212 research outputs found
Engineering the mode of morphogenetic signal presentation to promote branching from salivary gland spheroids in 3D hydrogels
No full textM.S.Xerostomia and Sjӧgren’s Syndrome are conditions associated with loss in salivary volume that is needed to regulate the health of the oral cavity. Current therapies are limited to the introduction of artificial saliva and muscarinic receptor agonists, pilocarpine and cevimeline that induce saliva secretion from residual acinar cells. Regenerative tissue engineering provides a promising platform to solve this problem in the long term by helping rebuild the gland. The salivary tissue is a highly branched network of cells, which enables an increase in surface area without a major increase in glandular volume for high fluid output. Previously we developed a fibrin hydrogel (FH) decorated with laminin-111 peptides (L1p-FH) and supports three-dimensional (3D) gland microstructures containing polarized acinar cells. Here we expand on these results and show that co-culture of gland cells with mesenchymal stem cells produces migrating branches of gland cells into the L1p-FH and we identify FGF7 as the principal morphogenetic signal responsible for branching. On the other hand, another FGF family member and know gland morphogen, FGF10 increased proliferation but did not promote migration and therefore, limited the number and length of branched structures grown into the gel. By controlling the mode of growth factor presentation and delivery, we can control the length and cellularity of branches as well as formation of new nodes/clusters within the hydrogel. Such spatial delivery of two or more morphogens may facilitate engineering of anatomically complex tissues/mini organs such as glands that can be used to address developmental questions or as platforms for drug discovery
A novel Bayesian strategy for the identification of spatially-varying parameters and model validation in inverse problems: an application to elastography
No full textThe present paper proposes a novel Bayesian, computational strategy in the context of model-based inverse problems in elastostatics. On one hand we attempt to provide probabilistic estimates of the material properties and their spatial variability that account for the various sources of uncertainty. On the other hand we attempt to address the question of model fidelity in relation to the experimental reality and particularly in the context of the material constitutive law adopted. This is especially important in biomedical settings when the inferred material properties will be used to make decisions/diagnoses. We propose an expanded parametrization that enables the quantification of model discrepancies in addition to the constitutive parameters. We propose scalable computational strategies for carrying out inference and learning tasks and demonstrate their effectiveness in numerical examples with noiseless and noisy synthetic data.<br/
Hertzian Fields: Exploring WiFi microwave signals as a spatial and embodied sensing medium for art
No full textThesis (Ph.D.)--University of Washington, 2023This dissertation is centered around a series of three artworks (Hertzian Fields) that explore WiFi as a spatial and embodied sensing medium. These works use a new sensing technique developed by the author that leverages the interference of the human body on WiFi signals to create highly responsive live performance and interactive systems. Hertzian Field #1 (2014) is an augmented reality immersive environment using sound to explore the materiality of WiFi communication through its interaction with space and the human body. Hertzian Field #2 (2016) is a 20'-25' augmented reality immersive performance for solo performer, WiFi fields, computers and surround sound that conjures a phenomenology of the hertzian medium explored through sound and movement. The Water Within (Hertzian Field #3 and #3.1) is a reactive wet sauna: an intimate multi-sensory environment of complete immersion, combining WiFi sensing fields, machine listening software, embedded 3D sound, hot steam, and architectural design. Steered by the flows and variable densities of water molecules traced in steam and bodies by (ab)using WiFi, it creates a regenerative post-relational experience that celebrates interference, signal-loss, and disconnecting. The piece exists in two iterations and formats: an interactive installation (2016) and a composed interactive experience (2018).
The dissertation describes the author's conceptual and technical approach in using WiFi microwave signals as an artistic medium. It also examines the background, context, ideas and research processes that led to the creation of these works. In doing so, it lays the foundation for developing a better and deeper understanding of microwaves and WiFi signals, investigates their artistic potential, and discusses related approaches by other artists.
Chapter One (Introduction: The hertzian medium) introduces core ideas and concepts regarding the medium. This includes: a discussion on the impact of wirelessness in contemporary living and how it has transformed our interactions with and understanding of the world; an overview of the physics of electromagnetism and the electromagnetic spectrum; and an investigation of the hertzian (i.e. radio and microwaves) as a multilayered medium consisting of seven interconnected layers: physics, science, imagination, engineering, use, impact, regulation.
Chapter Two (The birth of a medium: Energy becomes technology) introduces a media archaeological approach as a method for grasping what the medium affords, and how our imagination of what we can use it for has developed over time. It presents an overview of key developments in hertzian science, imagined and realized applications, and their impact. This chapter focuses primarily on the early years around Heinrich Hertz’s discovery of electromagnetism, looking at the birth of wireless technologies relevant to the Hertzian Field series: communication, broadcast, hacking and electronic warfare, navigation, meteorology, radio astronomy, and radar, before closing with a section on the development of WiFi.
Chapter Three (Radar and Direction-Finding in sonic art and beyond) surveys musical instruments and artworks based on spatial and/or embodied uses of the hertzian as a sensing medium. The emphasis is on sound-centric practices and specific technologies that have been used to this extent: from capacitative / electric field sensing, to musical instruments utilizing direction-finding principles, to spatial uses of broadcast radio, to doppler radar systems. Instruments discussed include: Theremin and Terpsitone; Pupitre d'Espace; Radio Baton; Marimba Lumina. Artworks by the following artists are examined: Max Neuhaus; Edwin van der Heide; Christina Kubisch; John Cage; Philippa Cullen; Liz Phillips; Sonia Cillari; Tetsuo Kogawa; Anna Friz; Edward Ihnatowicz; Steve Mann; Joe Paradiso / MIT Lab; Arthur Elsenaar; Godfried-Willem Raes.
Chapter Four (First hertzian explorations: From the network to the body, from WiFi to Radar) turns to the author's own work. It presents the first phase (2010-14) of his research trajectory on the hertzian medium, and introduces three projects in which he explored WiFi and broadcast radio.
Chapter Five (Ubiquitous sensing with radio waves and microwaves) dives into the technological context influencing the author's research. It introduces the field of Ubiquitous Sensing and discusses relevant localization and device-free sensing techniques, concluding with a discussion on the physics and biological factors involved so as to comprehend how and why such techniques work.
Chapter Six (Wireless Information Retrieval: Sensing with WiFi signals) presents the device-free WiFi-sensing technique that the author developed for the Hertzian Field series. Combining elements from Ubiquitous Sensing and Music Information Retrieval, this technique performs multi-layered feature extraction on the Received Signal Strength Indication (RSSI) of WiFi Beacon frames to deduce a variety of information related to the movement of uninstrumented bodies, and to changes in environmental factors (e.g. humidity).
Chapter Seven (Composing Hertzian Fields) discusses strategies for creating works with this technique, and examines the three works of the Hertzian Field series in detail. It finally touches on ideas for future work by the author
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Engineered Vascular Tissue Generated by Cellular Self-Assembly
No full textSmall diameter vascular grafts comprised entirely from cells and cell-derived extracellular matrix (ECM) have shown promise in clinical trials and may have potential advantages as in vitro vascular tissue models. A challenge with current cell-derived tissue engineering approaches is the length of time required to generate strong, robust tissue. There is a lack of alternative methods to rapidly assemble cells into a 3D format without the support of a scaffold. Toward the goal of engineering a new approach to rapidly synthesizing vascular tissue constructs entirely from cells, we have developed and characterized a strategy for creating cell-derived tissue rings by cellular self-assembly. The focus of this thesis was to develop the system to rapidly generate engineered tissue rings, and to evaluate their structural and functional properties.
To generate tissue rings, rat smooth muscle cells (SMCs) were seeded into round-bottomed, ring-shaped agarose wells with varying inner post diameters (2, 4, and 6 mm). Within 24 hours of seeding, cells aggregated, contracted, and formed robust tissue that could be removed from their wells and handled. If kept in culture, the thickness of these tissue rings increased with time. Mechanical analysis of the tissue showed that it was stronger after only 8 days in culture than engineered tissues generated by other approaches (such as seeding cells in biopolymer gels) cultured and tested at similar time points. Histological staining of the tissue rings revealed high cell densities throughout, along with the presence of glycosaminoglycans and some collagen. We also found that we could use the tissue rings as building blocks to generate larger tubular structures. Briefly, tissue rings were removed from the agarose wells and transferred onto silicone tubing mandrels. Once the rings were placed in contact with each other on the mandrel, they were cultured to allow the rings to fuse together. We found that the ability of tissue rings to fuse decreased with increasing ring “pre-culture” duration, and that we were able to generate fully fused tissue tubes in as little as 8 days (with only one day of ring pre-culture and seven days of fusion).
In the last section of this thesis, we established the feasibility of using primary human SMCs to generate self-assembled tissue rings, similar to the self-assembled rings generated with rat SMCs. Compared to the rat SMC rings, human SMC rings were stronger, stiffer and appeared to contain increased levels of collagen. These data showed that human SMCs are capable of self-assembling into tissue rings similar to rat SMCs, and may therefore be used to create engineered human vascular tissue.
Overall, we have developed a platform technology that can be used to screen the effects of culture parameters on the structure, mechanics, and function of vascular tissue. We anticipate that through the use of this technology, we can further improve vascular grafts by better understanding factors which promote ECM synthesis and SMC contraction. We can use these results directly toward the generation of vascular grafts by fusing self-assembled cell rings together to form tissue tubes. These novel bioengineered vascular tissues may also serve as a method to produce in vitro models to help further our understanding of vascular diseases, as well as facilitate pre-clinical screening of vascular tissue responses to pharmacologic therapies
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Engineering the Keratinocyte Microenvironment: Harnessing Topography to Direct Cellular Function
No full textSkin wound healing presents a challenging and expensive clinical problem with nearly 20 million wounds requiring intervention leading to an annual cost of more than $8 million. Tissue engineered skin substitutes are valuable not only as a clinical therapy for chronic wounds and severe traumas, but also as in vitro 3D model systems to investigate wound healing and skin pathogenesis. However, these substitutes are limited by a lack of topography at the dermal-epidermal junction (DEJ). In contrast, the native DEJ is characterized by a series of dermal papillae which project upward into the epidermal layer and create physical topographic microniches that support keratinocyte stem cell clustering. In this thesis, we created novel 3D skin model systems to investigate the role of microtopography in regulating keratinocyte function and cell fate using scaffolds containing precisely engineered topographic features. We hypothesized that the microtopography of the DEJ creates distinct keratinocyte microniches that promote epidermal morphogenesis and modulate keratinocyte stem cell clustering which can be harnessed to create a more robust skin substitute that expedites wound closure. Using photolithographic techniques, we created micropatterned DEJ analogs and micropatterned dermal-epidermal regeneration matrices (µDERM) which couple a dermal support matrix to a micropatterned DEJ analog. We found that the incorporation of microtopography into our in vitro skin model resulted in a thicker, more robust epidermal layer. Additionally, we identified three distinct functional keratinocyte niches: the proliferative niche in narrow channels, the synthetic niche in wide channels and the keratinocyte stem cell niche in narrow channels and corner topographies. Ultimately, incorporation of both narrow and wide channels on a single construct allowed us to recreate native keratinocyte stem cell patterning in vitro. These model systems will allow us to investigate the role of cellular microniches in regulating cellular function and epidermal disease pathogenesis as well as to identify topographic cues that enhance the rate of wound healing
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Designing Bioengineered Skin Substitutes Containing Microfabricated Basal Lamina Analogs to Enhance Skin Regeneration
No full textBioengineered skin substitutes have been developed to treat burn and non-healing wounds; however limitations still hinder their clinical success rates. Optimizing these current design strategies requires an understanding of how biochemical and topographical features of the native tissue modulate keratinocyte processes involved in tissue functionality. In this thesis, a novel bioengineered skin substitute was developed that contains a microfabricated basal lamina analog that recapitulates the native microenvironment found at the dermal-epidermal junction (DEJ). In native skin, this microenvironment consists of both biochemical and topographical cues which play critical roles in maintaining tissue architecture and overall homeostasis with the external environment.
Therefore, we hypothesize that microfabricated basal lamina analogs with extracellular matrix cues and three-dimensional features that mimics the cellular microenvironment of the DEJ will promote enhanced epithelialization and increase epidermal stem cell clustering on the surface of bioengineered skin substitutes.
We determined that the extracellular matrix protein fibronectin (FN) found in the cellular microenvironment of the DEJ enhanced keratinocyte attachment, proliferation, and epithelialization of a collagen based basal lamina analog. It was also found that the collagen material used to create the basal lamina analog as well as the FN conjugation strategy to this material significantly influenced the bioactivity of FN and its ability to modulate keratinocyte functions through integrin based mechanism. To investigate spatial tissue organization and the role it plays in the cellular microenvironment of the DEJ on epithelialization and epidermal stem cell localization, we used photolithography coupled with materials processing techniques to create microfabricated basal lamina analogs. It was determined that epidermal thicknesses found in narrow channels of microfabricated basal lamina analogs (50 µm and 100 µm widths with 200 µm depths) were similar to cultures on de-epithelialized acellular dermis and native foreskin tissues after 7 days of in vitro culture. We also determined that the microfabricated basal lamina analogs created an epidermal stem cell niche that promoted epidermal stem cell clustering in the channels which is critical for longevity of the tissue.
Overall, we developed a platform technology that was specifically used to produce a highly functional bioengineered skin substitute with regenerative capacity that mimics native skin. We anticipate through the use of this technology, we can further improve bioengineered skin substitutes by incorporating epidermal structures of native skin including hair follicles and sweat glands as well as improve overall cosmetic appearance. Additionally, this novel bioengineered skin substitute can serve as a model system to further our understanding of pathological conditions and diseases of the skin as well as facilitate robust preclinical screenings of epidermal responses to new therapeutic agents as well as to cosmetic and chemical products
CDH2 and CDH11 act as regulators of stem cell fate decisions
No full textAbstractAccumulating evidence suggests that the mechanical and biochemical signals originating from cell–cell adhesion are critical for stem cell lineage specification. In this review, we focus on the role of cadherin mediated signaling in development and stem cell differentiation, with emphasis on two well-known cadherins, cadherin-2 (CDH2) (N-cadherin) and cadherin-11 (CDH11) (OB-cadherin). We summarize the existing knowledge regarding the role of CDH2 and CDH11 during development and differentiation in vivo and in vitro. We also discuss engineering strategies to control stem cell fate decisions by fine-tuning the extent of cell–cell adhesion through surface chemistry and microtopology. These studies may be greatly facilitated by novel strategies that enable monitoring of stem cell specification in real time. We expect that better understanding of how intercellular adhesion signaling affects lineage specification may impact biomaterial and scaffold design to control stem cell fate decisions in three-dimensional context with potential implications for tissue engineering and regenerative medicine
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