Interstitial lung disease | EPFL Graph Search

Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium (the tissue and space around the alveoli (air sacs) of the lungs. It concerns alveolar epithelium, pulmonary capillary endothelium, basement membrane, and perivascular and perilymphatic tissues. It may occur when an injury to the lungs triggers an abnormal healing response. Ordinarily, the body generates just the right amount of tissue to repair damage, but in interstitial lung disease, the repair process is disrupted, and the tissue around the air sacs (alveoli) becomes scarred and thickened. This makes it more difficult for oxygen to pass into the bloodstream. The disease presents itself with the following symptoms: shortness of breath, nonproductive coughing, fatigue, and weight loss, which tend to develop slowly, over several months. The average rate of survival for someone with this disease is between three and five years. The term ILD is used

3D multi-chamber fluidic systems for analysis of angiogenesis in biomaterials: development, characterization and applications

Carmen Bonvin

The cellular processes leading to capillary morphogenesis depend on external stimuli, in particular flow and morphogen gradients. Several devices have been designed to study these interactions in vitro. However, most of these devices allow a single experiment at a time, making it difficult to compare multiple conditions, which is needed for most biology experiments. Furthermore, it can be of great interest to use the same set of cells. Here we present two multi-chamber interstitial flow systems for side-by-side culture with the capability to follow the dynamics of individual cells. While a 9-chamber system was designed for cell culture or co-culture under radial flow, a multi-chamber migration assay allows studying cell migration into biomaterials under a constant flow profile. The effects of flow on lymphatic and blood endothelial cell morphology, as well as the extent of organization induced by VEGF, were observed. In addition, we demonstrated the feasibility of studying cell-cell interactions as well as cell-matrix interactions in a fibroblast and tumor cell co-culture. The two systems presented will allow for the study of interstitial flow and its effects

2009

Effects of dynamic environments on extracellular morphogen gradients

Mark Fleury

Tissue morphogenesis and remodeling is often orchestrated by cell-secreted proteins, referred to as morphogens that can trigger cellular responses in addition to modifying the local extracellular matrix (ECM). Of specific interest is the distribution of cell secreted proteins in the cell microenvironment and how this distribution can lead to varied responses. Morphogens often provide directional cues, and as such their specific distribution is critical to the signaling that they induce, in other words cells are sensitive to morphogen gradients and not just absolute amounts. Natural cellular environments in native tissue involve three dimensional ECM and are typically subjected to dynamic conditions such as interstitial flow (IF). Despite the importance of the extracellular environment in signaling, very little is known regarding the effects of mechanical stresses and subtle interstitial flows. This thesis examines the role of IF on morphogen gradients using mass transport models to elucidate mechanisms responsible for several specific biological phenomena including in vitro capillary formation and lymphatic metastasis of tumor cells. In vitro capillary formation had been shown in our lab to be separately enhanced by bound VEGF alone and slow IF alone, with the combination of these two conditions resulting in marked increase in organization. Using our computational model we were able to propose a novel mechanistic model to explain this synergy. Specifically showed how, through the combined effects of IF and matrix-bound growth factors, cells could create their own biased chemokine gradients without recourse to internal amplification methods. This process, which we have termed "autologous chemotaxis," drives directional signaling and migration in the direction of flow. This can occur even at very low Peclet numbers, when diffusion still dominates the overall transport, but convection changes the shape of the gradient, which is what a cell responds to. We then examined the effects of IF on tumor cell migration to explore a novel mechanism of lymphatic metastasis. Tumors often produce high amounts of proteoglycans creating a microenvironment is rich in morphogen binding sites, and tumors are also a source of interstitial flow due to their leaky vasculature. The lymphatic system drains interstitial fluid, therefore IF is always directed toward lymphatic capillaries. The lymphatic system is also a common route of tumor metastasis, which is what lead us to study the role of IF mediated chemotaxis. A computational model of an in vitro tumor invasion assay was constructed that predicted tumor cell migration that was in very good agreement with the in vitro experimental results. This phenomenon was further studied by modeling an in vivo geometry and examining the factors controlling autologous gradient formation in a physiological setting. In conclusion, we have demonstrated the importance of convective mass transport at very low flow velocities in a biological context. While these velocities are low enough that the convective effects would typically be ignored, their subtle effects on pericellular mass transport can be translated into relevant and observable morphogenic responses.

EPFL2007

In vitro lymphatic endothelial morphogenesis

Carolyn Yong Pullin

Cell organization into functional multicellular three-dimensional structures is a long-standing challenge. In particular, engineering of vascularized tissues requires both blood and lymphatic neovascular network formation in a simultaneous and coordinated fashion. While extensive in vitro investigations in blood and lymphangiogenesis have identified a vast array of cellular phenomena and key cellular and extracellular bioactive substances, the dynamic natural cellular environment and its regulatory role in governing cellular response and interactions remain largely unclear. Furthermore, the wealth of existing knowledge describing the molecular regulation of vessel morphogenesis is heavily biased towards the angiogenic growth of blood capillaries, despite the importance of the lymphatic system. This thesis first addresses the differential gene regulation of isolated microvascular lymphatic endothelial cells (LECs) in response to the lymphatic growth factor VEGF-C and to fluid shear stress using gene arrays and QRT-PCR. First, characteristic of a response to a growth factor stimulus, the largest numbers of differentially expressed genes in response to VEGF-C stimulation were transcription factors and cell cycle related. A number of genes known to be important in angiogenesis, tumorigenesis and tumor invasion, and transport of proteins, solutes, and lipids were also affected. Interestingly, a number of genes related to lipid metabolism as well as neurogenesis were also responsive to VEGF-C stimulation. Further analysis of these genes may not only provide insight into the molecular mechanisms underlying lymphangiogenesis and associated pathogenesis, but may also identify other important roles of VEGF-C. The ability of lymphatic endothelium to sense and actively regulate drainage function is poorly understood, and shear stress is likely a key indicator of lymphatic drainage function. Thus, LECs were exposed to 0, 2 and 20 dyn/cm2 shear stress as representative of chronic lymphedema, normal, and acute inflammatory conditions, respectively. Important adaptive responses to both low and high shear stress conditions that were correlated to lymphatic function, including changes in gene expression patterns related to water and solute transport, cell-cell and cell-matrix adhesion, inflammatory cytokines and cell cycle were found. These changes were consistent with increased transport function, both active and passive, in high shear conditions and indicate that during lymphedema, lymphatic endothelium shuts down transport functions. These data demonstrate a functional-adaptive response of lymphatic endothelium to flow conditions, thus indicating that the lymphatic endothelium plays an active role in regulating their drainage function. It has been previously shown in our lab that in vitro blood and lymphatic morphogenesis are differentially enhanced by interstitial flow. Using a three-dimensional tissue culture model, the molecular mechanisms orchestrating endothelial cell morphogenesis, specifically gene regulation of the lymphatic microvascular system was investigated, focusing on genes implicated in both cellular morphogenesis and lymphatic development. Finally, concurrent angiogenesis and lymphangiogenesis were studied in vitro to examine the influences and crosstalk between blood and lymphatic microvascular development. The data suggest that both blood endothelial cell (BEC) and LEC in vitro capillary morphogenesis are enhanced by the presence of BEC-secreted factors, and these effects are, in part, mediated through proliferative and migratory responses of which the latter was induced by VEGFR-2 and VEGFR-3 signaling for BECs and LECs, respectively. When maintained in mixed three-dimensional cultures, both homotypic and heterotypic interactions between LECs and BECs were observed. Furthermore, capillary morphogenesis and interactions were enhanced and distinct when under the additional influence of interstitial flow. In conclusion, the novelties of the work presented in this dissertation include studies of 1) overall LEC gene response to its primary growth factor VEGF-C and biophysical factor, fluid flow and 2) the genetic regulation underlying the morphogenetic processes of LECs under interstitial flow in vitro, by using unique approaches which combine bioengineering principles to address fundamental biological questions and thereby contribute to this novel niche which has so far been neglected. Furthermore, the importance of biophysical processes along with crucial biochemical signal regulation is demonstrated in the concurrent induction of angiogenesis and lymphangiogenesis. Such are the requisites for the understanding of microvascular development and the determination of useful design principles for the in vitro vascularization of engineered tissues.