In order to make stem cell therapy more accessible for practitioners, we decided to prepare our mesenchymal stem cells (MSCs) from other horses. This phenomenon is called “allogenic stem cell therapy”. In contrast to pluripotent stem cells, the safe use of allogenic MSCs has been described in both humans and horses (Carrade et al., 2011a; Carrade et al., 2011b; Fang et al., 2007). In addition, Guest has reported in 2008 that the injection of allogenic MSCs in equine tendon lesions did not induce any increase in cell mediated immune response in comparison to autologous MSCs (from the same animal). The low immunogenicity of these cells suggests that MSCs can be transplanted universally without matching between donors and recipients. It has to be mentioned though, that the donor animals should be stalled in quarantine and repeated blood testing for transmittable diseases is required.
The donor MSCs used by GST are negative for the typical rejection proteins, MHC class II and slightly express MHC class I. Also chondrogenic induction does not alter the MHC levels, reflecting low immunogenicity, which should be permissive for allogenic transplantations.
Several studies have even reported the successful use of allogenic human MSCs to treat patients suffering from therapy-resistant graft versus host disease (Fang et al., 2007; Ringden et al., 2006). By using allogenic MSCs, we have the opportunity to select high quality MSCs and perform a bacteriological examination at the moment the stem cell samples are frozen. These samples leave the lab as soon as the bacteriological examination confirms their sterility.