Characterization of the cardiogenesis of embryonic stem cells

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 114-127).Cardiovascular diseases persist as the leading cause of mortality worldwide. Stem cell therapy, aimed to restore contractility and proper vasculature, has gained considerable attention as an attractive therapeutic option. However, proper cell differentiation, survival and integration in an infarcted zone remain elusive. This thesis aims to utilize in vitro techniques to obtain a systematic characterization of how individual stimulations can affect the cardiogenesis process of embryonic stem cells. First, a compliant microfluidic system was developed to study the individual and combined effects of culture dimensions and uniaxial cyclic stretch on the differentiation process. A smaller culture dimension, with a characteristic length scale of hundreds of micrometers, dramatically enhanced differentiation partly due to an accumulation of cell-secreted and cardiogenic BMP2. Uniaxial cyclic stretch, on the other hand, inhibited differentiation. With this microfluidic platform and a GFP-reporting differentiation cell line, effects of various external stimuli on differentiation were systematically studied. Next, the effects of collagen I and cell alignment, two biophysical signatures of the adult myocardium, on promoting phenotypic changes of isolated embryonic stem cell derived cardiomyocytes (ESCDMs) were investigated. Effects of collagen I depended on how it was presented to the cells and overlaying collagen gel impeded cell elongation. Binucleation. characteristic of maturing cardiomyocytes, was reduced with soluble collagen supplement and nanoscale topography and was associated with an increase in cytokinesis. Both nanoscale topography and microcontact printing resulted in aligned cardiomyocyte monolayers but produced different morphologies. Lastly, the lessons learned from studying the aforementioned processes were applied to test the utility of ESCDMs as biological actuators. Three proof-of-concept experiments were conducted: ESCDM monolayers were able to contract synchronously as a cell-assemble, force generated by the cell monolayer was estimated to be comparable to that by neonatal myocytes and lastly, the direction of contraction could be controlled with surface patterning. This work advances our understanding on the cardiogenic potential of murine embryonic stem cells and elucidated complex biological questions with well-characterized and controlled tissue engineering techniques.by Chen-rei Wan.Ph.D

2010 IMSAloquium, Student Investigation Showcase

IMSA students engage in investigations in nanotechnology, particle physics, law, neonatal medicine, literature, transplantation biology, water purity, the educational achievement gap, neurobiology and memory, ethics, theatre, discrete mathematics, economics, and more.https://digitalcommons.imsa.edu/archives_sir/1002/thumbnail.jp

06. 2010 IMSAloquium Student Investigation Showcase

https://digitalcommons.imsa.edu/class_of_2010/1004/thumbnail.jp

Embryonic Stem Cells

Embryonic stem cells are one of the key building blocks of the emerging multidisciplinary field of regenerative medicine, and discoveries and new technology related to embryonic stem cells are being made at an ever increasing rate. This book provides a snapshot of some of the research occurring across a wide range of areas related to embryonic stem cells, including new methods, tools and technologies; new understandings about the molecular biology and pluripotency of these cells; as well as new uses for and sources of embryonic stem cells. The book will serve as a valuable resource for engineers, scientists, and clinicians as well as students in a wide range of disciplines

Removal of antagonistic spindle forces can rescue metaphase spindle length and reduce chromosome segregation defects

Regular Abstracts - Tuesday Poster Presentations: no. 1925Metaphase describes a phase of mitosis where chromosomes are attached and oriented on the bipolar spindle for subsequent segregation at anaphase. In diverse cell types, the metaphase spindle is maintained at a relatively constant length. Metaphase spindle length is proposed to be regulated by a balance of pushing and pulling forces generated by distinct sets of spindle microtubules and their interactions with motors and microtubule-associated proteins (MAPs). Spindle length appears important for chromosome segregation fidelity, as cells with shorter or longer than normal metaphase spindles, generated through deletion or inhibition of individual mitotic motors or MAPs, showed chromosome segregation defects. To test the force balance model of spindle length control and its effect on chromosome segregation, we applied fast microfluidic temperature-control with live-cell imaging to monitor the effect of switching off different combinations of antagonistic forces in the fission yeast metaphase spindle. We show that spindle midzone proteins kinesin-5 cut7p and microtubule bundler ase1p contribute to outward pushing forces, and spindle kinetochore proteins kinesin-8 klp5/6p and dam1p contribute to inward pulling forces. Removing these proteins individually led to aberrant metaphase spindle length and chromosome segregation defects. Removing these proteins in antagonistic combination rescued the defective spindle length and, in some combinations, also partially rescued chromosome segregation defects. Our results stress the importance of proper chromosome-to-microtubule attachment over spindle length regulation for proper chromosome segregation.postprin

Psr1p interacts with SUN/sad1p and EB1/mal3p to establish the bipolar spindle

Regular Abstracts - Sunday Poster Presentations: no. 382During mitosis, interpolar microtubules from two spindle pole bodies (SPBs) interdigitate to create an antiparallel microtubule array for accommodating numerous regulatory proteins. Among these proteins, the kinesin-5 cut7p/Eg5 is the key player responsible for sliding apart antiparallel microtubules and thus helps in establishing the bipolar spindle. At the onset of mitosis, two SPBs are adjacent to one another with most microtubules running nearly parallel toward the nuclear envelope, creating an unfavorable microtubule configuration for the kinesin-5 kinesins. Therefore, how the cell organizes the antiparallel microtubule array in the first place at mitotic onset remains enigmatic. Here, we show that a novel protein psrp1p localizes to the SPB and plays a key role in organizing the antiparallel microtubule array. The absence of psr1+ leads to a transient monopolar spindle and massive chromosome loss. Further functional characterization demonstrates that psr1p is recruited to the SPB through interaction with the conserved SUN protein sad1p and that psr1p physically interacts with the conserved microtubule plus tip protein mal3p/EB1. These results suggest a model that psr1p serves as a linking protein between sad1p/SUN and mal3p/EB1 to allow microtubule plus ends to be coupled to the SPBs for organization of an antiparallel microtubule array. Thus, we conclude that psr1p is involved in organizing the antiparallel microtubule array in the first place at mitosis onset by interaction with SUN/sad1p and EB1/mal3p, thereby establishing the bipolar spindle.postprin

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied