The integrity of peripheral nerves relies on communication between axons and Schwann cells. The axonal signals that ensure myelin maintenance are distinct from those that direct myelination and are largely unknown. Here we show that ablation of the prion protein PrP(C) triggers a chronic demyelinating polyneuropathy (CDP) in four independently targeted mouse strains. Ablation of the neighboring Prnd locus, or inbreeding to four distinct mouse strains, did not modulate the CDP. CDP was triggered by depletion of PrP(C) specifically in neurons, but not in Schwann cells, and was suppressed by PrP(C) expression restricted to neurons but not to Schwann cells. CDP was prevented by PrP(C) variants that undergo proteolytic amino-proximal cleavage, but not by variants that are nonpermissive for cleavage, including secreted PrP(C) lacking its glycolipid membrane anchor. These results indicate that neuronal expression and regulated proteolysis of PrP(C) are essential for myelin maintenance.

Mutations in the parkin gene are the most common cause of recessive familial Parkinson disease (PD). Parkin has been initially characterized as an ubiquitin E3 ligase, but the pathological relevance of this activity remains uncertain. Recently, an impressive amount of evidence has accumulated that parkin is involved in the maintenance of mitochondrial function and biogenesis. We used a human neuroblastoma cell line as a model to study the influence of endogenous parkin on mitochondrial genomic integrity. Using an unbiased chromatin immunoprecipitation approach, we found that parkin is associated physically with mitochondrial DNA (mtDNA) in proliferating as well as in differentiated SH-SY5Y cells. In vivo, the association of parkin with mtDNA could be confirmed in brain tissue of mouse and human origin. Replication and transcription of mtDNA were enhanced in SH-SY5Y cells over-expressing the parkin gene. The ability of parkin to support mtDNA-metabolism was impaired by pathogenic parkin point mutations. Most importantly, we show that parkin protects mtDNA from oxidative damage and stimulates mtDNA repair. Moreover, higher susceptibility of mtDNA to reactive oxygen species and reduced mtDNA repair capacity was observed in parkin-deleted fibroblasts of a PD patient. Our data indicate a novel role for parkin in directly supporting mitochondrial function and protecting mitochondrial genomic integrity from oxidative stress.

Because of their insufficient biocompatibility and high thrombogenicity, small diameter artificial vascular prostheses still do not show a satisfactory patency rate. In vitro endothelialization of artificial grafts before implantation has been established experimentally years ago, but, this procedure is extremely time consuming and expensive. This study deals with the coating of graft surfaces with capture molecules (aptamers) for circulating endothelial progenitor cells (EPCs), mimicking a prohoming substrate to fish out EPCs from the bloodstream after implantation and to create an autologous functional endothelium. Using the SELEX technology, aptamers with a high affinity to EPCs were identified, isolated, and grafted onto polymeric discs using a blood compatible star-PEG coating. A porcine in vitro model that demonstrates the specific adhesion of EPCs and their differentiation into vital endothelial-like cells within 10 days in cell culture is presented. We suggest that the rapid adhesion of EPCs to aptamer-coated implants could be useful to promote endothelial wound healing and to prevent increased neointimal hyperplasia. We hypothesize that future in vivo self-endothelialization of blood contacting implants by homing factor mimetic capture molecules for EPCs may bring revolutionary new perspectives towards clinical applications of stem cell and tissue engineering strategies.

In the hippocampus of Borna disease virus (BDV)-infected newborn rats, dentate granule cells undergo progressive cell death. BDV is noncytolytic, and the pathogenesis of this neurodevelopmental damage in the absence of immunopathology remains unclear. A suitable model system to study early events of the pathology is lacking. We show here that organotypic hippocampal slice cultures from newborn rat pups are a suitable ex vivo model to examine BDV neuropathogenesis. After challenging hippocampal slice cultures with BDV, we observed a progressive loss of calbindin-positive granule cells 21 to 28 days postinfection. This loss was accompanied by reduced numbers of mossy fiber boutons when compared to mock-infected cultures. Similarly, the density of dentate granule cell axons, the mossy fiber axons, appeared to be substantially reduced. In contrast, hilar mossy cells and pyramidal neurons survived, although BDV was detectable in these cells. Despite infection of dentate granule cells 2 weeks postinfection, the axonal projections of these cells and the synaptic connectivity patterns were comparable to those in mock-infected cultures, suggesting that BDVinduced damage of granule cells is a postmaturation event that starts after mossy fiber synapses are formed. In summary, we find that BDV infection of rat organotypic hippocampal slice cultures results in selective neuronal damage similar to that observed with infected newborn rats and is therefore a suitable model to study BDV-induced pathology in the hippocampus.Borna disease virus (BDV) is a nonsegmented negativestrand RNA virus that persistently infects the central nervous system (CNS) and causes behavioral abnormalities in a broad range of vertebrates (17,25). Depending on the age and immune status of the host, BDV infection may present as immune-mediated neurological disease with fatal outcome (Borna disease) or subtle behavioral alterations without overt inflammation (17,25). BDV infection is potentially linked to psychiatric diseases, as BDV-specific antibodies were identified in sera of psychiatric patients with higher prevalence than in sera from control cohorts (24). However, attempts to confirm human BDV by nonserological methods, including detection of viral nucleic acid by nested reverse transcription-PCR or virus isolation, revealed inconsistent results (35); this issue is therefore still controversial.Rats are the best-characterized animal models for studying BDV-induced pathogenesis. Depending on the age of the rat at the time of infection, the spectrum of BDV-caused diseases ranges from a progressive immune-mediated meningoencephalitis to behavioral abnormalities (17,25,26). In adult immunocompetent rats, BDV infection causes a biphasic disease characterized by a classical immune-mediated CNS disorder. This disease is associated with massive neuronal destruction and behavioral disturbances, the near-resolution of inflammatory infiltrates, virus persistence, and signs of chronic neurological disease. In contrast to infected adult rats, infection of neon...

Infection of newborn rats with Borne disease virus (BDV) results in selective degeneration of granule cell neurons of the dentate gyrus (DG). To study cellular countermechanisms that might prevent this pathology, we screened for rat strains resistant to this BDV-induced neuronal degeneration. To this end, we infected hippocampal slice cultures of different rat strains with BDV and analyzed for the preservation of the DG. Whereas infected cultures of five rat strains, including Lewis (LEW) rats, exhibited a disrupted DG cytoarchitecture, slices of three other rat strains, including Sprague-Dawley (SD), were unaffected. However, efficiency of viral replication was comparable in susceptible and resistant cultures. Moreover, these rat strain-dependent differences in vulnerability were replicated in vivo in neonatally infected LEW and SD rats. Intriguingly, conditioned media from uninfected cultures of both LEW and SD rats could prevent BDV-induced DG damage in infected LEW hippocampal cultures, whereas infection with BDV suppressed the availability of these factors from LEW but not in SD hippocampal cultures. To gain further insights into the genetic basis for this rat strain-dependent susceptibility, we analyzed DG granule cell survival in BDV-infected cultures of hippocampal neurons derived from the F1 and F2 offspring of the crossing of SD and LEW rats. Genomewide association analysis revealed one resistance locus on chromosome (chr) 6q16 in SD rats and, surprisingly, a locus on chr3q21-23 that was associated with susceptibility. Thus, BDV-induced neuronal degeneration is dependent on the host genetic background and is prevented by soluble protective factors in the disease-resistant SD rat strain.hippocampus | neurotropic viruses | postnatal development B orna disease virus (BDV) is a nonsegmented, negative-sense RNA virus that persistently infects the CNS, resulting in behavioral syndromes and disease in a wide range of mammalian and avian species (1-3). Experimental infection of adult rats provokes an immune-mediated disease with associated meningoencephalomyelitis and progressive movement disorders (1). In contrast, infection of newborn rats causes no overt cellular immune response, but the hippocampus of BDV-infected newborn Lewis (LEW) or Wistar rats' dentate granule cells (DGCs) nonetheless progressively degenerate (1, 4). This BDV-induced neuronal degeneration can also be observed in infected organotypic hippocampal slice cultures from newborn LEW rats (5). Using this ex vivo tissue culture system, we recently showed that DGC degeneration in the hippocampus is a postmaturation event after the dentate gyrus (DG) is completely formed. Consistently, progressive loss of DGCs is observed 14 d post infection (PI) of hippocampal slice cultures, accompanied by the retraction of mossy fiber axons (5). The molecular mechanisms contributing to this pathology are unknown; however, aberrant zinc homeostasis (6) and activation of poly (ADP ribose) polymerase 1 and caspase 3 (7) might contribute to DGC degeneration. Inte...