Comparison of GDF5 and GDNF as Neuroprotective Factors for Postnatal Dopamine Neurons in Ventral Mesencephalic Cultures Juliann D. Jaumotte 1 and Michael J. Zigmond 1,2,3 * 1 Department of Neurology, Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, Pennsylvania 2 Department of Neurobiology, University of Pittsburgh, Pittsburgh, Pennsylvania 3 Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania Loss of dopamine neurons is associated with the motor deficits that occur in Parkinson’s disease. Although many drugs have proven to be useful in the treatment of the symptoms of this disease, none has been shown to have a significant impact on the development of the disease. However, we believe that several neurotrophic factors have the potential to reduce its progression. Glial cell line- derived neurotrophic factor (GDNF), a member of the transforming growth factor-b superfamily of neurotrophic factors, has been extensively studied in this regard. Less attention has been paid to growth/differentiation factor 5 (GDF5), another member of the same superfamily. This study compares GDNF and GDF5 in dissociated cultures prepared from ventral mesencephalon and in organotypic co-cultures containing substantia nigra, striatum, and neo- cortex. We report that both GDNF (10–500 ng/ml) and GDF5 (100–500 ng/ml) promoted the survival of dopamine neurons from the substantia nigra of postnatal rats, although GDNF was considerably more potent than GDF5. In contrast, neither factor had any significant effect on the survival of dopamine neurons from the rat ventral tegmen- tal area. Using organotypic co-cultures, we also compared GDF5 with GDNF as chemoattractants for the innervation of the striatum and the neocortex by dopamine neurons from the substantia nigra. The addition of either GDF5 or GDNF (100–500 ng/ml) caused innervation by dopamine neurons into the cortex as well as the striatum, which did not occur in untreated cultures. Our results are consistent with similar findings suggesting that GDF5, like GDNF, deserves attention as a possible therapeutic intervention for Parkinson’s disease. V C 2014 Wiley Periodicals, Inc. Key words: Parkinson’s disease; organotypic co- cultures Parkinson’s disease (PD) is a progressive neurologi- cal disease that affects approximately 1% of the population over 60 years of age. A neuropathological hallmark of the disease is the loss of dopamine (DA) neurons in the sub- stantia nigra (SN), which is largely responsible for the motor deficits associated with the disorder. Current treat- ments for PD often act to alleviate the symptoms of PD but do not significantly slow disease progression, and they also, inevitably, have side effects. However, several neuro- trophic factors (NTFs) have been shown to have neuro- protective and neurorestorative effects on DA neurons in animal and cellular models (Sullivan and Toulouse, 2011; Allen et al., 2013; Kordower and Bjorklund, 2013) and in some open-label clinical trials (Sherer et al., 2006; Patel et al., 2013) and, thus, have potential as therapeutic agents. The transforming growth factor-b (TGFb) super- family of NTFs contains 35 proteins that encompass bone morphogenetic proteins (BMPs), growth/differentiation factors (GDFs), the TGFb subfamily, the glial cell line- derived neurotrophic factor (GDNF) family, and a few other additional proteins. GDNF is an example of a mem- ber of the TGFb superfamily that can protect DA neurons against spontaneous cell death in vitro (Lin et al., 1993). Moreover, by using in vivo models, GDNF has been shown to protect against the neurotoxic effects of 6- hydroxydopamine (6-OHDA; Hoffer et al., 1994; Gash et al., 1995; Opacka-Juffry et al., 1995; Fox et al., 2001; Cohen et al., 2011) and 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP; Tomac et al., 1995; Cheng et al., 1998; Gerhardt et al., 1999; Kells et al., 2010). Contract grant sponsor: National Institute of Neurological Disorders and Stroke (NINDS); contract grant number: NS 19608; Contract grant sponsor: NINDS; contract grant number: NS 070825; Contract grant sponsor: Johnson and Johnson Regenerative Therapies; Contract grant sponsor: University of Pittsburgh *Correspondence to: M. J. Zigmond, PhD, Department of Neurology, Pittsburgh Institute for Neurodegenerative Diseases, University of Pitts- burgh, 7016 Biomedical Science Tower 3, Pittsburgh, PA 15260. E-mail: zigmond@pitt.edu Received 4 February 2014; Revised 13 May 2014; Accepted 13 May 2014 Published online 11 June 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jnr.23425 V C 2014 Wiley Periodicals, Inc. Journal of Neuroscience Research 92:1425–1433 (2014)