Developmentally-Inspired Engineering Of An Inductive Biomaterial for Odontogenesis

Increasing demands for organ transplants and the depleting supply of available organs has heightened the need for alternatives to this growing problem. Tissue engineers strive to regenerate organs in the future; however doing so requires a fundamental understanding of organ development and its key processes. The first chapter of this thesis provides a brief overview of developmentally inspired engineering, specifically in the context of how I approach this challenge in this thesis. The second chapter provides an in depth review of current and past work focused on organ regeneration from a developmentally-inspired perspective, and using tooth formation as a model system. The third chapter describes the design and fabrication of a thermoresponsive polymer inspired by an embryonic induction mechanism, and demonstrates its ability to induce tooth differentiation in vitro and in vivo. This is effectively a 3D `shrink wrap'-like polymer sponge that constricts when it is warmed to body temperature and induces compaction of cells contained within it, hence recapitulating the mesenchymal condensation process that has been shown to be a key induction mechanism that triggers formation of various epithelial organs, including tooth in the embryo. The fourth chapter describes the fabrication of a novel microarray screening platform consisting of a unique set of ECM proteins (collagen VI, tenascin, and combination of the two at different coating densities) on an array of soft substrates (~130-1500 Pa) that are physiologically relevant to the embryonic microenvironment. This technology demonstrated the capacity to analyze combinatorial effects of these ECM proteins and soft substrates on cell density, cell area and odontogenic differentiation in murine mandible embryonic mesenchymal cells. The fifth chapter of this thesis summarizes and discusses the advantages, limitations and future potential of the findings described in the previous two chapters in the context of organ engineering and regeneration. Taken together, the work and results presented in this thesis have led to the development of new insights, approaches and tools for studying organ formation and potentially inducing organ regeneration, which are inspired by key developmental mechanisms used during embryonic organ formation.Engineering and Applied Science

A combinatorial cell-laden gel microarray for inducing osteogenic differentiation of human mesenchymal stem cells

Development of three dimensional (3D) microenvironments that direct stem cell differentiation into functional cell types remains a major challenge in the field of regenerative medicine. Here, we describe a new platform to address this challenge by utilizing a robotic microarray spotter for testing stem cell fates inside various miniaturized cell-laden gels in a systematic manner. To demonstrate the feasibility of our platform, we evaluated the osteogenic differentiation of human mesenchymal stem cells (hMSCs) within combinatorial 3D niches. We were able to identify specific combinations, that enhanced the expression of osteogenic markers. Notably, these ‘hit' combinations directed hMSCs to form mineralized tissue when conditions were translated to 3D macroscale hydrogels, indicating that the miniaturization of the experimental system did not alter stem cell fate. Overall, our findings confirmed that the 3D cell-laden gel microarray can be used for screening of different conditions in a rapid, cost-effective, and multiplexed manner for a broad range of tissue engineering applications

Developmentally-Inspired Shrink-Wrap Polymers for Mechanical Induction of Tissue Differentiation

A biologically inspired thermoresponsive polymer has been developed that mechanically induces tooth differentiation in vitro and in vivo by promoting mesenchymal cell compaction as seen in each pore of the scaffold. This normally occurs during the physiological mesenchymal condensation response that triggers tooth formation in the embryo.Chemistry and Chemical Biolog

Mechanical induction of dentin-like differentiation by adult mouse bone marrow stromal cells using compressive scaffolds

Tooth formation during embryogenesis is controlled through a complex interplay between mechanical and chemical cues. We have previously shown that physical cell compaction of dental mesenchyme cells during mesenchymal condensation is responsible for triggering odontogenic differentiation during embryogenesis, and that expression of Collagen VI stabilizes this induction. In addition, we have shown that synthetic polymer scaffolds that artificially induce cell compaction can induce embryonic mandible mesenchymal cells to initiate tooth differentiation both in vitro and in vivo. As embryonic cells would be difficult to use for regenerative medicine applications, here we explored whether compressive scaffolds coated with Collagen VI can be used to induce adult bone marrow stromal cells (BMSCs) to undergo an odontogenic lineage switch. These studies revealed that when mouse BMSCs are compressed using these scaffolds they increase expression of critical markers of tooth differentiation in vitro, including the key transcription factors Pax9 and Msx1. Implantation under the kidney capsule of contracting scaffolds bearing these cells in mice also resulted in local mineralization, calcification and production of dentin-like tissue. These findings show that these chemically-primed compressive scaffolds can be used to induce adult BMSCs to undergo a lineage switch and begin to form dentin-like tissue, thus raising the possibility of using adult BMSCs for future tooth regeneration applications

Career intentions of medical students in the UK: a national, cross-sectional study (AIMS study)

Objective To determine current UK medical students’ career intentions after graduation and on completing the Foundation Programme (FP), and to ascertain the motivations behind these intentions.Design Cross-sectional, mixed-methods survey of UK medical students, using a non-random sampling method.Setting All 44 UK medical schools recognised by the General Medical Council.Participants All UK medical students were eligible to participate. The study sample consisted of 10 486 participants, approximately 25.50% of the medical student population.Outcome measures Career intentions of medical students postgraduation and post-FP, motivations behind these career intentions, characterising the medical student population and correlating demographic factors and propensity to leave the National Health Service (NHS).Results The majority of participating students (8806/10 486, 83.98%) planned to complete both years of the FP after graduation, with under half of these students (4294/8806, 48.76%) intending to pursue specialty training thereafter. A subanalysis of career intentions after the FP by year of study revealed a significant decrease in students’ intentions to enter specialty training as they advanced through medical school. Approximately a third of surveyed students (3392/10 486, 32.35%) intended to emigrate to practise medicine, with 42.57% (n=1444) of those students not planning to return. In total, 2.89% of students intended to leave medicine altogether (n=303). Remuneration, work-life balance and working conditions were identified as important factors in decision-making regarding emigration and leaving the profession. Subgroup analyses based on gender, type of schooling, fee type and educational background were performed. Only 17.26% of surveyed students were satisfied or very satisfied with the overall prospect of working in the NHS.Conclusions The Ascertaining the career Intentions of UK Medical Students study highlights UK students’ views and career intentions, revealing a concerning proportion of those surveyed considering alternative careers or emigration. Addressing factors such as remuneration, work-life balance and working conditions may increase retention of doctors and improve workforce planning efforts

Search for CPCP violation in D0^0→\to KS0^0_\mathrm{S}KS0^0_\mathrm{S} decays in proton-proton collisions at s\sqrt{s} = 13 TeV

International audienceA search is reported for charge-parity D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$$CP$ violation in D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ decays, using data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6 fb$^{-1}$, which consists of about 10 billion events containing a pair of ẖadrons, nearly all of which decay to charm hadrons. The flavor of the neutral D meson is determined by the pion charge in the reconstructed decays D$^{*+}$$\to$ D$^0\pi^+$ and D$^{*-}$$\to$ D$^0\pi^-$. The D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$$CP$ asymmetry in D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ is measured to be $A_{CP}$( K$^0_\mathrm{S}$K$^0_\mathrm{S}$) = (6.2 $\pm$ 3.0 $\pm$ 0.2 $\pm$ 0.8)%, where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the D$^0$ $\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ $CP$ asymmetry in the D$^0$ $\to$ K$^0_\mathrm{S}\pi^+\pi^-$ decay. This is the first D$^0$ $\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ $CP$ asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state

Search for the Z boson decay to ττμμ\tau\tau\mu\mu in proton-proton collisions at s\sqrt{s} = 13 TeV

International audienceThe first search for the Z boson decay to $\tau\tau\mu\mu$ at the CERN LHC is presented, based on data collected by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb$^{-1}$. The data are compatible with the predicted background. For the first time, an upper limit at the 95% confidence level of 6.9 times the standard model expectation is placed on the ratio of the Z $\to$ $\tau\tau\mu\mu$ to Z $\to$ 4$\mu$ branching fractions. Limits are also placed on the six flavor-conserving four-lepton effective-field-theory operators involving two muons and two tau leptons, for the first time testing all such operators

Search for soft unclustered energy patterns in proton-proton collisions at 13 TeV

International audienceThe first search for soft unclustered energy patterns (SUEPs) is performed using an integrated luminosity of 138 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}$ = 13 TeV collected in 2016-2018 by the CMS detector at the LHC. Such SUEPs are predicted by Hidden Valley models with a new, confining force with a large 't Hooft coupling. In events with boosted topologies, selected by high-threshold hadronic triggers, the multiplicity and sphericity of clustered tracks are used to reject the background from standard model quantum chromodynamics. With no observed excess of events over the standard model expectation, limits are set on the cross section for production via gluon fusion of a scalar mediator with SUEP-like decays