1. McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15219, USA.
2. Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15219, USA.
3. Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15219, USA.
4. Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15219, USA.
5. Center of Biologic Imaging, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.