Rhino Mouse Research Articles

Comparison of CD271 (Adapalene) and All-Trans Retinoic Acid in Human Skin: Dissociation of Epidermal Effects and CRABP-II mRNA Expression

A new synthetic retinoid analogue, adapalene (6-[3-(1-adamantyl)-4-methoxyphenyl]-2-naphthoic acid, CD271), which is relatively selective for retinoic acid receptor beta, was noted to be an effective comedolytic agent in the rhino mouse model and to have clinical efficacy against acne. In pursuit of this observation, we studied the effects of CD271 on the development of erythema, spongiosis, and epidermal hyperplasia as well as other well-characterized markers of in vivo retinoid action after 4 d of occluded topical treatment. The objective of the study was to elucidate further those parameters associated with potential clinical efficacy. Twenty-five subjects were treated with 0.1% all-trans retinoic acid cream, all-trans retinoic acid vehicle, 0.1% CD271 gel, or CD271 vehicle under occlusion for 4 d. Only all-trans retinoic acid induced erythema (p < 0.01 versus all other treatments). Similarly, histologic analysis revealed that epidermal hyperplasia and spongiosis were induced only by all-trans retinoic acid (p < 0.01 versus all other treatments). By immunohistochemical analysis: all-trans retinoic acid increased expression of epidermal transglutaminase, involucrin, and calgranulin (p < 0.05 versus all other treatments). In contrast to these data, both CD271 and all-trans retinoic acid caused marked and significant (p < 0.05) elevation of cellular retinoic acid-binding protein-II (CRABP-II) messenger ribonucleic acid steady-state levels as judged by quantitative RNA blot analysis. Although CD271 treatment did not lead to erythema or affect epidermal morphology, its ability to induce a marker of retinoid action (i.e., CRABP-II) was 70% the potency of all-trans retinoic acid. This study suggests that CRABP-II gene expression may be a more sensitive indicator of retinoid biologic activity in skin than are erythema or changes in epidermal morphology and differentiation.

Topical all/trans retinoic acid rapidly corrects the follicular abnormalities of the rhino mouse. An ultrastructural study.

Topical all-trans retinoic acid (RA) has been shown to transform the horn-filled utriculi of the rhino mouse into normal follicles. We studied the early events by light and electron microscopy. Reduction in diameters of the utriculi was quantified by image analysis of whole mounts. Topical RA at 0.05% in ethanol/propylene glycol was applied daily and biopsies were taken after 1, 2, 3 and 6 days of treatment. By electron microscopy, after 3 days of RA treatment there was a great increase in the size and density of laminated membrane coating granules (MCGs) which had fused to the apical membranes of the upper granular cells. Thereafter, corneocytes within the lumina of the utriculi showed fewer desmosomes and a loss of intercellular material, accompanied by detachment from each other. Conversion to normal follicles was complete by 6 days. In whole mounts examined after 3 days of RA, there was a 75% reduction in the mean diameter of the utriculi. These results suggest that extrusion of the contents of enlarged MCGs into the intercellular corneocyte spaces facilitated separation of corneocytes, leading to rapid shedding, perhaps through the action of desmosome-lysing proteases. The conversion to normal follicles is consistent with the established role of retinoids in correcting abnormal differentiation.

An automated in vitro dermal absorption procedure: III. In vivo and in vitro comparison with the insect repellent N, N-diethyl- m-toluamide in mouse, rat, guinea pig, pig, human and tissue-cultured skin

Cross-species in vitro dermal absorption tests were conducted with the 14C-ring-labelled insect repellent, DEET ( N, N-diethyl- m-toluamide), dissolved in acetone and applied to skin sections (0.5 mm) from a dermatome at a dose rate of about 30 μg/cm 2. Skin permeation was determined using an automated in vitro dermal absorption procedure, and was calculated from the percentage recovery of 14C-activity in the receiver solution. Listed in decreasing order, the total percentage of in vitro dermal absorption obtained by 48 hr post-exposure for the six skin types (n = 4) was: 36 ± 27.5% (rhino mouse), 28 ± 4.2% (human), 21 ± 2.2% (rat), 15 ± 0.8% (pig), 13 ± 9.6% (tissue cultured Testskin) and 11 ± 1.4% (hairless guinea pig). Lag times for DEET in vitro dermal absorption in the six skin types ranged from 0.6 hr (human) to 1.9 hr (rat). The 14C-activity recovered in soapy water rinses of the skin specimens at 24 hr post-exposure ranged from 4% (rat) to 18% (mouse). The percentage recovery in methanol skin washes, skin digests, and of 14C-volatiles collected in air traps at 48 hr post-exposure are reported. The total mass balance recovery ranged from 70% (Testskin) to 93% (human). Comparative in vivo studies demonstrated 38 ± 10.3% (n = 4) and 26 ± 5.4% (n = 4) urinary recovery in rats and guinea pigs, respectively, by 14 days post-exposure. Total faecal percentage recovery 14 days post-exposure was 1 ± 0.5% for rats and 3 ± 0.8% for guinea pigs. A tissue autopsy conducted at 14 days post-exposure demonstrated a total tissue recovery of 2 ± 0.4% 14C-DEET in rats and 1 ± 0.3% in guinea pigs. Total percentage recovery in skin removed from the dose site at 14 days post-exposure was 0.2 ± 0.11% and 0.1 ± 0.06% in rats and guinea pigs, respectively. Soapy water skin washes conducted at 24 hr post-exposure had 8 ± 0.5% recovery for rats and 5 ± 2.8% recovery for guinea pigs. Total mass balance recovery was 84 ± 9.2% and 108 ± 2.9% for rats and guinea pigs, respectively. In summary, the in vitro data underestimated the dermal absorption observed in vivo and tentative explanations for this lack of agreement are discussed.

Growth of the mammary gland in rhino mouse.

The rhino mouse, so called because of its characteristic rhinocerous-like skin cannot raise its young. Although the animal has rudimentary mammary glands, these are thought to be defective due to their impossibility to raise their young. Morphological observations of the female mammary glands of rhino mice (hrrh/hrrh) were carried out and the results were compared with those of their normal litter mates (hrrh/+) at various ages from 1 month to 1 year. No morphological differences in mammary gland development was seen between the rhino mice and their normal litter mates, and normal secretory changes were observed in the rhino mice after delivery. Mouse mammary tumor virus (MMTV) expression and the occurrence of hyperplastic alveolar nodule (HAN) were analogous to these features in phenotypically normal hrrh/+ mice. Further, the sweat glands in the rhino mouse were normal. Thus, anomalies in the rhino mouse appeared to be limited to the skin and pilosebaceous apparatus.

Adapalene, a new chemical entity with retinoid activity.

Adapalene is a novel chemical entity which, in terms of pharmacology, behaves similar to tretinoin, but is chemically and photochemically stable. It has a particular selectivity profile for the known nuclear retinoic acid receptors with low affinity for RAR alpha and no transactivating potential for RXR alpha. This receptor profile could imply that adapalene, in contrast to tretinoin, affects the terminal differentiation pathway of epidermal cells rather than their proliferation. Furthermore, adapalene does not bind to members of the cellular retinoic acid binding protein family. Adapalene has comedolytic activity in the topical rhino mouse model. It exerts a moderate-to-potent anti-inflammatory effect in a series of in vitro and in vivo models. In comparative clinical studies involving 72 acne patients, the efficacy of adapalene was comparable, if not superior, to tretinoin, but adapalene was better tolerated. The data reviewed in this paper indicate that adapalene should be particularly beneficial in the treatment of acne.

Site-specific drug delivery to pilosebaceous structures using polymeric microspheres.

In order to improve the therapeutic index of adapalene, a new drug under development for the treatment of acne, site-specific delivery to the hair follicles using 50:50 poly(DL-lactic-co-glycolic acid) microspheres as particulate carriers was investigated in vitro and in vivo. The percutaneous penetration pathway of the microspheres was shown to be dependent on their mean diameter. Thus, after topical application onto hairless rat or human skin, adapalene-loaded microspheres (5-microns diameter) were specifically targeted to the follicular ducts and did not penetrate via the stratum corneum. The in vitro release of adapalene from the microspheres into artificial sebum at 37 degrees C was controlled and faster than the in vivo sebum excretion in humans. Aiming to reduce either the applied dose of drug or the frequency of administration, different formulations of adapalene-loaded microspheres were evaluated in vivo in the rhino mouse model. A dose-related comedolytic activity of topical formulations of adapalene-loaded microspheres was observed in this model. Furthermore, by applying a site-specific drug delivery system (0.1% adapalene) every other day or by administering a 10-fold less concentrated targeted formulation (0.01%) every day, a pharmacological activity equivalent to a daily application of an aqueous gel containing drug crystals (0.1% adapalene) was observed. Since an aqueous gel containing 10% adapalene-loaded microspheres was not irritating in a rabbit skin irritancy test, this formulation was applied onto forearms of human volunteers. Site-specific drug delivery was further evidenced by follicular biopsy. Since an aqueous gel containing 10% adapalene-loaded microspheres was not irritating in a rabbit skin irritancy test, this formulation was applied onto forearms of human volunteers. Site-specific drug delivery was further evidenced by follicular biopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Topical Retinoids on Cytoskeletal Proteins: Implications for Retinoid Effects on Epidermal Differentiation

In vivo effects of retinoids on epidermal differentiation were investigated by analyzing cytoskeletal proteins in rhino mice treated topically with all-trans-retinoic acid (RA) and other retinoids (13-cis-retinoic acid, etretinate, TTNPB). Non-disulfide-linked cytoskeletal proteins, including keratins from the epidermal "living layers," were first selectively extracted using 9.5 M urea; subsequently, keratins of the stratum corneum were isolated using 9.5 M urea plus a reducing agent. Gel electrophoresis and immunoblot analysis showed that urea extracts of epidermis from vehicle-treated skin were composed predominantly of four major keratins (analogous to human epidermal keratins K1, K5, K10, and K14), and the keratin filament-associated protein filaggrin. In contrast, extracts of epidermis from retinoid-treated skin contained additional keratins (K6, K16, and K17) and almost no detectable filaggrin. Furthermore, similar analysis of stratum corneum keratins demonstrated that extracts from RA-treated skin did not contain the partially proteolyzed keratins typically observed in stratum corneum extracts of control animals. Hyperplasia-inducing agents (salicylic acid, croton oil) caused an increase in keratins K6, K16, and K17, but they did not effect filaggrin or alter proteolysis of stratum corneum keratins. The result that RA induced expression of keratins K6, K16, and K17, as commonly expressed in hyperproliferative epidermis, is consistent with the notion that retinoids increase epidermal cell proliferation in the basal and/or lower spinous layers. The findings that topical RA decreased filaggrin expression and reduced proteolysis of stratum corneum keratins, despite increased size and number of granular cells and the presence of an anucleate stratum corneum, suggest that topical RA may also modulate a later stage of epidermal differentiation involved in stratum corneum formation.

Interaction between Dermal Papilla and Bulge: The Rhino Mouse Mutation as a Model System

Interaction between Dermal Papilla and Bulge: The Rhino Mouse Mutation as a Model System

Sequence of morphological events during topical application of retinoic acid on the rhino mouse skin

In a study of the comedolytic action of retinoids on the epidermal pseudocomedones of rhino mouse skin, the earliest changes and the sequence of events induced by the treatment were investigated. Rhino mice were treated topically with all-trans retinoic acid and at various time intervals from day 0 to 3 weeks, histological and ultrastructural studies as well as quantification of mast cells were performed. The earliest changes occurred in the dermis after 2 days of treatment and were characterized by degranulation of mast cells, clumping and association of Langerhans cells and lymphocytes. During the second week of treatment there was hyperplasia, hypergranulosis and an increase in the number of membrane coating granules with disorganization of the horny layer both of the epidermis and the follicular epithelium. These changes in the proliferation and the differentiation of keratinocytes resulted in a comedolytic effect. Associated with these epidermal changes there were changes in the dermis with an increased number of mast cells and a decreased number of Langerhans cells.

The rhino mouse model: the effects of topically applied all-trans retinoic acid and CD271 on the fine structure of the epidermis and utricle wall of pseudocomedones

The histological and ultrastructural effects following 3 weeks' topical treatment with two agents (all-trans retinoic acid and a new synthetic retinoid-like substance, CD271) were evaluated on the epidermis and the epithelial wall of the pseudocomedones in rhino mouse skin. The comedolytic effects of these drugs were similar, and consisted of a reduction of the utricular diameter, with normalization of follicular units. Morphological examinations revealed a hyperplastic response with an increase in the number of cell layers of both epidermis and follicular epithelium, and modifications in keratinocyte differentiation. Ultrastructural changes in the epidermis and epithelial wall were observed mainly in the granular and horny layers, with increased desquamation, and a decrease in the cohesiveness of corneocytes. During the first week of treatment, some cutaneous toxic effects were noticed, but they normalized within two weeks. On the other hand, a fine granular material persisted in the intercellular spaces. It is confirmed that the skin of the rhino mouse is a good model for the evaluation of the comedolytic effects of drugs. Moreover, it reveals the specific effects of retinoids on epidermal differentiation. We have demonstrated that topically applied CD271 induces modifications similar to those obtained with all-trans retinoic acid. It is thus concluded that CD271 is a potentially effective anti-acne agent.

Quantification of Epidermal Histological Changes Induced by Topical Retinoids and CD271 in the Rhino Mouse Model Using a Standardized Image Analysis Technique

The rhino mouse has been used as an experimental model to screen topically active comedolytic agents. Adult rhino mice were treated on the back once daily for 5 consecutive days per week during 3 weeks. Skin histological preparations were analyzed by image analysis techniques to quantify the number of epidermal comedones, comedo profile and epidermal thickness. Using both a negative (treated with acetone) and a positive (treated with Aberel gel 0.025%) control group of animals in all experiments conducted over a period of about 3 years, we defined the upper and lower limit of acceptability of the results. Topical treatment with an acetone solution of all-trans retinoic acid (0.01, 0.03, 0.1%) and 13-cis-retinoic acid (0.1%) induced comedolysis and a marked increase in epidermal thickness. Commercial preparations of all-trans retinoic acid (Aberel lotion, gel and cream, Retin A cream, Retacnyl cream) presented a similar comedolytic activity. However, the epidermal thickening was higher with Retin A and weaker with Retacnyl. CD271, a new modulator of cell differentiation, applied either in acetone solution (0.01, 0.1%) or in lotion, gel or cream formulations (0.1%) also demonstrated a marked activity (i.e. comedolysis and epidermal thickening). These data confirm that the rhino mouse model can be used to assay drugs applied either in solvent or in topical formulations. Activity in this model compares favorably with published clinical observations in the treatment of acne.

A Direct Comparison of Pharmacologic Effects of Retinoids on Skin Cells in vitro and in vivo

The purpose of these studies was to directly compare the pharmacologic effects of retinoids on cutaneous cells in vitro and in vivo. Previously, it was demonstrated that all-trans-retinoic acid stimulates the proliferation of growth-arrested human keratinocytes and fibroblasts in culture. In the present studies, all-trans-retinoic acid was compared to three other retinoids--13-cis-retinoic acid, P-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-napthalenyl-1-p ropenyl] benzoic acid (TTNPB) and M-[(E)-2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-napthalenyl-1-p ropenyl] benzoic acid (meta-carboxy-TTNPB]--for growth stimulation using a cultured human squamous epithelial cell line (UM-SCC-1) and human dermal fibroblasts. These four retinoids were also evaluated for their effects on reduction of horn-filled utriculi when topically applied to the skin of rhino mice. All-trans-retinoic acid stimulated proliferation of both fibroblasts and epithelial cells over concentrations ranging from 0.01 to 1.0 micrograms/ml. In fibroblasts, 13-cis-retinoic acid was less potent than all-trans-retinoic acid, whereas, in epithelial cells these two retinoids were equipotent. In contrast, TTNPB was more potent than all-trans-retinoic acid at stimulating the growth of both fibroblasts and epithelial cells. The analog, meta-carboxy-TTNPB was essentially inactive as a growth stimulator of both cell types. In the rhino mouse utriculus reduction model, the rank order of potency for the retinoids was the same as that for in vitro cell growth stimulation (TTNPB greater than all-trans-retinoic acid greater than 13-cis-retinoic acid). Meta-carboxy-TTNPB was inactive at reducing utriculi at a dose of 5,000 times the ED50 of TTNPB.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of genetically determined immunodeficiency on epidermal dendritic cell populations in C57BL/6J mice

Mice homozygous for three different recessive mutations known to cause pleiotropic defects in the immune system and in the skin were used to evaluate the relationship between the classical immune system and dendritic epidermal cell populations. Numbers of Langerhans cells (LCs) and Thy-1+ dendritic cells (Thy-1+DEC) were determined using indirect immunofluorescence microscopy of epidermal whole mounts taken from viable motheaten (mev), nude (nu), and rhino (rhhr) mice. All mutants were maintained on the C57BL/6J strain background and were compared with their respective littermate normal controls. Viable motheaten mice had normal numbers of LCs at 1 month of age. However, by 8 weeks of age, LC density had decreased threefold. Nude and rhino mice had normal numbers of LCs at all ages tested. There was no significant effect of the viable motheaten mutation on numbers of Thy-1+DEC. Although nude mice showed normal numbers of Thy-1+ DEC at 1 month of age, these athymic mice had a threefold decrease in numbers of such cells by 6 months. In contrast to the reduced numbers of Thy-1+DEC seen in nude mice, rhino mice showed a four- to fivefold increase in the numbers of these epidermal cells at all ages tested. These findings suggest new mouse models for investigating the development, regulation, and biological properties of epidermal dendritic cell populations.

The [formula omitted] rhino mutant: Description of a unique murine model of autoimmunity

The BALB c HuDI-hr rh rhino mutant, which is no longer available, was an unusual murine model with prominent hepatic inflammation and fibrosis. The current report describes the early appearance of hepatic portal tract inflammation and antinuclear antibodies in the RHJ Le mouse, a related rhino mutant which is distributed from a commercial source. All homozygous RHJ Le rhino (hr rh hr rh) mice examined serially from 2 to 18 months of age developed inflammation of hepatic portal tracts. In 81 per cent of mice, portal and central veins were infiltrated with mononuclear cells. Focal infiltrates were found in salivary, Harderian and lacrimal glands and in the pancreas. Isolated animals had myositis involving skeletal muscle and myocardium. Heterogeneous antinuclear antibodies were detected in sera from 100 per cent of rhino mice and antibodies to DNA were present in 28 per cent of mice aged 6 months. Homozygous HRS J hairless ( hr hr ) and BALB c controls failed to show consistent abnormalities in exocrine glands or liver. We conclude that the RHJ Le rhino mutant spontaneously develops antinuclear antibodies and mononuclear cell infiltration in liver and exocrine glands. These animals provide unique opportunities to examine inflammatory lesions localized to specific target organs in an animal model of autoimmunity.

Electron Microscopic Detection of Virus Particles in the Rhino Mouse

The rhino mouse, an experimental model for systemic lupus erythematosus, was found to have murine leukemia virus particles present in the skin. Immunoperoxidase studies with anti-type C virus antibody indicated viral antigen presence in the sebaceous cells and surrounding follicular cysts of the dermis. Electron microscope studies show virus particles, both type C extracellularly and type A intracellularly, around follicular cysts. Virus particle was labeled with specific ferritin-conjugated antitype C virus antibody.

Topical and Systemic Effects of Retinoids on Horn-Filled Utriculus Size in the Rhino Mouse. A Model to Quantify “Antikeratinizing” Effects of Retinoids

A method was developed to quantify the "antikeratinizing" effects of various retinoids (all-trans-retinoic acid, 13-cis-retinoic acid, motretinide, etretinate) in rhino mouse skin, which contains many keratinized pilosebaceous structures or horn-filled utriculi. Mean utriculus diameters in whole mount epidermis were determined and dose-response relationships were constructed after topical or oral administration of test retinoids. All-trans-retinoic acid was 3.7x, 12.5x, and 50x more potent than 13-cis-retinoic acid, etretinate, and motretinide, respectively, after topical administration. Administered orally, all-trans-retinoic acid was 2.3x more potent than 13-cis-retinoic acid. At 5 mg/kg, each retinoid produced a significant reduction in utriculus size. The rhino mouse model represents a novel and useful assay to quantify antikeratinizing activity and potency differences of biologically active retinoids.

Animal assays for anti-psoriatic, retinoid and sun protective agents.

It is possible to evaluate different dermatological therapeutic agents intended for human use in a variety of animal assays. This review will discuss some of these assays, and attempt to correlate animal and human skin responses. Psoriasis is a disease where changes in epidermal proliferation may be an important factor. It is possible to assay potential anti-psoriatic agents by measuring their ability to suppress DNA synthesis in the epidermis of hairless mice. This assay is predictive of the anti-psoriatic effectiveness of numerous agents including a variety of anti-proliferative drugs and anthralin, and has been used to evaluate the potential efficacy of purified coal tar shampoos and body preparations. The activity of the polyamine biosynthesis enzyme ornithine decarboxylase (ODC) is elevated in psoriatic skin, and it is induced in mouse epidermis by tape stripping. Retinoids can inhibit the induction of ODC activity, and this inhibition may be used to evaluate novel synthetic retinoids. Retinoids have beneficial effects on the abnormal keratinization found in various diseases. Rhino mice have multiple keratin-filled epidermal utricles, and the size of these is reduced by retinoid treatment. Observing the changes in the size of the utricles can be utilized to evaluate the effects of retinoids on keratinization. Sunscreen agents are tested on human volunteers by observing their ability to inhibit the erythema induced by exposure to solar-simulated light, to obtain a sun protection factor (SPF). It is possible to utilize the ability of sunscreens to inhibit other actinic-induced changes in the skin using animals. Parameters that may be measured include changes in DNA synthesis and ODC activity in the epidermis following ultraviolet irradiation. Some of these assays correlate well with human SPF determinations.

Histologic Changes in the Skin of the Rhino Mouse (hrrhhrrh) Induced by Retinoids

The effects of four retinoids, all-trans-retinoic acid (RA), 13-cis-retinoic acid (13-cis-RA), aromatic retinoid, and arotinoid ethyl ester ( arotinoid ) were examined on the skin of the rhino mouse. Rhino mouse skin is characterized by the presence of keratin-containing utricles attached to the epidermis, and subcutaneous cysts, both of which are derived from hair follicles. The utricles were examined in horizontal sheets of epidermis, and in vertical histologic sections. After applications of 0.1 ml of 0.1% RA, 0.1% 13-cis-RA, 0.1% aromatic retinoid, or 0.001% arotinoid in acetone to the dorsal skin for 5 days a week for 2 weeks, there was a reduction of utricle diameter to 45%, 52%, 30%, and 31% of acetone-treated controls, respectively. Histologic examination of the epidermis revealed that a dose-dependent hyperplasia and thickening of the epidermis and the stratum granulosum was induced by the retinoids when given at subtoxic doses, being most marked after arotinoid or RA. The thickness of the walls of the utricles also increased with increasing dose of retinoid, paralleling the changes in the epidermis. After doses of 0.1% RA and 0.001% arotinoid , the utricles resembled the hair follicles of hairless mice. Hyperplasia of the epidermis appears to be a primary effect of retinoids or rhino mouse skin. Hyperproliferation of the utricle wall is accompanied by a reduction in the size of the utricle lumen, preceding eventual differentiation of the utricles to normal-looking pilar units.

Susceptibility of rhino mouse to Mycobacterium leprae

It was important to find out the suitable animal which is a laboratory animal and susceptible to M. leprae, and Kohsaka et al. previously reported the establishment of experimental lepromatous leprosy with congenitally athymic nude mouse.It was interested to use rhino mouse which is an immune-deficient animal with disappearance of thymus in early stage, therefore, an attempt to inoculate M. leprae into the rhino mouse was carried out.Eight- and five-month old rhino mice (rhrh) of genetic background A/H were inoculated with Mycobacterium leprae in order to find out another model of exprimental lepromatous leprosy with laboratory animal other than nude mouse. All of inoculated rhino mice indicated the multiplication of the bacilli in the foot pads at the site of inoculation bacteriologically and histopathologically even though the proliferation was not so remarkable as in nude mouse.Rhino mouse could survive for more than 15 months under conventional circumstances, but there is no significant proliferation of M. leprae in the mouse as compeared to nude mouse, and it is suggested that rhino mouse is not so useful for leprosy research because of the difficulties of its rearing and breeding.

Immunopathology of rhino mouse, an autosomal recessive mutant with murine lupus-like disease.

Detection of high incidence of antinuclear antibodies (ANA) was reported in young homozygous rhino mice employing formalinized chicken erythrocyte nuclei as substrate for indirect immunofluorescence (IF) assay. The titers of ANA heightened with increasing age, and attained to 1:1024 by the time mice reached 5 months of age. The occurrence of ANA was associated with development of splenic and hepatic fibrosis, glomerulonephritis and abnormalities of lymphoreticular tissue. The granular deposits of IgG and C3 detected by direct IF were initially found at the basement membrane of dermal‐epidermal junction of rhino mice aged 2.5 months. These deposits distributed progressively in the fibrotic areas of spleen and liver, and renal glomerular tufts at 5 months of age. Dense deposits revealed by electron microscopy were found in the regions where IF of IgG and G3 was observed. Acid buffer eluates from liver and kidney contained IgG reactive with nuclear antigens. Importance of homozygous rhino gene was discussed in relation to development of autoimmune disorders of these mice.