Nevertheless this whole area offers huge potential, not least because it is easy to deliver and in his article A.J. Hannan (pp. 13–25) explores these aspects of neural regeneration. While trying to recruit

new cells to sites of injury or loss is important, what is ultimately learn more needed of them is for them to make connections and integrate into existing neural networks. This is obviously complex, but if the right cells can be persuaded to replace those lost then they should have an intrinsic ability to find their right target assuming they can grow their axons to such targets. This is a problem in the adult CNS where many inhibitors to axonal growth exist [7] and has been a major issue for many diseases and regenerative therapies especially in the spinal cord – where pathway reconstitution is needed more than cell replacement. E.R. Burnside and E.J. Bradbury (pp. 26–59) in their article discuss how this has been investigated and treated in the field of spinal cord repair, which has led to the use of blocking antibodies, enzymes to breakdown the extracellular matrix and other agents designed to allow axonal growth and stability. While the recruitment of endogenous repair processes makes intuitive sense as a strategy by which to repair the

CNS, it clearly fails in most circumstances otherwise we would never see patients with neurological deficits suffering from such disorders of the CNS. Nowhere is Ganetespib ic50 this more apparent than in the

case of chronic neurodegenerative disorders such as PD and HD. Thus in both disorders the grafting of exogenous sources of cells to replace those lost as part of the core disease process has been investigated with varying degrees of success. In the case of PD, the tissue best suited to do this nearly has been the developing human foetal ventral midbrain (mesencephalon) while in HD it has been the developing human foetal ganglionic eminence. In both cases the strategy involves transplanting in the developing dopaminergic and striatal neuroblasts with the expectation that they will survive, differentiate into their mature counterparts (which have been lost in the disease process) and connect with and to the host brain and by so doing repair the brain and restore the patient back to a more normal neurological state. In the case of PD this approach has been shown to work albeit rather inconsistently [8] and G.H. Petit et al. (pp. 60–70) take us through the history of this field as well as its future prospects. They highlight the reasons why it may work as well as some of the limitations of this approach – not least the possibly that the graft may ultimately acquire the pathology of the disease it is used to treat. This theme is taken up by G. Cisbani and F. Ciccheti (pp. 71–90) who lay out the data for the failure of striatal grafts to produce significant long terms benefits in most patients with HD transplanted to date.