Composite tissue transplantation in rats: Fusion of donor muscle to the recipient site

Abstract

Little information currently exists on the repair of muscular tissue at the site of an amputation stump. This study examined the healing process of muscular tissue following composite limb transplantation using transgenic rat models. Methods Green fluorescent protein (GFP) transgenic rats were used to study the process of connection of donor muscle with the recipient. A DsRed2/GFP double-reporter transgenic rat and an NCre transgenic rat were used to study cell fusion. These rats have the unique characteristic of changing red fluorescence to green fluorescence by Cre/LoxP recombination when cell-to-cell fusion occurs between the two transgenic strains. Orthotopic hind limb transplantation was performed in two combinations: GFP transgenic rat to Wild Wistar rat and DsRed2/GFP transgenic rat to NCre transgenic rat. Results We observed extension of donor-derived GFP + myofibers into recipient site a few weeks after limb transplantation. A histologic study of the DsRed2/GFP transgenic rat to the NCre transgenic rat combination showed that red myofibers of the DsRed2/GFP rat were partly replaced by green myofibers as a result of Cre-mediated recombination. PCR analysis detected both the recombined transgene (330 bp) and the nonrecombined gene (1420 bp) in muscle around the junction. These findings indicate that the muscles sutured between the amputation stumps fused with each other and that donor–recipient hybrid cells were formed at the muscle junction following limb transplantation. Conclusions This basic information shows muscle fusion between donor and recipient at the site of composite tissue transplant using newly established transgenic rats.