Macrophage activation and skeletal muscle healing following traumatic injury

Following injury to different tissues, macrophages can contribute to both regenerative and fibrotic healing. These seemingly contradictory roles of macrophages may be related to the markedly different phenotypes that macrophages can assume upon exposure to different stimuli. We hypothesized that fibrotic healing after traumatic muscle injury would be dominated by a pro‐fibrotic M2a macrophage phenotype, with M1 activation limited to the very early stages of repair. We found that macrophages accumulated in lacerated mouse muscle for at least 21 days, accompanied by limited myofibre regeneration and persistent collagen deposition. However, muscle macrophages did not exhibit either of the canonical M1 or M2a phenotypes, but instead up‐regulated both M1‐ and M2a‐associated genes early after injury, followed by down‐regulation of most markers examined. Particularly, IL‐10 mRNA and protein were markedly elevated in macrophages from 3‐day injured muscle. Additionally, though flow cytometry identified distinct subpopulations of macrophages based on high or low expression of TNFα, these subpopulations did not clearly correspond to M1 or M2a phenotypes. Importantly, cell therapy with exogenous M1 macrophages but not non‐activated macrophages reduced fibrosis and enhanced muscle fibre regeneration in lacerated muscles. These data indicate that manipulation of macrophage function has potential to improve healing following traumatic injury. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

The folliculin-FNIP1 pathway deleted in human Birt-Hogg-Dube syndrome is required for murine B-cell development

Birt-Hogg-Dubé (BHD) syndrome is an autosomal dominant disorder characterized by cutaneous fibrofolliculomas, pulmonary cysts, and kidney malignancies. Affected individuals carry germ line mutations in folliculin (FLCN), a tumor suppressor gene that becomes biallelically inactivated in kidney tumors by second-hit mutations. Similar to other factors implicated in kidney cancer, FLCN has been shown to modulate activation of mammalian target of rapamycin (mTOR). However, its precise in vivo function is largely unknown because germ line deletion of Flcn results in early embryonic lethality in animal models. Here, we describe mice deficient in the newly characterized folliculin-interacting protein 1 (Fnip1). In contrast to Flcn, Fnip1(-/-) mice develop normally, are not susceptible to kidney neoplasia, but display a striking pro-B cell block that is entirely independent of mTOR activity. We show that this developmental arrest results from rapid caspase-induced pre-B cell death, and that a Bcl2 transgene reconstitutes mature B-cell populations, respectively. We also demonstrate that conditional deletion of Flcn recapitulates the pro-B cell arrest of Fnip1(-/-) mice. Our studies thus demonstrate that the FLCN-FNIP complex deregulated in BHD syndrome is absolutely required for B-cell differentiation, and that it functions through both mTOR-dependent and independent pathways.     

Neuropsychological test performance before and after HIV-1 seroconversion: the Multicenter AIDS Cohort Study

The objective of this study is to compare neuropsychological test performance before and after HIV-1 seroconversion in order to identify possible acute changes in psychomotor speed, memory, attention, and concentration secondary to seroconversion. The study utilized mixed effects models to examine longitudinal neuropsychological test data. We conducted a nested cohort study of 362 male HIV-1 seroconverters enrolled in the Multicenter AIDS Cohort Study. We used linear mixed models with random subject effects to compare repeated neuropsychological test outcomes from 5 years before seroconversion to 2 years after seroconversion on the Trail Making Test (parts A and B), Symbol-Digit Test, Grooved Pegboard (dominant and non-dominant hands), Stroop Color-Interference Test, Rey Auditory Verbal Learning Test, and the CalCAP Reaction Time Test. We found no significant changes in the time-dependent score after seroconversion for the majority of neuropsychological tests used in the Multicenter AIDS Cohort Study. There was a significant change in time trend after seroconversion on part B of the Trail Making Test (p?=?0.042), but the difference only represented a 2 % decrease in performance. We found the following characteristics to be associated with worse neuropsychological test performance: lower education levels, history of depression, older age, and no previous neurocognitive testing (p?<?.05). Our results suggest that despite a 50 % decrease in CD4 cell count immediately following infection, HIV-1 does not appear to have a measurable effect on psychomotor or complex cognitive processing for up to 2 years following infection, using this set of neurocognitive measures.     

Dementia in Down’s syndrome: an MRI comparison with Alzheimer’s disease in the general population

Background

Down’s syndrome (DS) is the most common genetic cause of intellectual disability. People with DS are at an increased risk of Alzheimer’s disease (AD) compared to the general population. Neuroimaging studies of AD have focused on medial temporal structures; however, to our knowledge, no in vivo case–control study exists comparing the anatomy of dementia in DS to people with AD in the general population. We therefore compared the in vivo brain anatomy of people with DS and dementia (DS+) to those with AD in the general population.

Method

Using MRI in 192 adults, we compared the volume of whole brain matter, lateral ventricles, temporal lobes and hippocampus in DS subjects with and without dementia (DS+, DS-), to each other and to three non-DS groups. These included one group of individuals with AD and two groups of controls (each age-matched for their respective DS and general population AD cohorts).

Results

AD and DS+ subjects showed significant reductions in the volume of the whole brain, hippocampus and temporal lobes and a significant elevation in the volume of the lateral ventricle, compared to their non-demented counterparts. People with DS+ had a smaller reduction in temporal lobe volume compared to individuals with AD.

Conclusions

DS+ and AD subjects have a significant reduction in volume of the same brain regions. We found preliminary evidence that DS individuals may be more sensitive to tissue loss than others and have less ‘cognitive reserve’.