Open Access Kent State (OAKS)

Decellularized extracellular matrix components isolated from animal sources have shown much clinical promise in the treatment of several wound care indications including a variety of dermal ulcerations (diabetic, pressure, venous, e.g.), full-thickness trauma wounds affecting the skin and skeletal muscle, and post-operative surgical wounds. The purpose of this study was to evaluate the biocompatibility of three sources of decellularized matrix wound care products using a novel tissue engineered dermal cellular proliferation assay. Deceullarized basement matrices derived from porcine small intestinal submucosa (pSIS), porcine peritoneal membrane (pPM), and ovine forestomach (oFS), respectively, were tested for their ability to support the engraftment and proliferation of human neonatal dermal fibroblasts. Cells were seeded onto each respective membrane using a custom, non-adherent, cell culture system and cultured for 2 weeks. At 3, 5, 7, and 14 days time points cultures were assayed for proliferation and matrix integration using the PrestoBlue cell viability assay and fluorescent confocal laser scanning microscopy, respectively. Human dermal fibroblast attachment to all three materials was relatively low compared to conventional two-dimensional culture systems. However, pSIS displayed a consistently, but not statistically significant, greater level of fluorescence intensity in the cell viability assay, and qualitatively displayed a superior ability to support engraftment of dermal fibroblasts in comparison to pPM and oFS matrices. These data indicate that pSIS supports the attachment and growth of dermal cells in vitro, which may underscore the success of this material in pre-clinical and clinical wound healing studies.

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by deposition of amyloid plaques in the brain. Amyloid-β (AB) fragments (1-42) are the main components of plaques and are formed by the sequential cleavage of amyloid precursor protein (APP) by β-secretase and ϒ-secretase. Another enzyme, α-secretase, cleaves within the amyloid-β sequence preventing it from aggregating. Previous studies have shown that peripheral administration of a non-aggregating form of the metabolic hormone amylin, an amyloid with similar aggregating properties, improves cognitive function in mouse models of AD and reduces amyloid-β plaque levels. However, how this hormone regulates amyloid-β levels is not known. The purpose of our research was to study the effects of amylin administration on the levels of pro-aggregation soluble amyloid-β fragments (1-42) the expression of α- and β-secretases and the C-terminal fragments that result from enzyme cleavage in the APP/PS1 mouse model of AD. Our data indicate that amylin treatment reduced formic acid-soluble Amyloid-β 1-42 fragments (aggregates). These reductions were paralleled by general upregulation of cleavage enzymes. Taken together, our data demonstrate that amylin may be a potential new therapeutic target for Alzheimer’s disease through its ability to regulate amyloid-beta processing and aggregation.

Keywords: Amylin, Alzheimer’s disease, amyloid-β, APP, α-secretase, β-secretase.

Alzheimer’s disease (AD) is one of the most prevalent neurodegenerative diseases today. Oxidative stress has been proposed as a key pathological feature in AD. Previous studies in our laboratory show that administration of peptide hormone amylin in mouse models of AD improves cognitive function and reduces oxidative stress damage to membranes. However, how amylin provides neuroprotection against oxidative stress damage is not known. To address this question we treated APP/PS1 mice, a mouse model of AD, with amylin for two months and also treated primary hippocampal neurons from these mice with various doses of amylin. From these treatments, we determined the levels of various oxidative enzymes and stress signaling proteins known to be altered in the AD brain and important in the regulation of oxidative stress damage. Our data shows that, in vitro, amylin is able to dose-dependently protect primary hippocampal neurons from oxidative insults (H₂O₂). Further, in vivo, a two month treatment with amylin is able to reduce AD-associated upregulation of the Heme-oxygenase-1 (HO-1), an enzyme known to be activated in response to high levels of oxidative stress. Importantly, these reductions in HO-1 paralleled upregulations of MnSOD expression, a classic endogenous antioxidant enzyme, and reductions in levels of phosphorylated JNK, known to be increased during cellular stress. Taken together our data demonstrates that amylin may be improving CNS function through its ability to reduce oxidative stress damage, both by upregulating endogenous protective systems and preventing the activation of cellular cascades.

Chronic inflammatory responses have adverse effects on the memory retaining areas of the brain, such as hippocampus and neocortex. Understanding how inflammation influences hippocampal neurobiology during aging is of significant importance to the study of normal senescence and neurodegenerative diseases, and knowledge of the various factors involved in cognitive impairment may lead to a better understanding of what causes the adverse effects to memory and what treatments could be used to fight memory loss. Microglia are an important line of defense against various brain insults, and as such are a key component of the inflammatory cascade. By examining the brains of cognitively assessed canines, we will determine the inflammatory response in the hippocampus using microglial immunohistochemistry as a marker for immune function. Immunostaining was performed on hippocampal sections of both normal and behaviorally impaired canines. Quantitative analyses will be conducted using unbiased stereological methods (Stereologer, St. Petersburg, FL). We hypothesize that we will observe elevated numbers of activated microglia in the hippocampi of cognitively impaired animals than in the hippocampi of aged, non-impaired canines, and that the observed increases will correlate with behavioral performance. Our results in the canine may provide a more relevant model of natural aging and disease processes in humans than do genetically modified mice, and help elucidate future targets in the inflammatory cascade upon which to focus treatments that may benefit patients with age-related cognitive impairment, Alzheimer’s Disease, and dementias.