As reviewed in the article by Perry and colleagues (2014) in this volume, ample evidence has documented the contributions of peer support (PS) to health, health care, and prevention. Building on that foundation, this article discusses characteristics, contexts, and dissemination of PS, including (a) fundamental aspects of the social support that is often central to it; (b) cultural influences and ways PS can be tailored to specific groups; (c) key features of PS and the importance of ongoing support and backup of peer supporters and other factors related to its success; (d ) directions in which PS can be expanded beyond prevention and chronic disease management, such as in mental health or interventions to prevent rehospitalization; (e) other opportunities through the US Affordable Care Act, such as through patientcentered medical homes and chronic health homes; and ( f ) organizational and policy issues that will govern its dissemination. All these demonstrate the extent to which PS needs to reflect its contexts-intended audience, health problems, organizational and cultural settings-and, thus, the importance of dissemination policies that lead to flexible response to contexts rather than constraint by overly prescriptive guidelines.

Parkinson disease (PD)2 motor symptoms arise from the progressive degeneration of dopaminergic neurons (DAn). Experimental therapies, based on the cell replacement of the lost substantia nigra pars compacta (SNpc) DAn using human ventral mesencephalic (VM) fetal tissue provided proof of principle of a therapeutic effect of the transplants on a long term basis (1). However, in addition to ethical problems related to fetal tissue procurement, practical limitations were found, like the need for large amounts of VM tissue and the elevated cell death rate of the transplanted cells (2).As an alternative, human neural stem cells (hNSCs) derived from the developing and adult central nervous system were initially used, but they were inefficient for DAn generation (3). Another stem cell source, the embryonic stem cells, required long and difficult differentiation protocols as well as neuronal and DAn progenitor selection to obtain high amounts of DAn (4, 5). Previous transplantation studies established that the generation of functional SNpc DAn in vivo was highly dependent on the regional tissue origin, the VM being the optimal region (6), and that only DAn with SNpc properties (meaning adequate patterning, transcription factor, and differentiated protein profile) were able to reinervate the striatum and induce a therapeutic effect (7). Therefore, human fetal VM-derived cell strains were established (8, 9), but their use was hindered by a limited and unstable DA differentiation potential (10) (as it was previously described for rodent and human VM neurospheres (11, 12)) and DA-related oxidative stress (13).To the human cell lines of VM origin previously reported (8, 14), we have recently contributed a new immortalized human fetal VM NSC line (hVM1), which shows a great potential for the generation of SNpc DAn in vitro (15). In the present work, we have aimed at increasing our understanding of key factors involved in phenotypical stability, DAn generation, and functional maturation both in vitro and in vivo.