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Fall 2007 Symposium – Regeneration and Repair in the Nervous System
The first BSI mini-symposium, held Dec. 14th, 2007, was focused on Regeneration and Repair in the Nervous System. It grew out of a series of discussions within two groups, one focused on regeneration in the brain and spinal cord and one on regeneration in the peripheral nervous system, led by Larry Schramm and by Tom Brushart and Ahmet Hoke, respectively. The symposium included talks from speakers chosen to bring new perspectives, in many cases from outside the regeneration field. In addition, 30 posters were presented describing projects in Hopkins faculty labs. The speakers and posters represented a wide range of expertise and departments, including neuroscience, neurology, biomedical engineering, radiology, anesthesiology, neurosurgery, ophthalmology, and others. Interchange around the posters took place in a two-hour interval over lunch.
The mini-symposium was held in the Tilghman Room, which just accommodated the 140 attendees. Posters were in the concourse outside. Several themes came out of this day and the preceding group discussions.
• The PNS is often regarded as able to regenerate and restore function effectively. In man, the challenges for effective PNS regeneration rival those in the CNS.
• While independent discussions have been useful, the shared needs outnumber the needs specific to the CNS or PNS alone.
• Relatively little has been done to bring the wealth of knowledge in neurodevelopment into the regeneration field. Some of the most provocative talks and posters challenged the regeneration community to go to school on advances in developmental neurobiology, especially in terms of the growth cone guidance, axonal pathfinding, and fine specification of neuronal phenotypes.
• While much of the focus and the recent success has been on overcoming inhibitors of outgrowth in the CNS and promoting axonal extension, successful outgrowth accomplishes little if appropriate synaptic contact fails to be made. The biology of synaptogenesis is rapidly evolving, and there may be opportunities to foster appropriate connectivity in models of short-distance regeneration. Slices in vitro may offer a model for exploring this issue.
• The ensheathing cells are limiting factors in successful regeneration. This is clearest in the PNS, where the late death of denervated Schwann cells profoundly impairs regeneration. In the CNS, the relative roles of astrocytes and NG2 cells are not understood.
• The challenges of short-distance and long-distance regeneration are so different as to be qualitatively distinct.
• Stem cell approaches are not limited to transplant models; in situ generation of neural stem cells into neuronal or glial precursors deserves exploration.
• Finally, collateral sprouting, often ignored as a resource for functional restoration, offers a potential means of accomplishing simple reinnervation that could provide benefit in selected settings.