wendy liu - Academia.edu (original) (raw)

Papers by wendy liu

Cellular and Molecular Life Sciences, 2014

Macrophages are tissue-resident immune cells that play a critical role in maintaining homeostasis... more Macrophages are tissue-resident immune cells that play a critical role in maintaining homeostasis and fighting infection. In addition, these cells are involved in the progression of many pathologies including cancer and atherosclerosis. In response to a variety of microenvironmental stimuli, macrophages can be polarized to achieve a spectrum of functional phenotypes. This review will discuss some emerging evidence in support of macrophage phenotypic regulation by physical and mechanical cues. As alterations in the physical microenvironment often underlie pathophysiological states, an understanding of their effects on macrophage phenotype and function may help provide mechanistic insights into disease pathogenesis.

Materials Today, 2005

In this review, we highlight some of the recent advances in understanding how environmental cues,... more In this review, we highlight some of the recent advances in understanding how environmental cues, presented through cellular adhesions, can regulate cellular processes such as proliferation and differentiation. We discuss how these findings may impact design considerations for new materials in biology.

Tissue Engineering, 2004

The ability to spatially control cell adhesion and multicellular organization is critical to many... more The ability to spatially control cell adhesion and multicellular organization is critical to many biomedical and tissue-engineering applications. This work describes a straightforward method to micropattern cells onto glass, silicone rubber, and polystyrene using commercially available reagents. An elastomeric polydimethylsiloxane stamp is used to contact-transfer extracellular matrix protein onto a surface followed by blocking cell adhesion in the surrounding regions by the physisorption of Pluronic surfactants. Using self-assembled monolayers of alkanethiols on gold as model surfaces to control surface wettability, we found that protein printing was most effective at intermediate to highly wetting surfaces whereas Pluronic adsorption occurred at intermediate to low wetting surfaces. Within a regimen of intermediate wettability both techniques were applied in conjunction to restrict cell adhesion to specified patterns. Adjusting the wettability of common tissue culture substrates to the same intermediate range again allowed the micropatterning of cells, suggesting that this approach is likely to be generally applicable to many types of materials. This technique therefore may allow for wider adoption of cell patterning.

Proceedings of The National Academy of Sciences, 2005

Spatial patterns of cellular growth generate mechanical stresses that help to push, fold, expand,... more Spatial patterns of cellular growth generate mechanical stresses that help to push, fold, expand, and deform tissues into their specific forms. Genetic factors are thought to specify patterns of growth and other behaviors to drive morphogenesis. Here, we show that tissue form itself can feed back to regulate patterns of proliferation. Using microfabrication to control the organization of sheets of cells, we demonstrated the emergence of stable patterns of proliferative foci. Regions of concentrated growth corresponded to regions of high tractional stress generated within the sheet, as predicted by a finite-element model of multicellular mechanics and measured directly by using a micromechanical force sensor array. Inhibiting actomyosin-based tension or cadherin-mediated connections between cells disrupted the spatial pattern of proliferation. These findings demonstrate the existence of patterns of mechanical forces that originate from the contraction of cells, emerge from their multicellular organization, and result in patterns of growth. Thus, tissue form is not only a consequence but also an active regulator of tissue growth. morphogenesis ͉ pattern formation ͉ micropatterning ͉ cytoskeleton ͉ mechanotransduction Substrate Fabrication. Micropatterned substrata containing fibronectin-coated islands were fabricated as described in ref. 24. Briefly, glass coverslips were coated by electron beam evaporation with 2.0 nm of Ti, followed by 15 nm of Au. Elastomeric stamps containing a relief of the desired pattern were inked in an ethanolic solution of 2 mM hexadecanethiol (Sigma), dried under nitrogen, and placed in conformal contact for 2 s with the Au-coated coverslips. The unstamped regions of the coverslips were rendered nonadhesive by immersing them in an ethanolic solution of 2 mM tri(ethylene glycol)-terminated alkanethiol (Prochimia, Golansk, Poland) for 1 h. Substrata were rinsed, sterilized in ethanol, and incubated in 25 g͞ml fibronectin in PBS for 2 h.

Biomaterials for Cardiac Regeneration, 2014

ABSTRACT The use of implantable biomaterials in cardiovascular system is growing, in part because... more ABSTRACT The use of implantable biomaterials in cardiovascular system is growing, in part because of the improvement of biotechnology. These biomaterials provide opportunities for effective treatment of cardiovascular diseases with minimal associated morbidities. However, in doing so, there are concerns regarding the immune responses to these implants, and in particular, long-term reactions are crucial. The relatively recent advent of tissue engineered implants promises to revolutionize patient specific devices, yet it comes with the added complexity of understanding host–implant compatibility. In this chapter, we discuss the current comprehension related to immune reactions to implants, both cell-based and acellular. Tissue and organ rejection in the cardiovascular setting are discussed together with the immunologic considerations for grafts, patches, and heart valves. We explore the use of stem cells in cardiovascular bioprostheses as well as their associated advantages and potential risks. Lastly, potential future directions of tissue-engineered cardiac bioprostheses are discussed.

BioMEMS and Biomedical Nanotechnology, 2006

Methods in Molecular Biology, 2007

Traditional methods to study cell-cell adhesion have been limited by their inability to manipulat... more Traditional methods to study cell-cell adhesion have been limited by their inability to manipulate cell-cell interactions without simultaneously affecting other microenvironmental factors. Here we describe a novel method that enables the culture of cells with precise simultaneous control of both cell-cell and cell-substratum adhesion. Using microfabricated stamps of poly(dimethylsiloxane), we construct bowtie-shaped agarose microwells into which cells can be cultured. The degree to which cells spread is controlled by the size of the microwell; cell-cell contacts form between neighboring cells within the microwell. This chapter describes the details of stamp fabrication, agarose microwell construction, and cell culture in micropatterned substrata.

Adhesion Protein Protocols, 2007

Traditional methods to study cell-cell adhesion have been limited by their inability to manipulat... more Traditional methods to study cell-cell adhesion have been limited by their inability to manipulate cell-cell interactions without simultaneously affecting other microenvironmental factors. Here we describe a novel method that enables the culture of cells with precise simultaneous control of both cell-cell and cell-substratum adhesion. Using microfabricated stamps of poly(dimethylsiloxane), we construct bowtie-shaped agarose microwells into which cells can be cultured. The degree to which cells spread is controlled by the size of the microwell; cell-cell contacts form between neighboring cells within the microwell. This chapter describes the details of stamp fabrication, agarose microwell construction, and cell culture in micropatterned substrata.

Materials Today, 2005

1 . To study cell biology, cells are typically removed from their host organism and cultured on a... more 1 . To study cell biology, cells are typically removed from their host organism and cultured on a plastic culture dish -an environment unlike their natural, physiological environment 2 . Thus, cells tend to lose many of their normal functions and often dedifferentiate for reasons that are not well understood.

Biomaterials, 2011

The non-specific host response to implanted biomaterials is often a key challenge of medical devi... more The non-specific host response to implanted biomaterials is often a key challenge of medical device design. To evaluate biocompatibility, measuring the release of reactive oxygen species (ROS) produced by inflammatory cells in response to biomaterial surfaces is a well-established method. However, the detection of ROS in response to materials implanted in vivo has not yet been demonstrated. Here, we develop a bioluminescence whole animal imaging approach to observe ROS released in response to subcutaneously-implanted materials in live animals. We compared the real-time generation of ROS in response to two representative materials, polystyrene and alginate, over the course of 28 days. High levels of ROS were observed near polystyrene, but not alginate implants, and persisted throughout the course of 28 days. Histological analysis revealed that high levels of ROS correlated not only with the presence of phagocytic cells at early timepoints, but also fibrosis at later timepoints, suggesting that ROS may be involved in both the acute and chronic phase of the foreign body response. These data are the first in vivo demonstration of ROS generation in response to implanted materials, and describe a novel technique to evaluate the host response.

SSRN Electronic Journal, 2000

Organizational Behavior and Human Decision Processes, 2007

In this research, we investigate the impact of significant life experiences on intertemporal deci... more In this research, we investigate the impact of significant life experiences on intertemporal decisions among young adults. A series of experiments focus specifically on the impact of experiencing the death of a close other by cancer. We show that such an experience, which bears information about time, is associated with making decisions that favor the long-term future over short-term interests (Studies 1 and 2). Underlying this effect appears to be increased salience and concreteness regarding one’s future life course, shifting focus away from the present toward the long run (Studies 3 and 4). Finally, we explore the shift caused by a cancer death of a public figure and examine its stability over time (Study 5). Implications for research on intertemporal decision making and the impact of life events on perceptions and preferences are discussed.

Journal of Consumer Research, 2009

Assortment size has been shown to influence whether consumers make a choice, but could it also in... more Assortment size has been shown to influence whether consumers make a choice, but could it also influence what they choose? Five studies demonstrate that because choosing from larger assortments is often more difficult, it leads people to select options that are easier to ...

Journal of Consumer Research, 2008

This research examines how a focus on time versus money can lead to two distinct mind-sets that a... more This research examines how a focus on time versus money can lead to two distinct mind-sets that affect consumers' willingness to donate to charitable causes. The results of three experiments, conducted both in the lab and in the field, reveal that asking individuals to think about "how much time they would like to donate" (vs. "how much money they would like to donate") to a charity increases the amount that they ultimately donate to the charity. Fueling this effect are differential mindsets activated by time versus money. Implications for the research on time, money, and emotional well-being are discussed.

Cellular and Molecular Life Sciences, 2014

Macrophages are tissue-resident immune cells that play a critical role in maintaining homeostasis... more Macrophages are tissue-resident immune cells that play a critical role in maintaining homeostasis and fighting infection. In addition, these cells are involved in the progression of many pathologies including cancer and atherosclerosis. In response to a variety of microenvironmental stimuli, macrophages can be polarized to achieve a spectrum of functional phenotypes. This review will discuss some emerging evidence in support of macrophage phenotypic regulation by physical and mechanical cues. As alterations in the physical microenvironment often underlie pathophysiological states, an understanding of their effects on macrophage phenotype and function may help provide mechanistic insights into disease pathogenesis.

Materials Today, 2005

In this review, we highlight some of the recent advances in understanding how environmental cues,... more In this review, we highlight some of the recent advances in understanding how environmental cues, presented through cellular adhesions, can regulate cellular processes such as proliferation and differentiation. We discuss how these findings may impact design considerations for new materials in biology.

Tissue Engineering, 2004

The ability to spatially control cell adhesion and multicellular organization is critical to many... more The ability to spatially control cell adhesion and multicellular organization is critical to many biomedical and tissue-engineering applications. This work describes a straightforward method to micropattern cells onto glass, silicone rubber, and polystyrene using commercially available reagents. An elastomeric polydimethylsiloxane stamp is used to contact-transfer extracellular matrix protein onto a surface followed by blocking cell adhesion in the surrounding regions by the physisorption of Pluronic surfactants. Using self-assembled monolayers of alkanethiols on gold as model surfaces to control surface wettability, we found that protein printing was most effective at intermediate to highly wetting surfaces whereas Pluronic adsorption occurred at intermediate to low wetting surfaces. Within a regimen of intermediate wettability both techniques were applied in conjunction to restrict cell adhesion to specified patterns. Adjusting the wettability of common tissue culture substrates to the same intermediate range again allowed the micropatterning of cells, suggesting that this approach is likely to be generally applicable to many types of materials. This technique therefore may allow for wider adoption of cell patterning.

Proceedings of The National Academy of Sciences, 2005

Spatial patterns of cellular growth generate mechanical stresses that help to push, fold, expand,... more Spatial patterns of cellular growth generate mechanical stresses that help to push, fold, expand, and deform tissues into their specific forms. Genetic factors are thought to specify patterns of growth and other behaviors to drive morphogenesis. Here, we show that tissue form itself can feed back to regulate patterns of proliferation. Using microfabrication to control the organization of sheets of cells, we demonstrated the emergence of stable patterns of proliferative foci. Regions of concentrated growth corresponded to regions of high tractional stress generated within the sheet, as predicted by a finite-element model of multicellular mechanics and measured directly by using a micromechanical force sensor array. Inhibiting actomyosin-based tension or cadherin-mediated connections between cells disrupted the spatial pattern of proliferation. These findings demonstrate the existence of patterns of mechanical forces that originate from the contraction of cells, emerge from their multicellular organization, and result in patterns of growth. Thus, tissue form is not only a consequence but also an active regulator of tissue growth. morphogenesis ͉ pattern formation ͉ micropatterning ͉ cytoskeleton ͉ mechanotransduction Substrate Fabrication. Micropatterned substrata containing fibronectin-coated islands were fabricated as described in ref. 24. Briefly, glass coverslips were coated by electron beam evaporation with 2.0 nm of Ti, followed by 15 nm of Au. Elastomeric stamps containing a relief of the desired pattern were inked in an ethanolic solution of 2 mM hexadecanethiol (Sigma), dried under nitrogen, and placed in conformal contact for 2 s with the Au-coated coverslips. The unstamped regions of the coverslips were rendered nonadhesive by immersing them in an ethanolic solution of 2 mM tri(ethylene glycol)-terminated alkanethiol (Prochimia, Golansk, Poland) for 1 h. Substrata were rinsed, sterilized in ethanol, and incubated in 25 g͞ml fibronectin in PBS for 2 h.

Biomaterials for Cardiac Regeneration, 2014

ABSTRACT The use of implantable biomaterials in cardiovascular system is growing, in part because... more ABSTRACT The use of implantable biomaterials in cardiovascular system is growing, in part because of the improvement of biotechnology. These biomaterials provide opportunities for effective treatment of cardiovascular diseases with minimal associated morbidities. However, in doing so, there are concerns regarding the immune responses to these implants, and in particular, long-term reactions are crucial. The relatively recent advent of tissue engineered implants promises to revolutionize patient specific devices, yet it comes with the added complexity of understanding host–implant compatibility. In this chapter, we discuss the current comprehension related to immune reactions to implants, both cell-based and acellular. Tissue and organ rejection in the cardiovascular setting are discussed together with the immunologic considerations for grafts, patches, and heart valves. We explore the use of stem cells in cardiovascular bioprostheses as well as their associated advantages and potential risks. Lastly, potential future directions of tissue-engineered cardiac bioprostheses are discussed.

BioMEMS and Biomedical Nanotechnology, 2006

Methods in Molecular Biology, 2007

Traditional methods to study cell-cell adhesion have been limited by their inability to manipulat... more Traditional methods to study cell-cell adhesion have been limited by their inability to manipulate cell-cell interactions without simultaneously affecting other microenvironmental factors. Here we describe a novel method that enables the culture of cells with precise simultaneous control of both cell-cell and cell-substratum adhesion. Using microfabricated stamps of poly(dimethylsiloxane), we construct bowtie-shaped agarose microwells into which cells can be cultured. The degree to which cells spread is controlled by the size of the microwell; cell-cell contacts form between neighboring cells within the microwell. This chapter describes the details of stamp fabrication, agarose microwell construction, and cell culture in micropatterned substrata.

Adhesion Protein Protocols, 2007

Traditional methods to study cell-cell adhesion have been limited by their inability to manipulat... more Traditional methods to study cell-cell adhesion have been limited by their inability to manipulate cell-cell interactions without simultaneously affecting other microenvironmental factors. Here we describe a novel method that enables the culture of cells with precise simultaneous control of both cell-cell and cell-substratum adhesion. Using microfabricated stamps of poly(dimethylsiloxane), we construct bowtie-shaped agarose microwells into which cells can be cultured. The degree to which cells spread is controlled by the size of the microwell; cell-cell contacts form between neighboring cells within the microwell. This chapter describes the details of stamp fabrication, agarose microwell construction, and cell culture in micropatterned substrata.

Materials Today, 2005

1 . To study cell biology, cells are typically removed from their host organism and cultured on a... more 1 . To study cell biology, cells are typically removed from their host organism and cultured on a plastic culture dish -an environment unlike their natural, physiological environment 2 . Thus, cells tend to lose many of their normal functions and often dedifferentiate for reasons that are not well understood.

Biomaterials, 2011

The non-specific host response to implanted biomaterials is often a key challenge of medical devi... more The non-specific host response to implanted biomaterials is often a key challenge of medical device design. To evaluate biocompatibility, measuring the release of reactive oxygen species (ROS) produced by inflammatory cells in response to biomaterial surfaces is a well-established method. However, the detection of ROS in response to materials implanted in vivo has not yet been demonstrated. Here, we develop a bioluminescence whole animal imaging approach to observe ROS released in response to subcutaneously-implanted materials in live animals. We compared the real-time generation of ROS in response to two representative materials, polystyrene and alginate, over the course of 28 days. High levels of ROS were observed near polystyrene, but not alginate implants, and persisted throughout the course of 28 days. Histological analysis revealed that high levels of ROS correlated not only with the presence of phagocytic cells at early timepoints, but also fibrosis at later timepoints, suggesting that ROS may be involved in both the acute and chronic phase of the foreign body response. These data are the first in vivo demonstration of ROS generation in response to implanted materials, and describe a novel technique to evaluate the host response.

SSRN Electronic Journal, 2000

Organizational Behavior and Human Decision Processes, 2007

In this research, we investigate the impact of significant life experiences on intertemporal deci... more In this research, we investigate the impact of significant life experiences on intertemporal decisions among young adults. A series of experiments focus specifically on the impact of experiencing the death of a close other by cancer. We show that such an experience, which bears information about time, is associated with making decisions that favor the long-term future over short-term interests (Studies 1 and 2). Underlying this effect appears to be increased salience and concreteness regarding one’s future life course, shifting focus away from the present toward the long run (Studies 3 and 4). Finally, we explore the shift caused by a cancer death of a public figure and examine its stability over time (Study 5). Implications for research on intertemporal decision making and the impact of life events on perceptions and preferences are discussed.

Journal of Consumer Research, 2009

Assortment size has been shown to influence whether consumers make a choice, but could it also in... more Assortment size has been shown to influence whether consumers make a choice, but could it also influence what they choose? Five studies demonstrate that because choosing from larger assortments is often more difficult, it leads people to select options that are easier to ...

Journal of Consumer Research, 2008

This research examines how a focus on time versus money can lead to two distinct mind-sets that a... more This research examines how a focus on time versus money can lead to two distinct mind-sets that affect consumers' willingness to donate to charitable causes. The results of three experiments, conducted both in the lab and in the field, reveal that asking individuals to think about "how much time they would like to donate" (vs. "how much money they would like to donate") to a charity increases the amount that they ultimately donate to the charity. Fueling this effect are differential mindsets activated by time versus money. Implications for the research on time, money, and emotional well-being are discussed.