Transplantation of induced pluripotent stem cell-derived neurospheres for peripheral nerve repair

Abstract

In spite of the extensive research using induced pluripotent stem (iPS) cells, the therapeutic potential of iPS cells in the treatment of peripheral nerve injury is largely unknown. In this study, we repaired peripheral nerve gaps in mice using tissue-engineered bioabsorbable nerve conduits coated with iPS cell-derived neurospheres. The secondary neurospheres derived from mouse iPS cells were suspended in each conduit (4000,000 cells per conduit) and cultured in the conduit in three-dimensional (3D) culture for 14 days. We then implanted them in the mouse sciatic nerve gaps (5 mm) (iPS group; n = 10). The nerve conduit alone was implanted in the control group (n = 10). After 4, 8 and 12 weeks, motor and sensory functional recovery in mice were significantly better in the iPS group. At 12 weeks, all the nerve conduits remained structurally stable without any collapse and histological analysis indicated axonal regeneration in the nerve conduits of both groups. However, the iPS group showed significantly more vigorous axonal regeneration. The bioabsorbable nerve conduits created by 3D-culture of iPS cell-derived neurospheres promoted regeneration of peripheral nerves and functional recovery in vivo. The combination of iPS cell technology and bioabsorbable nerve conduits shows potential as a future tool for the treatment of peripheral nerve defects.

Introduction

Recently, there have been great advancements in the study of induced pluripotent stem cells (iPS) cells in the field of regenerative medicine [1], [2]. The iPS cells have the ability to differentiate into various types of somatic cells, such as cardiomyocytes, hepatic cells, and pancreatic cells, and thus have been used for understanding the mechanisms of diseases, development of new drugs, and for regenerative therapy including cell implantation [3], [4], [5], [6], [7]. Recently, methods for neural induction of iPS cells have been established by Okada and Miura [8], [9]. In these studies, iPS cells were differentiated into neural precursor cell aggregates, so called neurospheres, which are then able to differentiate into neurons and glial cells. By application of the same method of neural induction of iPS cells for the regenerative therapy of the central nervous system, Nakamura et al. confirmed that grafted human-iPS-cell-derived neurospheres promoted motor functional recovery after spinal cord injury in mice [10], [11], [12]. However, there have been few reports of the application of iPS cells for regenerative therapy of peripheral nerves. The purpose of this study was to repair sciatic nerve gaps in mice using bioabsorbable nerve conduits coated with iPS cell-derived neurospheres, utilizing the neural induction of iPS cells for peripheral nerve regeneration.