Reconstitution of neural functions in the spinal cord through neural stem cells expressing the neural cell adhesion molecule L1

  Melitta Schachner, PhD Zentrum für Molekulare Neurobiologie University of Hamburg Martinistraße 52  D20246- Hamburg Germany

Neural stem cells have recently been shown to be potent and versatile mediators of regeneration in the lesioned central nervous system. They can integrate into the tissue, differentiate into neuronal cells, and grow axons leading to the formation of new synapses and partial restoration of lost functions. The neural cell adhesion molecule L1 has been shown to be a good neurite outgrowth promoter. L1 is upregulated by neurons and Schwann cells after a peripheral nerve lesion and has been implicated in axon regeneration. We propose to test the effect of L1 expressed by genetically manipulated neural stem cells on neuronal differentiation, survival and neurite outgrowth in a mammalian model of spinal cord regeneration


Cell adhesion molecule L1-transfected embryonic stem cells with enhanced survival support regrowth of corticospinal tract axons in mice after spinal cord injury

Previous studies have indicated that the cell adhesion molecule L1 enhances neuronal survival and neurite outgrowth. L1-mediated promotion of neurite outgrowth has been shown to occur also in an inhibitory environment not only in vitro, but also in vivo. To further investigate the effects of L1 in spinal cord injury, we transfected embryonic stem cells with a plasmid encoding the full length mouse L1 molecule under the control of PGK promoter. An embryonic stem cell line derived from C57BL/6J transgenic mice that expresses green fluorescent protein under control of the β-actin promoter was transfected with L1 and injected into the lesion site of 3-month-old C57BL/6J female mice 7 days after compression injury. Non-transfected embryonic stem cells were detectable at the lesion site 3 days after transplantation, but lost their cellular integrity 7 days after transplantation and were scarcely detectable one month after transplantation. By contrast, L1-transfected embryonic stem cells remained detectable one month after transplantation in numbers similar to those of the injected cells and had extended processes. Furthermore, compared with the few detectable non-transfected stem cells which remained at the injection site one month after transplantation, L1-transfected embryonic stem cells had migrated away rostrally and caudally from the lesion. Anterogradely labeled corticospinal tract axons showed interdigitation with L1-transfected embryonic stem cells that, in comparison to non-transfected stem cells, extended further into the lesion site one month after transplantation and, in some cases, regrew beyond it. Our observations encourage the use of L1-transfected embryonic stem cells that express L1 not only at the cell surface, but also as a soluble and secreted form with the aim to condition the inhibitory environment for homophilic L1-enhanced axon regrowth not only in spinal cord regeneration, but also in other lesion paradigms.

Neural cell adhesion molecule L1 - transfected embryonic stem cells promote functional recovery after lesion of the mouse striatum.

We have generated a murine embryonic stem cell line constitutively expressing L1 at all stages of neural differentiation to monitor the effects on stem cell differentiation, migration,and ability to influence drug induced rotation behavior in an animal model of Huntington’s disease. Transfection of L1 enhanced neuronal differentiation of these cells in vitro and in vivo and decreased astrocytic differentiation in vivo. L1 expression also increased the yield of GABAergic neurons and enhanced migration of neural precursor cells into the lesioned striatum. Mice grafted with L1 expressing cells showed recovery in rotation behavior when compared to mice that had received mock-transfected cells, thus demonstrating for the first time that a recognition molecule is capable of improving functional recovery in a syngeneic transplantation paradigm.