Dundee Experimental Bald Rat Research Articles

Animal Models for Alopecia Areata: What and Where?

Disease is not limited to humans. Rather, humans are but another mammal in a continuum, and as such, often share similar if not identical diseases with other mammalian species. Alopecia areata (AA) is such a disease. Natural disease occurs in humans, nonhuman primates, many domestic animals, and laboratory rodents. However, to be useful as models of human disease, affected animals need to be readily available to the research community, closely resemble the human disease, be easy to work with, and provide reproducible data. To date, the laboratory mouse (most if not all of the C3H substrains) and the Dundee experimental bald rat fit these criteria. Manipulations using full-thickness skin grafts or specific immune cell transfers have improved the models. New mouse models that carry a variety of genetic-based immunodeficiencies can now be used to recapitulate the human immune system and allow for human full-thickness skin grafts onto mice to investigate human-specific mechanistic and therapeutic questions. These models are summarized here including where they can currently be obtained from public access repositories.

The C3H/HeJ mouse and DEBR rat models for alopecia areata: review of preclinical drug screening approaches and results

The C3H/HeJ inbred mouse strain and the Dundee Experimental Bald Rat (DEBR) strain spontaneously develop adult onset alopecia areata (AA), a cell-mediated disease directed against actively growing hair follicles. The low frequency of AA and the inability to predict the stage of AA as it evolves in the naturally occuring C3H/HeJ model of AA can be converted into a highly predictable system by grafting full thickness skin from AA-affected mice to normal haired mice of the same strain. The rat DEBR model develops spontaneous AA at a higher frequency than in the mouse model but they are more expensive to use in drug studies owing to their larger size. Regardless of the shortcomings of either model, these rodent models can be used succesfully to screen novel or approved drugs for efficacy to treat human AA. As the pathogenesis of AA follows the canonical lymphocytic co-stimulatory cascade in the mouse AA model, it can be used to screen compounds potentially useful to treat a variety of cell-mediated diseases. Efficacy of various agents can easily be screened by simply observing the presence, rate, and cosmetic acceptability of hair regrowth. More sophisticated assays can refine how the drugs induce hair regrowth and evaluate the underlying pathogenesis of AA. Some drugs commonly used to treat human AA patients work equally as well in both rodent models validating their usefulness as models for drug efficacy and safety for humanAA.

Alopecia areata im Tiermodell – Neue Einblicke in Pathogenese und Therapie einer T‐Zell‐vermittelten Autoimmunerkrankung

ZusammenfassungDie Möglichkeiten zur Erforschung der Pathogenese der Alopecia areata und zur Entwicklung neuer Therapieansätze sind beim Menschen aus ethischen Gründen begrenzt. Daher ist die Entwicklung geeigneter Tiermodelle für die Alopecia areata sinnvoll. Mit der Dundee experimental bald rat (DEBR) und der C3H/HeJ‐Maus stehen mittlerweile zwei gut charakterisierte Tiermodelle der Alopecia areata zur Verfügung, an denen Studien zur Genetik, Pathogenese und Therapie der Alopecia areata durchgeführt werden können. Ein besonderer Vorteil der C3H/HeJ‐Maus besteht in der Möglichkeit, die Alopecia areata durch Hauttransplantation experimentell zu induzieren, und dann den Einfluß verschiedener Faktoren auf den Verlauf der Erkrankung zu untersuchen. Durch Untersuchungen an der C3H/HeJ‐Maus und der DEBR konnte die T‐Zell‐vermittelte Autoimmunpathogenese der Alopecia areata bestätigt werden, und es ließen sich einzelne Mechanismen dieser T‐Zell‐vermittelten Immunreaktion analysieren. Ausgehend von diesen Erkenntnissen ergeben sich verschiedene neue Optionen für die Therapie der Alopecia areata wie die Blockade des Lymphozytenhomings durch Applikation eines monoklonalen Anti‐CD44v10‐Antikörpers oder die Hemmung der T‐Zell‐Aktivierung durch Blockade kostimulatorischer Moleküle. Therapeutische Studien am Maus‐ und Rattenmodell sprechen dafür, daß die topische Applikation von Tacrolimus zur Behandlung der Alopecia areata des Menschen im Prinzip geeignet ist, sofern sich die Galenik verbessern läßt. Zukünftige Untersuchungen zum Wirkmechanismus des allergischen Kontaktekzems in der Behandlung der Alopecia areata sollen dazu dienen, eine auf dieser Behandlung aufbauende, spezifischere Therapie zu entwickeln.

The potential role of cytokines and T cells in alopecia areata.

T cells play an important role in alopecia areata (AA) because AA can be reinduced by the injection of hair follicle-specific CD8+ T cells into AA scalp biopsies, which were grafted onto scid mice, and the depletion of CD8+ T cells restores hair growth in the Dundee experimental bald rat. Moreover, AA can be transferred by grafting of alopecic skin from C3H/HeJ mice with AA-like hair loss onto unaffected littermates, but the onset of AA is inhibited by i.p. injection of anti-CD44v10 antibodies. Interestingly, grafted anti-CD44v10-treated mice have decreased numbers of CD8+ T cells within the skin. Beside T cells several clinical and experimental data point towards cytokines that might be crucial inducers of hair loss in AA. An aberrant expression of cytokines of the Thl type and IL-1beta has been detected in scalp areas involved by AA, and polymorphisms of cytokine genes such as IL-1-receptor antagonist, IL-1alpha, and TNF-alpha have been shown to determine disease susceptibility and severity. Moreover, IL-1 has been shown to be a potent inhibitor of human hair growth in vitro. Such IL-1-incubated hair follicles show ultrastructural changes similar to those observable in vivo. On the other hand mice transgenic for IL-1alpha develop patchy hair loss and during the depilation-induced hair cycle in C57/BL6 mice, members of the IL-1 family are overexpressed with the onset of spontaneous catagen. Taking all of the presently available data together, we may hypothesize that CD8+ T cells are of crucial importance in AA by their interaction with MHC-I restricted autoantigens, and cytolysis of their target cells. Hair loss, however, may occur because proinflammatory cytokines may interfere with the hair cycle leading to premature arrest of hair cycling.

Topical FK506: a potent immunotherapy for alopecia areata? Studies using the Dundee experimental bald rat model.

We elected to examine the efficacy of the topically applied immunosuppressive agent FK506 (Prograf) in the treatment of alopecia areata (AA) using the Dundee experimental bald rat (DEBR) model. Thirty lesional DEBR rats were allocated to five groups of six. Group 1 rats received 0.1 mL of a 0.25% solution of FK506 within a 2 x 2 cm marked area on one bald flank twice a week (125 micrograms FK506/cm2 per week) for 8 weeks, while the contralateral flank was left untreated. In group II, 0.05 mL of a 0.1% solution of FK 506 was applied 5 days per week on one flank (62.5 micrograms FK506/ cm2 per week) and control vehicle to the opposite flank for 8 weeks. Group III rats were treated as in group II except that drug and vehicle were applied twice a week (25 micrograms FK506/cm2 per week) for 4 weeks. A positive control group received orally administered cyclosporin A (CsA) (10 mg/kg daily) for 8 weeks and a further group was left untreated. Rats were regularly examined and photographed with skin biopsies taken from groups II and III. All FK 506-treated rats regrew hair at the site of drug application within 14-21 days. Growth continued for 3 weeks beyond termination of treatment after which gradual hair loss was observed. No hair growth was seen as a result of vehicle application and hair loss continued on untreated areas and in the untreated control group. Immunohistology revealed a drastic reduction in the follicular inflammatory infiltrate at the site of the FK506 application. The oral CsA group responded by simultaneous regrowth of hair over the whole body. Our findings suggest that FK506 may have considerable potential as a topical treatment for AA.

In vivodepletion of CD8+T cells restores hair growth in the DEBR model for alopecia areata

Alopecia areata (AA) is a putative autoimmune disease in which anagen hair follicles are the target of immune cell attack. While both CD4+ and CD8+ T lymphocytes are prominent in the infiltrate, their respective roles in the pathogenesis of AA remain unknown. Here we directly investigated the activity of CD8+ cells in the inhibition of hair growth using the Dundee experimental bald rat (DEBR) model for AA. Eight lesional DEBRs were fully depleted of their CD8+ cells by intraperitoneal injection of OX-8 monoclonal antibody (MoAb) specific for these cells over a 15-day therapy course. A control group of eight lesional rats was injected with the irrelevant MoAb OX-21. Sequential blood samples were analysed by flow cytometry to observe changes in the CD8+ cell population and macrophotography used to record changes in hair growth activity. All eight CD8+ depleted rats started to regrow hair within 29 days from the start of treatment, the final response ranging from sparse regrowth to a near normal coat. While two rats maintained their new pelage, the remainder lost hair as the CD8+ population in peripheral blood increased. Two of the control rats also showed hair regrowth over the experimental period of 156 days. These results suggest that CD8+ cells play an active part in the pathogenesis of AA. As hair production did not fully recover in all animals, immune mechanisms other than CD8+ cells may be involved in effecting hair loss. However, analysis of CD8+ cell levels in the skin of CD8+ depleted rats may help resolve their full importance in AA.

Oral cyclosporin A restores hair growth in the DEBR rat model for alopecia areata

The Dundee experimental bald rat (DEBR) undergoes hair loss associated with the development of peri- and intrafollicular mononuclear cell infiltrates, as occurs in human alopecia areata. We studied the effect of orally administered cyclosporin A (10 mg/kg; 5 days/week for 7 weeks) on established lesional DEBR rats displaying extensive areas of hair loss. New hairs appeared after 10 days and there was simultaneous regrowth of hair over the whole body with restoration of a full pelt by 5 weeks. Semiquantitative histological examination of flank skin biopsies revealed early reduction of the cellular infiltrate associated with conversion of dystrophic anagen follicles to normal, hair-producing follicles. These results confirm the value of the DEBR model of alopecia areata in evaluating existing and new therapies for this disease in humans.

Immunohistological study of the development of the cellular infiltrate in the pelage follicles of the DEBR model for alopecia areata.

The Dundee experimental bald rat (DEBR) undergoes hair loss associated with perifollicular infiltrates of mononuclear cells (MNC), a pathological characteristic of human alopecia areata (AA). To investigate further the pathogenesis of the disease in this animal model, we have studied the development, composition and extent of the perifollicular MNC infiltration in young (6-week-old), prelesional (3-month-old), active lesional, and established lesional DEBR rats, using 6-week- and 6-month-old Wistar rats as normal controls. The proportions of hair follicles showing infiltration by MNC and their main subsets were determined using immunohistochemical staining of serial cryostat sections of flank skin biopsies. There was a good correlation between the degree of leucocyte (OX-1+) infiltration of anagen hair follicles and the development of hair loss. In 6-week-old DEBR skin, there were few perifollicular cells expressing MHC class II, with positively stained dendritic cells in the dermis above the sebaceous gland. There was a sparse perifollicular distribution of CD4+ cells (W3/25) and macrophages (ED-1+). No CD8+ cells (OX-8+) were seen associated with DEBR hair follicles, and only small numbers were present in Wistar rats. In prelesional DEBR rats there was an increased perifollicular presence of MHC class II+ cells, macrophages, and particularly of CD8+ cells, with little change in CD4+ cells. Active and established lesional rats, i.e. animals with overt loss of hair, showed a significant increase in the degree of MNC infiltration and the proportion of infiltrated follicles, the majority of which were in dystrophic anagen. In the perifollicular infiltrate the CD4+:CD8+ ratio was approximately 2:1. An intrafollicular infiltrate was prominent, and was composed of CD8+ cells and macrophages, with bulbar and suprabulbar keratinocytes expressing MHC class II antigens. CD4+ cells were not detected in follicular epithelium. ICAM-1 expression correlated with MNC infiltration. These results show marked similarities to lesional human AA. They also focus on a possible active role for CD8+ cells in the pathogenesis of hair loss in the DEBR rat.

The DEBR rat: an animal model of human alopecia areata

The Dundee experimental bald rat (DEBR) is reported as a model for human alopecia areata. Parallels with human alopecia areata were observed in relation to the gradual and patchy loss of hair and the penetration of both pelage and vibrissa follicles by mononuclear cells. In particular, the apparent disruption of the follicles within the precortical region of the epidermal component and consequent alterations of normal geometrical relationships between dermal and epidermal components relate directly to similar studies on human alopecia areata. In comparison with other previously described hypotrichotic rodent mutants, the DEBR rat exhibits a unique mechanism of hair loss which may provide important information regarding the pathomechanism of human alopecia areata.

Immunobiological studies on the alopecic (DEBR) rat

The Dundee experimental bald rat (DEBR) has been proposed as an animal model of human alopecia areata, which is suspected of being an autoimmune disease. This study was carried out to establish whether the immunological changes observed in the lesional DEBR rat correlated with studies of human alopecia areata. The immune infiltrate was characterized using immunoperoxidase techniques on cryostat sections of vibrissa follicles. Indirect immunofluorescence was used to quantify the peripheral blood leucocytes. Some parallels were observed in the infiltration of human and DEBR rat follicles by T lymphocytes. In contrast, pre-lesional DEBR rat follicles, which are not available for investigation in human alopecia areata, were not penetrated by leucocytes and MHC class II antigens were expressed in the precortical region of the epidermal component of these follicles. Quantification of peripheral blood leucocytes showed significant increases in both T-lymphocyte subsets during lesional expression. We consider that the pre-lesional form of the rat may provide important information as a model for the pre-lesional and uninvestigated form of alopecia areata in man.