Current progress in use of adipose derived stem cells in peripheral nerve regeneration

Unlike central nervous system neurons; those in the peripheral nervous system have the potential for full regeneration after injury. Following injury, recovery is controlled by schwann cells which replicate and modulate the subsequent immune response. The level of nerve recovery is strongly linked to the severity of the initial injury despite the significant advancements in imaging and surgical techniques. Multiple experimental model shave been used with varying successes to augment the natural regenerative processes which occur following nerve injury. Stem cell therapy in peripheral nerve injury may be an important future intervention to improve the best attainable clinical results. In particular adipose derived stem cells(ADSCs) are multipotent mesenchymal stem cells similar to bone marrow derived stem cells, which are thought to have neurotrophic properties and the ability to differentiate into multiple lineages. They are ubiquitous within adipose tissue; they can form many structures resembling the mature adult peripheral nervous system. Following early in vitro work; multiple small and large animal in vivo models have been used in conjunction with conduits, autografts and allografts to successfully bridge the peripheral nerve gap. Some of the ADSC related neuroprotective and regenerative properties have been elucidated however much work remains before a model can be used successfully in human peripheral nerve injury(PNI). This review aims to provide a detailed overview of progress made in the use of ADSC in PNI, with discussion on the role of a tissue engineered approach for PNI repair.     

Arrestin from nucleated red blood cells binds to bovine rhodopsin in a light-dependent manner

Using a panel of monoclonal antibodies, it has previously been demonstrated that the cytosol of nucleated red cells (trout and turkey) contains a protein similar to arrestin, a soluble protein found so far only in the photosensitive cells and which, by binding to photoexcited rhodopsin, inhibits the phototransduction process. The role of this arrestin-like protein in non-photosensitive cells is questionable. In this report we present evidence that partially purified red blood cell arrestin (RBC arrestin) behaves functionally like bovine retinal arrestin: it binds to phosphorylated bovine rhodopsin only when this receptor has been photoactivated. Thus RBC arrestin and bovine retinal arrestin are closely related both structurally and functionally. By analogy with the function of retinal arrestin, it is proposed that RBC arrestin is involved in desensitization of membrane transport proteins and/or adrenergic receptors.     

Human sterol 27-hydroxylase (CYP27) overexpressor transgenic mouse model. Evidence against 27-hydroxycholesterol as a critical regulator of cholesterol homeostasis

CYP27-overexpressed transgenic mice were generated with the use of a human full-length CYP27 coding region cloned into a ubiquitous expression vector. Positive transgenic mice were identified by tail DNA genotyping and high fecal 27-hydroxycholesterol content. The levels of 27-hydroxycholesterol were found to be 3-5 times higher in the circulation and the tissues of the overexpressed mice when compared with littermate controls. There were no gross morphological differences between the overexpressed mice and their controls. Total cholesterol and triglyceride levels were not affected by overexpression of CYP27. Serum lathosterol was also normal, suggesting a normal rate of cholesterol synthesis. Serum levels of 7alpha-hydroxycholesterol were unaffected, suggesting a normal rate of bile acid formation in the pathway involving cholesterol 7alpha-hydroxylase. Biliary bile acid composition was slightly affected by CYP27 overexpression in female but not in male mice. Fecal levels of neutral steroids were slightly but significantly increased in overexpressor female mice but not in male mice. Levels of 24-hydroxycholesterol in the circulation were significantly reduced in the overexpressed mice, probably as a consequence of a recently described catabolic pathway involving CYP27. Combined with the results of our previous work on mice with a disruption of the CYP27 gene, the present results suggest that the levels of 27-hydroxycholesterol are not of critical importance for cholesterol homeostasis in mice.     

Isolation and characterization of an aggresome determinant in the NF2 tumor suppressor

Schwannomin (Sch) is the product of the NF2 tumor suppressor gene. The NF2 gene is mutated in patients affected by neurofibromatosis type 2, a syndrome associated with multiple tumors of the nervous system. Here we found that Sch, when its N-terminal FERM domain was misfolded by the pathogenetic mutation Delta F118, formed aggresomes, i.e. aggregates that cluster at the centrosome as a result of microtubule-dependent transport. Strikingly the related protein ezrin affected by the same mutation did not form aggresomes even though its FERM domain was similarly misfolded. By studying ezrin/Sch chimeras, we delineated a sequence of 61 amino acids in the C terminus of Sch that determined the formation of aggresomes. Aggresome formation by these chimeras was independent from their rate of degradation. Sch(535-595) was sufficient to induce aggresomes of a green fluorescent fusion protein in vivo and aggregates of a glutathione S-transferase fusion protein in vitro. Taken together, these results suggest that aggresome formation is controlled primarily by aggresome determinants, which are distinct from degradation determinants, or from misfolding, through which aggresome determinants might be exposed.     

Evidence in oyster of a plasma extracellular superoxide dismutase which binds LPS

We have characterized in the oyster Crassostrea gigas an extracellular superoxide dismutase (Cg-EcSOD) which appears to bind lipopolysaccharides (LPS). The protein has been purified from the oyster plasma and identified as a Cu/ZnSOD according to its N-terminal sequencing and biological activity. Cg-EcSOD expression and synthesis are restricted to hemocytes as revealed by in situ hybridization and immunocytochemistry. Cg-EcSOD-expressing hemocytes were seen in blood circulation, in connective tissues, and closely associated to endothelium blood vessels. Cg-EcSOD presents in its amino acid sequence a LPS-binding motif found in the endotoxin receptor CD14 and we show that the protein displays an affinity to Escherichia coli bacteria and with LPS and Lipid A. Additionally, an RGD motif known to be implicated in the association to membrane integrin receptor is present in the amino acid sequence. The purified Cg-EcSOD was shown to bind to oyster hemocytes and to be immunocolocalized with a beta-integrin-like receptor.     

Phosphoinositide binding and phosphorylation act sequentially in the activation mechanism of ezrin

Ezrin, a membrane-actin cytoskeleton linker, which participates in epithelial cell morphogenesis, is held inactive in the cytoplasm through an intramolecular interaction. Phosphatidylinositol 4,5-bisphosphate (PIP2) binding and the phosphorylation of threonine 567 (T567) are involved in the activation process that unmasks both membrane and actin binding sites. Here, we demonstrate that ezrin binding to PIP2, through its NH2-terminal domain, is required for T567 phosphorylation and thus for the conformational activation of ezrin in vivo. Furthermore, we found that the T567D mutation mimicking T567 phosphorylation bypasses the need for PIP2 binding for unmasking both membrane and actin binding sites. However, PIP2 binding and T567 phosphorylation are both necessary for the correct apical localization of ezrin and for its role in epithelial cell morphogenesis. These results establish that PIP2 binding and T567 phosphorylation act sequentially to allow ezrin to exert its cellular functions.     

Plasmodium falciparum genotype population dynamics in asymptomatic children from Senegal

In areas where malaria is endemic, infected individuals generally harbor a mixture of genetically distinct Plasmodium falciparum parasite populations. For the first time, we studied temporal variations of blood parasite densities and circulating genotypes in asymptomatic Senegalese children, at time intervals as short as 4-12 h. Twenty-one Senegalese children, presenting with an asymptomatic P. falciparum infection, were sampled eight times within three days. Parasite density was assessed by thick blood smears, and all infecting genotypes were quantified by the fragment-analysis method. Parasite densities showed dramatic fluctuations up to a 1 to 1,000 ratio, with at least one peak of parasite density. Polyclonal infections were detected in all children, with a multiplicity of infection of 5.2-6.8 genotypes per child. A single sample never reflected the full complexity of the parasite populations hosted by a given individual. Genotypes with different behaviors were detected in all children, some genotypes undergoing major fluctuations, while others were highly stable during the follow-up. A single peripheral blood sampling does not reflect the total parasite load. Repeated sampling is needed to have a more detailed scheme of parasite population dynamics and a better knowledge of the true complexity of an infection.     

A hotspot of Toxoplasma gondii Africa 1 lineage in Benin: How new genotypes from West Africa contribute to understand the parasite genetic diversity worldwide

Through international trades, Europe, Africa and South America share a long history of exchanges, potentially of pathogens. We used the worldwide parasite Toxoplasma gondii to test the hypothesis of a historical influence on pathogen genetic diversity in Benin, a West African country with a longstanding sea trade history. In Africa, T. gondii spatial structure is still non-uniformly studied and very few articles have reported strain genetic diversity in fauna and clinical forms of human toxoplasmosis so far, even in African diaspora. Sera from 758 domestic animals (mainly poultry) in two coastal areas (Cotonou and Ouidah) and two inland areas (Parakou and Natitingou) were tested for T. gondii antibodies using a Modified Agglutination Test (MAT). The hearts and brains of 69 seropositive animals were collected for parasite isolation in a mouse bioassay. Forty-five strains were obtained and 39 genotypes could be described via 15-microsatellite genotyping, with a predominance of the autochthonous African lineage Africa 1 (36/39). The remaining genotypes were Africa 4 variant TUB2 (1/39) and two identical isolates (clone) of Type III (2/39). No difference in terms of genotype distribution between inland and coastal sampling sites was found. In particular, contrarily to what has been described in Senegal, no type II (mostly present in Europe) was isolated in poultry from coastal cities. This result seems to refute a possible role of European maritime trade in Benin despite it was one of the most important hubs during the slave trade period. However, the presence of the Africa 1 genotype in Brazil, predominant in Benin, and genetic analyses suggest that the triangular trade was a route for the intercontinental dissemination of genetic strains from Africa to South America. This supports the possibility of contamination in humans and animals with potentially imported virulent strains.