Review of Alterations in Perlecan-Associated Vascular Risk Factors in Dementia.

Perlecan is a heparan sulfate proteoglycan protein in the extracellular matrix that structurally and biochemically supports the cerebrovasculature by dynamically responding to changes in cerebral blood flow. These changes in perlecan expression seem to be contradictory, ranging from neuroprotective and angiogenic to thrombotic and linked to lipid retention. This review investigates perlecan's influence on risk factors such as diabetes, hypertension, and amyloid that effect Vascular contributions to Cognitive Impairment and Dementia (VCID). VCID, a comorbidity with diverse etiology in sporadic Alzheimer's disease (AD), is thought to be a major factor that drives the overall clinical burden of dementia. Accordingly, changes in perlecan expression and distribution in response to VCID appears to be injury, risk factor, location, sex, age, and perlecan domain dependent. While great effort has been made to understand the role of perlecan in VCID, additional studies are needed to increase our understanding of perlecan's role in health and in cerebrovascular disease.

Perlecan, A Multi-Functional, Cell-Instructive, Matrix-Stabilizing Proteoglycan With Roles in Tissue Development Has Relevance to Connective Tissue Repair and Regeneration.

This review highlights the multifunctional properties of perlecan (HSPG2) and its potential roles in repair biology. Perlecan is ubiquitous, occurring in vascular, cartilaginous, adipose, lymphoreticular, bone and bone marrow stroma and in neural tissues. Perlecan has roles in angiogenesis, tissue development and extracellular matrix stabilization in mature weight bearing and tensional tissues. Perlecan contributes to mechanosensory properties in cartilage through pericellular interactions with fibrillin-1, type IV, V, VI and XI collagen and elastin. Perlecan domain I - FGF, PDGF, VEGF and BMP interactions promote embryonic cellular proliferation, differentiation, and tissue development. Perlecan domain II, an LDLR-like domain interacts with lipids, Wnt and Hedgehog morphogens. Perlecan domain III binds FGF-7 and 18 and has roles in the secretion of perlecan. Perlecan domain IV, an immunoglobulin repeat domain, has cell attachment and matrix stabilizing properties. Perlecan domain V promotes tissue repair through interactions with VEGF, VEGF-R2 and α2ß1 integrin. Perlecan domain-V LG1-LG2 and LG3 fragments antagonize these interactions. Perlecan domain V promotes reconstitution of the blood brain barrier damaged by ischemic stroke and is neurogenic and neuroprotective. Perlecan-VEGF-VEGFR2, perlecan-FGF-2 and perlecan-PDGF interactions promote angiogenesis and wound healing. Perlecan domain I, III and V interactions with platelet factor-4 and megakaryocyte and platelet inhibitory receptor promote adhesion of cells to implants and scaffolds in vascular repair. Perlecan localizes acetylcholinesterase in the neuromuscular junction and is of functional significance in neuromuscular control. Perlecan mutation leads to Schwartz-Jampel Syndrome, functional impairment of the biomechanical properties of the intervertebral disc, variable levels of chondroplasia and myotonia. A greater understanding of the functional working of the neuromuscular junction may be insightful in therapeutic approaches in the treatment of neuromuscular disorders. Tissue engineering of salivary glands has been undertaken using bioactive peptides (TWSKV) derived from perlecan domain IV. Perlecan TWSKV peptide induces differentiation of salivary gland cells into self-assembling acini-like structures that express salivary gland biomarkers and secrete α-amylase. Perlecan also promotes chondroprogenitor stem cell maturation and development of pluripotent migratory stem cell lineages, which participate in diarthrodial joint formation, and early cartilage development. Recent studies have also shown that perlecan is prominently expressed during repair of adult human articular cartilage. Perlecan also has roles in endochondral ossification and bone development. Perlecan domain I hydrogels been used in tissue engineering to establish heparin binding growth factor gradients that promote cell migration and cartilage repair. Perlecan domain I collagen I fibril scaffolds have also been used as an FGF-2 delivery system for tissue repair. With the availability of recombinant perlecan domains, the development of other tissue repair strategies should emerge in the near future. Perlecan co-localization with vascular elastin in the intima, acts as a blood shear-flow endothelial sensor that regulates blood volume and pressure and has a similar role to perlecan in canalicular fluid, regulating bone development and remodeling. This complements perlecan's roles in growth plate cartilage and in endochondral ossification to form the appendicular and axial skeleton. Perlecan is thus a ubiquitous, multifunctional, and pleomorphic molecule of considerable biological importance. A greater understanding of its diverse biological roles and functional repertoires during tissue development, growth and disease will yield valuable insights into how this impressive proteoglycan could be utilized successfully in repair biology.

In Vivo protection from SARS-CoV-2 infection by ATN-161 in k18-hACE2 transgenic mice.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an infectious disease that has spread worldwide. Current treatments are limited in both availability and efficacy, such that improving our understanding of the factors that facilitate infection is urgently needed to more effectively treat infected individuals and to curb the pandemic. We and others have previously demonstrated the significance of interactions between the SARS-CoV-2 spike protein, integrin α5ß1, and human ACE2 to facilitate viral entry into host cells in vitro. We previously found that inhibition of integrin α5ß1 by the clinically validated small peptide ATN-161 inhibits these spike protein interactions and cell infection in vitro. In continuation with our previous findings, here we have further evaluated the therapeutic potential of ATN-161 on SARS-CoV-2 infection in k18-hACE2 transgenic (SARS-CoV-2 susceptible) mice in vivo. We discovered that treatment with single or repeated intravenous doses of ATN-161 (1 mg/kg) within 48 h after intranasal inoculation with SARS-CoV-2 lead to a reduction of lung viral load, viral immunofluorescence, and improved lung histology in a majority of mice 72 h post-infection. Furthermore, ATN-161 reduced SARS-CoV-2-induced increased expression of lung integrin α5 and αv (an α5-related integrin that has also been implicated in SARS-CoV-2 interactions) as well as the C-X-C motif chemokine ligand 10 (Cxcl10), further supporting the potential involvement of these integrins, and the anti-inflammatory potential of ATN-161, respectively, in SARS-CoV-2 infection. To the best of our knowledge, this is the first study demonstrating the potential therapeutic efficacy of targeting integrin α5ß1 in SARS-CoV-2 infection in vivo and supports the development of ATN-161 as a novel SARS-CoV-2 therapy.

Perlecan Domain-V Enhances Neurogenic Brain Repair After Stroke in Mice.

The extracellular matrix fragment perlecan domain V is neuroprotective and functionally restorative following experimental stroke. As neurogenesis is an important component of chronic post-stroke repair, and previous studies have implicated perlecan in developmental neurogenesis, we hypothesized that domain V could have a broad therapeutic window by enhancing neurogenesis after stroke. We demonstrated that domain V is chronically increased in the brains of human stroke patients, suggesting that it is present during post-stroke neurogenic periods. Furthermore, perlecan deficient mice had significantly less neuroblast precursor cells after experimental stroke. Seven-day delayed domain V administration enhanced neurogenesis and restored peri-infarct excitatory synaptic drive to neocortical layer 2/3 pyramidal neurons after experimental stroke. Domain V's effects were inhibited by blockade of α2ß1 integrin, suggesting the importance of α2ß1 integrin to neurogenesis and domain V neurogenic effects. Our results demonstrate that perlecan plays a previously unrecognized role in post-stroke neurogenesis and that delayed DV administration after experimental stroke enhances neurogenesis and improves recovery in an α2ß1 integrin-mediated fashion. We conclude that domain V is a clinically relevant neuroprotective and neuroreparative novel stroke therapy with a broad therapeutic window.

Impact of stroke co-morbidities on cortical collateral flow following ischaemic stroke.

Acute hyperglycaemia and chronic hypertension worsen stroke outcome but their impact on collateral perfusion, a determinant of penumbral life span, is poorly understood. Laser-speckle contrast imaging (LSCI) was used to determine the influence of these stroke comorbidities on cortical perfusion after permanent middle cerebral artery occlusion (pMCAO) in spontaneously hypertensive stroke prone rats (SHRSP) and normotensive Wistar rats. Four independent studies were conducted. In animals without pMCAO, cortical perfusion remained stable over 180 min. Following pMCAO, cortical perfusion was markedly reduced at 30 min then gradually increased, via cortical collaterals, over the subsequent 3.5 h. In the contralateral non-ischaemic hemisphere, perfusion did not change over time. Acute hyperglycaemia (in normotensive Wistar) and chronic hypertension (SHRSP) attenuated the restoration of cortical perfusion after pMCAO. Inhaled nitric oxide did not influence cortical perfusion in SHRSP following pMCAO. Thus, hyperglycaemia at the time of arterial occlusion or pre-existing hypertension impaired the dynamic recruitment of cortical collaterals after pMCAO. The impairment of collateral recruitment may contribute to the detrimental effects these comorbidities have on stroke outcome.

Performance of motor associated behavioural tests following chronic nicotine administration.

BACKGROUND: Nicotine has shown potential therapeutic value for neurodegenerative diseases though there are concerns that it may induce behavioural deficits. PURPOSE: The present study sought to determine the effect of chronic nicotine administration on overall motor functions and coordination. METHODS: Forty adult female and male Wistar rats were randomly grouped into 4 groups. Treated groups were administered nicotine via subcutaneous injections at doses of 0.25, 2 and 4 mg/kg body weight for 28 days. Control groups received normal saline. All animals were monitored for the first few minutes after each injection for any observed immediate effect of drug administration. Motor associated behavioural tests performed include: open field test, string test for grip strength and limb impairment, movement initiation and step test. RESULTS: Nicotine induced muscular convulsions within the first 1-5 minutes following daily subcutaneous injections, throughout the period of administration. This was observed to be more severe in females. Nicotine did not produce major alterations in overall motor functions and coordination in both females and males. CONCLUSION: The present study shows chronic nicotine treatment produces muscular convulsion but no major deficit in overall motor function and coordination and that any observed alterations may just be transient effects.