearly undetectable during remission, this population expanded dramatically at relapse, strongly suggesting it functions as a reservoir of therapy-resistant cells. Not aligning with any known B cell subtype, these cells exhibit a unique transcriptional identity defined by a complex regulatory program. Through PySCENIC, we identified a dense network of regulons enriched for transcription factors associated with stem-like properties, cellular plasticity, and immune evasion, including IKZF2, PBX1, LEF1, and IRF8. This suggests that chemotherapy resistance in DLBCL may arise from a shared phenotypic state maintained through distinct transcriptional programs rather than fixed genetic alterations. Among the key pathways implicated, Wnt signaling stands out as particularly compelling. This pathway has been extensively studied in human DLBCL, where it contributes to chemotherapy resistance by promoting stem-like characteristics in malignant B cells. The enrichment of LEF1 regulons within the resistant population raises the possibility that Wnt signaling is similarly active in resistant clones in canine DLBCL. LEF1 regulons also suggest activation of Akt signaling, a pathway linked to resistance in human DLBCL. These findings highlight the importance of longitudinal sampling at diagnosis, remission, and relapse to uncover the cellular and molecular basis of treatment resistance, an approach rarely feasible in human studies alone. Our single cell approach, powered by advanced machine learning and comparative oncology, identifies a persistent, adaptable subpopulation likely responsible for relapse. This work not only provides mechanistic insights into tumor evolution under therapeutic pressure but also opens new avenues to target resistant subclone, reinforcing the translational potential of canine models in advancing precision medicine for human DLBCL.

Non-contact anterior cruciate ligament (ACL) rupture is a common serious orthopaedic disease in humans and dogs. Familial risk has been recognized in both species but interactions between genetic effects and environmental risk are not understood. We investigated ACL rupture heritability, genetic architecture, selection pressure, sharing of risk genes and biological pathways, and polygenic risk score (PRS) prediction of disease risk. In both species, ACL rupture has moderate heritability, is likely under negative selection, and has a highly polygenic architecture where thousands of variant effects act together to influence disease risk. In dogs, we found hotspots of regional heritability. We also confirmed sharing of multiple risk genes. Our findings challenge the dogma that non-contact ACL rupture is predominantly due to a single overload injury event. Our results also suggest that accurate PRS prediction of ACL rupture risk is an achievable goal in both species, enabling identification of individuals for personalized medical care. Cross-species genetic analysis in humans and dogs sheds light on the complexity of the intrinsic genetic contribution and the biological pathways that influence risk of non-contact anterior cruciate ligament rupture, a heritable disease.

Purpose (the aim of the study): Ligaments are short bands of fibrous connective tissue responsible for transmitting load from bone to bone across joints and guiding normal joint motion. Cruciate ligaments within the human knee joint, particularly the anterior cruciate ligament (ACL), are susceptible to degeneration, resulting in pain, reduced mobility and development of the degenerative joint disease of osteoarthritis (OA). There is currently a paucity of knowledge on why certain individuals are at high risk to non-contact ACL degeneration, which will eventually lead to OA.The dog is a naturally-occurring spontaneous model of non-contact ACL degeneration, with certain dog breeds such as the Labrador retriever being at a high-risk of ligament injury.

OBJECTIVE The aim of this study was to investigate whether plasma neurofilament light chain (pNfL) concentration was altered in Labrador Retrievers with idiopathic laryngeal paralysis (ILP) compared to a control population. A secondary aim was to investigate relationships between age, height, weight, and body mass index in the populations studied. ANIMALS 123 dogs: 62 purebred Labrador Retrievers with ILP (ILP Cases) and 61 age-matched healthy medium- to large-breed dogs (Controls). METHODS Dogs, recruited from August 1, 2016, to March 1, 2022, were categorized as case or control based on a combination of physical exam, neurologic exam, and history. Blood plasma was collected, and pNfL concentration was measured. pNfL concentrations were compared between ILP Cases and Controls. Covariables including age, height, and weight were collected. Relationships between pNfL and covariables were analyzed within and between groups. In dogs where 2 plasma samples were available from differing time points, pNfL concentrations were measured to evaluate alterations over time. RESULTS No significant difference in pNfL concentration was found between ILP Cases and Control ( P = .36). pNfL concentrations had moderate negative correlations with weight and height in the Control group; other variables did not correlate with pNfL concentrations in ILP Case or Control groups. pNfL concentrations do not correlate with ILP disease status or duration in Labrador Retrievers. CLINICAL RELEVANCE There is no evidence that pNfL levels are altered due to ILP disease duration or progression when compared with healthy controls. When evaluating pNfL concentrations in the dog, weight and height should be considered.

Late-onset peripheral neuropathy (LPN) is a heritable canine neuropathy commonly found in Labrador retrievers and is characterized by laryngeal paralysis and pelvic limb paresis. Our objective was to establish canine LPN as a model for human hereditary peripheral neuropathy by classifying it as either an axonopathy or myelinopathy and evaluating length-dependent degeneration. We conducted a motor nerve conduction study of the sciatic and ulnar nerves, electromyography (EMG) of appendicular and epaxial musculature, and histologic analysis of sciatic and recurrent laryngeal nerves in LPN-affected and control dogs. LPN-affected dogs exhibited significant decreases in compound muscle action potential (CMAP) amplitude, CMAP area, and pelvic limb latencies. However, no differences were found in motor nerve conduction velocity, residual latencies, or CMAP duration. Distal limb musculature showed greater EMG changes in LPN-affected dogs. Histologically, LPN-affected dogs exhibited a reduction in the number of large-diameter axons, especially in distal nerve regions. In conclusion, LPN in Labrador retrievers is a common, spontaneous, length-dependent peripheral axonopathy that is a novel animal model of age-related peripheral neuropathy that could be used for fundamental research and clinical trials.

OBJECTIVE:Cruciate ligament rupture (CR) in Labrador Retrievers is a complex polygenic disease with high heritability. The environmental contribution to CR risk remains poorly characterized. An accurate genetic risk test for CR in the Labrador Retriever has been developed. This enables evaluation of environmental risk with knowledge of genetic disease predisposition through study of dogs with phenotypic disease status that is discordant with their genetic risk. The objective of this study was to identify environmental factors that contribute to CR in Labrador Retrievers through evaluation of dogs with clinical phenotypes that are discordantly predicted with the use of genetic markers. METHODS:Dogs were prospectively recruited between January 2013 and December 2022. To study discordant subjects, case dogs with a posterior risk probability value < 0.75 and control dogs with a posterior risk probability of > 0.25, determined with the use of an average of 8 statistical models, were selected. The environmental factors investigated were neuter status, age of neuter, withers height measured at the dorsal-most ridge between the scapulae, weight, body mass index, and athletic activity. RESULTS:Ninety three dogs were discordant: 58 dogs were discordant CR cases, and 35 dogs were discordant CR controls. Neutering before 12 months of age was a significant risk factor for CR development. Sex, neuter status, or status as an athlete was not associated with CR risk. CONCLUSIONS:Neutering before 12 months of age influences risk of CR in Labrador Retrievers. CLINICAL RELEVANCE:This information can inform management decisions about Labrador Retrievers regarding age of neutering, body condition, and athletic activity. The primary factor influencing CR development in Labrador Retrievers is polygenic intrinsic genetic risk.

Background: : Trichophytobezoars have been reported in a variety of mammalian taxa, including macropods, but successful antemortem diagnosis and surgical excision in macropods is rare. Case description: : An 11-month-old, castrated male, red-necked wallaby (Notamacropus rufogriseus) was presented for evaluation of a sudden onset of lethargy, anorexia, tremoring, and ataxia. The wallaby was hospitalized and started on supportive care. Baseline bloodwork showed wa low normal white blood cell count and a low normal potassium. Abdominal radiography and computed tomography were subsequently performed and demonstrated severe gastric dilatation secondary to gastric and small intestinal foreign bodies. Based on the diagnostic imaging findings, a laparotomy with gastrotomy and enterotomy was performed to successfully remove the gastric and small intestinal foreign bodies, which were trichophytobezoars. The wallaby recovered fully from the procedure.Conclusions and case relevance: : Abdominal radiography and computed tomography were strongly supportive of intestinal mechanical obstruction. Gastrotomy and enterotomy successfully relieved a small intestinal mechanical obstruction in a clinically ill macropod who, postoperatively, was apparently healthy for at least 14 months. Gas-trointestinal bezoars should be considered a differential diagnosis for macropods with nonspecific gastrointestinal signs.

OBJECTIVE:To determine the presentation, diagnosis, progression, and family risk of fibrotic myopathy, a disease with marked breed predisposition in the German Shepherd Dog (GSD).ANIMALS:41 dogs prospectively recruited to the University of Wisconsin-Madison Comparative Genetics and Orthopedic Laboratory between November 2019 to August 2022.METHODS:Medical records of dogs diagnosed with fibrotic myopathy were reviewed upon referral. The following data were recorded: sex, age, weight, regio interscapularis (withers) height, date of neutering, coat color and length, and age at fibrotic myopathy diagnosis. A pedigree was also obtained.RESULTS:In the study population, breeds included 37 GSDs, a Belgian Malinois, a Belgian Malinois cross, and 2 dogs with a GSD phenotype and no pedigree. Mean age at fibrotic myopathy diagnosis was 5.9 ± 2.0 years, and duration of lameness before diagnosis was 5.6 months and ranged from 0.75 to 18 months. Males were overrepresented at 61% of the study population. Inherited familial risk for fibrotic myopathy in the GSD was supported by pedigree analysis.CLINICAL RELEVANCE:This was the largest case series of fibrotic myopathy to date, providing a more comprehensive look at presentation and progression of the disease. The longer duration of lameness in bilaterally affected dogs likely represents disease progression rather than a more severe phenotype. Family history data support a genetic contribution to fibrotic myopathy, suggesting that further genetic investigation is warranted.

Introduction: Spontaneous rupture of tendons and ligaments is common in several species including humans. In horses, degenerative suspensory ligament desmitis (DSLD) is an important acquired idiopathic disease of a major energy-storing tendon-like structure. DSLD risk is increased in several breeds, including the Peruvian Horse. Affected horses have often been used for breeding before the disease is apparent. Breed predisposition suggests a substantial genetic contribution, but heritability and genetic architecture of DSLD have not been determined. Methods: To identify genomic regions associated with DSLD, we recruited a reference population of 183 Peruvian Horses, phenotyped as DSLD cases or controls, and undertook a genome-wide association study (GWAS), a regional window variance analysis using local genomic partitioning, a signatures of selection (SOS) analysis, and polygenic risk score (PRS) prediction of DSLD risk. We also estimated trait heritability from pedigrees. Results: Heritability was estimated in a population of 1,927 Peruvian horses at 0.22 ± 0.08. After establishing a permutation-based threshold for genome-wide significance, 151 DSLD risk single nucleotide polymorphisms (SNPs) were identified by GWAS. Multiple regions of enriched local heritability were identified across the genome, with strong enrichment signals on chromosomes 1, 2, 6, 10, 13, 16, 18, 22, and the X chromosome. With SOS analysis, there were 66 genes with a selection signature in DSLD cases that was not present in the control group that included the TGFB3 gene. Pathways enriched in DSLD cases included proteoglycan metabolism, extracellular matrix homeostasis, and signal transduction pathways that included the hedgehog signaling pathway. The best PRS predictive performance was obtained when we fitted 1% of top SNPs using a Bayesian Ridge Regression model which achieved the highest mean of R 2 on both the probit and logit liability scales, indicating a strong predictive performance. Discussion: We conclude that within-breed GWAS of DSLD in the Peruvian Horse has further confirmed that moderate heritability and a polygenic architecture underlies the trait and identified multiple DSLD SNP associations in novel tendinopathy candidate genes influencing disease risk. Pathways enriched with DSLD risk variants include ones that influence glycosaminoglycan metabolism, extracellular matrix homeostasis, signal transduction pathways.

A 2-year-old male neutered Rat Terrier was presented for alopecia, recurrent urinary tract infections, and urinary incontinence. Abdominal ultrasound and CT identified a thin, tubular, paired structure arising from the craniodorsal aspect of an enlarged, cystic prostate. An atypical uterus masculinus was initially suspected, however it was then identified that the patient had chronic exogenous estrogen exposure, and surgical resection and histopathology was consistent with an enlarged and inflamed vas deferens. Vas deferens enlargement and vasitis secondary to chronic hyperestrogenism should be considered for a tubular, paired structure arising from the craniodorsal prostate in a male dog.

Degenerative suspensory ligament desmitis is a progressive idiopathic condition that leads to scarring and rupture of suspensory ligament fibers in multiple limbs in horses. The prevalence of degenerative suspensory ligament desmitis is breed related. Risk is high in the Peruvian Horse, whereas pony and draft breeds have low breed risk. Degenerative suspensory ligament desmitis occurs in families of Peruvian Horses, but its genetic architecture has not been definitively determined. We investigated contrasts between breeds with differing risk of degenerative suspensory ligament desmitis and identified associated risk variants and candidate genes. We analyzed 670k single nucleotide polymorphisms from 10 breeds, each of which was assigned one of the four breed degenerative suspensory ligament desmitis risk categories: control (Belgian, Icelandic Horse, Shetland Pony, and Welsh Pony), low risk (Lusitano, Arabian), medium risk (Standardbred, Thoroughbred, Quarter Horse), and high risk (Peruvian Horse). Single nucleotide polymorphisms were used for genome-wide association and selection signature analysis using breed-assigned risk levels. We found that the Peruvian Horse is a population with low effective population size and our breed contrasts suggest that degenerative suspensory ligament desmitis is a polygenic disease. Variant frequency exhibited signatures of positive selection across degenerative suspensory ligament desmitis breed risk groups on chromosomes 7, 18, and 23. Our results suggest degenerative suspensory ligament desmitis breed risk is associated with disturbances to suspensory ligament homeostasis where matrix responses to mechanical loading are perturbed through disturbances to aging in tendon (PIN1), mechanotransduction (KANK1, KANK2, JUNB, SEMA7A), collagen synthesis (COL4A1, COL5A2, COL5A3, COL6A5), matrix responses to hypoxia (PRDX2), lipid metabolism (LDLR, VLDLR), and BMP signaling (GREM2). Our results do not suggest that suspensory ligament proteoglycan turnover is a primary factor in disease pathogenesis.

Numerous reports describe complication rates associated with oromaxillofacial oncologic surgery in dogs, however, investigation regarding the impact of the surgical environment on the incidence of complications is under reported. The objective of this retrospective cohort study, including 226 dogs surgically treated for oromaxillofacial tumors between January 1, 1997 and December 31, 2018, is to evaluate the impact of the surgical environment on the incidence of complications in oromaxillofacial oncologic surgery in dogs. A secondary objective is to report the incidence of local complications in oromaxillofacial oncologic surgery and characterize the type, timing, and severity of complications encountered. Incidence of complications was identified to be 69.9%. No significant association was identified between the incidence, timing, or severity of complications and the training background of the clinician, physical location of the procedure, or the ostectomy instrument used. These results suggest that the surgical environment has little impact on the incidence, timing, and severity of complications in dogs undergoing oromaxillofacial oncologic surgery. The results also emphasize the importance of preparing the surgical team and the client for a high incidence of complications associated with oromaxillofacial oncologic surgery in dogs and indicate that both short-term and long-term follow up is important in these cases. Oromaxillofacial surgery performed by residents-in-training within a veterinary teaching environment with adequate supervision appears to be safe.

Background Osteosarcoma (OSA) is a devastating disease that is common in the Irish Wolfhound breed. The aim of this study was to use a pedigree-based approach to determine the heritability of OSA in the Irish Wolfhound using data from a large publically available database. Results The pedigree used for this study included 5110 pure-bred Irish Wolfhounds, including 332 dogs diagnosed with OSA and 360 control dogs; dogs were considered controls if they lived over 10 years of age and were not reported to have developed OSA. The estimated heritability of OSA in the Irish Wolfhound was 0.65. Conclusion The results of this study indicate that OSA in the Irish Wolfhound is highly heritable, and support the need for future research investigating associated genetic mutations.

OBJECTIVE:To evaluate outcomes in cats undergoing subtotal colectomy for the treatment of idiopathic megacolon and to determine whether removal versus nonremoval of the ileocecocolic junction (ICJ) was associated with differences in outcome.ANIMALS:166 client-owned cats.PROCEDURES:For this retrospective cohort study, medical records databases of 18 participating veterinary hospitals were searched to identify records of cats with idiopathic megacolon treated by subtotal colectomy from January 2000 to December 2018. Data collection included perioperative and surgical variables, complications, outcome, and owner perception of the procedure. Data were analyzed for associations with outcomes of interest, and Kaplan-Meier survival time analysis was performed.RESULTS:Major perioperative complications occurred in 9.9% (15/151) of cats, and 14% (12/87) of cats died as a direct result of treatment or complications of megacolon. The median survival time was not reached. Cats with (vs without) a body condition score < 4/9 (hazard ratio [HR], 5.97), preexisting heart disease (HR, 3.21), major perioperative complications (HR, 27.8), or long-term postoperative liquid feces (HR, 10.4) had greater hazard of shorter survival time. Constipation recurrence occurred in 32% (24/74) of cats at a median time of 344 days and was not associated with retention versus removal of the ICJ; however, ICJ removal was associated with long-term liquid feces (OR, 3.45), and a fair or poor outcome on owner assessment (OR, 3.6).CONCLUSIONS AND CLINICAL RELEVANCE:Results indicated that subtotal colectomy was associated with long survival times and a high rate of owner satisfaction. Removal of the ICJ was associated with less favorable outcomes in cats of the present study.

Anterior cruciate ligament (ACL) rupture is a common condition that disproportionately affects young people, 50% of whom will develop knee osteoarthritis (OA) within 10 years of rupture. ACL rupture exhibits both hereditary and environmental risk factors, but the genetic basis of the disease remains unexplained. Spontaneous ACL rupture in the dog has a similar disease presentation and progression, making it a valuable genomic model for ACL rupture. We leveraged the dog model with Bayesian mixture model (BMM) analysis (BayesRC) to identify novel and relevant genetic variants associated with ACL rupture. We performed RNA sequencing of ACL and synovial tissue and assigned single nucleotide polymorphisms (SNPs) within differentially expressed genes to biological prior classes. SNPs with the largest effects were on chromosomes 3, 5, 7, 9, and 24. Selection signature analysis identified several regions under selection in ACL rupture cases compared to controls. These selection signatures overlapped with genome-wide associations with ACL rupture as well as morphological traits. Notable findings include differentially expressed ACSF3 with MC1R (coat color) and an association on chromosome 7 that overlaps the boundaries of SMAD2 (weight and body size). Smaller effect associations were within or near genes associated with regulation of the actin cytoskeleton and the extracellular matrix, including several collagen genes. The results of the current analysis are consistent with previous work published by our laboratory and others, and also highlight new genes in biological pathways that have not previously been associated with ACL rupture. The genetic associations identified in this study mirror those found in human beings, which lays the groundwork for development of disease-modifying therapies for both species.