Hybrid Hydrogels for Harnessing Mesenchymal Stem Cell Secretome

The low engraftment and retention rate of mesenchymal stem cells (MSCs) at the target site indicates that the potential benefits of MSC-based therapies can be attributed to their paracrine signaling. In this study, the influence of decellularized extracellular matrices (dECM) on pro-angiogenic signaling of MSC was investigated. Effect of cell passage number on ECM secretion and subsequently, on regulation of MSC secretome was also explored. The study revealed upregulated expression of angiogenesis-related factors upon culturing MSCs on dECMs irrespective of media supplementation. In addition, dECM generated in presence of ascorbic acid promoted expression of angiogenic molecules as compared to dECM derived in absence of media supplementation. Further, it was observed that the effectiveness of dECM to stimulate angiogenic signaling of MSCswas reduced as cell passage number was increased from P3 to P5. The activity of MSC-secreted biomolecules investigated by assessing the proliferation as well as capillary morphogenesis of human umbilical vein endothelial cells (HUVECs) supported the Proteome Profiler data. Working towards the goal of creating a biomaterial capable of recapitulating the multifactorial aspects of the stem cell environment, ECM deposited by MSCs was collected and introduced into alginate solution to create a hybrid material. Alginate concentration was varied while keeping the dECM concentration constant. Swelling ratio, degradation and diffusion of the hybrid hydrogels were explored in comparison to dECM-free (alginate only) gels. Results found that both degradation and diffusion characteristics were impacted by the introduction of matrix proteins. Lastly, the printability of the hybrid hydrogels at various printing pressures was also explored using Cellink’s INKREDIBLE bioprinter. Optimal printing pressures for each bioink composition was explored, and it was revealed that dECM addition improved the bioink’s printability at lower printing pressures in comparison to dECM-free gels.Master of Science in EngineeringBioengineering, College of Engineering & Computer ScienceUniversity of Michigan-Dearbornhttps://deepblue.lib.umich.edu/bitstream/2027.42/152428/1/Victoria Sears Final Thesis.pdfDescription of Victoria Sears Final Thesis.pdf : Restricted to UM users only

Model Reactions Involving Ester Functional Groups during Thermo‐Oxidative Degradation of Biodiesel

Biodiesel is a renewable fuel used in diesel engines that is typically blended with diesel fuel. However, biodiesel is susceptible to oxidation, which has the potential to produce higher molecular weight materials that may adversely impact vehicle fuel‐system performance. To investigate the chemical reactions potentially important in biodiesel oxidation, four different types of chemical reactions involving esters were studied: (1) ester formation (reactions of acids with alcohols), (2) alcoholysis (reactions of alcohols with esters), (3) acidolysis (reaction of acids with esters), and (4) ester exchange (reactions between two esters). Experiments with representative model compounds were used to evaluate these reactions at 90 °C with aeration; conditions previously used to simulate thermo‐oxidative degradation during biodiesel aging. Reactions were monitored using gas chromatography, fourier transform infrared (FTIR) spectroscopy, and total acid number (TAN). Evidence is presented suggesting that alcoholysis and ester formation (Reactions 1 and 2), catalyzed by carboxylic acids, are important reactions of esters that could lead to larger molecules. Acidolysis (Reaction 3) proceeded at a comparatively slow rate and ester exchange reaction products (Reaction 4) were not detected under these aging conditions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151841/1/aocs12277_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151841/2/aocs12277.pd

Model Reactions Involving Ester Functional Groups during Thermo‐Oxidative Degradation of Biodiesel

Biodiesel is a renewable fuel used in diesel engines that is typically blended with diesel fuel. However, biodiesel is susceptible to oxidation, which has the potential to produce higher molecular weight materials that may adversely impact vehicle fuel‐system performance. To investigate the chemical reactions potentially important in biodiesel oxidation, four different types of chemical reactions involving esters were studied: (1) ester formation (reactions of acids with alcohols), (2) alcoholysis (reactions of alcohols with esters), (3) acidolysis (reaction of acids with esters), and (4) ester exchange (reactions between two esters). Experiments with representative model compounds were used to evaluate these reactions at 90 °C with aeration; conditions previously used to simulate thermo‐oxidative degradation during biodiesel aging. Reactions were monitored using gas chromatography, fourier transform infrared (FTIR) spectroscopy, and total acid number (TAN). Evidence is presented suggesting that alcoholysis and ester formation (Reactions 1 and 2), catalyzed by carboxylic acids, are important reactions of esters that could lead to larger molecules. Acidolysis (Reaction 3) proceeded at a comparatively slow rate and ester exchange reaction products (Reaction 4) were not detected under these aging conditions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151841/1/aocs12277_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151841/2/aocs12277.pd

Castration delays epigenetic aging and feminizes DNA methylation at androgen-regulated loci.

In mammals, females generally live longer than males. Nevertheless, the mechanisms underpinning sex-dependent longevity are currently unclear. Epigenetic clocks are powerful biological biomarkers capable of precisely estimating chronological age and identifying novel factors influencing the aging rate using only DNA methylation data. In this study, we developed the first epigenetic clock for domesticated sheep (Ovis aries), which can predict chronological age with a median absolute error of 5.1 months. We have discovered that castrated male sheep have a decelerated aging rate compared to intact males, mediated at least in part by the removal of androgens. Furthermore, we identified several androgen-sensitive CpG dinucleotides that become progressively hypomethylated with age in intact males, but remain stable in castrated males and females. Comparable sex-specific methylation differences in MKLN1 also exist in bat skin and a range of mouse tissues that have high androgen receptor expression, indicating that it may drive androgen-dependent hypomethylation in divergent mammalian species. In characterizing these sites, we identify biologically plausible mechanisms explaining how androgens drive male-accelerated aging

Focal Adhesion Kinase Is Required for Intestinal Regeneration and Tumorigenesis Downstream of Wnt/c-Myc Signaling

The intestinal epithelium has a remarkable capacity to regenerate after injury and DNA damage. Here, we show that the integrin effector protein Focal Adhesion Kinase (FAK) is dispensable for normal intestinal homeostasis and DNA damage signaling, but is essential for intestinal regeneration following DNA damage. Given Wnt/c-Myc signaling is activated following intestinal regeneration, we investigated the functional importance of FAK following deletion of the Apc tumor suppressor protein within the intestinal epithelium. Following Apc loss, FAK expression increased in a c-Myc-dependent manner. Codeletion of Apc and Fak strongly reduced proliferation normally induced following Apc loss, and this was associated with reduced levels of phospho-Akt and suppression of intestinal tumorigenesis in Apc heterozygous mice. Thus, FAK is required downstream of Wnt Signaling, for Akt/mTOR activation, intestinal regeneration, and tumorigenesis: Importantly, this work suggests that FAK inhibitors may suppress tumorigenesis in patients at high, risk of developing colorectal cancer