Thesis (M. Eng.)--Harvard-MIT Division of Health Sciences and Technology, 2004. / Includes bibliographical references (p. 76-77). / The focus of this study was to investigate the histology of tissue formed when fetal (16-20 days gestation) and neonatal (2 days old) rat lung cells were grown in a collagen-glycosaminoglycan scaffold. This project employed a collagen-GAG scaffold specifically developed for tissue engineering and investigated the effect of this substratum on the formation of lung histotypic structures in vitro. A cell isolation procedure was developed whereby 19-days gestation type II alveolar cells reaggregated to form alveolar-like structures. The effects of selected scaffold design variables including pore diameter and degradation rate of the substratum on lung tissue regeneration were explored. Lung cell behavior revealed as the cells interact with an analog of the extracellular matrix was also examined. Differences in fetal and neonatal lung cell behavior were identified using histological analysis. Lung cells were obtained from Sprague-Dawley rats after 16-, 19-, and 20-days of gestation and at 2 days after term. These cells were seeded into type I collagen-GAG matrices, sized 8mm in diameter by 2mm in thickness. The medium used, F12K and Ham's nutrient mixture, was supplemented with 10% fetal bovine serum. A seeding density between 1 to 5 million cells per sponge sample was used. Histology studies were performed at termination periods of 2, 14, and 28 days. This paper describes the in vitro formation and long-term maintenance of alveolar-like structures from enzymatically dissociated 19-days gestation fetal rat lung cells cultured on a collagen sponge substrate as a model system for lung tissue engineering. / by Patty P. Chen. / M.Eng.

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2007. / Includes bibliographical references (leaves 152-157). / There is a pressing need in minimally-invasive surgery for novel imaging methods that can rapidly and accurately localize the surgical instrument and its target. We have developed two novel localization methods for the guidance of cardiac ablation and other minimally-invasive therapies. The first method, the Inverse Solution Guidance Algorithm (ISGA), is for the non-invasive and rapid localization of the site of origin of an arrhythmia and an ablation catheter tip from body-surface ECG signals. We have substantially developed ISGA to provide accurate catheter guidance even in the presence of significant electrical inhomogeneities, and we have evaluated the method in numerical simulations and phantom studies. Due to the rapidity of arrhythmic origin localization, ISGA may prove a highly effective means of guiding the ablative therapy of hemodynamically-unstable VT. The second method, the Bioelectrical Image Guidance (BIG) Method, is a novel algorithm for the accurate and inexpensive guidance of a wide-range of minimally-invasive surgeries, from cardiac ablation to breast cancer biopsy. / (cont.) The surgical instrument is localized within a detailed 3-D MRI or CT image by applying currents to the body surface and comparing the potentials measured at the instrument tip with potential distributions simulated prior to the surgery. We have developed and evaluated this method in numerical simulations. We have also built an experimental guidance system and tested it in a phantom model. Our results indicate that the BIG Method may one day provide an accurate and convenient means by which to guide minimally-invasive surgery within a highly detailed anatomical image. / by Maya E. Barley. / Ph.D.

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008. / Includes bibliographical references (leaves 152-166). / Controlled-release drug-delivery systems enable efficient and defined administration of therapeutic agents to target tissues. However, ultimate drug distribution and pharmacologic effect are determined by target tissue pharmacokinetics. In muscular tissues, complex architecture that is further augmented by dynamic motion and contraction can alter the pharmacokinetics and deposition of locally delivered macromolecules. We developed a system and applied a quantitative schema to investigate the impact of controlled mechanical loads applied to skeletal and cardiac muscle tissue on intramuscular transport of locally delivered drug. In a series of studies, we examined how the interaction between architectural configuration and functional mechanics alters the transport of drugs across both physicochemical and binding properties. We correlated these pharmacokinetic effects with characteristic parameters in the physiologic range of the tissue to derive mechanistic insight into the fundamental structural and dynamic elements that underlie these effects. While previous studies have revealed the unilateral scaling of substrate uptake with mechanical influences, we elucidated an architecturally defined pharmacokinetic setpoint whereby maximal drug penetration corresponds with optimal muscle function. Our findings elucidate basic biologic design in muscle that optimizes the interface between tissue and its physical environment. The unique insights from our investigations have broad impact on current understanding of the pharmacokinetic influences of biologic form and function, and elucidate new clinical strategies for controlled release and local delivery of a wide range of therapeutic compounds to mechanically active tissues. / by Peter I-Kung Wu. / Ph.D.

Thesis (S.M.)--Harvard-MIT Division of Health Sciences and Technology, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 51-58). / It has become increasingly important for companies in the biopharmaceutical industry to maximize the clinical, commercial and economic impact of their products on a global scale. In this context, both Western and Asian firms have been engaging in international merger and acquisition (M&A) activities to improve global capabilities and competiveness. The M&A activities in the sector are driven by near-term expiration of blockbuster drug patents and marketplace pricing constraints, resulting in a perceived need to attain improved economies of scale. Across the industry, one can see an increased emphasis on biotechnology medicines (or biologics). Recent large business deals that have seen Pfizer acquire Wyeth, Merck acquire Schering-Plough and Roche complete the acquisition of Genentech all have some element of positioning around the exploitation of biologics for future growth. These trends are thought to put pressure on medium-/small-sized R&D firms to come up with competitive strategies in the global biologics market. Furthermore, the biologics market faces the threat of biosimilars (biogenerics or follow-on biologics). With the advent of expected changes in the US government healthcare policy, a number of companies will be facing competition from biosimilars in the near term. Mitigating the impact of the threat of biosimilars, to some extent, is the fact that manufacturing of most non-vaccine biologics is challenging because of the structural and biological complexity of the commercial product as well as the significant differences in the manufacturing process from one product to the next. Technical capacity and the ability to respond to shifting demands are likely to be one of the critical determinants for the success of individual companies in the biologics (and biosimilars) market. To meet the perceived needs, companies have either expanded their manufacturing capacity and capabilities by building inhouse facilities or by striking long-term supply deals through contract manufacturing organizations (CMOs). Utilizing highly efficient and cost-effective overseas biologics, CMOs could be a value-added business model for Western participants. The most dramatic cost-saving strategy would likely result from outsourcing operations to firms in emerging Asian countries like India and China. However, intellectual property protection and quality control issues have been considered problematic in these countries. In this context, other relatively well developed Asian countries-Japan, South Korea (referred to as Korea) and Singapore, which have relatively strong intellectual property protection and sophisticated manufacturing environments, might be strategic partners for Western firms in the contract biomanufacturing markets. In this research study, the current biopharmaceutical industry trends and global strategies of companies in Japan, Korea and Singapore were explored. As a sub-segment of the biopharmaceutical industry, the geographical features and defining characteristics of the biologics CMO market were examined. The framework for analysis was based on an assessment of the key contributing factors: capacity, capital and cost. The potential capabilities among emerging Asian participants in the global biologics CMO markets were assessed through personal interviews with senior/executive corporate managers of Asian domestic biopharmaceutical companies (principally Japanese and Korean firms). As the results indicate, the biopharmaceutical industry of each country has been influenced both by corporate strategy and government policy. The quantitative analyses show that the current biologics CMO market in these countries is underdeveloped with a few existing participants focusing on high-tech biomanufacturing of commercial products. In addition, the macro-and micro-environment of the biotechnology industry in these countries appears to be unfavorable for the development of a global biologics CMO market. Through individual interviews, it was found that biopharmaceutical corporate managers believe that the opportunities for growth/development of an Asian emerging CMO at the global level are modest, expressing the view that their direct presence in the biologics markets as global-scale CMO participants was unlikely to take place because of financial concerns (high risk investment and profit margin sharing), absence of a global network (no proven track record) and existence of an R&D-intensive corporate culture. In conclusion, while the capabilities of large and established domestic biopharmaceutical firms in these Asian countries certainly can meet regulatory, legal and technical requirements as emerging global CMO participants, the possibilities for development of a global CMO capability in these countries are likely to be small. Strategic considerations for the possible/likely development paths of the CMO market in these Asian countries are provided. / by Soo Jin Chun. / S.M.

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Metastasis, the migration of cancer cells from the primary site of tumorigenesis and the subsequent invasion of secondary tissues, causes the vast majority of cancer deaths. To spread, metastatic cells dramatically rearrange their shape in complex, dynamic fashions. Genes encoding signaling proteins that regulate cell shape in normal cells are often mutated in cancer, especially in highly metastatic disease. To study these key signaling proteins in locomotion and metastasis, we develop and validate statistical methods to extract information from highthroughput morphological data from genetic screens. Our contributions fall into three major categories. 1) To define and apply robust statistical measures to identify genes regulating morphological variability. We develop and thoroughly test methods for measuring morphological variability of single-cells populations, and apply these metrics to genetic screens in yeast and fly. We further apply these techniques to subsets of genes involved in cellular processes to study genetic contributions to variability in these processes. We propose new roles for genes as suppressors or enhancers of morphological noise. We validate our findings on the basis of known gene function and network architecture. 2) To perform inference of protein signaling relationships by utilizing high-throughput morphological data. We apply machine-learning techniques to systematically identify genetic interactions between proteins on the basis of image-based data from double-knockout screens. / (cont.) Next, we focus on RhoGTPases and RhoGTPase Activating Proteins (RhoGAPs) in Drosophila., where by using basic knowledge of network architecture we apply our techniques to detect signaling relationships. 3) To integrate expression data with high-throughput morphological data to study the mechanisms for determination of cell morphology. We utilize morphological and microarray data from fly screens. By comparing expression data between control treatment conditions and treatment conditions displaying morphological phenotypes (e.g. high population variability), we identify genes and pathways correlated with this class distinction, thereby validating our previous studies and providing further insight into the determination of morphology. A key challenge in systems biology is to analyze emerging high-throughput image-based data to understand how cellular phenotypes are genetically encoded. Our work makes significant contributions to the literature on high-throughput morphological study and describes a path for future investigation. / by Oaz Nir. / Ph.D.

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 211-225). / The cambium cells of the periosteum, which are known osteoprogenitor cells, have limited suitability for clinical applications of bone tissue engineering due to their low cell number (2-5 cells thick). Extracorporeal shock waves (ESWs) have been reported to cause thickening of the cambium layer and subsequent periosteal osteogenesis. This work proposes that ESW-therapy can be used as a non-invasive, inexpensive, and rapid method for stimulating cambium cell proliferation, and investigates the use of these cells for orthotopic bone growth. The response of periosteal cells to ESWs was evaluated using two different energy densities applied to either the intact femur or tibia of the rat. Just four days after application of ESWs, there was a significant 3- to 6-fold increase in cambium cell number and thickness. The most effective treatment of those tested was high dose ESW applied to the tibia. Immunohistochemical staining of the proliferated cells demonstrated osteoblasts and bone formation (osteocalcin stain); it also demonstrated extensive vonWillebrand factor expression, which reveals the vascular contribution to the proliferating cambium layer. In a rabbit model, ESW-thickened cambium layer cells were overlaid in situ on a porous calcium phosphate scaffold. At two weeks post-surgery, there was a significant increase in all outcome variables for the ESW-treated group when compared with controls: a 4-fold increase in osteoprogenitor tissue in the scaffold upper half, a 10- fold increase in osteoprogenitor tissue above the scaffold, and a 2-fold increase in callus size. The results successfully demonstrated the efficacy of ESW-stimulated periosteum for bone tissue engineering. / by Cathal John Kearney. / Ph.D.

Thesis (S.M.)--Harvard-MIT Division of Health Sciences and Technology, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 35-38). / Background: The optimal long-term antiplatelet therapy (APT) that balances the benefit of preventing myocardial infarction (MI) with the risk of severe bleeding is unknown in patients greater than one year after drug-eluting stent (DES) placement. Methods: We modeled life expectancy (LE) using published data by building a Markov model to compare several APT strategies composed of aspirin and clopidogrel, both as monotherapy and in various clinically plausible combinations. The base case examined a 65-year old person treated with a DES then continuous aspirin plus clopidogrel (Dual-Rx) for one year without complications. We considered risk of mortality from myocardial infarction and severe bleeding. We used a lifetime horizon and projected LE without quality-adjustment. Results: In the base-case analysis, APT yielding greatest LE was a toss-up between Dual-Rx indefinitely (LE of 13.48 years), clopidogrel indefinitely (LE of 13.45 years), and aspirin indefinitely (LE of 13.42 years); of the strategies considered, no APT was least preferred (LE of 13.36 years). All parameters were varied over plausible ranges in sensitivity analyses, including the duration of future treatment with clopidogrel (base-case, life long). The choice of APT remained a toss-up unless: the annual probability of MI fell below 0.0087 (base-case, 0.013) or the relative risk of systemic bleeding exceeded 1.52 (base case, 1.00), in which case clopidogrel indefinitely was preferred; or the efficacy of clopidogrel to prevent MI fell below 0.09 (base case, 0.20) or the relative risk of clopidogrel for severe gastrointestinal hemorrhage exceeded 3.33 (base case, 2.01), in which case aspirin indefinitely was preferred. Conclusions: For patients with a drug-eluting stent placed greater than one year ago, the antiplatelet therapy which yields the greatest life expectancy is a toss-up between dual antiplatelet therapy (clopidogrel plus aspirin indefinitely), clopidogrel indefinitely, and aspirin indefinitely. However, additional research (including a clinical trial, subgroup analysis, and modeling) is needed. / by J. Stewart Evans. / S.M.

Thesis (Sc. D.)--Harvard-MIT Division of Health Sciences and Technology, 2005. / Includes bibliographical references (p. 185-195). / Space-suited activity is critical for human spaceflight, and is synonymous with human planetary exploration. Space suits impose kinematic and kinetic boundary conditions that affect movement and locomotion, and in doing so modify the metabolic cost of physical activity. Metabolic requirements, found to be significantly elevated in space-suited activity, are a major driver of the allowable duration and intensity of extravehicular activity. To investigate how space suited locomotion impacts the energetics of walking and running, I developed a framework for analyzing energetics data, derived from basic thermodynamics, that clearly differentiates between muscle efficiency and energy recovery. The framework, when applied to unsuited locomotion, revealed that the human run-walk transition in Earth gravity occurs when energy recovery for walking and running are approximately equal. The dependence of muscle efficiency on gravity -during locomotion and under a particular set of assumptions- was derived as part of the framework. Next, I collected and transformed data from prior studies of suited and unsuited locomotion into a common format, and performed regression analysis. This analysis revealed that in reduced gravity environments, running in space suits is likely to be more efficient, per unit mass and per unit distance, than walking in space suits. Second, the results suggested that space suits may behave like springs during running. To investigate the spring-like nature of space suit legs, I built a lower-body exoskeleton to simulate aspects of the current NASA spacesuit, the Extravehicular Mobility Unit (EMU). / (cont.) Evaluation of the exoskeleton legs revealed that they produce knee torques similar to the EMU in both form and magnitude. Therefore, space suit joints such as the EMU knee joint behave like non-linear springs, with the effect of these springs most pronounced when locomotion requires large changes in knee flexion such as during running. To characterize the impact of space suit legs on the energetics of walking and running, I measured the energetic cost of locomotion with and without the lower-body exoskeleton in a variety of simulated gravitational environments at specific and self- selected Froude numbers, non-dimensional parameters used to characterize the run-walk transition. Exoskeleton locomotion increased energy recovery and significantly improved the efficiency of locomotion, per unit mass and per unit distance, in reduced gravity but not in Earth gravity. The framework was used to predict, based on Earth gravity data, the metabolic cost of unsuited locomotion in reduced gravity; there were no statistical differences between the predictions and the observed values. The results suggest that the optimal space-suit knee-joint torque may be non-zero: it may be possible to build a 'tuned space suit' that minimizes the energy cost of locomotion. Furthermore, the observed lowering of the self-selected run-walk transition Froude number during exoskeleton locomotion is consistent with the hypothesis that the run-walk transition is mediated by energy recovery. The major contributions of the dissertation include: 1. A model that predicts metabolic cost in non-dimensional form for unsuited locomotion across running and walking and across gravity levels, 2. / (cont.) An assessment of historical data that reveals the effect of pressure suits on work output and the metabolic cost of locomotion, 3. A method of simulating a space suit using a lower-body exoskeleton, and methods for designing and characterizing the exoskeleton, 4. An explanation for the differences in the energetic costs of walking and running in space suits, 5. Evidence that there is an optimal space suit leg stiffness, perhaps an optimal space suit leg stiffness for a given gravity environment, 6. Evidence, mostly indirect, that energy recovery plays a role in gait switching. / by Christopher Edward Carr. / Sc.D.

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2003. / Page 286 blank. / Includes bibliographical references. / Polyethylene wear is a significant clinical problem limiting the long-term survival of joint replacement prostheses, particularly in total hip arthroplasty (THA) and total knee arthroplasty (TKA). Although the tribology of joint replacement has consequently become an area of significant research, the effect of joint fluid on lubrication in the replaced joint has been largely overlooked. Several factors that affect the tribology of metal on polyethylene articulation in joint prostheses stem from the fluid lubricating the joint. In particular, the properties and composition of joint fluid likely contribute to fluid film lubrication and boundary lubrication in joint replacements, as they do in natural joints. The primary objective of this thesis is to examine the effect of natural variation in joint fluid composition and properties on friction, lubrication, and wear in joint arthroplasty. To achieve this goal, several parameters relating to the composition and mechanical properties of joint fluid are determined. Steady shear viscosity and linear viscoelastic properties of joint fluid are evaluated as indicators of its mechanical properties. Furthermore, concentrations of the hyaluronic acid, protein, and phospholipid in joint fluid are measured using standard biochemical techniques. / (cont.) The molecular weight of hyaluronic acid is also determined using size exclusion chromatography. These properties and components are evaluated in joint fluid from patients undergoing TKA and from patients undergoing surgical revision of an existing TKA (as well as from other patient groups). Results are considered in the context of previous studies of healthy and diseased synovial fluid. Correlations between and among components and flow properties are determined. Friction tests are performed on articulations between ultra-high molecular weight polyethylene (PE) and cobalt-chromium-molybdenum alloy (Co-Cr), materials commonly used in total joint replacement prostheses. These tests evaluate joint fluid samples as well as synthetic joint lubricants that are composed based on the range of compositions and properties determined. Certain components are found to increase friction in this articulation relative to water lubrication, but some joint fluid samples performed as well as bovine serum. / (cont.) Significant differences in tribology demonstrated by these experiments indicate that the composition of joint fluid affects the tribology of Co- Cr on PE joint prostheses, though the variability in friction could not be explained by physiological variation in the components examined. In related work, the relative importance of contact area and normal load is evaluated in the wear of a Co-Cr on PE articulation. Within a relevant range of contact stress, volumetric wear rate increased with increasing contact area, and was independent of normal load. The results of these tribological investigations are brought together in a conceptual framework under which to consider the wear of PE in TJA. / by Dan Mazzucco. / Ph.D.

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Growth and division are essential biological processes of cellular life. A crucial question concerning the origin of cellular life is how primitive cells (protocells) lacking complex biological machinery could grow and divide. To address this question, we first developed an effective method for preparing large monodisperse (uniform-sized) vesicles through a combination of extrusion and large-pore dialysis. The development of this preparation method has led us to the discovery of a simple but efficient pathway for the growth and division of the membrane envelope of a model protocell: growth of a large multilamellar fatty acid vesicle after being fed with fatty acid micelles leads to a series of remarkable shape transformations, from an initially spherical state to a long thread-like vesicle; under modest shear forces, the thread-like vesicle divides into multiple daughter vesicles. We have also discovered a different pathway that allows the long thread-like vesicles to divide without relying on external forces. Furthermore, in the course of studying fatty acid vesicles, we have discovered a striking phenomenon: intense illumination causes dye-packed vesicles of a few microns in diameter to explode, rapidly and locally releasing the encapsulated contents. The photoactivated release of substances from exploding vesicles in a highly spatio-temporally controlled manner suggests potential applications of this phenomenon in many areas across disciplines. / Ph.D.