Impaired Meningeal Lymphatic Vessel Development Worsens Stroke Outcome

The discovery of meningeal lymphatic vessels (LVs) has sparked interest in identifying their role in diseases of the central nervous system. Similar to peripheral LVs, meningeal LVs depend on vascular endothelial growth factor receptor-3 (VEGFR3) signaling for development. Here we characterize the effect of stroke on meningeal LVs, and the impact of meningeal lymphatic hypoplasia on post-stroke outcomes. We show that photothrombosis (PT), but not transient middle cerebral artery occlusion (tMCAo), induces meningeal lymphangiogenesis in young male C57Bl/J6 mice. We also show that Vegfr3wt/mut mice develop significantly fewer meningeal LVs than Vegfr3wt/wt mice. Again, meningeal lymphangiogenesis occurs in the alymphatic zone lateral to the sagittal sinus only after PT-induced stroke in Vegfr3wt/wt mice. Interestingly, Vegfr3wt/mut mice develop larger stroke volumes than Vegfr3wt/wt mice after tMCAo, but not after PT. Our results reveal differences between PT and tMCAo models of stroke and underscore the need to consider method of stroke induction when investigating the role of meningeal lymphatics. Taken together, our data indicate that ischemic injury can induce the growth of meningeal LVs and that the absence of these LVs can impact post-stroke outcomes

Thermosensitive Biodegradable Hydrogels for Local and Controlled Cerebral Delivery of Proteins: MRI-Based Monitoring of In Vitro and In Vivo Protein Release

Hydrogels have been suggested as novel drug delivery systems for sustained release of therapeutic proteins in various neurological disorders. The main advantage these systems offer is the controlled, prolonged exposure to a therapeutically effective dose of the released drug after a single intracerebral injection. Characterization of controlled release of therapeutics from a hydrogel is generally performed in vitro, as current methods do not allow for in vivo measurements of spatiotemporal distribution and release kinetics of a loaded protein. Importantly, the in vivo environment introduces many additional variables and factors that cannot be effectively simulated under in vitro conditions. To address this, in the present contribution, we developed a noninvasive in vivo magnetic resonance imaging (MRI) method to monitor local protein release from two injected hydrogels of the same chemical composition but different initial water contents. We designed a biodegradable hydrogel formulation composed of low and high concentration thermosensitive polymer and thiolated hyaluronic acid, which is liquid at room temperature and forms a gel due to a combination of physical and chemical cross-linking upon injection at 37 °C. The in vivo protein release kinetics from these gels were assessed by MRI analysis utilizing a model protein labeled with an MR contrast agent, i.e. gadolinium-labeled albumin (74 kDa). As proof of principle, the release kinetics of the hydrogels were first measured with MRI in vitro. Subsequently, the protein loaded hydrogels were administered in male Wistar rat brains and the release in vivo was monitored for 21 days. In vitro, the thermosensitive hydrogels with an initial water content of 81 and 66% released 64 ± 3% and 43 ± 3% of the protein loading, respectively, during the first 6 days at 37 °C. These differences were even more profound in vivo, where the thermosensitive hydrogels released 83 ± 16% and 57 ± 15% of the protein load, respectively, 1 week postinjection. Measurement of volume changes of the gels over time showed that the thermosensitive gel with the higher polymer concentration increased more than 4-fold in size in vivo after 3 weeks, which was substantially different from the in vitro behavior where a volume change of 35% was observed. Our study demonstrates the potential of MRI to noninvasively monitor in vivo intracerebral protein release from a locally administered in situ forming hydrogel, which could aid in the development and optimization of such drug delivery systems for brain disorders

MRI of spontaneous and therapy-induced vascular remodeling after experimental stroke

Although advances have been made toward elucidating the molecular mechanisms of stroke pathology, there are still no clinically effective strategies for poststroke brain repair. A potential therapeutic target, the peri-infarct area angiogenesis, is linked to neuronal survival, neurogenesis, and plasticity. The aim of this thesis was to shed light on vascular remodeling in stroke recovery and pave the way to an MRI-guided therapy that promotes neurorestoration. 1. Following a stroke, the primary injury site can disrupt functional connections in nearby and remotely associated brain regions, resulting in the development of secondary injuries. In Chapter II, we found that cerebral blood flow (CBF), quantified by arterial spin labeling (ASL) MRI was decreased in the thalamus 2 days after focal cerebral ischemia in rats. Partial thalamic CBF recovery occurred by day 7, after which the ipsilateral thalamus was chronically hyperperfused up to 3 months post-stroke. Endothelial cell immunohistochemistry showed increased angiogenesis in the ipsilateral thalamus at the end of the follow-up. Thus, thalamic pathology involved long-term hemodynamic changes and angiogenesis, which may support the removal of necrotic brain tissue, offset secondary neuronal degeneration, and contribute to tissue remodeling. 2. The pattern of vascular remodeling in relation to stroke recovery remains largely unclear. In Chapter III we used steady-state contrast-enhanced (ssCE)-MRI to assess the development of cerebral blood volume and microvessel density (MVD) in perilesional and exofocal areas from (sub)acute to chronic time points in a rat stroke model. In remote ipsilateral areas, the thalamus and substantia nigra – not part of the ischemic territory – MVD gradually increased between days 1 and 70, which was confirmed by histology. Therefore, initial microvascular collapse, with maintained collateral flow in larger vessels, is followed by dynamic revascularization in peri-lesional tissue, as well as remote subcortical nuclei. 3. Characterization of controlled release of (therapeutic) protein(s) from hydrogel drug-delivery systems under in vivo conditions is critical, as the in vivo environment introduces many additional variables and factors that cannot be effectively simulated under in vitro conditions. In Chapter IV we developed a non-invasive in vivo MRI method to monitor local protein release from biodegradable thermosensitive hydrogels injected into rat brain by utilizing gadolinium-labeled albumin as a model protein. Our results demonstrate the potential of MRI to non-invasively monitor in vivo intracerebral protein release from an in situ-forming hydrogel while simultaneously evaluating tissue status, which could aid in the development and optimization of such drug-delivery systems for brain disorders. 4. Vascular endothelial growth factor (VEGF) and Angiopoietin-1 (Ang1) are potent pro-angiogenic peptides, with suggested neuroprotective role in cerebral stroke. In Chapter V the effects of delayed, prolonged administration of VEGF and Ang1 on cerebrovascular remodeling and functional neurological recovery was determined in a rat stroke model. We injected an in situ-forming peptide hydrogel with controlled release of VEGF/Ang1, directly into the cortical infarction area. Injection was guided and release kinetics were measured with our newly developed MRI method in Chapter IV. The treatment resulted in significant recovery from sensorimotor deficits, accompanied by significantly increased vascularization in the perilesional cortex. Histology confirmed (re)vascularization of perilesional areas and neuronal sparing or neurogenesis. Increased vascular density was also measured in remote subcortical areas connected to the infarct (thalamus) in all groups, but significantly elevated number of neurons was only present in the treatment group. Thus, late treatment with intralesionally injected hydrogel carrying VEGF/Ang1 offers an effective strategy to support prolonged brain tissue regeneration and neurological recovery after stroke. The experimental results in this thesis support the concept that brain recovery is consistent with coordinated neovascularization both proximal and distal to the lesion, which may be exploited for post-stroke brain repair therapies

MRI of spontaneous and therapy-induced vascular remodeling after experimental stroke

Although advances have been made toward elucidating the molecular mechanisms of stroke pathology, there are still no clinically effective strategies for poststroke brain repair. A potential therapeutic target, the peri-infarct area angiogenesis, is linked to neuronal survival, neurogenesis, and plasticity. The aim of this thesis was to shed light on vascular remodeling in stroke recovery and pave the way to an MRI-guided therapy that promotes neurorestoration. 1. Following a stroke, the primary injury site can disrupt functional connections in nearby and remotely associated brain regions, resulting in the development of secondary injuries. In Chapter II, we found that cerebral blood flow (CBF), quantified by arterial spin labeling (ASL) MRI was decreased in the thalamus 2 days after focal cerebral ischemia in rats. Partial thalamic CBF recovery occurred by day 7, after which the ipsilateral thalamus was chronically hyperperfused up to 3 months post-stroke. Endothelial cell immunohistochemistry showed increased angiogenesis in the ipsilateral thalamus at the end of the follow-up. Thus, thalamic pathology involved long-term hemodynamic changes and angiogenesis, which may support the removal of necrotic brain tissue, offset secondary neuronal degeneration, and contribute to tissue remodeling. 2. The pattern of vascular remodeling in relation to stroke recovery remains largely unclear. In Chapter III we used steady-state contrast-enhanced (ssCE)-MRI to assess the development of cerebral blood volume and microvessel density (MVD) in perilesional and exofocal areas from (sub)acute to chronic time points in a rat stroke model. In remote ipsilateral areas, the thalamus and substantia nigra – not part of the ischemic territory – MVD gradually increased between days 1 and 70, which was confirmed by histology. Therefore, initial microvascular collapse, with maintained collateral flow in larger vessels, is followed by dynamic revascularization in peri-lesional tissue, as well as remote subcortical nuclei. 3. Characterization of controlled release of (therapeutic) protein(s) from hydrogel drug-delivery systems under in vivo conditions is critical, as the in vivo environment introduces many additional variables and factors that cannot be effectively simulated under in vitro conditions. In Chapter IV we developed a non-invasive in vivo MRI method to monitor local protein release from biodegradable thermosensitive hydrogels injected into rat brain by utilizing gadolinium-labeled albumin as a model protein. Our results demonstrate the potential of MRI to non-invasively monitor in vivo intracerebral protein release from an in situ-forming hydrogel while simultaneously evaluating tissue status, which could aid in the development and optimization of such drug-delivery systems for brain disorders. 4. Vascular endothelial growth factor (VEGF) and Angiopoietin-1 (Ang1) are potent pro-angiogenic peptides, with suggested neuroprotective role in cerebral stroke. In Chapter V the effects of delayed, prolonged administration of VEGF and Ang1 on cerebrovascular remodeling and functional neurological recovery was determined in a rat stroke model. We injected an in situ-forming peptide hydrogel with controlled release of VEGF/Ang1, directly into the cortical infarction area. Injection was guided and release kinetics were measured with our newly developed MRI method in Chapter IV. The treatment resulted in significant recovery from sensorimotor deficits, accompanied by significantly increased vascularization in the perilesional cortex. Histology confirmed (re)vascularization of perilesional areas and neuronal sparing or neurogenesis. Increased vascular density was also measured in remote subcortical areas connected to the infarct (thalamus) in all groups, but significantly elevated number of neurons was only present in the treatment group. Thus, late treatment with intralesionally injected hydrogel carrying VEGF/Ang1 offers an effective strategy to support prolonged brain tissue regeneration and neurological recovery after stroke. The experimental results in this thesis support the concept that brain recovery is consistent with coordinated neovascularization both proximal and distal to the lesion, which may be exploited for post-stroke brain repair therapies

Synthesis of functionalised β-keto amides by aminoacylation/domino fragmentation of β-enamino amides

Ethylenediamine-derived β-enamino amides are used as equivalents of amide enolate synthons in C-acylation reactions with N-protected amino acids. Domino fragmentation of the obtained intermediates leads to functionalised β-keto amides, bearing a protected amino group in their side chain

The need to foster self-efficacy among students : A multidimensional picture of Jönköping International Business School society

Entrepreneurship is defined as the process of developing, organizing, and managing a new business venture. It is considered as a process of great importance because it improves economic growth, prosperity, innovation and employment. Researchers have identified that different factors, such as individual's background, personal attributes, traits and beliefs, influence the intentions of entrepreneurs to launch a new start up. However, one specific element of personal attributes is seen as a key determinant of developing entrepreneurial intentions - self-efficacy. The purpose of this work is to determine how the individual's level of self-efficacy is influenced by cultural dimensions. For this purpose, Hofstede's model consisting of five cultural dimensions was used. In order to investigate the problem, an explorative approach with a quantitative strategy was conducted as a survey involving 154 students from Jönköping International Business School in Jönköping, Sweden. The results revealed that only one of the cultural dimensions (Long-term Orientation) has a direct effect on self-efficacy. The other four do not have significant correlation with the self-efficacy levels of students. Therefore, recommendations for further research on this topic are presented

3-Carbamoylmethyl-Indole-1-Carboxylic Acid Ethyl Ester

3-Carbamoylmethyl-Indole-1-Carboxylic Acid Ethyl Ester (an ethoxycarbonyl derivative of indole-3-acetamide) is obtained by Friedel–Crafts type cyclocondensation of γ-functionalized acetoacetamide in neat polyphosphoric acid

3-Carbamoylmethyl-Indole-1-Carboxylic Acid Ethyl Ester

3-Carbamoylmethyl-Indole-1-Carboxylic Acid Ethyl Ester (an ethoxycarbonyl derivative of indole-3-acetamide) is obtained by Friedel–Crafts type cyclocondensation of γ-functionalized acetoacetamide in neat polyphosphoric acid

Oxygenated Analogues of Santacruzamate A

A new approach for the synthesis of Santacruzamate A analogues is demonstrated. The method allows functionalization at position 3 of the gamma-aminobutyric fragment and carbon chain variation