Differential expression of genes in the RhoA/ROCK pathway in the hippocampus and cortex following intermittent hypoxia and high intensity interval training.

Neuroplasticity is regulated by a balance of neurotrophic factors and inhibitory molecules that are permissive and restrictive to central nervous system (CNS) adaptation, respectively. Intermittent hypoxia (IH) and high intensity interval training (HIIT) are known to upregulate neurotrophic factors which are associated with improvements in learning and memory and greater functional recovery following CNS insults. We investigated whether the RhoA/ROCK signaling pathway (known to restrict neuroplasticity) is also modulated by IH and HIIT in the hippocampus, cortex, and lumbar spinal cord of male Wistar rats. The gene expression of 25 RhoA/ROCK signaling pathway components was determined following IH or IH combined with HIIT (30 minutes/day, five days/week, for six weeks). IH included ten three-minute bouts which alternated between hypoxia (15% O2) and normoxia. IH+HIIT synchronized the hypoxia protocol with treadmill training at speeds of 50 cm.s-1 during hypoxia, and 15 cm.s-1 during normoxia. In the hippocampus, IH and IH+HIIT significantly downregulated aggrecan and Nogo-receptor 2 mRNA which are involved in the inhibition of neuroplasticity. However, IH and IH+HIIT significantly upregulated genes including Lingo-1, Ncan, NgR3, and Sema4d in the cortex. This is the first time IH and HIIT have been linked to the modulation of plasticity inhibiting pathways. These results provide a fundamental step towards elucidating the interplay between the neurotrophic and inhibitory mechanisms involved in experience-driven neural plasticity which will aid in optimizing physiological interventions for the treatment of cognitive decline or neurorehabilitation.

Spatiotemporal microvascular changes following contusive spinal cord injury.

Microvascular integrity is disrupted following spinal cord injury (SCI) by both primary and secondary insults. Changes to neuronal structures are well documented, but little is known about how the capillaries change and recover following injury. Spatiotemporal morphological information is required to explore potential treatments targeting the microvasculature post-SCI to improve functional recovery. Sprague-Dawley rats were given a T10 moderate/severe (200 kDyn) contusion injury and were perfuse-fixed at days 2, 5, 15, and 45 post-injury. Unbiased stereology following immunohistochemistry in four areas (ventral and dorsal grey and white matter) across seven spinal segments (n = 4 for each group) was used to calculate microvessel density, surface area, and areal density. In intact sham spinal cords, average microvessel density across the thoracic spinal cord was: ventral grey matter: 571 ± 45 mm-2, dorsal grey matter: 484 ± 33 mm-2, ventral white matter: 90 ± 8 mm-2, dorsal white matter: 88 ± 7 mm-2. Post-SCI, acute microvascular disruption was evident, particularly at the injury epicentre, and spreading three spinal segments rostrally and caudally. Damage was most severe in grey matter at the injury epicentre (T10) and T11. Reductions in all morphological parameters (95-99% at day 2 post-SCI) implied vessel regression and/or collapse acutely. Transmission electron microscopy (TEM) revealed disturbed aspects of neurovascular unit fine structure at day 2 post-SCI (n = 2 per group) at T10 and T11. TEM demonstrated a more diffuse and disrupted basement membrane and wider intercellular clefts at day 2, suggesting a more permeable blood spinal cord barrier and microvessel remodelling. Some evidence of angiogenesis was seen during recovery from days 2 to 45, indicated by increased vessel density, surface area, and areal density at day 45. These novel results show that the spinal cord microvasculature is highly adaptive following SCI, even at chronic stages and up to three spinal segments from the injury epicentre. Multiple measures of gross and fine capillary structure from acute to chronic time points provide insight into microvascular remodelling post-SCI. We have identified key vascular treatment targets, namely stabilising damaged capillaries and replacing destroyed vessels, which may be used to improve functional outcomes following SCI in the future.

Distinct structural and functional angiogenic responses are induced by different mechanical stimuli.

OBJECTIVE: Adequacy of the microcirculation is essential for maintaining repetitive skeletal muscle function while avoiding fatigue. It is unclear, however, whether capillary remodelling after different angiogenic stimuli is comparable in terms of vessel distribution and consequent functional adaptations. We determined the physiological consequences of two distinct mechanotransductive stimuli: (1) overload-mediated abluminal stretch (OV); (2) vasodilator-induced shear stress (prazosin, PR). METHODS: In situ EDL fatigue resistance was determined after 7 or 14 days of intervention, in addition to measurements of femoral artery flow. Microvascular composition (muscle histology) and oxidative capacity (citrate synthase activity) were quantified, and muscle PO2 calculated using advanced mathematical modelling. RESULTS: Compared to controls, capillary-to-fiber ratio was higher after OV14 (134%, p < .001) and PR14 (121%, p < .05), although fatigue resistance only improved after overload (7 days: 135%, 14 days: 125%, p < .05). In addition, muscle overload improved local capillary supply indices and reduced CS activity, while prazosin treatment failed to alter either index of aerobic capacity. CONCLUSION: Targeted capillary growth in response to abluminal stretch is a potent driver of improved muscle fatigue resistance, while shear stress-driven angiogenesis has no beneficial effect on muscle function. In terms of capillarity, more is not necessarily better.

The Role of TLR4, TNF-α and IL-1ß in Type 2 Diabetes Mellitus Development within a North Indian Population.

This study investigated the role of IL-1ß-511 (rs16944), TLR4-896 (rs4986790) and TNF-α-308 (rs1800629) polymorphisms in type 2 diabetes mellitus (T2DM) among an endogamous Northern Indian population. Four hundred fourteen participants (204 T2DM patients and 210 nondiabetic controls) were genotyped for IL-1ß-511, TLR4-896 and TNF-α-308 loci. The C allele of IL-1ß-511 was shown to increase T2DM susceptibility by 75% (OR: 1.75 [CI 1.32-2.33]). Having two parents affected by T2DM increased susceptibility by 5.7 times (OR: 5.693 [CI 1.431-22.648]). In this study, we have demonstrated a conclusive association with IL-1ß-511 locus and IL-1ß-511-TLR4-896 diplotype (CC-AA) and T2DM, which warrants further comprehensive analyses in larger cohorts.