While both macrophages and cardiomyocytes were observed to align parallel to the direction of strain, other cell types have been reported to align perpendicular to cyclic strain. For example, several studies have shown perpendicular alignment of smooth muscle cells, endothelial cells, and fibroblast when exposed to cyclic stretch. Cardiomyocytes have also been reported to align perpendicular to stretch, but only if cells were cultured for longer periods of time prior to the initiation of stretch. The orientation of cells in response to cyclic stretch is thought to be attributed in part to the frequency of stimulation: it is thought that low frequency strains allow time for cells to relax, and as a result, they align parallel to the applied strain. High frequency strains, on the other hand, do not allow time for relaxation, and thus, the cells align perpendicularly to minimize the force applied on them. This theory, however, is limited to stationary mechanically active cells, such as muscle cells and fibroblasts, and has yet to be shown in other cell types. The response of cells to cyclic stretch, therefore, is dependent on a number of factors of which include cell type, time of culture, and frequency of applied of strain.The design, building, and validation of the uniaxial cell stretcher, along with mechanobiological testing of the effects of cyclic stretch on different cell types, was demonstrated to have a positive impact on the learning experience of undergraduate students. Through their involvement on this project, the students perceived that they gained valuable skills and knowledge and experiences necessary to make informed career decisions. Nonetheless,curing cannabis the learning experience can still further be improved by implementing a few changes based on suggestions from the involved students.

For example, most of the students desired additional education in mechanobiology when first starting this project, as few were aware of the impact of mechanical forces in influencing cell function. This could be implemented through classroom learning in mechanobiology, which together with the project would promote foundational understanding, and help students formulate independent research questions and interests. Students also found that working with cells as well as the stretchers and stretchable membranes was challenging at first and wanted to have more time to practice basic techniques prior to running experiments. Again, a formal course with laboratory cell culture work may provide additional opportunities for practicing basic techniques. Finally, the students involved in this project suggested further collaboration between labs, particularly for the cell experiments, as conducting research on multiple cell types may have enhanced their learning experience in cell mechanobiology. We propose that this mechanical stretching device can serve as a platform for experiential learning for undergraduates in mechanobiology. This could be carried out as an independent research project by a group of 4–5 students, as was performed here, or could be scaled up to a laboratory course offered in conjunction with classroom learning. For the former, we believe that a few labs with long-range interest in mechanobiology of cells could collaborate to have an undergraduate student from each lab constitute a team that can mentor younger recruits. This was an extremely successful model in our experience, and provides the students with mentoring and project management experience, valued in both industry and graduate programs. Undergraduate involvement in research has previously been shown to have a positive impact on student learning and development.

Students who were involved in research perceived greater enhancement of cognitive and personal skills were more likely to pursue graduate degrees, and were more likely to have a faculty member play an important role on their career decisions, thus highlighting the impact of faculty involvement in undergraduate growth. While there are many perceived benefits of undergraduate involvement in research, there are some challenges associated with implementing the proposed project in the research environment. For example, differences in the requirements posed by each engineering curriculum could limit the time available to some students to work on this project as part of an interdisciplinary team. A potential solution to this challenge would be to provide a platform, such as through a course with both lecture and laboratory components, in which the requirements of all engineering disciplines can be satisfied. For implementing this project in a classroom setting, we anticipate at least three modules, which could take place across several semesters or quarters over the course of one year. In the first module, students would gain experience in device design and fabrication using software such as SOLIDWORKS and basic machine shop tools. The second module would encompass device validation and basic cell culture skills needed to perform biological experiments. Students would use image analysis and software such as IMAGEJ to analyze videos and measure strains applied to stretchable membranes. In addition, students would learn aseptic cell culture technique and grow cells on culture wells fabricated on membranes. Finally, the project would culminate in the third module with hypothesis-driven experimental studies. Students would develop hypotheses based on the literature and test them experimentally using their fabricated device. Through project-based learning, students have been shown to develop critical and innovative thinking and improved learning. Therefore, we propose that implementation of this project in the classroom would provide a novel experience for students in learning about cell mechanobiology.

Project-based classes are already offered at UCI, although none incorporate biological experimentation. For example, the Engineering seven series, which contains both a lecture and laboratory component, students design, build, and test a quadcopter, fitness tracker, or a microfluidic chip. The project described here can be implemented using this course framework but would likely require more than one academic quarter to complete design, fabrication, and cell-based experiments. Alternatively, the project can be integrated directly into UCI’s biomedical engineering curriculum, where undergraduate students are already required to learn CAD software and the basics of fabrication during their second year. An additional course would follow, where students learn about fundamentals in cellular mechanobiology and use their fabricated device in cell-based experiments. While a large-scale course may have broader impact and accommodate many students, the project may not have the same impact as an undergraduate research project where faculty-student interactions may be more predominant. Faculty involvement and direction in creating an experience similar to that of within the research environment would be critical in order to ensure student development and growth. Nonetheless, in any of the aforementioned formats, this project would provide students experiential learning in mechanical design and fabrication, testing and validation, and biological experimental design. The process involved in designing, fabricating, and validating a cell stretching platform and then using the created device to study the effects of mechanical strain on different cell types provides undergraduate students with unique experiences in learning cell mechanobiology. While experiential- and project-based learning may be prevalent in other engineering disciplines, biomedical engineering has traditionally followed a theory-based instructional model, which limits practice in applying expertise and knowledge gained to new contexts. This project not only offers undergraduate students experience in engineering design but also provides experience in cell and tissue culture and biological experimental design, both of which are difficult to obtain in a standard biomedical engineering curriculum. In addition, the process of working in interdisciplinary teams,how to dry cannabis presenting to different audiences, and interacting with graduate students and faculty helped undergraduate students to gain valuable knowledge and skills to improve learning and also help make informed career decisions. Ongoing efforts to improve the device including development of multi-well substrates for testing of many different conditions, modification of the device base to allow visualization of cells by microscopy during stretch, or addition of a three-dimensional hydrogel to the substrate to render a more physiological micro-environment for cells. The described device may be used for both research and educational purposes, as a low-cost, easy to build and maintain, hands-on experience for learning of how mechanical forces regulate cellular structure and function.Among young adults in the United States, cigarette smoking and marijuana use are strongly associated. In 2011, 36% of U.S. cigarette smokers aged 18–25 had used marijuana in the past month, almost three times the rate of the general adult population . A systematic review of studies of cigarette and marijuana co-use in adolescence and young adulthood found consistently significant associations .

There is also a reverse relationship, whereby those who use marijuana in early young adulthood are more likely to initiate cigarettes use and have a greater likelihood of developing nicotine dependence than their non-marijuana using peers . Combined smoking of cigarettes and marijuana in young adulthood has been associated with worse health outcomes than smoking either substance alone . There are multiple suggested mechanisms underlying the co-use of cigarettes and marijuana including both genetic and environmental factors . Limited research has focused directly on cognitive factors sustaining co-use, but cigarette and marijuana co-use may be perpetuated in part by similar beliefs about the two substances or that one substance supports the use of another. For example, in a study of 233 college students who smoked both cigarettes and marijuana, 65% smoked both substances in the same hour; 31% smoked cigarettes to prolong and sustain the effects of marijuana; and 55% had friends who engaged in these behaviors, suggesting that use is related both behaviorally and socially . Another explanation for perpetuation of co-use includes a phenomenon called “blunt chasing,” or the smoking of a cigarillo or cigar following a blunt , which reportedly increases the sense of euphoria from taking these drugs .The two most commonly used addictive substances among young adults, there is a need to examine whether behaviors and thoughts related to cigarettes and marijuana are similar among those who use both substances. If use and constructs associated with reducing use relate similarly across substances, it would support interventions that target both drugs simultaneously. Motivation to quit smoking cigarettes and marijuana is generally low among young adults , suggesting that the Transtheoretical Model of behavior change may be particularly appropriate to understand co-use of these substances. The TTM includes three interrelated constructs: stages of change, temptations to use, and decisional balance , that have been used to describe cigarette smoking and predict quitting . Our development and earlier analysis of a staging scale for marijuana use was found to relate to concurrent frequency of marijuana use, temptations to use, and cons of using marijuana, consistent with what has been found in the cigarette smoking literature . Among young people, relapse to cigarettes and marijuana use is also high among those who have made a quit attempt. For example, in a review of 52 studies, median rates of smoking relapse among adolescents aged 20 or young who made a cessation attempt were 34% after one week and 89% after 6 months . In a study of 385 marijuana users who had made a self-initiated quit attempt, 88% had relapsed within 5 years . Constructs of thoughts about abstinence, including desire to quit, perceived success at quitting, difficulty with staying quit, and abstinence goals, as originally described in Marlatt’s Relapse Prevention model , are also predictive of cigarette and other substance use outcomes and related to TTM constructs . Applied to marijuana, the thoughts about abstinence items assessing desire to quit, perceived success, anticipated difficulty, and abstinence goal correlated significantly with frequency of marijuana use and stage of change . Young people may think differently about their cigarette smoking and marijuana use. For example, the 2011 National Survey of Drug Use and Health showed that, 66% of youth age 12 to 17 perceived “great harm” from smoking one or more packs of cigarettes per day, compared to 45% for smoking marijuana once or twice a week . In a qualitative study of 99 adolescents who smoked cigarettes and marijuana, while most desired to quit smoking cigarettes at some point in the future, few intended to stop using marijuana . Conversely, among youth surveyed in an addictions treatment program, intention to quit smoking cigarettes was lower than intention to quit using drugs . Study of more representative samples is needed to explore cigarette and marijuana co-use patterns and cognitions. In a national, anonymous, cross-sectional survey of young adults who smoke cigarettes and use marijuana, the current investigation examined the relationship between: severity of use and quit attempts , thoughts about abstinence , and TTM constructs of stage of change, temptations, and decisional balance .