The utility of the minipig as an animal model in regulatory toxicology

Validation of Blood Volume Fraction Quantification with 3D Gradient Echo Dynamic Contrast-Enhanced Magnetic Resonance Imaging in Porcine Skeletal Muscle

The purpose of this study was to assess the accuracy of fractional blood volume (v_b) estimates in low-perfused and low-vascularized tissue using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). The results of different MRI methods were compared with histology to evaluate the accuracy of these methods under clinical conditions. v_b was estimated by DCE-MRI using a 3D gradient echo sequence with k-space undersampling in five muscle groups in the hind leg of 9 female pigs. Two gadolinium-based contrast agents (CA) were used: a rapidly extravasating, extracellular, gadolinium-based, low-molecular-weight contrast agent (LMCA, gadoterate meglumine) and an extracellular, gadolinium-based, albumin-binding, slowly extravasating blood pool contrast agent (BPCA, gadofosveset trisodium). LMCA data were evaluated using the extended Tofts model (ETM) and the two-compartment exchange model (2CXM). The images acquired with administration of the BPCA were used to evaluate the accuracy of v_b estimation with a bolus deconvolution technique (BD) and a method we call equilibrium MRI (EqMRI). The latter calculates the ratio of the magnitude of the relaxation rate change in the tissue curve at an approximate equilibrium state to the height of the same area of the arterial input function (AIF). Immunohistochemical staining with isolectin was used to label endothelium. A light microscope was used to estimate the fractional vascular area by relating the vascular region to the total tissue region (immunohistochemical vessel staining, IHVS). In addition, the percentage fraction of vascular volume was determined by multiplying the microvascular density (MVD) with the average estimated capillary lumen, π(d2)2, where d = 8μm is the assumed capillary diameter (microvascular density estimation, MVDE). Except for ETM values, highly significant correlations were found between most of the MRI methods investigated. In the cranial thigh, for example, the v_b medians (interquartile range, IQRs) of IHVS, MVDE, BD, EqMRI, 2CXM and ETM were v_b = 0.7(0.3)%, 1.1(0.4)%, 1.1(0.4)%, 1.4(0.3)%, 1.2(1.8)% and 0.1(0.2)%, respectively. Variances, expressed by the difference between third and first quartiles (IQR) were highest for the 2CXM for all muscle groups. High correlations between the values in four muscle groups—medial, cranial, lateral thigh and lower leg - estimated with MRI and histology were found between BD and EqMRI, MVDE and 2CXM and IHVS and ETM. Except for the ETM, no significant differences between the v_b medians of all MRI methods were revealed with the Wilcoxon rank sum test. The same holds for all muscle regions using the 2CXM and MVDE. Except for cranial thigh muscle, no significant difference was found between EqMRI and MVDE. And except for the cranial thigh and the lower leg muscle, there was also no significant difference between the v_b medians of BD and MVDE. Overall, there was good v_b agreement between histology and the BPCA MRI methods and the 2CXM LMCA approach with the exception of the ETM method. Although LMCA models have the advantage of providing excellent curve fits and can in principle determine more physiological parameters than BPCA methods, they yield more inaccurate results.

Comparative cardiovascular physiology and pathology in selected lineages of minipigs

The minipig has been increasingly recognized as a valid alternative to canines and nonhuman primates in regulatory toxicity. This article presents the results of cardiovascular assessments in the Yucatan, Hanford, Sinclair, and Göttingen minipigs conducted during nonclinical investigations and control toxicity testing. Cardiac electrophysiology was obtained using clinical electrocardiogram and surgical monitor units. Peripheral vessel diameter, velocity, and flow were obtained by Doppler ultrasonography, and cardiac vessel diameter was obtained postmortem. Anatomic parameters were obtained at necropsy. Histopathology assessments were conducted on heart, blood vessels, and kidneys. Collected data were compared to published cardiovascular measurements of adult humans to illustrate similarities and differences. Each lineage of minipigs was found to have specific anatomic and physiologic characteristics that may accurately reflect response of human cardiovascular systems in clinical investigations and toxicity testing. In conclusion, the interspecies similarities between the cardiovascular systems make these lineages of minipigs suitable as models for the human counterpart. In addition, these reported differences between lineages will aid investigators in selecting a relevant lineage of minipigs if specific cardiovascular parameters are required during drug safety evaluation.

Stereological analysis of size and density of hepatocytes in the porcine liver

The porcine liver is frequently used as a large animal model for verification of surgical techniques, as well as experimental therapies. Often, a histological evaluation is required that include measurements of the size, nuclearity or density of hepatocytes. Our aims were to assess the mean number-weighted volume of hepatocytes, the numerical density of hepatocytes, and the fraction of binuclear hepatocytes (BnHEP) in the porcine liver, and compare the distribution of these parameters among hepatic lobes and macroscopic regions of interest (ROIs) with different positions related to the liver vasculature. Using disector and nucleator as design-based stereological methods, the morphometry of hepatocytes was quantified in seven healthy piglets. The samples were obtained from all six hepatic lobes and three ROIs (peripheral, paracaval and paraportal) within each lobe. Histological sections (thickness 16 μm) of formalin-fixed paraffin-embedded material were stained with the periodic acid-Schiff reaction to indicate the cell outlines and were assessed in a series of 3-μm-thick optical sections. The mean number-weighted volume of mononuclear hepatocytes (MnHEP) in all samples was 3670 ± 805 μm³ (mean ± SD). The mean number-weighted volume of BnHEP was 7050 ± 2550 μm³ . The fraction of BnHEP was 4 ± 2%. The numerical density of all hepatocytes was 146 997 ± 15 738 cells mm^-3 of liver parenchyma. The porcine hepatic lobes contained hepatocytes of a comparable size, nuclearity and density. No significant differences were identified between the lobes. The peripheral ROIs of the hepatic lobes contained the largest MnHEP with the smallest numerical density. The distribution of a larger MnHEP was correlated with a larger volume of BnHEP and a smaller numerical density of all hepatocytes. Practical recommendations for designing studies that involve stereological evaluations of the size, nuclearity and density of hepatocytes in porcine liver are provided.

The Use of Minipigs for Preclinical Safety Assessment by the Pharmaceutical Industry: Results of an IQ DruSafe Minipig Survey

The use of minipigs in preclinical safety testing of pharmaceuticals is considered an alternative to the more traditional dog and nonhuman primate (NHP) nonrodent species. Substantial evidence exists to suggest that the anatomy, physiology, and biochemistry of minipigs are similar enough to humans to consider them as valid nonrodent models for pharmaceutical safety testing. Since the utilization of minipigs was last assessed over 5 years ago, the Preclinical Safety Leadership Group (DruSafe) of the International Consortium for Innovation and Quality in Pharmaceutical Development conducted this survey to provide an updated assessment of the utility, perceived value, and impediments to the use of minipigs in preclinical safety testing. Of the 32 participating members of DruSafe, 15 responded to the survey representing both large and small companies. Respondents indicated that the minipig has been utilized mostly for short-term safety assessment studies with dermal, oral, and parenteral routes of administration. Minipigs are widely accepted as appropriate models for cardiovascular assessments and have been used to a limited extent for reproductive toxicology testing. Overall responses indicated that safety testing for large molecules using this species is relatively low due to a lack of background data, reagents or biomarkers, concerns regarding immune system characterization and poor suitability for developmental toxicity assessments. Most companies utilized contract research organizations for definitive safety toxicity assessment studies. Conclusions of this survey indicate that minipig is an acceptable nonrodent species largely limited to studies using small molecules, primarily dermal products, and results are comparable to those reported 5 years ago.

The using of a piglets as a model for evaluating the dipyrone hematological effects

BACKGROUND

Dipyrone (MET, metamizole) is a non-steroidal anti-inflammatory drug commonly used both in human and in veterinary medicine. After oral administration, is broken down rapidly to metabolites which largely retain the activity of the parent drug. Its metabolites have analgesic, antipyretic and anti-inflammatory effects.

RESULTS

The subjects were eight healthy male Large White post-suckling piglets, weighing between 5.0 to 7.4 kg, of ages 35 ± 10 days. The animals were administered MET (100 mg/kg) by an intramuscular (I.M.) injection. The study calculated the value of several hemorheological parameters. Significant impact of MET treatment (p < 0.05) was proven in case: activated partial thromboplastin time; ratio of activated partial thromboplastin time; hemoglobin; hematocrit; mean corpuscular hemoglobin; mean corpuscular volume; red blood cells volume; white blood cells volume; prothrombin time index.

CONCLUSIONS

In summation, our observations suggest that a piglet model is useful for studying the impact of MET on hemorheological parameters.

Impact of Age on the Male Reproductive System from the Pathologist’s Perspective

Age, and in particular young age, can significantly impact the response to toxicants in animals and can greatly influence the interpretation of tissue changes by the toxicologic pathologist. Although this applies to multiple organ systems, the current review focuses on the male reproductive system. When performing microscopic evaluation of male reproductive organs, the toxicologic pathologist must be aware of the dynamic changes in histomorphology, predominantly driven by timed hormonal alterations, at various life stages. Specific challenges pathologists face are understanding the appearance of male reproductive tissues throughout the neonatal, infantile, and juvenile developmental periods, recognizing when normal looks abnormal during tissue development, defining sexual maturity, and working with high interanimal variability in maturation rate and histologic appearance in developing large laboratory animals, such as nonhuman primates, dogs, and pigs. This review describes postnatal development of the male reproductive system in the rat, demonstrates how assessing toxicity during a defined window of postnatal development in the rat may improve definition of toxicant timing and targets, and discusses challenges associated with the interpretation of toxicity in immature large animal species. The emphasis is on key age-related characteristics that influence the interpretation of tissue changes by the toxicologic pathologist.

Histological Development of Male Reproductive Organs in Microminipigs

Microminipigs are becoming increasingly attractive alternatives for various experimental applications, such as general toxicology studies, owing to their manageable size. However, there are limited studies on the male reproductive organs of microminipigs, particularly on the histological aspects of sexual maturity. To clarify the development of male reproductive organs, 35 male microminipigs, aged 0 to 12 months, were used in this study. Histological and histomorphological evaluation was performed based on spermatogenic development, measurement of tubular structure in testes and epididymides, and histological progress of accessory glands. In addition, spontaneous testicular changes were quantitatively assessed. Histologically, male microminipigs sexually matured around 4.5 months of age, when spermatogenesis in testes and structural development in genital organs were completed. Spontaneous testicular changes occurred in all the animals investigated. Multinucleated giant cell was most commonly observed, followed by hypospermatogenesis and tubular atrophy/hypoplasia. However, the number of affected tubules was less than 1% in testes after 4.5 months of age, suggesting that the influence of these changes on evaluation of toxicity studies may be minimal. It is preferable to use sexually mature animals in toxicology studies; therefore, the information obtained by the present study will be helpful for future toxicity evaluations in microminipigs.

Trauma as a Cause for Hepatopathy in Newborn Göttingen Minipigs

Routine husbandry procedures during animal toxicity studies can result in incidental pathological changes. We report on trauma-induced hepatopathy in newborn Göttingen minipigs. Sixty-four neonatal minipigs were allocated to 13- and 26-week treatment arms. There was a 4-week recovery period for both arms. The animals were divided into 2 treatment groups and a vehicle group and were dosed 3 times daily by direct oral administration using a syringe. During the feeding procedure in the first weeks, the animals had to be handled firmly. After 13 weeks, randomly distributed foci of degeneration/necrosis and focal congestion and/or hemorrhage were found in the livers of several animals from all groups. Reduced incidence and severity were evident in the recovery phase, and the lesions were absent after 26 weeks. These changes were considered as related to the manual handling of the animals. Knowledge of these findings is crucial for interpretation of studies utilizing newborn minipigs.

Social housing of non-rodents during cardiovascular recordings in safety pharmacology and toxicology studies

INTRODUCTION

The Safety Pharmacology Society (SPS) and National Centre for the Replacement, Refinement & Reduction of Animals in Research (NC3Rs) conducted a survey and workshop in 2015 to define current industry practices relating to housing of non-rodents during telemetry recordings in safety pharmacology and toxicology studies. The aim was to share experiences, canvas opinion on the study procedures/designs that could be used and explore the barriers to social housing.

METHODS

Thirty-nine sites, either running studies (Sponsors or Contract Research Organisations, CROs) and/or outsourcing work responded to the survey (51% from Europe; 41% from USA).

RESULTS

During safety pharmacology studies, 84, 67 and 100% of respondents socially house dogs, minipigs and non-human primates (NHPs) respectively on non-recording days. However, on recording days 20, 20 and 33% of respondents socially house the animals, respectively. The main barriers for social housing were limitations in the recording equipment used, study design and animal temperament/activity. During toxicology studies, 94, 100 and 100% of respondents socially house dogs, minipigs and NHPs respectively on non-recording days. However, on recording days 31, 25 and 50% of respondents socially house the animals, respectively. The main barriers for social housing were risk of damage to and limitations in the recording equipment used, food consumption recording and temperament/activity of the animals.

CONCLUSIONS

Although the majority of the industry does not yet socially house animals during telemetry recordings in safety pharmacology and toxicology studies, there is support to implement this refinement. Continued discussions, sharing of best practice and data from companies already socially housing, combined with technology improvements and investments in infrastructure are required to maintain the forward momentum of this refinement across the industry.

Strategies and First Advances in the Development of Prevascularized Bone Implants

Despite the great regenerative potential of human bone, large bone defects are a serious condition. Commonly, large defects are caused by trauma, bone disease, malignant tumor removal, and infection or medication-related osteonecrosis. Large defects necessitate clinical treatment in the form of autologous bone transplantation or implantation of biomaterials as well as the application of other available methods that enhance bone defect repair. The development and application of prevascularized bone implants are closely related to the development animal models and require dedicated methods in order to reliably predict possible clinical outcomes and the efficacy of implants. Cell sheet engineering, 3D-printing, arteriovenous loops, and naturally derived decellularized scaffolds and their respective testings in animal models are presented as alternative to the autologous bone graft in this article.

Comparison of mesenchymal stem cells and leukocytes from Large White and Göttingen Minipigs: Clues for stem cell-based immunomodulatory therapies

The mesenchymal stem cells (MSCs) are one of the most promising cell types for human and veterinary use and their therapeutic effect is associated with their immunomodulatory properties. Farm animal models, such as pigs, have become a valuable tool to evaluate the safety and efficacy of adoptively transferred MSCs in the setting of veterinary medicine. In order to evaluate the immunomodulatory effect of stem cell-based therapies in porcine breeds, a deep analysis and comparison of MSCs and leukocyte subsets are absolutely necessary. Here we provide a detailed analysis of bone-marrow derived MSCs and leukocyte subsets from Large White pigs and Göttingen Minipigs. Significant differences were observed between the two pig breeds in terms of T cell subsets that need to be considered for immune monitoring of stem cell-based therapies.

Single- and Bayesian Multi-Marker Genome-Wide Association for Haematological Parameters in Pigs

Haematological traits are important traits that show associations with immune and metabolic status, as well as diseases in humans and animals. Mapping genome regions that affect the blood cell traits can contribute to the identification of genomic features useable as biomarkers for immune, disease and metabolic status. A genome-wide association study (GWAS) was conducted using PorcineSNP60 BeadChips. Single-marker and Bayesian multi-marker approaches were integrated to identify genomic regions and corresponding genes overlapping for both methods. GWAS was performed for haematological traits of 591 German Landrace pig. Heritability estimates for haematological traits were medium to high. In total 252 single SNPs associated with 12 haematological traits were identified (NegLog10 of p-value > 5). The Bayesian multi-marker approach revealed 102 QTL regions across the genome, indicated by 1-Mb windows with contribution to additive genetic variance above 0.5%. The integration of both methods resulted in 24 overlapping QTL regions. This study identified overlapping QTL regions from single- and multi-marker approaches for haematological traits. Identifying candidate genes that affect blood cell traits provides the first step towards the understanding of the molecular basis of haematological phenotypes.

Distribution of Triamcinolone Acetonide after Intravitreal Injection into Silicone Oil-Filled Eye

There is increasing use of the vitreous cavity as a reservoir for drug delivery. We study the intraocular migration and distribution of triamcinolone acetonide (TA) after injection into silicone oil tamponade agent during and after vitrectomy surgery ex vivo (pig eye) and in vitro (glass bottle). For ex vivo assessment, intraocular migration of TA was imaged using real-time FLASH MRI scans and high-resolution T2W imaging and the in vitro model was monitored continuously with a video camera. Results of the ex vivo experiment showed that the TA droplet sank to the interface of silicone oil and aqueous almost immediately after injection and remained inside the silicone oil bubble for as long as 16 minutes. The in vitro results showed that, after the shrinkage of the droplet, TA gradually precipitated leaving only a lump of whitish crystalline residue inside the droplet for about 100 minutes. TA then quickly broke the interface and dispersed into the underlying aqueous within 15 seconds, which may result in a momentary increase of local TA concentration in the aqueous portion and potentially toxic to the retina. Our study suggests that silicone oil may not be a good candidate as a drug reservoir for drugs like TA.

Spermatogenesis in the Microminipig

The microminipig has considerable potential as an animal model to evaluate general toxicity; however, there are few studies on the male reproductive system, particularly regarding spermatogenesis. The objectives of the present study were to clarify the stages of the seminiferous epithelium cycle on the basis of spermiogenesis and to determine the duration of spermatogenesis in the microminipig. Eleven microminipigs from 6 to 9 months of age were used for histological analyses. Spermiogenesis and stages of the seminiferous epithelium cycle were classified according to the degree of acrosomal development as shown by the periodic acid-Schiff reaction. Three of the animals were intravenously injected with 5-bromo-2-deoxyuridine to determine the duration of spermatogenesis by immunohistochemistry. Spermiogenesis was classified into 15 steps according to the morphological development of the acrosome, nucleus, and flagellum. The seminiferous epithelium cycle was classified into 11 stages based on the steps of spermatid development and germ cell associations. The length of the seminiferous epithelium cycle and the overall spermatogenesis process in the microminipig were estimated to be approximately 9.1 and 40.9 days, respectively. The results indicate the potential application of the microminipig in the evaluation of testicular toxicity, such as spermatogenesis disruption, in general toxicity studies.

Development of immune organs and functioning in humans and test animals: Implications for immune intervention studies

A healthy immune status is mostly determined during early life stages and many immune-related diseases may find their origin in utero and the first years of life. Therefore, immune health optimization may be most effective during early life. This review is an inventory of immune organ maturation events in relation to developmental timeframes in minipig, rat, mouse and human. It is concluded that time windows of immune organ development in rodents can be translated to human, but minipig reflects the human timeframes better; however the lack of prenatal maternal-fetal immune interaction in minipig may cause less responsiveness to prenatal intervention. It is too early to conclude which immune parameters are most appropriate, because there are not enough comparative immune parameters. Filling these gaps will increase the predictability of results observed in experimental animals, and guide future intervention studies by assessing relevant parameters in the right corresponding developmental time frames.

"All pigs are equal" Does the background data from juvenile Göttingen minipigs support this?

For pediatric indications requiring juvenile toxicity testing, the rat is the preferred species. However, for some drugs it might not be an appropriate model or regulatory agencies may also request a non-rodent species. Due to the relatively recent use of Göttingen minipigs, little background data are available. This shortage of historical data can raise concerns with respect to interpretation, thus potentially discouraging investigators. This article presents background data from 82 piglets collected at different ages. The data described show the normal variations and changes which are important in the interpretations of these studies. Age-related changes were observed for several cardiac and clinical pathology parameters and in the haematopoietic tissues. Therefore, all pigs were not considered equal. It can be concluded that these data can be used as guidance, to support the concurrent study control data but cannot completely replace them.

A comparison of the anatomical structure of the pancreas in experimental animals

As basic knowledge for evaluation of pancreatic toxicity, anatomical structures were compared among experimental animal species, including rats, dogs, monkeys, and minipigs. In terms of gross anatomy, the pancreases of dogs, monkeys, and minipigs are compact and similar to that of humans. The rat pancreas is relatively compact at the splenic segment, but the duodenal segment is dispersed within the mesentery. In terms of histology, the islet of each animal is characterized by a topographic distribution pattern of α- versus β-cells. β-cells occupy the large central part of the rat islet, and α-cells are located in the periphery and occasionally exhibit cuffing. In dog islets, β-cells are distributed in all parts and α-cells are scattered in the center or periphery of the islet (at body and left lobe); whereas β-cells occupy all parts of the islet and no α-cells are present in the islet (at right lobe). Monkey islets show two distinct patterns, that is, α-cell-rich or β-cell-rich islets, and the former represent peripheral β-cells forming an irregular ring. Minipig islets show an irregular outline, and both α- and β-cells are present in all parts of the islet, intermingling with each other. According to morphometry, the endocrine tissue accounts for <2% of the pancreas roughly in rats and minipigs, and that of monkeys accounts for >7% of the pancreas (at tail). The endocrine tissue proportion tends to increase as the position changes from right to left in the pancreas in each species.

Restoration of normal embryogenesis by mitochondrial supplementation in pig oocytes exhibiting mitochondrial DNA deficiency

An increasing number of women fail to achieve pregnancy due to either failed fertilization or embryo arrest during preimplantation development. This often results from decreased oocyte quality. Indeed, reduced mitochondrial DNA copy number (mitochondrial DNA deficiency) may disrupt oocyte quality in some women. To overcome mitochondrial DNA deficiency, whilst maintaining genetic identity, we supplemented pig oocytes selected for mitochondrial DNA deficiency, reduced cytoplasmic maturation and lower developmental competence, with autologous populations of mitochondrial isolate at fertilization. Supplementation increased development to blastocyst, the final stage of preimplantation development, and promoted mitochondrial DNA replication prior to embryonic genome activation in mitochondrial DNA deficient oocytes but not in oocytes with normal levels of mitochondrial DNA. Blastocysts exhibited transcriptome profiles more closely resembling those of blastocysts from developmentally competent oocytes. Furthermore, mitochondrial supplementation reduced gene expression patterns associated with metabolic disorders that were identified in blastocysts from mitochondrial DNA deficient oocytes. These results demonstrate the importance of the oocyte’s mitochondrial DNA investment in fertilization outcome and subsequent embryo development to mitochondrial DNA deficient oocytes.

A single oral dose of a polyglucosamine influences the bioavailability of [9-(14)C]-Oleic acid in adult female Göttingen minipigs

Background

Worldwide obesity has nearly doubled since 1980 and is a leading risk for global deaths, profoundly affecting morbidity, mortality, health-care costs, and professional and personal quality of life. Treatment of obesity and its consequences include lifestyle intervention, pharmacotherapy, and bariatric surgery. Polyglucosamines have been proposed as an alternative strategy for treating obesity, by reducing the amount of absorbed fat through interaction with dietary fat through various mechanisms. The objective of this study is to investigate the influence of polyglucosamine on the bioavailability of the model compound [9-¹⁴C]-oleic acid in female Göttingen minipigs.

Method

The study consisted of two treatment groups, each consisting of six adult female Göttingen minipigs with a catheterized vena jugularis to enable frequent blood sampling. One group served as the untreated group (control) and the other group was pre-treated with 2 tablets of 500 mg formoline L112. After 30 min, all animals were dosed orally with [9-¹⁴C]-oleic acid. Excreta and blood samples were collected for analysis of radioactivity from 48 h pre-dose up to 144 h post-dosing. At sacrifice, the liver and contents of the gastrointestinal tract were collected for radioanalysis.

Results

Upon treatment with polyglucosamine (formoline L112), the T_max of [¹⁴C]-oleic acid in plasma was shifted from 4 to 16 h, and the C_max decreased significantly from 14.1 μg/g to 3.3 μg/g. In addition, upon treatment with polyglucosamine the internal exposure to [¹⁴C]-oleic acid as reflected by the area under the curve during the 0–12 h post-dose time interval (AUC_0-12h), is significantly decreased to 32.9 % of the plasma value of [¹⁴C]-oleic acid in untreated animals. Even up to 24 h post-dose, the AUC_0-24h is significantly decreased to 50.7 % of the plasma value in untreated animals and this significant effect is prolonged up to 60 h post-dose.

Conclusions

This study shows that treatment with polyglucosamine (formoline L112) reduces (as judged by C_max & AUC) and delays (as judged by T_max) fat absorption from the gastrointestinal tract into the systemic circulation and limits peak exposure to free fatty acids which may contribute to a more beneficial condition in overweight humans.

Biocompatibility and Systemic Safety of a Novel Implantable Annuloplasty Ring for the Treatment of Mitral Regurgitation in a Minipig Model

Prosthetic annuloplasty rings are a common treatment modality for mitral regurgitation, and recently, percutaneous implantation techniques have gained popularity due to their favorable safety profile. Although in common use, biocompatibility of annuloplasty rings has been reported only sparsely in the literature, and none of these reports used the percutaneous technique of implantation. We report on the biocompatibility and the systemic safety of a novel transcatheter mitral valve annuloplasty ring (AMEND™) in 6 minipigs. This device is composed of a nitinol tube surrounded by a braided polyethylene terephthalate fabric tube. The device produced no adverse inflammatory response, showing gradual integration between the metal ring and the fabric by normal host fibrocellular response, leading to complete neoendocardium coverage. There was no evidence for adverse reactions, rejection, or intolerance in the valvular structure. In 2 animals, hemopericardium resulted from the implantation procedure, leading to right-sided cardiac insufficiency with pulmonary edema and liver congestion. The findings reported herein can serve as a case study for the expected healing pathology reactions after implantation of transcatheter mitral valve annuloplasty rings.

Sexual Maturation in the Female Göttingen Minipig

In the literature, experimental data on sexual maturation of female Göttingen minipigs are lacking. This may impede a reliable evaluation of reproductive functioning, particularly in the young (immature) sow used in toxicity studies. To find suitable method(s) to detect ovulation during in-life, a pilot study was performed with 3 adult sows (approximately 10-11 months), followed by a study with 14 immature females (approximately 3-4 months). From the tested parameters, progesterone analysis was the most reliable predictor. First progesterone peaks were observed in 13 sows at 3.7-4.2 or 5.5-6.5 months with a cycle length of 17-22 days. One sow did not show progesterone release until necropsy at 7 months of age. Histopathology of the reproductive organs confirmed sexual maturity for all sows, except the one without progesterone peak. In conclusion, the age range of sexual maturity of female Göttingen minipigs (3.7-6.5 months) is much wider than previously thought, and in-life progesterone analysis is a useful tool to determine sexual maturity of individual animals.

TLR4 and TLR7/8 Adjuvant Combinations Generate Different Vaccine Antigen-Specific Immune Outcomes in Minipigs when Administered via the ID or IN Routes

The induction of high levels of systemic and mucosal humoral immunity is a key goal for many prophylactic vaccines. However, adjuvant strategies developed in mice have often performed poorly in the clinic. Due to their closer similarity to humans, minipigs may provide a more accurate picture of adjuvant performance. Based on their complementary signalling pathways, we assessed humoral immune responses to model antigens after co-administration with the toll-like receptor 4 (TLR4) stimulator glucopyranosyl lipid adjuvant (GLA-AF) or the TLR7/8 agonist resiquimod (R848) (alone and in combination) via the intradermal (ID), intranasal (IN) or combined routes in the Gottingen minipig animal model. Surprisingly, we discovered that while GLA-AF additively enhanced the adjuvant effect of R848 when injected ID, it abrogated the adjuvant activity of R848 after IN inoculation. We then performed a route comparison study using a CN54 gp140 HIV Envelope model antigen adjuvanted with R848 + GLA-AF (ID) or R848 alone (IN). Animals receiving priming inoculations via one route were then boosted by the alternate route. Although differences were observed in the priming phase (IN or ID), responses converged upon boosting by the alternative route with no observable impact resultant from the order of administration (ID/IN vs IN/ID). Specific IgG responses were measured at a distal mucosal site (vaginal), although there was no evidence of mucosal linkage as these closely reflected serum antibody levels. These data indicate that the complex in vivo cross-talk between innate pathways are likely tissue specific and cannot be predicted by simple in vitro models.

Is Science the Only Driver in Species Selection? An Internal Study to Evaluate Compound Requirements in the Minipig Compared to the Dog in Preclinical Studies

Dogs have been often chosen as a nonrodent species for preclinical development of small molecule drugs mainly due to availability and relative ease of handling. Recently, focus has increased on the minipig as a potential alternative to the dog, based on either scientific rationale or public opinion concerns. There are, however, other factors influencing nonrodent choices, in particular drug amount and synthesis time, which differ between species and therefore may impact the milestones of a drug development program. To assess the magnitude of compound need, a retrospective internal survey was conducted on drug amounts used in dog studies which were translated into the requirements for minipigs. Compound need approximately doubles if minipigs are used. Costs of compound are accordingly higher, and synthesis times are slightly increased. In our company, the differences were not considered significant enough to preclude the use of minipigs if the later preclinical program might benefit from improved human risk prediction.

Computed Tomography and Magnetic Resonance Imaging for Longitudinal Characterization of Lung Structure Changes in a Yucatan Miniature Pig Silicosis Model

Medical imaging is a rapidly advancing field enabling the repeated, noninvasive assessment of physiological structure and function. These beneficial characteristics can supplement studies in swine by mirroring the clinical functions of detection, diagnosis, and monitoring in humans. In addition, swine may serve as a human surrogate, facilitating the development and comparison of new imaging protocols for translation to humans. This study presents methods for pulmonary imaging developed for monitoring pulmonary disease initiation and progression in a pig exposure model with computed tomography and magnetic resonance imaging. In particular, a focus was placed on systematic processes, including positioning, image acquisition, and structured reporting to monitor longitudinal change. The image-based monitoring procedure was applied to 6 Yucatan miniature pigs. A subset of animals (n= 3) were injected with crystalline silica into the apical bronchial tree to induce silicosis. The methodology provided longitudinal monitoring and evidence of progressive lung disease while simultaneously allowing for a cross-modality comparative study highlighting the practical application of medical image data collection in swine. The integration of multimodality imaging with structured reporting allows for cross comparison of modalities, refinement of CT and MRI protocols, and consistently monitors potential areas of interest for guided biopsy and/or necropsy.

Minipigs in Translational Immunosafety Sciences: A Perspective

The porcine immune system has been studied especially with regard to infectious diseases of the domestic pig, highlighting the economic importance of the pig in agriculture. Recently, in particular, minipigs have received attention as alternative species to dogs or nonhuman primates in drug safety evaluations. The increasing number of new drug targets investigated to modulate immunological pathways has triggered renewed interest to further explore the porcine immune system. Comparative immunological studies of minipigs with other species broaden the translational models investigated in drug safety evaluations. The porcine immune system overall seems functionally similar to other mammalian species, but there are some anatomical, immunophenotypical, and functional differences. Here, we briefly review current knowledge of the innate and adaptive immune system in pigs and minipigs. In conclusion, more systematic and cross-species comparisons are needed to assess the significance of immunological findings in minipigs in the context of translational safety sciences.

Segregation of Naturally Occurring Mitochondrial DNA Variants in a Mini-Pig Model

The maternally inherited mitochondrial genome (mtDNA) is present in multimeric form within cells and harbors sequence variants (heteroplasmy). While a single mtDNA variant at high load can cause disease, naturally occurring variants likely persist at low levels across generations of healthy populations. To determine how naturally occurring variants are segregated and transmitted, we generated a mini-pig model, which originates from the same maternal ancestor. Following next-generation sequencing, we identified a series of low-level mtDNA variants in blood samples from the female founder and her daughters. Four variants, ranging from 3% to 20%, were selected for validation by high-resolution melting analysis in 12 tissues from 31 animals across three generations. All four variants were maintained in the offspring, but variant load fluctuated significantly across the generations in several tissues, with sex-specific differences in heart and liver. Moreover, variant load was persistently reduced in high-respiratory organs (heart, brain, diaphragm, and muscle), which correlated significantly with higher mtDNA copy number. However, oocytes showed increased heterogeneity in variant load, which correlated with increased mtDNA copy number during in vitro maturation. Altogether, these outcomes show that naturally occurring mtDNA variants segregate and are maintained in a tissue-specific manner across generations. This segregation likely involves the maintenance of selective mtDNA variants during organogenesis, which can be differentially regulated in oocytes and preimplantation embryos during maturation.

Unraveling the swine genome: implications for human health

The pig was first used in biomedical research in ancient Greece and over the past few decades has quickly grown into an important biomedical research tool. Pigs have genetic and physiological traits similar to humans, which make them one of the most useful and versatile animal models. Owing to these similarities, data generated from porcine models are more likely to lead to viable human treatments than those from murine work. In addition, the similarity in size and physiology to humans allows pigs to be used for many experimental approaches not feasible in mice. Research areas that employ pigs range from neonatal development to translational models for cancer therapy. Increasing numbers of porcine models are being developed since the release of the swine genome sequence, and the development of additional porcine genomic and epigenetic resources will further their use in biomedical research.

Comparison of complement activation-related pseudoallergy in miniature and domestic pigs: foundation of a validatable immune toxicity model

Complement activation-related pseudoallergy (CARPA) is an acute adverse immune reaction caused by many nanomedicines. There is a regulatory need for a sensitive and standardizable in vivo predictive assay. While domestic pigs are a sensitive animal model, miniature pigs are favored in toxicological studies yet their utility as a CARPA model has not yet been explored. Herein, we used liposomal doxorubicin and amphotericin B (Doxil/Caelyx and AmBisome), Cremophor EL and zymosan as CARPA triggers to induce reactions in miniature and domestic pigs, and compared the hemodynamic, hematological, biochemical, and skin alterations. The changes observed after administration of the test agents were very similar in both pig strains, suggesting that miniature pigs are a sensitive, reproducible, and, hence, validatable animal model for CARPA regulatory testing.

FROM THE CLINICAL EDITOR

With the advances in nanomedicine research, many new agents are now tested for use in clinical setting. Nonetheless, complement activation-related pseudoallergy (CARPA) is a well known phenomenon which can be caused by nanoparticles. In this study, the authors looked at and compared the use of domestic pigs versus miniature pigs as experimental animals for toxicological studies. Their findings confirmed the possible use of miniature pigs for regulatory testing.

Increased prediction accuracy using a genomic feature model including prior information on quantitative trait locus regions in purebred Danish Duroc pigs

Background

In animal breeding, genetic variance for complex traits is often estimated using linear mixed models that incorporate information from single nucleotide polymorphism (SNP) markers using a realized genomic relationship matrix. In such models, individual genetic markers are weighted equally and genomic variation is treated as a “black box.” This approach is useful for selecting animals with high genetic potential, but it does not generate or utilise knowledge of the biological mechanisms underlying trait variation. Here we propose a linear mixed-model approach that can evaluate the collective effects of sets of SNPs and thereby open the “black box.” The described genomic feature best linear unbiased prediction (GFBLUP) model has two components that are defined by genomic features.

Results

We analysed data on average daily gain, feed efficiency, and lean meat percentage from 3,085 Duroc boars, along with genotypes from a 60 K SNP chip. In addition information on known quantitative trait loci (QTL) from the animal QTL database was integrated in the GFBLUP as a genomic feature. Our results showed that the most significant QTL categories were indeed biologically meaningful. Additionally, for high heritability traits, prediction accuracy was improved by the incorporation of biological knowledge in prediction models. A simulation study using the real genotypes and simulated phenotypes demonstrated challenges regarding detection of causal variants in low to medium heritability traits.

Conclusions

The GFBLUP model showed increased predictive ability when enough causal variants were included in the genomic feature to explain over 10 % of the genomic variance, and when dilution by non-causal markers was minimal. In the observed data set, predictive ability was increased by the inclusion of prior QTL information obtained outside the training data set, but only for the trait with highest heritability.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0322-9) contains supplementary material, which is available to authorized users.

The Use of Minipig in Drug Discovery and Development: Pros and Cons of Minipig Selection and Strategies to Use as a Preferred Nonrodent Species

The pig was introduced more than 20 years ago in drug development following attempts of finding a species that shares better homology with human than the dog, based on biophysiological parameters. However, miniaturization, standardized breeding, and health status control were required before the pig could find a broader than niche application in pharmaceutical industry. During the years of experience with minipigs in pharmaceutical research and the science evolving rapidly, the selection of a nonrodent animal species for preclinical safety testing became primarily driven by pharmacological (target expression homologous function), pharmacokinetic, and biophysiological considerations. This offered a broad field of application for the minipig, besides the well-established use in dermal projects in all areas of drug development but also in novel approaches including genetically modified animals. In this article, we look at recent approaches and requirements in the optimal selection of a nonrodent model in pharmaceutical development and critically ask how good a choice the minipig offers for the scientist, how did the testing environment evolve, and what are the key requirements for a broader use of the minipig compared to the other well-established nonrodent species like dog or monkey.

Vehicle Systems and Excipients Used in Minipig Drug Development Studies

Minipigs have been used for dermal drug development studies for decades, and they are currently more frequently considered as the second nonrodent species for pivotal nonclinical studies, in lieu of the dog or nonhuman primate, for compounds delivered via standard systemic routes of administration. Little is known about the tolerability of different excipients in minipigs; sharing knowledge of excipient tolerability and compositions previously used in nonclinical studies may avoid testing of inadequate formulations, thereby contributing to reduced animal usage. This article reviews vehicles employed in the Göttingen® minipig based on the combined experience from a number of pharmaceutical companies and contract research organizations. The review includes vehicles tolerated for single or multiple dosing by the Göttingen minipig, some of which are not appropriate for administration to other common nonrodent species (e.g., dogs). By presenting these data for dermal, oral, subcutaneous, and intravenous routes of administration, studies to qualify these vehicles in minipigs can be minimized or avoided. Additionally, investigators may more frequently consider using the minipig in place of higher species if the tolerability of a vehicle in the minipig is known.

Miniature Swine Breeds in Toxicology and Drug Safety Assessments

The use of miniature swine as a nonrodent species in safety assessment has continued to expand for over a decade, and they are becoming routinely used in toxicology and in pharmacology as well as a model for human diseases. Miniature swine models are regularly used for regulatory toxicity studies designed to assess safety of new therapeutic compounds given through different routes of exposure and are used as an alternative model to the canine or the nonhuman primate. Translational preclinical swine study data presented support the current finding that miniature swine are the animal model of choice for assessment of drug absorption, tolerance, and systemic toxicity following systemic exposures. Because research investigators need to be familiar with important anatomic and histopathologic features of the miniature swine in order to place toxicopathologic findings in their proper perspective, clinical and anatomic pathology data from a large number of Sinclair, Hanford, Yucatan, and Göttingen breeds from control groups from a wide variety of studies performed between 2004 and 2014 will be presented, compared, and partially illustrated.

The minipig as a new model for the evaluation of doxorubicin-induced chronic toxicity

Doxorubicin can cause life-threatening toxic effects in several organs, with cardiotoxicity being the major concern. Although a large number of animal models have been utilized to study doxorubicin toxicity, several restrictions limit their use. Since the Göttingen minipig is an accepted species for non-clinical safety assessment and translation to man, we aimed at exploring its use as a non-rodent animal model for safety assessment and regulatory toxicity studies using doxorubicin. Three groups of three males and three females adult Göttingen minipigs received 1.5 mg kg(-1) , 3/2.3 mg kg(-1) or vehicle at intervals of 3 weeks for 7 cycles. Doxorubicin treatment resulted in a dose-related decrease in the erythrocytes, hemoglobin and hematocrit count, accompanied by leukopenia and thrombocytopenia. Bone marrow smears revealed dose-related hypocellularity. Urea and creatinine levels were elevated in treated animals, associated with proteinuria and hematuria. Histopathological evaluation detected nephropathy and atrophy of hematopoietic tissues/organs, mucosa of the intestinal tract and male genital tract. Cardiac lesions including chronic inflammation, endocardial hyperplasia, hemorrhage and myxomatous changes were evident in hematoxylin and eosin stains, and evaluation of semi-thin sections showed the presence of dose-related vacuolation in the atrial and ventricular cardiomyocytes. Cardiac troponin levels were increased in the high-dose group, but there was no direct correlation to the severity of the histopathological lesions. This study confirms that the Göttingen minipig has a comparable toxicity profile to humans and considering its anatomical, physiological, genetic and biochemical resemblance to humans, it should be considered as the non-rodent species of choice for studies on doxorubicin toxicity. Copyright © 2015 John Wiley & Sons, Ltd.

Functional analysis and transcriptional output of the Göttingen minipig genome

BACKGROUND

In the past decade the Göttingen minipig has gained increasing recognition as animal model in pharmaceutical and safety research because it recapitulates many aspects of human physiology and metabolism. Genome-based comparison of drug targets together with quantitative tissue expression analysis allows rational prediction of pharmacology and cross-reactivity of human drugs in animal models thereby improving drug attrition which is an important challenge in the process of drug development.

RESULTS

Here we present a new chromosome level based version of the Göttingen minipig genome together with a comparative transcriptional analysis of tissues with pharmaceutical relevance as basis for translational research. We relied on mapping and assembly of WGS (whole-genome-shotgun sequencing) derived reads to the reference genome of the Duroc pig and predict 19,228 human orthologous protein-coding genes. Genome-based prediction of the sequence of human drug targets enables the prediction of drug cross-reactivity based on conservation of binding sites. We further support the finding that the genome of Sus scrofa contains about ten-times less pseudogenized genes compared to other vertebrates. Among the functional human orthologs of these minipig pseudogenes we found HEPN1, a putative tumor suppressor gene. The genomes of Sus scrofa, the Tibetan boar, the African Bushpig, and the Warthog show sequence conservation of all inactivating HEPN1 mutations suggesting disruption before the evolutionary split of these pig species. We identify 133 Sus scrofa specific, conserved long non-coding RNAs (lncRNAs) in the minipig genome and show that these transcripts are highly conserved in the African pigs and the Tibetan boar suggesting functional significance. Using a new minipig specific microarray we show high conservation of gene expression signatures in 13 tissues with biomedical relevance between humans and adult minipigs. We underline this relationship for minipig and human liver where we could demonstrate similar expression levels for most phase I drug-metabolizing enzymes. Higher expression levels and metabolic activities were found for FMO1, AKR/CRs and for phase II drug metabolizing enzymes in minipig as compared to human. The variability of gene expression in equivalent human and minipig tissues is considerably higher in minipig organs, which is important for study design in case a human target belongs to this variable category in the minipig. The first analysis of gene expression in multiple tissues during development from young to adult shows that the majority of transcriptional programs are concluded four weeks after birth. This finding is in line with the advanced state of human postnatal organ development at comparative age categories and further supports the minipig as model for pediatric drug safety studies.

CONCLUSIONS

Genome based assessment of sequence conservation combined with gene expression data in several tissues improves the translational value of the minipig for human drug development. The genome and gene expression data presented here are important resources for researchers using the minipig as model for biomedical research or commercial breeding. Potential impact of our data for comparative genomics, translational research, and experimental medicine are discussed.

Effect of Bifidobacterium thermophilum RBL67 and fructo-oligosaccharides on the gut microbiota in Göttingen minipigs

Modulating the gut microbiota via dietary interventions is a common strategy to enhance the natural defence mechanisms of the host. Several in vitro studies have highlighted the probiotic potential of Bifidobacterium thermophilum RBL67 (RBL67) selected for its anti-Salmonella effects. The present study aimed to investigate the impact of RBL67 alone and combined with fructo-oligosaccharides (FOS) on the gut microbiota of Göttingen minipigs. Minipigs were fed a basal diet supplemented with 8 g/d probiotic powder (1×109 CFU/g in skim milk matrix) (probiotic diet (PRO)), 8 g/d probiotic powder plus 8 g/d FOS (synbiotic diet (SYN)) or 8 g/d skim milk powder (control), following a cross-sectional study design. Faecal and caecal microbiota compositions were analysed with pyrosequencing of 16S rRNA genes and quantitative PCR. Metabolic activity in the caecum and colon was measured by HPLC. 16S rRNA gene amplicon sequencing revealed that minipig faeces show close similarity to pig microbiota. During the treatments and at the time of killing of animals, RBL67 was consistently detected in faeces, caecum and colon at numbers of 105-106 16S rRNA copies/g content after feeding PRO and SYN diets. At the time of killing of animals, significantly higher Bifidobacterium numbers in the caecum and colon of SYN-fed minipigs were measured compared with PRO. Our data indicate that the Göttingen minipig may be a suitable model for gut microbiota research in pigs. Data from this first in vivo study of RBL67 colonisation suggest that the combination with FOS may represent a valuable symbiotic strategy to increase probiotic bacteria levels and survival in gastrointestinal tracts for feed and food applications.

Integrated Genome-wide association and hypothalamus eQTL studies indicate a link between the circadian rhythm-related gene PER1 and coping behavior

Animal personality and coping styles are basic concepts for evaluating animal welfare. Struggling response of piglets in so-called backtests early in life reflects their coping strategy. Behavioral reactions of piglets in backtests have a moderate heritability, but their genetic basis largely remains unknown. Here, latency, duration and frequency of struggling attempts during one-minute backtests were repeatedly recorded of piglets at days 5, 12, 19, and 26. A genome-wide association study for backtest traits revealed 465 significant SNPs (FDR ≤ 0.05) mostly located in QTL (quantitative trait locus) regions on chromosome 3, 5, 12 and 16. In order to capture genes in these regions, 37 transcripts with significant SNPs were selected for expressionQTL analysis in the hypothalamus. Eight genes (ASGR1, CPAMD8, CTC1, FBXO39, IL19, LOC100511790, RAD51B, UBOX5) had cis- and five (RANGRF, PER1, PDZRN3, SH2D4B, LONP2) had trans-expressionQTL. In particular, for PER1, with known physiological implications for maintenance of circadian rhythms, a role in coping behavior was evidenced by confirmed association in an independent population. For CTC1 a cis-expression QTL and the consistent relationship of gene polymorphism, mRNA expression level and backtest traits promoted its link to coping style. GWAS and eQTL analyses uncovered positional and functional gene candidates for coping behavior.

FcRn Expression on Placenta and Fetal Jejunum during Early, Mid-, and Late Gestation in Minipigs

Developmental toxicity testing of therapeutic antibodies is most often conducted in nonhuman primates owing to lack of cross-reactivity in other species. Minipigs may show cross-reactivity for some humanized antibodies but have not been used for developmental toxicity testing due to an assumed lack of embryo-fetal exposure. Unlike in humans, maternal IgGs do not cross the porcine placenta to reach the fetus. Some humanized IgGs, however, have a higher affinity for the neonatal Fc receptor (FcRn) and are more likely than endogenous antibodies to cross the placenta of animals. The major site of prenatal IgG transfer is the placenta, though FcRn in fetal intestine could also uptake maternal IgGs from swallowed amniotic fluid. Using immunohistochemistry andin situhybridization in this experiment, FcRn was found in minipig placenta and fetal intestine during early, mid-, and late gestation. To date, however, fetal exposure to maternally administered IgGs has never been demonstrated in the minipig.

Meganucleases Revolutionize the Production of Genetically Engineered Pigs for the Study of Human Diseases

Animal models of human diseases are critically necessary for developing an in-depth knowledge of disease development and progression. In addition, animal models are vital to the development of potential treatments or even cures for human diseases. Pigs are exceptional models as their size, physiology, and genetics are closer to that of humans than rodents. In this review, we discuss the use of pigs in human translational research and the evolving technology that has increased the efficiency of genetically engineering pigs. With the emergence of the clustered, regularly interspaced, short palindromic repeat (CRISPR)/CRISPR-associated (Cas) protein 9 system technology, the cost and time it takes to genetically engineer pigs has markedly decreased. We will also discuss the use of another meganuclease, the transcription activator-like effector nucleases , to produce pigs with severe combined immunodeficiency by developing targeted modifications of the recombination activating gene 2 (RAG2).RAG2mutant pigs may become excellent animals to facilitate the development of xenotransplantation, regenerative medicine, and tumor biology. The use of pig biomedical models is vital for furthering the knowledge of, and for treating human, diseases.

Cardiovascular imaging: what have we learned from animal models?

Cardiovascular imaging has become an indispensable tool for patient diagnosis and follow up. Probably the wide clinical applications of imaging are due to the possibility of a detailed and high quality description and quantification of cardiovascular system structure and function. Also phenomena that involve complex physiological mechanisms and biochemical pathways, such as inflammation and ischemia, can be visualized in a non-destructive way. The widespread use and evolution of imaging would not have been possible without animal studies. Animal models have allowed for instance, (i) the technical development of different imaging tools, (ii) to test hypothesis generated from human studies and finally, (iii) to evaluate the translational relevance assessment of in vitro and ex-vivo results. In this review, we will critically describe the contribution of animal models to the use of biomedical imaging in cardiovascular medicine. We will discuss the characteristics of the most frequent models used in/for imaging studies. We will cover the major findings of animal studies focused in the cardiovascular use of the repeatedly used imaging techniques in clinical practice and experimental studies. We will also describe the physiological findings and/or learning processes for imaging applications coming from models of the most common cardiovascular diseases. In these diseases, imaging research using animals has allowed the study of aspects such as: ventricular size, shape, global function, and wall thickening, local myocardial function, myocardial perfusion, metabolism and energetic assessment, infarct quantification, vascular lesion characterization, myocardial fiber structure, and myocardial calcium uptake. Finally we will discuss the limitations and future of imaging research with animal models.