Gradient and Dynamic Hydrogel Materials to Probe Dynamics in Cancer Stem Cell Phenotypes

Junmin Lee, Amr A Abdeen, Yanfen Li, Shamalee Goonetilleke, Kristopher A Kilian
ACS Applied Bio Materials, 2021, 4(1), 711-720
Publication year: 2021

The microenvironment of tumors shows high variability in stiffness compared to normal tissues, suggesting that spatiotemporal changes in mechanics play a role in development and progression. Here, we employ microengineered hydrogels with static, dynamic (magnetic field-mediated stiffening and softening), or gradient matrix elasticity to investigate the influence of matrix mechanics in modulating the stem cell-like phenotype in melanoma and breast cancer cells. Using immunofluorescence staining of molecular markers associated with a cancer stem cell (CSC) state, we show that a subtle increase in local stiffness promotes the CSC phenotype, while different mechanical properties in static or dynamic hydrogelswithout gradient profiles of mechanical propertieshave a negligible influence on phenotype switching toward a CSC state. Inhibition of integrins and downstream effectors of mechanotransduction reveals that distinct signaling pathways play a role in regulating the dynamic CSC state in melanoma and breast cancer cells. Our findings demonstrate how cancer cells respond to the local stiffness gradients with dynamic plasticity during progression.

Facilitating Engaging Journal Clubs in Online Upper-Level Undergraduate Courses

Engineering Education
Yanfen Li, Adam St Jean
Journal of Microbiology & Biology Education, 2021, 22(1), DOI: 10.1128/jmbe.v22i1.2637
Publication year: 2021

STEM curricula often prepare students with fundamental knowledge, allowing students to have strong backgrounds in technical concepts. However, upper-level students may lack the ability to critically analyze primary research articles, which is important for understanding the current state of the field. Journal clubs can be used within the classroom to facilitate discussion of recent work and teach students to critically analyze research and data. Traditional journal clubs (JCs) are conducted in face-to-face classrooms and consist of presentations and discussions. It is possible to adapt these techniques to form virtual Journal Clubs (vJCs) when courses are taught fully online; however, student engagement is often lacking and can lead to less knowledge gained in vJCs. In this article, we summarize several key teaching tips and best practices which we used to increase student engagement in vJCs. We found that vJCs, compared to JCs, equally increased student perceptions of their skills in reading, analyzing, and critiquing scientific literature and decreased their perceived levels of stress and frustration.

Exploring the relationship between student-perceived faculty encouragement, self-efficacy, and intent to persist in engineering programs

Engineering Education
Hsien-Yuan Hsu, Yanfen Li, Suzanne Dugger, James Jones
European Journal of Engineering Education, DOI: 10.1080/03043797.2021.1889469
Publication year: 2021

Copious research on Social Cognitive Career Theory has found student selfefficacy substantially related to persistence in engineering programs. The present exploratory study investigated the associations among faculty encouragement (a specific type of verbal persuasion in college context) and students’ selfefficacy, outcome expectations, and intent to persist in engineering majors using a sample of first-semester engineering students at a mid-sized public university. Analytical data were collected from 205 first-year engineering students in the fall semester at a mid-sized public four-year university in the United States. Results show that students’ perception of faculty encouragement can statistically significantly contribute to students’ selfefficacy and outcome expectations, supporting the hypothesis that studentperceived faculty encouragement was a source of selfefficacy and outcome expectations. Further, although students’ perception of faculty encouragement can influence students’ intent to persist, the effect was not directly transmitted; rather, it was found only through an indirect path via selfefficacy.

Using Arduinos to Transition a Bioinstrumentation Lab to Remote Learning

Engineering Education
Abiche H Dewilde, Yanfen Li
Biomedical Engineering Education, 2020,
Publication year: 2020

Bioinstrumentation is a required course in more than 75% of accredited BME programs. Like many other institutions, the bioinstrumentation lab at the University of Massachusetts Lowell (UMass Lowell) is a junior level course designed to provide the students with fundamental understanding of electrical circuits, circuit components, and bioinstrument design. The course meets weekly and the students progress through a series of labs where they build, test, and troubleshoot basic biosensor circuits. Example labs include building voltage dividers, active and passive filters, electrocardiogram (ECG), and electromyograph (EMG). Typically, these labs use a variety of equipments including function generators and oscilloscopes. UMass Lowell transitioned abruptly to remote learning during the spring semester of 2020 during which students were preparing to conduct their last lab (EMG) and begin their final semester project in groups of 2-3 students. Since the students no longer had access to the iWorx teaching kits and biosensors available in the lab, alternatives were explored which allowed students to still build and test circuits from home. It was determined that a cheap alternative is for each student to purchase the ELEGOO UNO Project Basic Starter Kit with Tutorial and UNO R3 Compatible with Arduino Integrated Development Environment (IDE). This paper describes our implementation appraoch.

Simultaneous cell traction and growth measurements using light

6. Shamira Sridharan*, Yanfen Li*, Louis Foucard, Hassaan Majeed, Basanta Bhaduri, Alex Levine, Kristopher A. Kilian, and Gabriel Popescu
Journal of Biophotonics, 2019, e201800182
Publication year: 2019

Characterizing the effects of force fields generated by cells on proliferation, migration and differentiation processes is challenging due to limited availability of nondestructive imaging modalities. Here, we integrate a new real‐time traction stress imaging modality, Hilbert phase dynamometry (HPD), with spatial light interference microscopy (SLIM) for simultaneous monitoring of cell growth during differentiation processes. HPD uses holographic principles to extract displacement fields from chemically patterned fluorescent grid on deformable substrates. This is converted into forces by solving an elasticity inverse problem. Since HPD uses the epi‐fluorescence channel of an inverted microscope, cellular behavior can be concurrently studied in transmission with SLIM. We studied the differentiation of mesenchymal stem cells (MSCs) and found that cells undergoing osteogenesis and adipogenesis exerted larger and more dynamic stresses than their precursors, with MSCs developing the smallest forces and growth rates. Thus, we develop a powerful means to study mechanotransduction during dynamic processes where the matrix provides context to guide cells toward a physiological or pathological outcome.

Quantitative phase imaging reveals matrix stiffness-dependent growth and migration of cancer cells.

Yanfen Li*, Michael J Fanous*, Kristopher A. Kilian, Gabriel Popescu
Scientific Reports, 2019, 1(9), 248
Publication year: 2019

Cancer progression involves complex signals within the tumor microenvironment that orchestrate proliferation and invasive processes. The mechanical properties of the extracellular matrix (ECM) within this microenvironment has been demonstrated to influence growth and the migratory phenotype that precedes invasion. Here we present the integration of a label-free quantitative phase imaging technique, spatial light interference microscopy (SLIM)—with protein-conjugated hydrogel substrates— to explore how the stiffness of the ECM influences melanoma cells of varying metastatic potential. Melanoma cells of high metastatic potential demonstrate increased growth and velocity characteristics relative to cells of low metastatic potential. Cell velocity in the highly metastatic population shows a relative insensitivity to matrix stiffness suggesting adoption of migratory routines that are independent of mechanics to facilitate invasion. The use of SLIM and engineered substrates provides a new approach to characterize the invasive properties of live cells as a function of microenvironment parameters. This work provides fundamental insight into the relationship between growth, migration and metastatic potential, and provides a new tool for profiling cancer cells for clinical grading and development of patient-specific therapeutic regimens.

Effects of substrate patterning on cellular spheroid growth and dynamics measured by gradient light interference microscopy (GLIM)

Michael J Fanous, Yanfen Li, Mikhail E Kandel, Amr A Abdeen, Kristopher A Kilian, Gabriel Popescu
Journal of biophotonics, 2019, e201900178.
Publication year: 2019

The development of three-dimensional (3D) cellular architectures during development and pathological processes involves intricate migratory patterns that are modulated by genetics and the surrounding microenvironment. The substrate composition of cell cultures has been demonstrated to influence growth, proliferation and migration in 2D. Here, we study the growth and dynamics of mouse embryonic fibroblast cultures patterned in a tissue sheet which then exhibits 3D growth. Using gradient light interference microscopy (GLIM), a label-free quantitative phase imaging approach, we explored the influence of geometry on cell growth patterns and rotational dynamics. We apply, for the first time to our knowledge, dispersion-relation phase spectroscopy (DPS) in polar coordinates to generate the radial and rotational cell mass-transport. Our data show that cells cultured on engineered substrates undergo rotational transport in a radially independent manner and exhibit faster vertical growth than the control, unpatterned cells. The use of GLIM and polar DPS provides a novel quantitative approach to studying the effects of spatially patterned substrates on cell motility and growth.

Vertical Integration of Cell-Laden Hydrogels with Bioinspired Photonic Crystal Membranes

Yi Pei, Sayyed Hamed Shahoei, Yanfen Li, Erik R. Nelson, Kristopher A. Kilian
Advanced Materials Interfaces, 2018.
Publication year: 2018

The native architecture of tissue segregates populations of cells through nanostructured membranes of biopolymers (e.g., basement membranes) which serve the dual purpose of providing scaffolding for cells and filtration through size‐exclusion. A multilayered approach to fabricate tissue scaffolds where populations of encapsulated cells are separated by porous silicon (PSi)‐based photonic crystal membranes with nano‐ and microstructure that mimics the basement membranes is reported here. The PSi films are fabricated to display discreet photonic bandgaps such that remote optical interrogation provides a specific resonance for each film. Through careful control of surface chemistry, nanostructured PSi films are engineered to serve as optical biosensors and biomolecule release reservoirs, where the optical signature can report on these distinct functions remotely using a simple light source. The promise of this approach is demonstrated as a “smart” tissue scaffolding by monitoring matrix metalloprotease (MMP) activity from encapsulated multilayered co‐cultures of mesenchymal stem cells and human microvascular endothelial cells, with concurrent attenuation of MMP activity through release of angiogenic‐modulating compounds. The integration of optically registered biosensing and drug‐release capabilities—within a multilayered hydrogel scaffold with multiple cell types—provides a new approach to tissue engineering where dynamic bioactivity can be monitored remotely in real‐time.

Surveillance of Cancer Stem Cell Plasticity Using an Isoform-Selective Fluorescent Probe for Aldehyde Dehydrogenase 1A1

Chelsea Anorma, Jamila Hedhli, Thomas E. Bearrood, Nicholas W. Pino, Sarah H. Gardner, Hiroshi Inaba, Pamela Zhang, Yanfen Li, Daven Feng, Sara E. Dibrell, Kristopher A. Kilian, Lawrence W. Dobrucki, Timothy M. Fan, and Jefferson Chan
ACS Central Science, 2018, 4 (8), 1045-1055
Publication year: 2018

Cancer stem cells (CSCs) are progenitor cells that contribute to treatment-resistant phenotypes during relapse. CSCs exist in specific tissue microenvironments that cell cultures and more complex models cannot mimic. Therefore, the development of new approaches that can detect CSCs and report on specific properties (e.g., stem cell plasticity) in their native environment have profound implications for studying CSC biology. Herein, we present AlDeSense, a turn-on fluorescent probe for aldehyde dehydrogenase 1A1 (ALDH1A1) and Ctrl-AlDeSense, a matching nonresponsive reagent. Although ALDH1A1 contributes to the detoxification of reactive aldehydes, it is also associated with stemness and is highly elevated in CSCs. AlDeSense exhibits a 20-fold fluorescent enhancement when treated with ALDH1A1. Moreover, we established that AlDeSense is selective against a panel of common ALDH isoforms and exhibits exquisite chemostability against a collection of biologically relevant species. Through the application of surface marker antibody staining, tumorsphere assays, and assessment of tumorigenicity, we demonstrate that cells exhibiting high AlDeSense signal intensity have properties of CSCs. Using these probes in tandem, we have identified CSCs at the cellular level via flow cytometry and confocal imaging, as well as monitored their states in animal models.

Work in Progress: Design of a First-Year Rhetoric Course for Engineering Students

Engineering Education
Mohammad Usama Zahid, Evin Scott Groundwater, Yanfen Li, Celia Mathews Elliott, Andrew Michael Smith, Dallas R Trinkle, Kelly Ritter, P. Scott Carney, Marcia Pool, Karin Jensen
Paper presented at 2017 ASEE Annual Conference & Exposition, Columbus, Ohio.
Publication year: 2017

This Work in Progress paper describes an initiative to intervene at a curricular level, asking engineering students to consider writing as an essential and crucial element of being an engineer- and developing rhetorical awareness and writing skills. Educators and employers deem communication skills as critical for undergraduates (1), and ABET recognizes this by including “an ability to communicate effectively” as one of its stated student outcomes (2). However, this is an area that engineering students themselves perceive as the greatest gap in their undergraduate education (3). Furthermore, many engineering students undervalue the importance of writing skills and buy into the myth of engineers as ‘bad writers,’ believing themselves to be poor writers and communicators.

To achieve these goals, a committee composed of engineers from a variety of fields along with composition studies experts from the Undergraduate Rhetoric Program developed a curriculum designed to focus on introducing engineers to relevant genres and types of writing prominent in many kinds of engineering. The “Writing in Engineering Fields” course, designed to mirror the university’s first-year composition course, aims to inculcate these skills in a single semester. Writing assignments will include genres such as lab reports, abstracts, problem statements, technical instructions, and more “public”-oriented kinds of engineering writing. Also included are rhetorical reflections that ask students to consider the choices made in their own writing and to understand writing as a process in which they engage.

The course is structured so that students begin with an introduction to the Grand Challenges concepts, culminating in an assignment that asks students to analyze the written and rhetorical choices made across three texts that reflect a particular Grand Challenge concern, along with a rhetorical reflection. In addition, students will be introduced to the purposes and aims of writing as an engineer, as well as being introduced to the variety of writing genres engineers must master. The course continues into a second unit focused on writing that is primarily written by engineers to be read by other engineers, and includes discussion/study of genres such as problem statements, “state-of-art” reviews, and technical instructions, among others. This middle unit culminates in two different major assignments, a set of technical instructions and a ”state-of-art” review for the student’s chosen engineering field, each also having a rhetorical reflection attached. The final unit shifts to considering how engineers must be capable of writing towards non-engineering audiences as well as technically knowledgeable audiences, so this unit returns to asking students to consider the rhetorical choices required, culminating in a “remix” of an earlier assignment into a different, more public genre.

The course efficacy in achieving established goals will be assessed through a series of short surveys designed to evaluate students’ attitudes toward and perceptions of technical writing, along with an assessment of students’ proficiency in writing by a panel of faculty judges drawn from both the English and Engineering. The control group will consist of student volunteers taking the traditional first-year academic writing course and students who received no first-year writing instruction.

We believe that engineering students, some of whom may have tested out of the first-year composition requirements before their arrival, will find this course more relevant and engaging and will challenge the myth of engineers being poor or disinterested writers. In the longer term, professors in the students’ particular engineering disciplines will be better able to address specific, highly technical engineering genres, as their students will have been introduced to many of them, as well as to rhetorical and genre principles of writing in general.

Overcoming Difficulties in Research Statement Preparation for the Academic Job Search: Expansion of a Peer-Focused Professional Development Program

Engineering Education
Kaitlin I Tyler, Yanfen Li, Nicole D. Jackson, Wan-Ting Chen, Chaoyang Liu, Rohit Bhargava
Paper presented at 2017 ASEE Annual Conference & Exposition, Columbus, Ohio.
Publication year: 2017

According to data from ASEE, women were awarded 23.1% of engineering doctoral degrees and held 15.7% of tenured/tenure-track faculty positions in 2015 versus 21.3% and 12.7% in 2009, respectively 1,2. This slight increase over six years is encouraging but also serves to highlight the continuing paucity of female engineering faculty. The causes are multifaceted, including a perceived lack of academic work-life balance, a diminished self-confidence after a PhD, and a lack of existing role models. To combat this problem, graduate students and faculty at a large public university started a multi-month professional development program designed to strengthen the preparation of prospective female faculty candidates. The main goal of the program is to address the gender gap in engineering academia by knowledge dissemination in a collaborative community. We strive to provide information to our participants through seminars and panel discussions, followed by peer review groups to share and review application materials. This is the third iteration of the program and significant changes have been made to further increase its efficacy. One major development is expanding the research statement segment of our programming. In this paper, we examine the effectiveness of this new structure and explore in further detail how to successfully break down the research statement writing process into tangible segments. Lastly, we explore the differences between the two structures and make preliminary comments on the success of our program’s expansion.

Matrix Mechanics Influence Fibroblast–Myofibroblast Transition by Directing the Localization of Histone Deacetylase 4

Yanfen Li, Claire B. Tang, Kristopher A. Kilian
Cellular and Molecular Bioengineering, Pages 1-11
Publication year: 2017

Introduction—The propagation of mechanochemical signals from the extracellular matrix to the cell nucleus has emerged as a central feature in regulating cellular differentiation and de-differentiation. This process of outside-in signaling and the associated mechanotransduction pathways have been well described in numerous developmental and pathological contexts. However, it remains less clear how mechanotransduction influences the activity of chromatin modifying enzymes that direct gene expression programs.

Objectives—The primary objective of this study was to explore how matrix mechanics and geometric confinement influence histone deacetylase (HDAC) activity in fibroblast culture. Methods—Polyacrylamide hydrogels were formed and functionalized with fibronectin patterns using soft lithography. Primary mouse embryonic fibroblasts (MEFs) were cultured on the islands until confluent, fixed, and immunolabeled for microscopy.

Results—After 24 h MEFs cultured on soft hydrogels (0.5 kPa) show increased expression of class I HDACs relative to MEFs cultured on stiff hydrogels (100 kPa). A member of the class II family, HDAC4 shows a similar trend; however, there is a pronounced cytoplasmic localization on soft hydrogels suggesting a role in outside-in cytoplasmic signaling. Pharmacological inhibitor studies suggest that the opposing activities of extracellular related kinase 1/2 (ERK) and protein phosphatase 2a (PP2a) influence the localization of HDAC4. MEFs cultured on the soft hydrogels show enhanced expression of markers associated with a fibroblast– myofibroblast transition (Paxillin, aSMA).

Conclusions—We show that the phosphorylation state and cellular localization of HDAC4 is influenced by matrix mechanics, with evidence for a role in mechanotransduction and the regulation of gene expression associated with fibroblast–myofibroblast transitions. This work establishes a link between outside-in signaling and epigenetic regulation, which will assist efforts aimed at controlling gene regulation in engineered extracellular matrices.

Keeping Current: An Update on the Structure and Evaluation of a Program for Graduate Women Interested in Engineering Academia

Engineering Education
Nicole D. Jackson, Kaitlin I. Tyler, Yanfen Li, Wan-Ting Chen, Chaoyang Liu, Rohit Bhargava
Paper presented at 2017 ASEE Annual Conference & Exposition, Columbus, Ohio.
Publication year: 2017

According to data from the ASEE, women were awarded 23.1% of doctoral degrees and held 15.7% of tenured/tenure-track faculty faculty positions in 2015 versus 21.3% and 12.7% in 2009, respectively [1, 2]. While promising, the “leaky pipeline” remains a persistent problem in the recruitment of underrepresented people into tenure track positions. To help overcome this barrier, we have created a program to improve the competitiveness of underrepresented applicants in the tenure-track faculty recruitment process at a large public university. The program activities are two-fold. First, seminars and panel discussions led by faculty representing different engineering disciplines cover a variety of topics related to the job search process. Second, peer review sessions over the course of several months allow students to develop their own application materials. Since its founding in 2014, the program has been evaluated by considering four elements: content, format, pace, and climate. The evaluations in the first two years were based on conducting pre-, mid-, and post-surveys as well as voluntary one-on-one exit interviews. For the program’s third year, we made significant changes based on past participant feedback. Specific topics were expanded to increase understanding and improve familiarity with the application process. The evaluation structure was revised to increase immediate feedback. In this paper, we discuss how the program has evolved over the three years as well as how our methods for program monitoring have been revised. By incorporating these changes, we aim to continue to prepare high quality female faculty candidates, thereby diminishing the gender gap in engineering academia.

Cytoskeletal Priming of Mesenchymal Stem Cells to a Medicinal Phenotype

Amr A Abdeen*, Junmin Lee*, Yanfen Li, Kristopher A Kilian
Regenerative Engineering and Translational Medicine, 2017, 3, 5-14
Publication year: 2017

Mesenchymal stem cell (MSC) therapy is a promising approach for the treatment of cardiovascular disease, demonstrating pronounced trophic, immunomodulatory, and pro-angiogenic activity. However, clinical efficacy has suffered from broad variability, presumably due to cell death upon implantation, and the heterogeneous population of autologous cells. Micropatterning single cells in the same geometry can normalize the phenotype in a population, and variations in subcellular curvature will guide focal adhesion, cytoskeletal organization, and the regulation of distinct epigenetic marks to orchestrate a medicinal secretome. Within 2 days, activated cells show elevated expression of pericyte markers and will recapitulate functional pericyte activity through enhanced association with endothelial cell tubules in co-culture. MSCs are believed to undergo a temporary switch in vivo to an activated state in response to injury; thus, we propose engineering actomyosin contractility after isolation can similarly activate MSCs, which may serve as a general approach to prime a medicinal phenotype for cell-based therapies.

"Blinded" Grading Rubrics for Bioengineering Lab Reports (Work in Progress)

Engineering Education
Yanfen Li, Philip A. Jensen, Paul Anthony Jensen, Karin Jensen
Paper presented at 2017 ASEE Annual Conference & Exposition, Columbus, Ohio.
Publication year: 2017

Large introductory laboratory courses are often assessed with a large number of written assignments requiring multiple graders. Consistency between graders for lab reports is an important issue for both students and instructors in order to maintain accuracy and fairness. This challenge is enhanced by the need for graduate student teaching assistants who often receive limited instruction on grading and have little or no experience grading technical writing documents. When presented with detailed rubrics, graders have preconceived notions about the definitions of “satisfactory” or “unsatisfactory” or similar descriptors and how these evaluations equate to a numeric grade. Even detailed rubrics that provide point designations for each item can result in inconsistent grading if graders have a preconceived notion of the overall score range that a report should fall into. To address these challenges, we propose using a “blinded” rubric where graders are encouraged to assess assignments only by qualitative descriptions on a rubric and not assign quantitative scores or points. Pre-assigned point designations for each statement on the rubric are then applied after the grader has evaluated all the reports. We hypothesize that this process will increase inter-grader consistency, increase grader confidence in evaluating work, and reduce overall grading time. We piloted this approach in a sophomore bioengineering laboratory course that employed three graduate student teaching assistants. Our preliminary results indicate that grader consistency increased using the blinded rubric system. Graders also reported greater confidence in their assessments. Further, graders reported spending less time grading assignments when they were asked only to select qualitative statements and not assign quantitative point values for their selection on the rubric. We are currently assessing student perceptions of this grading process, including fairness of the system and whether or not blinding graders to the initial point designations will encourage student-grader conversations to focus on the evaluations instead of points deducted.

Progesterone Alleviates Endometriosis via Inhibition of Uterine Cell Proliferation, Inflammation and Angiogenesis in an Immunocompetent Mouse Model

Comparative Bioscience
Yanfen Li* , Malavika K. Adur* , Athilakshmi Kannan, Juanmahel Davila, Yuechao Zhao, Romana A. Nowak, Milan K. Bagchi, Indrani C. Bagchi, Quanxi Li
Public Library of Science, 2016, 11 (10), e0165347
Publication year: 2016

Endometriosis, defined as growth of the endometrial cells outside the uterus, is an inflammatory disorder that is associated with chronic pelvic pain and infertility in women of childbearing age. Although the estrogen-dependence of endometriosis is well known, the role of progesterone in development of this disease remains poorly understood. In this study, we developed a disease model in which endometriosis was induced in the peritoneal cavities of immunocompetent female mice, and maintained with exogenous estrogen. The endometriosis-like lesions that were identified at a variety of ectopic locations exhibited abundant blood supply and extensive adhesions. Histological examination revealed that these lesions had a well-organized endometrial architecture and fibrotic response, resembling those recovered from clinical patients. In addition, an extensive proliferation, inflammatory response, and loss of estrogen receptor alpha (ERα) and progesterone receptor (PR) expression were also observed in these lesions. Interestingly, administration of progesterone before, but not after, lesion induction suppressed lesion expansion and maintained ERα and PR expressions. These progesterone-pretreated lesions exhibited attenuation in KI67, CD31, and pro-inflammatory cytokine expression as well as macrophage infiltration, indicating that progesterone ameliorates endometriosis progression by inhibiting cell proliferation, inflammation and neovascularization. Our studies further showed that suppression of global DNA methylation by application of DNA methyltransferase inhibitor to female mice bearing ectopic lesions restrained lesion expansion and restored ERα and PR expression in eutopic endometrium and ectopic lesions. These results indicate that epigenetic regulation of target gene expression via DNA methylation contributes, at least in part, to progesterone resistance in endometriosis.

Patterned porous silicon photonic crystals with modular surface chemistry for spatial control of neural stem cell differentiation

Tiffany H. Huang*, Yi Pei*, Douglas Zhang, Yanfen Li, and Kristopher A. Kilian
Nanoscale, 2016, 8, 10891-10895.
Publication year: 2016

We present a strategy to spatially define regions of gold and nanostructured silicon photonics, each with materials-specific surface chemistry, for azide–alkyne cycloaddition of different bioactive peptides. Neural stem cells are spatially directed to undergo neurogenesis and astrogenesis as a function of both surface properties and peptide identity.

Preparing Female Engineering Doctoral Students for the Academic Job Market Through a Training Program Inspired by Peer Review

Engineering Education
Yanfen Li, Danielle J. Mai, Elizabeth M. Horstman, Rohit Bhargava
Paper presented at 2015 ASEE Annual Conference & Exposition, Seattle, Washington. 10.18260/p.24584
Publication year: 2015

According to data collected by the National Science Foundation, women were conferred roughly 40% of doctoral degrees in STEM fields from 2002-2012, yet in 2010, women accounted for only 27% of tenure-track assistant professorships in engineering.1 The ‘leaky pipeline’ of women in STEM fields remains an ongoing discussion, with potential causes including student impressions of work-life balance in academia, a lack of role models in engineering, and decreased self-confidence following a doctoral degree. The Graduate Committee of the Society of Women Engineers (GradSWE) at the University of Illinois at Urbana-Champaign has launched a program to specifically target the gender gap in engineering by improving the strength of faculty position applications from female doctoral students. The Illinois Female Engineers in Academic Training (iFEAT) is a multi-month program designed to strengthen the applications of female faculty candidates. Specifically, iFEAT provides informational resources for prospective faculty candidates through seminars and panel discussions, followed by peer review groups for students to share and review application materials. iFEAT aims to address several causes of the ‘leaky pipeline’ by increasing candidate confidence, introducing students to role models, and changing student perceptions of academic life. The program also aims to foster a supportive community through increased trainee interactions with faculty and peers. The peer review groups also provide opportunities for trainees to learn from each other, find mentors, and establish future relationships. Twelve female doctoral students were selected as iFEAT trainees based on their academic record, standing in their graduate program, and demonstrated commitment to academia. Surveys administered at the beginning, mid-point, and end of the program request trainees to self-report their aspirations and intentions for the academic job search, the progress of their application materials, and their confidence level in the application process. We seek to quantify any changes in the trainees’ goals, perceived preparation levels, and confidence levels throughout the program. As trainees progress through iFEAT and gain information about the application process, we will note shifts in perception of the most challenging and most important components of the application process. We will also monitor any changes in trainee career aspirations, including candidates’ preferred type(s) of institutions and academic positions, plans to conduct postdoctoral research, and anticipated application timeline. Trainees are also given the option to participate in a post-program interview, which is intended to uncover the reasoning behind any confirmations of or major changes in career plans and perceptions. Ultimately, we seek to track student outcomes from the program and uncover factors that may contribute to or prevent the ‘leaky pipeline’ of female engineers in academia.

Bridging the gap: from 2D cell culture to 3D microengineered extracellular matrices

Yanfen Li, Kristopher A Kilian
Advanced Healthcare Materials, 2015, 4 (18), 2780-2796.
Publication year: 2015
Historically the culture of mammalian cells in the laboratory has been
performed on planar substrates with media cocktails that are optimized to
maintain phenotype. However, it is becoming increasingly clear that much of
biology discerned from 2D studies does not translate well to the 3D micro-
environment. Over the last several decades, 2D and 3D microengineering
approaches have been developed that better recapitulate the complex
architecture and properties of in vivo tissue. Inspired by the infrastructure
of the microelectronics industry, lithographic patterning approaches have
taken center stage because of the ease in which cell-sized features can be
engineered on surfaces and within a broad range of biocompatible materials.
Patterning and templating techniques enable precise control over extracel-
lular matrix properties including: composition, mechanics, geometry, cell–
cell contact, and diffusion. In this review article we explore how the fi eld
of engineered extracellular matrices has evolved with the development of
new hydrogel chemistry and the maturation of micro- and nano- fabrication.
Guided by the spatiotemporal regulation of cell state in developing tissues,
techniques for micropatterning in 2D, pseudo-3D systems, and patterning
within 3D hydrogels will be discussed in the context of translating the infor-
mation gained from 2D systems to synthetic engineered 3D tissues.

A Program for Graduate Women in Engineering Pursuing Academic Careers (iFEAT: Illinois Female Engineers in Academia Training)

Engineering Education
Elizabeth M. Horstman, Danielle J. Mai, Yanfen Li, Rohit Bhargava
Paper presented at 2015 ASEE Annual Conference & Exposition, Seattle, Washington. 10.18260/p.23429
Publication year: 2015

According to data collected by the National Science Foundation, women were conferred roughly 40% of doctoral degrees in STEM fields from 2002-2012, yet in 2010, women accounted for only 27% of tenure-track assistant professorships in engineering.1 While the gender gap in STEM fields remains an ongoing discussion,2-4 programs that provide resources and support for female engineering doctoral students interested in pursuing academic careers may help to address this gap. The University of Illinois at Urbana-Champaign regularly hosts seminars and afternoon-long workshops for doctoral students to learn about the academic job application process. Although these seminars and workshops are effective at disseminating information, they do little to encourage students to seriously consider, prepare for, and apply to faculty positions. To address the aforementioned issue, the Graduate Committee of the Society of Women Engineers (GradSWE) at Illinois developed the Illinois Female Engineers in Academia Training (iFEAT) program. iFEAT is a multi-month program with seminars and panel discussions, which are geared toward informing participants about the academic job application process, and independent peer review groups, which provide feedback on prepared application materials. Specific aims of iFEAT are for participants to demonstrate increased knowledge of the faculty position application process, to prepare tangible application materials, and to increase confidence in their application packages. To ensure program development, iFEAT will be evaluated primarily based on program (i)content, (ii) format, (iii) pace, and (iv) climate. The program structure was designed to encourage communication and camaraderie among participants and faculty. Approximately every 3 weeks,students will attend a seminar or faculty panel discussion. Between each of these major events,student peer review groups will share and review application materials. Seminars will provide information about applying for a faculty position, tailoring cover letters to specific job postings,understanding (or developing) a teaching philosophy, applying for funding (transforming a research statement into a funding proposal), and determining ideal recommenders (learning to cultivate relationships with potential recommenders). Panel discussions will widen students’perspectives toward developing a unique research statement, understanding the interview process, and negotiating a start-up package. Independent peer review groups will provide the primary form of feedback on application materials. Near the end of the program, students will‘submit’ their application packages to a different peer group that will act as a ‘search committee.’All members of the ‘search committee’ will read other applicants’ packages and provide anonymous feedback to the applicants. This process will help students better understand how search committees operate, as well as broaden the scope of their teaching and research statements. At the end of iFEAT, students will have a peer-reviewed draft of application materials, as well as access to professors who support the development and advancement of female faculty in engineering. Through iFEAT, we hope to increase the representation of women in academia, as well as improve the competitiveness of Illinois graduates seeking academic careers.

Cardiorespiratory fitness mediates the effects of aging on cerebral blood flow

Benjamin Zimmerman, Bradley P Sutton, Kathy A Low, Mark A Fletcher, Chin Hong Tan, Nils Schneider-Garces, Yanfen Li, Cheng Ouyang, Edward L Maclin, Gabriele Gratton, Monica Fabiani
Frontiers in aging neuroscience, 2014, 6, 59
Publication year: 2014

The brain’s vasculature is likely to be subjected to the same age-related physiological and anatomical changes affecting the rest of the cardiovascular system. Since aerobic fitness is known to alleviate both cognitive and volumetric losses in the brain, it is important to investigate some of the possible mechanisms underlying these beneficial changes. Here we investigated the role that estimated cardiorespiratory fitness (eCRF) plays in determining the relationship between aging and cerebral blood flow (CBF) in a group of older adults (ages 55–85). Using arterial spin labeling to quantify CBF, we found that blood flow in the gray matter was positively correlated with eCRF and negatively correlated with age. Subsequent analyses revealed that eCRF fully mediated the effects of age on CBF in the gray matter, but not in the white matter. Additionally, regional measures of CBF were related to regional measures of brain volume. These findings provide evidence that age-related effects on cerebrovascular health and perfusion in older adults are largely influenced by their eCRF levels.

Basigin null mutant male mice are sterile and exhibit impaired interactions between germ cells and Sertoli cells

Comparative Bioscience
Jiajia Bi, Yanfen Li, Fengyun Sun, Anja Saalbach, Claudia Klein, David J Miller, Rex Hess, Romana A Nowak
Developmental biology, 2013, 380 (2), 145-156
Publication year: 2013

Basigin (BSG) is a multifunctional glycoprotein that plays an important role in male reproduction since male knockout (KO) mice are sterile. The Bsg KO testis lacks elongated spermatids and mature spermatozoa, a phenotype similar to that of alpha-mannosidase IIx (MX) KO mice. MX regulates formation of N-acetylglucosamine (GlcNAc) terminated N-glycans that participate in germ cellSertoli cell adhesion. Results showed that Bsg KO spermatocytes displayed normal homologous chromosome synapsis and progression through meiosis. However, only punctate expression of the round spermatid marker SP-10 in the acrosomal granule of germ cells of Bsg KO mice was detected indicating that spermatogenesis in Bsg KO mice was arrested at the early round spermatid stages. We observed a large increase in the number of germ cells undergoing apoptosis in Bsg KO testes. Using lectin blotting, we determined that GlcNAc terminated N-glycans are linked to BSG. GlcNAc terminated N-glycans were significantly reduced in Bsg KO testes. These observations indicate that BSG may act as a germ cell-Sertoli cell attachment molecule. Loss of BSG significantly reduced adhesion between GC-2 and SF7 cells. Moreover, wild type testes showed strong expression of N-cadherin (CDH2) while expression was greatly reduced in the testes of Bsg KO mice. In addition, the integrity of the blood-testis barrier (BTB) was compromised in Bsg KO testes. In conclusion, although some Bsg KO spermatogonia can undergo normal progression to the spermatocyte stage, BSG-mediated germ cell-Sertoli cell interactions appear to be necessary for integrity of the BTB and spermatocyte progression to mature spermatozoa.