Stem Cell Reports Repor t Equine-Induced Pluripotent Stem Cells Retain Lineage Commitment Toward Myogenic and Chondrogenic Fates Mattia Quattrocelli, 1 Giorgia Giacomazzi, 1 Sarah Y. Broeckx, 2 Liesbeth Ceelen, 3 Selin Bolca, 3 Jan H. Spaas, 2,5, * and Maurilio Sampaolesi 1,4,5, * 1 Translational Cardiomyology Lab, Stem Cell Biology and Embryology Unit, Department Development and Regeneration, KU Leuven, 3000 Leuven, Belgium 2 Global Stem Cell Technology, ANACURA Group, 9940 Evergem, Belgium 3 Pathlicon, ANACURA Group, 9940 Evergem, Belgium 4 Division of Human Anatomy, Department of Public Health, Experimental and Forensic Medicine, University of Pavia, 27100 Pavia, Italy 5 Co-senior author *Correspondence: jan.spaas@anacura.com (J.H.S.), maurilio.sampaolesi@med.kuleuven.be (M.S.) http://dx.doi.org/10.1016/j.stemcr.2015.12.005 This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). SUMMARY Induced pluripotent stem cells (iPSCs) hold great potential not only for human but also for veterinary purposes. The equine industry must often deal with health issues concerning muscle and cartilage, where comprehensive regenerative strategies are still missing. In this re- gard, a still open question is whether equine iPSCs differentiate toward muscle and cartilage, and whether donor cell type influences their differentiation potential. We addressed these questions through an isogenic system of equine iPSCs obtained from myogenic mesoangio- blasts (MAB-iPSCs) and chondrogenic mesenchymal stem cells (MSC-iPSCs). Despite similar levels of pluripotency characteristics, the myogenic differentiation appeared enhanced in MAB-iPSCs. Conversely, the chondrogenic differentiation was augmented in MSC-iPSCs through both teratoma and in vitro differentiation assays. Thus, our data suggest that equine iPSCs can differentiate toward the myogenic and chondrogenic lineages, and can present a skewed differentiation potential in favor of the source cell lineage. INTRODUCTION Horses are invaluable animals for companionship and sport. The equine industry creates an estimated economic impact of US$300 billion worldwide, and novel means for addressing equine health issues are constantly required (Tecirlioglu and Trounson, 2007). Musculoskeletal prob- lems, including pathologies or injuries of muscle and carti- lage, constitute a leading health threat among horses (Smith et al., 2014). As an example, equine atypical myop- athy has been increasingly reported over recent years (Vo- tion and Serteyn, 2008), and equine osteochondrosis is relatively frequent across different breeds (van Weeren and Jeffcott, 2013). Therefore, the quest for novel tools for muscle and cartilage repair is still compelling. In this regard, stem cells may support the needs of veterinary medicine (Cebrian-Serrano et al., 2013). In equine prac- tice, mesenchymal stem cells (MSCs) are commonly used to treat tendinitis and osteoarthritis (Schnabel et al., 2013). However, a comprehensive regenerative approach tailored to both muscle and cartilage is still missing, espe- cially for large-scale applications. Importantly, considering the obvious difficulties of in vivo trials, in vitro models constitute a useful, first-line trial platform for addressing differentiation and heterogeneity of stem cells (Goodell et al., 2015). To this end, induced pluripotent stem cells (iPSCs) hold great potential, in light of their tremendous expansion capacity and wide differentiation potential (Ya- manaka, 2009). Recently, iPSCs have been generated from equine fibroblasts (Breton et al., 2013) and keratinocytes (Sharma et al., 2014); however, their differentiation poten- tial toward myocytes or chondrocytes remains unknown. Furthermore, iPSCs tend to retain, at least partially, the intrinsic fate propensity of the cell source (Sanchez-Freire et al., 2014). In mice, iPSCs derived from resident myogenic pericytes, i.e. mesoangioblasts (MABs), show biased myogenic differentiation in both teratoma and in vitro differentiation assays (Quattrocelli et al., 2011). However, it is still unknown whether it is possible to discriminate the intrinsic equine iPSC propensity toward the myogenic and the chondrogenic lineages. To address this question, isogenic settings need to reduce the vari- ability introduced by genetic background (Kotini et al., 2015). Relevantly for putative veterinary applications, the choice of the cell source should be confined to somatic compartments at facilitated reach, e.g. blood and superfi- cial muscle biopsies. Equine peripheral blood has been recently used to isolate circulating progenitors, exhibiting MSC properties (Spaas et al., 2013) and differentiating in chondrocytes (Broeckx et al., 2014). With regard to the muscle, it is still unknown whether equine MABs can be isolated with similar characteristics to murine, canine, or Stem Cell Reports j Vol. 6 j 55–63 j January 12, 2016 j ª2016 The Authors 55