No description available.

Direct in vivo cellular reprogramming offers the potential for local neural replacement to promote post-stroke neural regeneration and recovery. Pericytes are perivascular cells involved in blood-brain barrier maintenance under physiological conditions but are reprogrammed into multipotent induced neural progenitor cells (i-NPCs) in response to ischemia. The atypical protein kinase C (aPKC)-CREB binding protein (CBP) pathway regulates ischemia-activated pericyte (a-pericyte) reprogramming and neuronal differentiation. Our previous work showed that the pathway inhibitor compound C (CpdC) facilitated a- pericyte reprogramming into i-NPCs in culture, and that monoacylglycerol lipase (Mgll) inhibitor JZL184 was able to promote NPC differentiation to generate newborn neurons by mimicking pathway activation. In this regard, we propose to use acute CpdC treatment followed by chronic JZL184 treatment to enhance reprogramming of a-pericytes into i-NPCs and subsequently promote their neuronal differentiation, ultimately improving post-stroke functional recovery. Using the endothelin-1 (ET-1)/L-NAME ischemic stroke model in a pericyte lineage tracing transgenic mouse line, I characterized the ability of a-pericytes in the ischemic lesion site to generate neural (i-NPC, newborn neurons) and non-neural (microglia and fibroblasts) cell types. The CpdC+JZL184 treatment had early effects on enhancing a- pericyte reprogramming efficiency to produce i-NPCs at 7 days post-stroke and promoting their differentiation to generate neuroblasts at 14 days post-stroke. However, it did not affect stroke volume and produced minimal alterations to the pattern of post-stroke motor function recovery. Interestingly, I discovered a novel role of tamoxifen treatment prior to stroke in regulating reprogramming of a-pericytes and efficacy of compound C treatment. These studies inform the necessity of optimization of drug delivery for better control over the timing and duration to directly target in vivo i-NPC reprogramming and reveal a novel pharmacological paradigm to control the aPKC-CBP pathway.

Ischaemic heart disease accounts for approximately 7 million deaths worldwide on a yearly basis and this figure is only set to rise as life expectancy in developing countries increases. Although no longer considered a post mitotic organ, the adult heart demonstrates only a very limited capacity for regeneration. Consequently ischaemic injury results in massive loss of contractile cardiomyocytes with damaged myocardium replaced by a non-contractile and poorly conductive collagen scar. This in turn often leads to the development of heart failure. Enhancing or supplementing the myocardial regenerative capacity of the heart is thus a key goal in the development of effective therapies for the treatment of cardiac infarction. Several stem cell populations of non-cardiac origin have been investigated for their capacity to contribute to myocardial repair when therapeutically transplanted into injured hearts. Recent efforts have focused on the “next generation” of donor cells, endogenous cardiac progenitor cells, as these are thought to be better adapted to survival in the cardiac environment and to possess enhanced cardiomyocyte differentiation potential. Pericytes, proposed as the source of the elusive mesenchymal stem cells (MSC) within multiple tissues, are a potential new cell type for use in regenerative medicine. This study tests the hypothesis that pericytes and another perivascular progenitor population, the adventitial cell, from foetal cardiac tissue will positively contribute to the repair of the myocardium post injury. Staining of human foetal ventricular myocardium confirmed the presence of large numbers of both cell types with pericytes tightly associated with capillaries and adventitial cells primarily located in the outer, adventitial layer of muscular arteries. CD146+ CD34- pericytes and CD146- CD34+ adventitial cells were isolated by FACS and expanded in culture. On examination of gene and protein expression both populations stably expressed a similar panel of pericyte markers, MSC markers and cardiac transcription factors as well as c-kit, a cardiac progenitor cell candidate marker. Co-culture with neo-natal rat cardiomyocytes induced expression of an additional cardiac progenitor marker Isl-1 and a mature cardiomyocyte marker ANP in adventitial cells but not pericytes. Labelled, co-cultured, perivascular progenitors readily adhered to rat cells but did not appear to contract independently. De-methylation of perivascular progenitors prior to co-culture resulted in expression of sarcomeric proteins and spontaneous cytoplasmic calcium fluctuations in both populations but more commonly in pericytes. This suggests that cardiac perivascular cells contain a minor sub-population capable of cardiomyocyte differentiation. When these populations were injected into the infarcted hearts of NOD/SCID mice, the animals treated with adventitial cells had significantly reduced cardiac function at 21 days post-surgery on ultrasound examination. An increased scar area and a non-significant trend towards increased scar length and a decreased wall thickness were also observed. Transplanted cells of both groups were detected in low numbers 21 days after injection. Adventitial cells were retained much more readily and in both populations retained cells exhibited three key morphologies: fibroblast type; macrophage type; and cardiomyocyte type. The majority of cells adopted a fibroblast type morphology, lesser numbers a macrophage like morphology and only rare cells a cardiomyocyte like morphology. Both fibroblast and cardiomyocyte type cells had single, human nuclear antigen positive nuclei suggesting true differentiation rather than cell fusion and pericytes exhibited an enhanced ability to differentiate into cardiomyocytes. This supports the in-vitro findings of a minor pro-cardiomyogenic subset within the perivascular cell population. As a result of these findings the starting hypothesis was modified to propose that perivascular cells play a significant role in cardiac fibrosis, largely mediated through expression of surface integrin receptors. This was tested using mice expressing fluorescent proteins under the control of the PDGFR-β promoter and mice in which the αv integrin subunit, common to 5 integrin receptors, had been deleted on the surface of PDGFR-β+ cells. Immunostaining and flow cytometry revealed the PDGFR-β expression to be tightly restricted to perivascular cells and co-expressed with the fibroblast markers, vimentin, PDGFR-α, CD90.2 and CD34 in a subset of cells. Cardiac fibroblasts isolated from reporter mouse hearts revealed strong expression of PDGFR-α and CD34 but PDGFR-β expression in only approximately 20% of the population on flow cytometry. Following angiotensin II induced cardiac hypertrophy and fibrosis approximately 50% of fibroblasts expanding the interstitium were PDGFR-β+. Genetic deletion of the αv integrin subunit on PDGFR-β+ cells resulted in a reduction in cardiac interstitial collagen content of about 50% compared to wild type controls. These findings suggest that the cardiac perivascular PDGFR-β+ population is heterogeneous with a sub-population likely to be fibroblasts or fibroblast progenitors and that the development of cardiac interstitial fibrosis is in part modulated by integrin receptor expression on these cells. In summary this study provides evidence of the existence of a pro-fibrotic progenitor population, which co-express pericyte and MSC markers, within the cardiac perivascular niche. These cells contribute to cardiac fibrosis both on transplantation and endogenously following cardiac injury with the latter mediated via αv integrin expression. Within the perivascular progenitor population however there also appears to be a minor subset of pro-cardiomyogenic cells which are able to adopt a cardiomyocyte phenotype both in-vitro and in-vivo.

Multicellular spheroids have emerged as a promising tool for drug delivery, cancer therapy, and tissue engineering. Compared to 2D monolayers, spheroids provide a more realistic representation of the 3D cellular environment, enabling better understanding of the signaling cascades and growth factors involved in vivo. The formation of in vitro spheroids involves the aggregation of several cells that proliferate to grow into larger spheroids. Biophysical cues provide crucial information for the cells to assemble into 3D structures. We used suspended fiber networks to demonstrate a new way to form and spatially pattern spheroids comprised of human pericytes. We show that fiber architecture (aligned vs. crosshatched), diameter (200, 500, and 800 nm), and contractility influence spheroids in their spontaneous formation, growth, and maintenance, and report a dynamic trade of cells between adjacent spheroids through remodeled fiber networks. We found that aligned fiber networks promoted spheroid formation independent of fiber diameter, while large-diameter crosshatched networks abrogated spheroid formation, promoting growth of 2D monolayers. Thus, a mixture of diameters and architectures allowed for spatial patterning of spheroids and monolayers within a single system. We further quantified various dynamic interactions and describe the forces involved during spheroid formation, cell efflux from spheroids, and show the loss and recovery of spheroid forces with pharmacological perturbation of Rho-associated protein kinase (ROCK). Thus, we develop new insights on the dynamics of spheroids using suspended fiber networks of varying diameters and architectures, with the potential to connect matrix biology with developmental, disease, and regenerative biology. / Master of Science / In recent years, studies involving multicellular spherical aggregates or 'spheroids' have gained popularity since they capture the 3D cellular environments seen within the body more realistically when compared to 2D cell culture systems (such as monolayers) traditionally used for biological studies. These spheroids resemble organs and tissues in terms of their structure and function better and are increasingly being studied for an array of applications such as drug delivery, cancer therapy, as implants and in tissue regeneration and tissue engineering. The cellular microenvironment consists of fibrous proteins of varying diameter arranged in various geometric patterns, which can influence the growth and culture of spheroids. Here, we use our Spinneret-Based Tunable Engineered Parameters (STEP) technique to fabricate fibrous networks with precise control over fiber diameter and architecture and study how biophysical cues can influence the formation and culture of spheroids. Using aortic pericytes, we show that fiber architecture (aligned vs. crosshatched) and diameter (200, 500, and 800 nm) can control how pericytes aggregate into either 2D monolayers or 3D spheroids. We study the effect of each of these parameters to show that stiffer, denser fibers are robust networks which the cells refrain from remodeling, and thus lead to monolayers while more compliant and sparser networks are easily remodeled to promote spheroid formation. Thus, we spatially pattern a mixture of 3D spheroids and 2D monolayers in a single system by varying the parameters at different regions. We quantify various interactions such as spheroid formation, spheroid merging, spheroid migration, cell efflux from spheroids and the dynamic contractile forces exerted on the matrix by spheroids during these interactions. We also show that contractility has a major role in spheroid formation and to maintain their structure and look at the changes in the gene expressions associated with contractility during the formation and growth of spheroids. Thus, we develop new knowledge in controlling the growth of pericytes into 2D and 3D structures and show that our fiber networks can be an essential platform for studying spheroids.

Skeletal muscle is dynamic and actively regenerates following damage or altered functional demand. Regeneration is essential for the maintenance of muscle mass and, when dysregulated as a result of disease or aging, can lead to losses in functional capacity and increased mortality. Limited data exist on the molecular mechanisms that govern skeletal muscle regeneration in humans. Therefore, the overall objective of this dissertation was to characterize early molecular alterations in human skeletal muscle to strenuous exercise known to induce a muscle regenerative response. Thirty-five subjects completed 100 eccentric (muscle lengthening) contractions (EC) of the knee extensors with one leg and muscle biopsies were taken from both legs 3 h post-EC. The sample from the non-EC leg served as the control. A well-powered transcriptomic screen and network analysis using Ingenuity Pathway software was first conducted on mRNA from the biopsy samples. Network analysis identified the transcription factor NF-kappaB (NF-kB) as a key molecular element affected by EC. Conformational qRT-PCR confirmed alterations in genes associated with NF-kappaB. A transcription factor ELISA, using nuclear extracts from EC and control muscle samples showed a 1.6 fold increase in NF-kB DNA binding activity following EC. Immunohistochemical experiments then localized the majority of NF-kB positive nuclei to cells in the interstitium, which stained positive for markers of pericyte cells and not satellite cells. To ascertain the mechanistic significance of NF-kB activation following muscle damage, in vitro analyses were carried out using a novel primary pericyte/myoblast co-culture model. Primary pericyte/myoblast co-culture experiments demonstrated that pericytes, transfected with a DNA vector designed to drive NF-kB activation, enhanced proliferation and inhibited myogenic differentiation of co-cultured skeletal muscle myoblasts. Furthermore, reduced NF-kB activation led to enhanced myogenic potential of primary pericytes. Taken together, the data in this dissertation suggest that NF-kB dependent signaling in pericytes regulates myogenic differentiation in a cell- and non-cell autonomous manner and may affect the early regenerative response following muscle damage by inhibiting differentition and promoting proliferation of muscle satellite cells.

O microambiente tumoral é composto por células, como fibroblastos, células do sistema imune, células endoteliais e pericitos, envoltas por uma matriz extracelular, além de possuir fatores solúveis que participam da comunicação celular. Nas últimas décadas, têm-se entendido cada vez melhor seu papel na iniciação e progressão dos tumores. É de fundamental importância, portanto, entender a biologia dos seus componentes e como podem agir em favor do desenvolvimento tumoral. Diversos trabalhos demonstram que há uma associação entre a presença dos pericitos nos vasos tumorais com a agressividade e prognóstico de alguns tipos de câncer. Uma vez ativadas, além do papel estrutural, essas células modulam as atividades das células endoteliais durante a formação de novos vasos, além de adquirirem propriedades como proliferação e migração. Neste contexto, os pericitos passam a secretar fatores importantes na comunicação célula-a-célula e liberam enzimas moduladoras na matriz extracelular. A lisil oxidase (LOX) é uma das principais enzimas que atuam sobre a matriz extracelular. Já está bem descrito que, quando superexpressa em células tumorais, a LOX pode alterar a migração e invasão dessas células, promovendo a geração de metástases. Entretanto, pouco se sabe a respeito da atuação dessa enzima sobre os demais componentes celulares do estroma tumoral, como os pericitos. Sendo assim, o presente trabalho teve como objetivo principal verificar se enzima LOX é relevante para a ativação de propriedades dos pericitos que possam contribuir para suas funções pró-tumorigênicas, como migração, proliferação e formação de vasos. Os resultados foram gerados avaliando essas atividades dos pericitos após pré-tratamento de 24 horas com β-aminopropionitrile (βAPN), um inibidor irreversível da LOX. Foram utilizadas duas linhagens de pericitos derivados de tecido normal (adiposo e muscular) e duas linhagens de pericitos provenientes de tecido tumores do sistema nervoso central (neuroblastoma e ependimoma). Este composto foi capaz de diminuir a capacidade de migração das células de todas as linhagens testadas e, de maneira geral, tornou o processo de formação de estruturas tubulares in vitro menos eficiente. Entretanto, não foram observadas alterações na proliferação celular. Os dados indicam, portanto, que a enzima LOX pode ser importante para a ativação dos pericitos e, possivelmente, influenciem no seu comportamento no microambiente tumoral / The tumor microenvironment is composed of non-cancer cells, such as fibroblasts, immune cells, endothelial cells and pericytes, surrounded by an extracellular matrix, in addition to soluble factors involved in cellular crosstalk. In the last decades, it has been better understood its role in the initiation and progression of tumors. It is critical, therefore, to understand the biology of its components and how they can act in favor of tumor development. Several studies show an association between the presence of pericytes in tumor vessels with aggressiveness and prognosis of some cancers. Once activated, these cells modulate the activities of endothelial cells during the new vessels formation, and acquire properties as proliferation and migration. In this context, pericytes triggers the secretion of important factors in cell-to-cell communication and release modulating enzymes of extracellular matrix. The lysyl oxidase (LOX) is one of the main enzymes that act on the extracelular matrix. It is well described that when overexpressed in tumor cells, LOX can alter the migration and invasion of these cells, promoting the generation of metastases. However, little is known about the role of this enzyme over other cellular components of the tumor stroma, such as pericytes. Therefore, the aim of this study was to verify whether LOX enzyme is relevant to the activation of properties of the pericytes that could contribute to its pro-tumorigenic functions such as migration, proliferation and vessel formation. All the results were generated by evaluation of the activities of these pericytes after 24 hours pretreatment with β-aminopropionitrile (βAPN), an irreversible inhibitor of LOX. This study used two cell lines of pericytes derived from normal tissue (fat and muscle) and two isolated from tissue of the central nervous system. The βAPN was able to reduce the migration of cells of all tested cell lines and, in general, alter the tubular formation in vitro. However, changes in cell proliferation weren′t observed. The data showed, that the LOX family may be important for the activation of pericytes and possibly influence on their behavior in the tumor microenvironment

O microambiente tumoral é composto por células, como fibroblastos, células do sistema imune, células endoteliais e pericitos, envoltas por uma matriz extracelular, além de possuir fatores solúveis que participam da comunicação celular. Nas últimas décadas, têm-se entendido cada vez melhor seu papel na iniciação e progressão dos tumores. É de fundamental importância, portanto, entender a biologia dos seus componentes e como podem agir em favor do desenvolvimento tumoral. Diversos trabalhos demonstram que há uma associação entre a presença dos pericitos nos vasos tumorais com a agressividade e prognóstico de alguns tipos de câncer. Uma vez ativadas, além do papel estrutural, essas células modulam as atividades das células endoteliais durante a formação de novos vasos, além de adquirirem propriedades como proliferação e migração. Neste contexto, os pericitos passam a secretar fatores importantes na comunicação célula-a-célula e liberam enzimas moduladoras na matriz extracelular. A lisil oxidase (LOX) é uma das principais enzimas que atuam sobre a matriz extracelular. Já está bem descrito que, quando superexpressa em células tumorais, a LOX pode alterar a migração e invasão dessas células, promovendo a geração de metástases. Entretanto, pouco se sabe a respeito da atuação dessa enzima sobre os demais componentes celulares do estroma tumoral, como os pericitos. Sendo assim, o presente trabalho teve como objetivo principal verificar se enzima LOX é relevante para a ativação de propriedades dos pericitos que possam contribuir para suas funções pró-tumorigênicas, como migração, proliferação e formação de vasos. Os resultados foram gerados avaliando essas atividades dos pericitos após pré-tratamento de 24 horas com β-aminopropionitrile (βAPN), um inibidor irreversível da LOX. Foram utilizadas duas linhagens de pericitos derivados de tecido normal (adiposo e muscular) e duas linhagens de pericitos provenientes de tecido tumores do sistema nervoso central (neuroblastoma e ependimoma). Este composto foi capaz de diminuir a capacidade de migração das células de todas as linhagens testadas e, de maneira geral, tornou o processo de formação de estruturas tubulares in vitro menos eficiente. Entretanto, não foram observadas alterações na proliferação celular. Os dados indicam, portanto, que a enzima LOX pode ser importante para a ativação dos pericitos e, possivelmente, influenciem no seu comportamento no microambiente tumoral / The tumor microenvironment is composed of non-cancer cells, such as fibroblasts, immune cells, endothelial cells and pericytes, surrounded by an extracellular matrix, in addition to soluble factors involved in cellular crosstalk. In the last decades, it has been better understood its role in the initiation and progression of tumors. It is critical, therefore, to understand the biology of its components and how they can act in favor of tumor development. Several studies show an association between the presence of pericytes in tumor vessels with aggressiveness and prognosis of some cancers. Once activated, these cells modulate the activities of endothelial cells during the new vessels formation, and acquire properties as proliferation and migration. In this context, pericytes triggers the secretion of important factors in cell-to-cell communication and release modulating enzymes of extracellular matrix. The lysyl oxidase (LOX) is one of the main enzymes that act on the extracelular matrix. It is well described that when overexpressed in tumor cells, LOX can alter the migration and invasion of these cells, promoting the generation of metastases. However, little is known about the role of this enzyme over other cellular components of the tumor stroma, such as pericytes. Therefore, the aim of this study was to verify whether LOX enzyme is relevant to the activation of properties of the pericytes that could contribute to its pro-tumorigenic functions such as migration, proliferation and vessel formation. All the results were generated by evaluation of the activities of these pericytes after 24 hours pretreatment with β-aminopropionitrile (βAPN), an irreversible inhibitor of LOX. This study used two cell lines of pericytes derived from normal tissue (fat and muscle) and two isolated from tissue of the central nervous system. The βAPN was able to reduce the migration of cells of all tested cell lines and, in general, alter the tubular formation in vitro. However, changes in cell proliferation weren′t observed. The data showed, that the LOX family may be important for the activation of pericytes and possibly influence on their behavior in the tumor microenvironment

No description available.

The vasculature is a highly intricate system of "highways" that shuttles blood from the heart to every tissue and organ in the human body. These vessels are responsible for carrying oxygen, trafficking hormones, delivering nutrients, and removing waste products from the body. The formation of a functioning vascular system depends on the close coordination of many cell types and, on the capillary level, specifically endothelial cells and pericytes as well as the surrounding protein microenvironment, known as the extracellular matrix (ECM). Impaired coordination amongst the cellular and protein constituents results in the improper functioning of the vascular network and can eventually contribute to the failure of organ systems. This dissertation research focuses on how improper ECM deposition affects vascular assembly. We utilized several approaches to affect ECM composition, specifically: 1) hypoxia exposure and 2) reducing ECM pharmacologically and utilizing lentiviral-mediated silencing of Type IV Collagen (Col-IV, gene Col4a1) expression. In these experimental settings, we observed downstream changes in the coordination between endothelial cells and pericytes while forming vascular networks. In short, this dissertation work suggests that excess ECM deposition, and particularly that of Col-IV, has unique deleterious effects on the developing vasculature as compared to reduced ECM deposition. The findings from this work suggest mechanisms underlying how the vasculature may be destabilized in hypoxia-associated pathologies, such as preeclampsia. / Doctor of Philosophy / Every tissue and organ in the human body receives blood from the heart via the extremely complex network of "highways" known as the vasculature. These vessels oversee moving nutrients, oxygen, hormones, and waste materials out of the body. At the capillary level, endothelial cells and pericytes, as well as the surrounding protein milieu known as the extracellular matrix (ECM), are required for the development of a functional vascular system. If the vascular network fails to develop and operate properly because of poor protein and cellular coordination, it can eventually lead to the failure of organ systems. The study for this dissertation focuses on how vascular development is impacted by insufficient ECM deposition. We used several strategies to modify the composition of the ECM, including 1) hypoxia exposure, 2) pharmaceutical ECM reduction, and 3) lentiviral-mediated delivery of shRNA to silence Type IV Collagen (Col-IV, gene Col4a1) production. We noticed alterations in the coordination between endothelial cells and pericytes as vascular networks were being formed in these experimental environments. In summary, this dissertation work contends that, in contrast to reduced ECM deposition, excess ECM deposition, and specifically that of Col-IV, has distinct detrimental consequences on the developing vasculature. The results of this study offer methods by which diseases associated with hypoxia, such preeclampsia, may cause the vasculature to become unstable.

Traumatic brain injury (TBI) can cause a number of deleterious effects to the neurovascular system, including reduced cerebral blood flow (CBF), vascular regression, and ischemia, resulting in cognitive decline. Research into therapeutic targets to restore neurovascular function following injury has identified endothelial EphA4 receptor tyrosine kinase as a major regulator of vascular regrowth. The research outlined herein utilizes an endothelial-specific EphA4 knockout mouse model (KO-EphA4flf/Tie2-Cre) to determine the extent to which this receptor may influence vascular regrowth following TBI. Analysis of the colocalization and proximity of endothelial and mural cell markers (i.e. PECAM-1 and PDGFRβ, respectively) in immunohistochemically-stained brain sections demonstrates that EphA4 silencing does not seem to affect the physical association between, nor total amounts of, endothelial cells and pericytes, between genotypes by 4 days post-injury (dpi). Nevertheless, these measures demonstrate that these cell types may preferentially proliferate and/or expand into peri-lesion tissue in both KO-EphA4flf/Tie2-Cre) and WT-EphA4fl/fl mice. These data further suggest that both genotypes experience homogeneity of PECAM-1 and PDGFRβ expression between regions of the injury cavity. Gene expression analysis using mRNA samples from both genotypes reveals that KO-EphA4flf/Tie2-Cre CCI-injured mice experience increased expression of Vegfa, Flt1, and Fn (Fibronectin) compared to sham-injured condition knockouts. These results demonstrate changes in expression of angiogenic factors in the absence of early differences in patterns of vessel formation, which may underlie improved vascular regrowth, as well as outline a potential mechanism wherein the interplay between these factors and EphA4 silencing may lead to improved cognitive outcomes following TBI. / Master of Science / Every day in the United States, an average of 155 people die due to the consequences of traumatic brain injury (TBI), with many survivors suffering life-long debilitating effects, including deficits in behavior, mobility, and cognitive ability. Because of this, there is a need for researchers to identify therapeutic strategies to stimulate recovery and improve patient outcomes. Recent advancements in the field of vascular biology have identified the regrowth of the blood vessels in the brain following TBI-induced damage as an important step in the recovery process, since the resulting increases in blood flow to damaged tissue will provide oxygen and nutrients necessary to fuel recovery. The work presented in this Masters thesis follows in this vein by examining a protein receptor known as EphA4, which is found on cells within blood vessels and has been implicated in reducing the rate of vessel growth under injury conditions. By blocking the activity of EphA4, we hoped to find increased vascular regrowth following brain injury in mice. During the experiments outlined herein, it was found that there were no statistically significant differences in vessel-associated cell densities between mice with or without EphA4 activity 4 days after injury, but there were differences in the levels of proteins and/or signals associated with vessel growth. Based on these results, we conclude that removing EphA4 activity increases expression of these pro-vessel growth proteins in mouse brains following injury at these early time points, potentially leading to increased vessel growth and improved recovery over subsequent weeks following injury.