Evidence that glial cells attenuate G47R transthyretin accumulation in the central nervous system.

Amyloidogenic protein forms amyloid aggregations at membranes leading to dysfunction of amyloid clearance and amyloidosis. Glial cells function in the clearance and degradation of amyloid ß (Aß) in the brain. This study aimed to clarify the reason why amyloid transthyretin (ATTR) rarely accumulates in the CNS. We pathologically analyzed the relationship between amyloid deposition with basement membranes or glial cells in a rare case of ATTR leptomeningeal amyloidosis. In addition, we compared the cytotoxicity of ATTR G47R, the amyloidosis-causing mutation in the case studied (n = 1), and Aß in brains from patients with cerebral amyloid angiopathy (n = 6). In the subarachnoid space of the ATTR G47R case, most amyloids accumulated at the components of basement membranes. On the CNS surface, ATTR accumulations were retained by astrocytic end feet. In areas where glial end feet enveloped ATTR, ubiquitination and micro-vacuolation of ATTR was evident. The colocalization of GFAP and ubiquitin was also evident. The accumulation of ATTR G47R in the CNS was negatively correlated with the prevalence of astrocytes. Quantitatively, amyloid deposits along the vessels were mostly partial in cerebral Aß angiopathy cases and nearly complete along the basement membrane in the ATTR G47R case. The vascular expressions of type IV collagen and smooth muscle actin were severely reduced in areas with ATTR G47R deposition, but not in areas with Aß deposition. The vascular protein level recovered in the ATTR G47R case when vessels entered into areas of parenchyma that were rich in astrocytes. In addition, the strong interactions between the transthyretin variant and basement membranes may have led to dysfunction of transthyretin clearance and leptomeningeal amyloidosis. The present study was the first to show that glial cells may attenuate G47R transthyretin accumulation in the CNS.

Pioglitazone promotes peripheral nerve remyelination after crush injury through CD36 upregulation.

In our previous study, we found that CD36-deficient mice showed significant delays in peripheral nerve remyelination after sciatic nerve crush injury and suggested that CD36 played an important role in the restoration of injured peripheral nerves. The aim of this study was to investigate whether CD36 upregulation can promote peripheral nerve remyelination. We made crush injury that caused demyelination and mild axonal degeneration to sciatic nerves and investigated the effect of pioglitazone (PIO) on the remyelination post-injury in C57Bl/6 wild-type and CD36-deficient mice. The immunohistochemistry with anti-CD36 antibody showed that CD36 was upregulated in macrophages infiltrating peripheral nerves from the wild-type mice by PIO administration at 1 week post-injury. The lectin histochemistry represented that infiltrating macrophages lessened in the wild-type mice at 3 weeks post-injury by PIO administration. General histopathology and morphometry indicated that thinly myelinated fibers and naked axons diminished in PIO-treated wild-type mice compared with non-treated wild-type mice at 3 weeks post-injury. No significant differences were observed in remyelination and number of infiltrating macrophages between PIO-treated and non-treated CD36-deficient mice. These results indicate that PIO promotes peripheral nerve remyelination possibly through CD36. It may be possible to apply PIO to the remedy against demyelinating neuropathies.

GNE myopathy caused by a synonymous mutation leading to aberrant mRNA splicing.

GNE myopathy is a rare autosomal recessive myopathy caused by bi-allelic mutations in GNE. We report the case of a 36-year-old man who presented with typical clinical and pathological features of GNE myopathy including distal dominant muscle weakness from the age of 29 and numerous rimmed vacuoles on muscle biopsy. Targeted next-generation sequencing revealed a novel synonymous mutation, c.1500A>G (p.G500=), together with a common Japanese mutation c.620A>T (p.D207V). The cDNA analysis of the biopsied muscle revealed that this synonymous mutation creates a cryptic splice donor site that causes aberrant splicing. This report will expand our understanding of the genetic heterogeneity of GNE myopathy emphasizing the importance of interpreting synonymous variants in genetic testing.

The role of CD36 in peripheral nerve remyelination after crush injury.

We previously demonstrated that the deficiency of class A macrophage scavenger receptor type I/II was involved in the delayed phagocytosis of degraded myelin by macrophages in class A macrophage scavenger receptor type I/II knockout mice after crush injury of the sciatic nerve [Naba et al. (2000) Exp. Neurol., 166, 83-89]. In order to elucidate the role of CD36, one of the scavenger receptors, here we inflicted crush injury to the sciatic nerves of CD36 knockout mice and investigated the remyelination after crush injury in comparison with that of class A macrophage scavenger receptor type I/II knockout mice. Although we previously reported a lot of onion-bulbs in class A macrophage scavenger receptor type I/II knockout mice at 3 weeks, the number of onion-bulbs was limited both in CD36 knockout mice and wild-type mice. In the morphometry, the remyelination was seriously delayed, and the infiltrating macrophages into the nerve fascicles were quite frequent in CD36 knockout mice compared with wild-type mice at 3 and 6 weeks postinjury. The immunohistochemistry with the monoclonal antibody reacted with oxidized phosphatidylcholine and oil red O staining were positive in wild-type mice, but were negative in CD36 knockout mice, suggesting that the oxidation of phosphatidylcholine and the generation of neutral lipids in macrophages were disturbed in CD36 knockout mice. We hypothesize that the delayed phagocytosis by macrophages and the defect in reuse of lipids from degraded myelin are related to seriously delayed remyelination and a small number of onion-bulbs in CD36 knockout mice.