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Materials engineered to elicit targeted cellular responses in regenerative medicine must display bioligands with precise spatial and temporal control. Although materials with temporally regulated presentation of bioadhesive ligands using external triggers, such as light and electric fields, have been recently realized for cells in culture, the impact of in vivo temporal ligand presentation on cell-material responses is unknown. Here, we present a general strategy to temporally and spatially control the in vivo presentation of bioligands using cell adhesive peptides with a protecting group that can be easily removed via transdermal light exposure to render the peptide fully active. We demonstrate that non-invasive, transdermal time-regulated activation of cell-adhesive RGD peptide on implanted biomaterials regulates in vivo cell adhesion, inflammation, fibrous encapsulation, and vascularization of the material. This work shows that triggered in vivo presentation of bioligands can be harnessed to direct tissue reparative responses associated with implanted biomaterials.

Reduction of cerebral blood flow is an important risk factor for dementia states and other brain dysfunctions. In present study, the effects of permanent occlusion of common carotid arteries (2VO), a well established experimental model of brain ischemia, on memory function were investigated, as assessed by reference and working spatial memory protocols and the object recognition task; cell damage to the hippocampus, as measured through changes in immunoreactivity for GFAP and the neuronal marker NeuN was also studied. The working hypothesis is that metabolic impairment following hypoperfusion will affect neuron and glial function and result in functional damage. Adult male Wistar rats were submitted to the modified 2VO method, with the right common carotid artery being occluded first and the left one week later, and tested seven days, three and six months after the ischemic event. A significant cognitive deficit was found in both reference and working spatial memory, as well as in the object recognition task, three and six months after surgery. Neuronal death and reactive astrogliosis were already present at 7 days and continued for up to 3 months after the occlusion; interestingly, there was no significant reduction in hippocampal volume. Present data suggests that cognitive impairment caused by brain hypoperfusion is long - lasting and persists beyond the time point of recovery from glial activation and neuronal loss.

We report on the synthesis and properties of a photoactivatable caged RGD peptide and its application for phototriggering integrin and cell binding to surfaces. We analyzed in detail (i) the differences in the integrin binding affinity of the caged and uncaged forms via quartz crystal microbalance (QCM) studies, (ii) the efficiency and yield of the photolytic uncaging reaction, (iii) the biocompatibility of the photolysis byproducts and irradiation conditions and (iv) the possibility of site, temporal and density control of integrin binding and, therefore, human cell attachment, (v) the possibility of in situ generation of cell patterns and cell gradients by controlling the exposure. These studies provide a clear picture of the potential and limitations of caged ligands for integrin-mediated cell adhesion and demonstrate the application of this approach to control and study other types of cell interactions and response.

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Neonatal hypoxia-ischemia (HI) is an important cause of neurological deficits in humans, and the Levine-Rice model of experimental HI in the rat mimics the human brain lesion and the following sensory motor deficits and cognitive disabilities. With the growing evidence that sex influences all levels of brain functions, this Mini-Review highlights studies in which sex was a controlled variable and that provided evidence of sexual dimorphism in behavioral outcome, extension of brain damage, mechanisms of lesion, and treatment efficacy in the rat neonatal HI model. It was shown that 1) females have greater memory deficits; 2) cell death is dependent mainly on caspase activation in females; 3) males are more susceptible to oxidative stress; and 4) treatments acting on distinct cell death pathways afford sex-dependent neuroprotection. These tentative conclusions, along with growing evidence from other fields of neurobiology, support the need for scientists to design their experiments considering sex as an important variable; otherwise, important knowledge will continue to be missed. It is conceivable that sex can influence the development of efficacious therapeutic tools to treat neonates suffering from brain HI. V C 2016 Wiley Periodicals, Inc.

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