The ferret as an animal model in cerebrovascular research

Anatomical features for an adequate choice of the experimental animal model in biomedicine: III. Ferret, goat, sheep, and horse

The anatomical characteristics of each of the many species today employed in biomedical research are very important when selecting the correct animal model(s), especially for conducting translational research. In previous papers, these features have been considered for fish (D'Angelo et al. Ann. Anat, 2016, 205:75), the most common laboratory rodents, rabbits, and pigs (Lossi et al. 2016). I here follow this line of discussion by dealing with the importance of proper knowledge of ferrets, goats, sheep, and horses' main anatomical features in translational research.

Establishing the ferret as a gyrencephalic animal model of traumatic brain injury: Optimization of controlled cortical impact procedures

BACKGROUND

Although rodent TBI studies provide valuable information regarding the effects of injury and recovery, an animal model with neuroanatomical characteristics closer to humans may provide a more meaningful basis for clinical translation. The ferret has a high white/gray matter ratio, gyrencephalic neocortex, and ventral hippocampal location. Furthermore, ferrets are amenable to behavioral training, have a body size compatible with pre-clinical MRI, and are cost-effective.

NEW METHODS

We optimized the surgical procedure for controlled cortical impact (CCI) using 9 adult male ferrets. We used subject-specific brain/skull morphometric data from anatomical MRIs to overcome across-subject variability for lesion placement. We also reflected the temporalis muscle, closed the craniotomy, and used antibiotics. We then gathered MRI, behavioral, and immunohistochemical data from 6 additional animals using the optimized surgical protocol: 1 control, 3 mild, and 1 severely injured animals (surviving one week) and 1 moderately injured animal surviving sixteen weeks.

RESULTS

The optimized surgical protocol resulted in consistent injury placement. Astrocytic reactivity increased with injury severity showing progressively greater numbers of astrocytes within the white matter. The density and morphological changes of microglia amplified with injury severity or time after injury. Motor and cognitive impairments scaled with injury severity.

COMPARISON WITH EXISTING METHOD(S)

The optimized surgical methods differ from those used in the rodent, and are integral to success using a ferret model.

CONCLUSIONS

We optimized ferret CCI surgery for consistent injury placement. The ferret is an excellent animal model to investigate pathophysiological and behavioral changes associated with TBI.

Is the ferret a suitable species for studying perinatal brain injury?

•

Ferret brain architecture, composition, and development are similar to humans.

•

Postnatal ferret brain development is comparable to that of premature infants.

•

Ferrets have potential to model preterm and term neonatal brain injury.

•

Ferrets may fulfill the need for an intermediate model species of neurodevelopment.

•

Many opportunities exist to expand the use of ferrets as research subjects.

Complications of prematurity often disrupt normal brain development and/or cause direct damage to the developing brain, resulting in poor neurodevelopmental outcomes. Physiologically relevant animal models of perinatal brain injury can advance our understanding of these influences and thereby provide opportunities to develop therapies and improve long-term outcomes. While there are advantages to currently available small animal models, there are also significant drawbacks that have limited translation of research findings to humans. Large animal models such as newborn pig, sheep and nonhuman primates have complex brain development more similar to humans, but these animals are expensive, and developmental testing of sheep and piglets is limited. Ferrets (Mustela putorius furo) are born lissencephalic and undergo postnatal cortical folding to form complex gyrencephalic brains. This review examines whether ferrets might provide a novel intermediate animal model of neonatal brain disease that has the benefit of a gyrified, altricial brain in a small animal. It summarizes attributes of ferret brain growth and development that make it an appealing animal in which to model perinatal brain injury. We postulate that because of their innate characteristics, ferrets have great potential in neonatal neurodevelopmental studies.

Isolation, characterization, and functional analysis of ferret lymphatic endothelial cells

The lymphatic endothelium (LE) serves as a conduit for transport of immune cells and soluble antigens from peripheral tissues to draining lymph nodes (LNs), contributing to development of host immune responses and possibly dissemination of microbes. Lymphatic endothelial cells (LECs) are major constituents of the lymphatic endothelium. These specialized cells could play important roles in initiation of host innate immune responses through sensing of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs), including toll-like receptors (TLRs). LECs secrete pro-inflammatory cytokines and chemokines to create local inflammatory conditions for recruitment of naïve antigen presenting cells (APCs) such as dendritic cells (DCs) to sites of infection and/or vaccine administration. In this study, we examined the innate immune potential of primary LEC populations derived from multiple tissues of an animal model for human infectious diseases - the ferret. We generated a total of six primary LEC populations from lung, tracheal, and mesenteric LN tissues from three different ferrets. Standard RT-PCR characterization of these primary LECs showed that they varied in their expression of LEC markers. The ferret LECs were examined for their ability to respond to poly I:C (TLR3 and RIG-I ligand) and other known TLR ligands as measured by production of proinflammatory cytokine (IFNα, IL6, IL10, Mx1, and TNFα) and chemokine (CCL5, CCL20, and CXCL10) mRNAs using real time RT-PCR. Poly I:C exposure induced robust proinflammatory responses by all of the primary ferret LECs. Chemotaxis was performed to determine the functional activity of CCL20 produced by the primary lung LECs and showed that the LEC-derived CCL20 was abundant and functional. Taken together, our results continue to reveal the innate immune potential of primary LECs during pathogen-host interactions and expand our understanding of the roles LECs might play in health and disease in animal models.

Expression of cadherin superfamily genes in brain vascular development

Cadherins are Ca2+-dependent cell adhesion molecules that are important in vertebrate nervous system development. We identified seven members of the cadherin superfamily (cadherin-4, cadherin-5, cadherin-6, cadherin-6, cadherin-11, protocadherin-1, and protocadherin-17) and an intracellular binding partner of delta-protocadherins, protein phosphatase 1alpha, as novel markers for developing blood vessels in the ferret brain. Some of the cadherin molecules are restricted to specific brain regions or a subset of blood vessels. The expression levels show a peak during perinatal vascular development. Our results suggest that multiple cadherins, which are also involved in neurogenesis, are regulators of angiogenesis in developing vertebrate brain.

Clinical and histological evaluation of ligature-induced periodontitis in the domestic ferret

The aim of this study was to evaluate the clinical and histological characteristics of ligature induced periodontitis in 12 domestic ferrets. On day 0, silk ligatures were placed at the gingival margin level of selected experimental teeth. The contralateral teeth served as control teeth. On day 14, 4 animals and on day 28, 8 animals were sacrificed. Clinical measurements including gingival index (GI), probing pocket depth (PPD) and probing attachment level (PAL) were taken in 5 animals on days 0, 14 and 28. Histological sections were prepared for light microscopy. The histometric measurements performed were (1) the distance between the cemento-enamel junction (CEJ) and the alveolar bone crest and (2) the distance between CEJ and connective tissue attachment level. The number of sections with root resorption areas was also observed. Cell counts were taken in 4 different areas. Clinical results showed, on days 14 and 28, a significant increase of the mean values of PPD and PAL at the experimental teeth when compared to the control teeth. The histometric results showed a significant loss of connective tissue attachment and bone loss in the experimental teeth on day 14. On day 28, the results were similar, although more sections with root resorption areas were observed in the experimental teeth. The predominant inflammatory cell in all the 4 experimental areas analyzed was polymorphonuclears (PMN), and they were mainly increased in areas closely related to the junctional epithelium. The results indicate that the domestic ferret may be used as an experimental animal in the ligature-induced periodontitis model.