Muscle spindle reinnervation using transplanted embryonic dorsal root ganglion cells after peripheral nerve transection in rats

Abstract

Objectives: Muscle spindles are proprioceptive receptors in the skeletal muscle. Peripheral
nerve injury results in a decreased number of muscle spindles and their
morphologic deterioration. However, the muscle spindles recover when skeletal
muscles are reinnervated with surgical procedures, such as nerve suture or
nerve transfer. Morphological changes in muscle spindles by cell-transplantation
procedure have not been reported so far. Therefore, we hypothesized that
transplantation of embryonic sensory neurons may improve sensory neuron in the skeletal
muscle and reinnervate the muscle spindles.

Materials
and Methods: We collected sensory
neurons from dorsal root ganglions of 14-day-old rat embryos and prepared
a rat model of peripheral nerve injury, by performing sciatic nerve transection
and allowing for a period of one week before which we performed the cell
transplantations. Six months later, the morphological changes of muscle spindles
in cell transplantation group was compared with naïve control and surgical
control groups.

Results: Our
results demonstrated that transplantation of embryonic dorsal root ganglion
cells induced regeneration of sensory nerve fiber and reinnervation of muscle
spindles in the skeletal muscle. Moreover, Calbindin D-28k immunoreactivity in
intrafusal muscle fibers was maintained for six months after denervation in the
cell transplantation group, whereas it disappeared in the surgical control
group. Conclusions: Cell
transplantation therapies could serve as selective targets to modulate
mechanosensory function in the skeletal muscle.