Accelerated aging phenotype in mice with conditional deficiency for mitochondrial superoxide dismutase in the connective tissue Nicolai Treiber, 1 * Pallab Maity, 1 * Karmveer Singh, 1 * Matthias Kohn, 1 * Alexander F. Keist, 1 Florentina Ferchiu, 1 Lea Sante, 1 Sebastian Frese, 2 Wilhelm Bloch, 2 Florian Kreppel, 3 Stefan Kochanek, 3 Anca Sindrilaru, 1 Sebastian Iben, 1 Josef Ho ¨ gel, 4 Michael Ohnmacht, 5 Lutz E. Claes, 5 Anita Ignatius, 5 Jin H. Chung, 6 Min J. Lee, 6 York Kamenisch, 7 Mark Berneburg, 7 Thorsten Nikolaus, 8 Kerstin Braunstein, 9 Anne-Dorte Sperfeld, 9 Albert C. Ludolph, 8,9 Karlis Briviba, 10 Meinhard Wlaschek 1 and Karin Scharffetter-Kochanek 1,8 1 Department of Dermatology and Allergic Diseases, University of Ulm, D-89081 Ulm, Germany 2 Department of Molecular and Cellular Sports Medicine, German Sports University, D-50927 Cologne, Germany 3 Department of Molecular Medicine, Division of Gene Therapy, University of Ulm, D-89081 Ulm, Germany 4 Institute for Human Genetics, University of Ulm, D-89081 Ulm, Germany 5 Institute of Orthopaedic Research and Biomechanics, University of Ulm, D-89081 Ulm, Germany 6 Department of Dermatology, Seoul National University Hospital, Seoul 110-744, Korea 7 Department of Dermatology, University of Tuebingen, D-72076 Tuebingen, Germany 8 Competence Center for Gerontology and Aging Research, D-89081 Ulm, Germany 9 Department of Neurology, University of Ulm, D-89081 Ulm, Germany 10 Institute of Nutritional Physiology, Federal Research Centre for Nutrition and Food, D-76131 Karlsruhe, Germany Summary The free radical theory of aging postulates that the pro- duction of mitochondrial reactive oxygen species is the major determinant of aging and lifespan. Its role in aging of the connective tissue has not yet been established, even though the incidence of aging-related disorders in connective tissue-rich organs is high, causing major disability in the elderly. We have now addressed this question experimentally by creating mice with condi- tional deficiency of the mitochondrial manganese super- oxide dismutase in fibroblasts and other mesenchyme- derived cells of connective tissues in all organs. Here, we have shown for the first time that the connective tissue- specific lack of superoxide anion detoxification in the mitochondria results in reduced lifespan and premature onset of aging-related phenotypes such as weight loss, skin atrophy, kyphosis (curvature of the spine), osteopo- rosis and muscle degeneration in mutant mice. Increase in p16 INK4a , a robust in vivo marker for fibroblast aging, may contribute to the observed phenotype. This novel model is particularly suited to decipher the underlying mecha- nisms and to develop hopefully novel connective tissue- specific anti-aging strategies. Key words: Aging; connective tissue; mitochondria; p16 INK4a ; reactive oxygen species; Sod2. Introduction Although reactive oxygen species (ROS) are part of normal regu- latory circuits, imbalance or loss of cellular redox homoeostasis during aging results in oxidative stress (Sies, 1986, 1991), caus- ing damage to cellular components. Apart from permanent genetic damage involving protooncogenes and tumour suppres- sor genes, ROS activate cytoplasmic signal transduction path- ways that are related to growth, differentiation, tissue homoeostasis and senescence. Therefore, ROS have been impli- cated to play a causal role in tissue degeneration and – if deviant in composition and concentration – also in cancer and aging. Increased ROS concentration occurs in senescent fibroblast in vitro and in vivo (Scharffetter-Kochanek et al., 1997; Allen et al., 1999; Hutter et al., 2002; Shin et al., 2005). Fibroblasts constitute the principal component of the connective tissue. As such, fibroblasts occur in virtually every tissue and organ of the body. The capacity of fibroblasts to synthesize and organize the extracellular matrix and to communicate with other cells and tis- sues makes them a so far underestimated central component in organ homoeostasis and aging. Notably, the incidence of aging- related disorders such as skin- and muscle atrophy, osteoporosis and delayed wound healing are particularly high in connective tissue-rich organs including skin, bone and muscle causing major disability in the elderly. Skin aging is characterized by the loss of the elastic and collagen fibre network due to dysfunc- tional fibroblasts (Fisher et al., 2008; Quan et al., 2010) leading to wrinkle formation, reduced tensile strength and impaired Correspondence Karin Scharffetter-Kochanek, MD, Department of Dermatology and Allergic Diseases, University of Ulm, Maienweg 12, 89081 Ulm, Germany. Tel.: ++49 731 50057501; fax: ++49 731 50057502; e-mail: karin.scharffetter-kochanek@uniklinik-ulm.de Accepted for publication 13 November 2010 *These authors contributed equally. ª 2010 The Authors Aging Cell ª 2010 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland 239 Aging Cell (2011) 10, pp239–254 Doi: 10.1111/j.1474-9726.2010.00658.x Aging Cell