The Tight Skin mouse is a genetically induced animal model of tissue fibrosis caused by a large in-frame mutation in the gene encoding fibrillin-1 (Fbn-1). We examined the influence of gender on the collagen content of tissues in C57BL/6J wild type (+/+) and mutant Tight Skin (Tsk/+) mice employing hydroxyproline assays. Tissue sections were stained with Masson’s trichrome to identify collagen in situ. Adult Tsk/+ mice skin contains ~15% more collagen, on average, than skin from +/+ mice of the same gender. The heart of Tsk/+ males had significantly more collagen than that of +/+ males. No significant gender differences were found in lungs and kidney collagen content. Overall, the collagen content of Tsk/+ males and +/+ males was higher than that of their Tsk/+ and +/+ female counterparts, respectively. Our data confirm increased deposition of collagen in skin and hearts of Tsk/+ mice; however, the effects of the Tsk mutation on collagen content are both tissue specific and gender specific. These results indicate that comparative studies of collagen content between normal and Tsk/+ mice skin and internal organs must take into account gender differences caused by expression of the androgen receptor. 1. Introduction Systemic sclerosis (SSc, scleroderma) is a systemic autoimmune disease of unknown etiology characterized by excessive accumulation of collagen in the skin and internal organs, including the gastrointestinal tract, lungs, heart, and kidneys . Besides the often progressive fibrotic process, the pathogenesis of this disorder is characterized by severe microvascular alterations and distinct immunological abnormalities in cellular and humoral responses . The etiologic factors involved in the development and progression of SSc are still unclear thus, study of animal models of the disease is likely to provide valuable information about its pathogenesis and allow identification of potentially effective therapeutic approaches. Mammalian model systems that reproduce all the features of human SSc are not available. Two spontaneous mouse mutations, Tight Skin (Tsk) and Tight Skin 2 (Tsk2), recapitulate some, but not all, features of this disease [3, 4]. The Tsk mutation occurred spontaneously in the inbred mouse strain B10.D2(58N)/Sn . Homozygous Tsk/Tsk mice die in utero by day 8 of gestation, while heterozygous Tsk/+ mice survive to adulthood. Tsk/+ mice have thickened skin which is bound tightly to subcutaneous tissue under the dermis and lacks the pliability and elasticity of normal skin [5, 6]. Several other features in Tsk/+ mice include an
M. C. Green, H. O. Sweet, and L. E. Bunker, “Tight skin, a new mutation of the mouse causing excessive growth of connective tissue and skeleton,” The American Journal of Pathology, vol. 82, no. 3, pp. 493–512, 1976.
G. A. Rossi, G. W. Hunninghake, J. E. Gadek et al., “Hereditary emphysema in the tight-skin mouse. Evaluation of pathogenesis,” The American Review of Respiratory Disease, vol. 129, no. 5, pp. 850–855, 1984.
C. Gardi, P. A. Martorana, M. M. de Santi, P. van Even, and G. Lungarella, “A biochemical and morphological investigation of the early development of genetic emphysema in tight-skin mice,” Experimental and Molecular Pathology, vol. 50, no. 3, pp. 398–410, 1989.
P. A. Martorana, P. van Even, C. Gardi, and G. Lungarella, “A 16-month study of the development of genetic emphysema in tight-skin mice,” The American Review of Respiratory Disease, vol. 139, no. 1, pp. 226–232, 1989.
C. Goldstein, P. Liaw, S. A. Jimenez, A. M. Buchberg, and L. D. Siracusa, “Of mice and Marfan: genetic linkage analyses of the fibrillin genes, Fbn1 and Fbn2, in the mouse genome,” Mammalian Genome, vol. 5, no. 11, pp. 696–700, 1994.
P. J. Christner, L. D. Siracusa, D. F. Hawkins et al., “A high-resolution linkage map of the tight skin 2 (Tsk2) locus: a mouse model for scleroderma (SSc) and other cutaneous fibrotic diseases,” Mammalian Genome, vol. 7, no. 8, pp. 610–612, 1996.
P. J. Christner, J. Peters, D. Hawkins, L. D. Siracusa, and S. A. Jiménez, “The tight skin 2 mouse: an animal model of scleroderma displaying cutaneous fibrosis and mononuclear cell infiltration,” Arthritis and Rheumatism, vol. 38, no. 12, pp. 1791–1798, 1995.
T. Kodera, T. L. McGaha, R. Phelps, W. E. Paul, and C. A. Bona, “Disrupting the IL-4 gene rescues mice homozygous for the tight-skin mutation from embryonic death and diminishes TGF-β production by fibroblasts,” Proceedings of the National Academy of Sciences of the United States of America, vol. 99, no. 6, pp. 3800–3805, 2002.
R. Lemaire, J. H. Korn, J. M. Shipley, and R. Lafyatis, “Increased expression of type I collagen induced by microfibril-associated glycoprotein 2: novel mechanistic insights into the molecular basis of dermal fibrosis in scleroderma,” Arthritis and Rheumatism, vol. 52, no. 6, pp. 1812–1823, 2005.
J. Bayle, J. Fitch, K. Jacobsen, R. Kumar, R. Lafyatis, and R. Lemaire, “Increased expression of Wnt2 and SFRP4 in Tsk mouse skin: role of Wnt signaling in altered dermal fibrillin deposition and systemic sclerosis,” Journal of Investigative Dermatology, vol. 128, no. 4, pp. 871–881, 2008.
M. H. Bocchieri, P. J. Christner, P. D. Henriksen, and S. A. Jimenez, “Immunological characterization of (tight skin/NZB)F1 hybrid mice with connective tissue and autoimmune features resembling human systemic sclerosis,” Journal of Autoimmunity, vol. 6, no. 3, pp. 337–351, 1993.
T. McGaha, S. Saito, R. G. Phelps et al., “Lack of skin fibrosis in tight skin (Tsk) mice with targeted mutation in the interleukin-4Rα and transforming factor-β genes,” Journal of Investigative Dermatology, vol. 116, no. 1, pp. 136–143, 2001.
E. Saito, M. Fujimoto, M. Hasegawa et al., “CD19-dependent B lymphocyte signaling thresholds influence skin fibrosis and autoimmunity in the tight-skin mouse,” Journal of Clinical Investigation, vol. 109, no. 11, pp. 1453–1462, 2002.
R. M. Baxter, T. P. Crowell, M. E. McCrann, E. M. Frew, and H. Gardner, “Analysis of the tight skin (Tsk1/+) mouse as a model for testing antifibrotic agents,” Laboratory Investigation, vol. 85, no. 10, pp. 1199–1209, 2005.
M. S. Markova, J. Zeskand, B. McEntee, J. Rothstein, S. A. Jimenez, and L. D. Siracusa, “A role for the androgen receptor in collagen content of the skin,” Journal of Investigative Dermatology, vol. 123, no. 6, pp. 1052–1056, 2004.
R. Lemaire, G. Farina, E. Kissin et al., “Mutant fibrillin 1 from tight skin mice increases extracellular matrix incorporation of microfibril-associated glycoprotein 2 and type I collagen,” Arthritis and Rheumatism, vol. 50, no. 3, pp. 915–926, 2004.