557 research outputs found
New Directions in Photopolymerizable Biomaterials
No full textAbstractThis article is based on the Outstanding Young Investigator Award presentation given by Kristi S. Anseth at the 2001 MRS Spring Meeting on April 17, 2001, in San Francisco. Anseth was recognized for “innovative work in polymeric biomaterials for drug delivery, bone and cartilage repair, and tissue engineering, and for outstanding leadership potential in this interdisciplinary field of materials research.”Photopolymerization provides many advantages as a technique for the fabrication of biomaterials. Temporal and spatial control, along with the diversity in material properties found with photopolymerizable materials, are advantageous in the biomaterials industry. For instance, multifunctional anhydride monomers form highly cross-linked surface-eroding networks directly in bone defects. These networks have good mechanical properties that are maintained with degradation and have the potential to restore tissue-like properties to bone during the healing process. Additionally, cartilage-forming cells photoencapsulated in hydrogel networks secrete an extracellular matrix as the hydrogel is resorbed and may provide a treatment alternative for cartilage defects that do not heal spontaneously. Finally, transdermal polymerization (photopolymerization through the skin) of multifunctional monomers is a noninvasive technique that is being developed for tissue regeneration and wound-healing applications.</jats:p
The Role of Matrix Properties in Directing Valvular Interstitial Cell Phenotype
No full textThis thesis presents the development of hydrogel platforms to study the fibroblast-to-myofibroblast transition in valvular interstitial cells (VICs). These systems were used to characterize the effects of extracellular matrix cues on VICs, as well as the synergies between mechanical and biochemical signals. First, the impact of culture platform on VIC phenotype was assessed by culturing VICs in peptide-functionalized poly(ethylene glycol) hydrogels (2D and 3D) and comparing them to those cultured on tissue culture polystyrene (TCPS). Expression of the myofibroblast marker α-smooth muscle actin (αSMA), as well as by a global analysis of the transcriptional profiles1 demonstrated that TCPS caused significant perturbations in gene expression from the native VIC phenotype. The dimensionality of the hydrogel (2D vs 3D) was particularly influential in the regulation of genes related to cell structure and motility, developmental processes, proliferation and differentiation, and transport; these findings motivated the use of 3D cultures for the following experiments.
The effect of matrix modulus, particularly matrix stiffening, on encapsulated VICs was investigated2. To vary the matrix modulus without dramatic changes in VIC morphology, a method was developed for in situ stiffening of cell-laden hydrogels using sequential gelation steps. In contrast with prior findings in 2D, increased stiffness resulted in lower levels of myofibroblast activation, and suggested that stiffness alone was not sufficient to cause pathological activation of VICs to the myofibroblast phenotype in 3D. To facilitate the investigation of additional stimuli in a physiologically-relevant context, a high-throughput technique to encapsulate VICs within 3D hydrogels was developed and used to study VIC response to dynamic changes in matricellular signals3. A thiol-ene photoclick reaction provided temporal control over the presentation of peptide ligands to study their effects on VIC morphology and myofibroblast properties. Collectively, these studies demonstrate the ability to study and direct VIC phenotype through the temporal presentation of mechanical and biochemical cues in 3D polymer matrices. References 1. Mabry, K. M., Payne, S. Z. & Anseth, K. S. Microarray analyses to quantify advantages of 2D and 3D hydrogel culture systems in maintaining the native valvular interstitial cell phenotype. Submitted. 2. Mabry, K. M., Lawrence, R. L. & Anseth, K. S. Dynamic stiffening of poly(ethylene glycol)-based hydrogels to direct valvular interstitial cell phenotype in a three-dimensional environment. Biomaterials 49, 47–56 (2015). 3. Mabry, K. M., Schroeder, M. E., Payne, S. Z. & Anseth, K. S. Three-dimensional high-throughput cell encapsulation platform to</p
The Role of Matrix Properties in Directing Valvular Interstitial Cell Phenotype
No full textThis thesis presents the development of hydrogel platforms to study the fibroblast-to-myofibroblast transition in valvular interstitial cells (VICs). These systems were used to characterize the effects of extracellular matrix cues on VICs, as well as the synergies between mechanical and biochemical signals. First, the impact of culture platform on VIC phenotype was assessed by culturing VICs in peptide-functionalized poly(ethylene glycol) hydrogels (2D and 3D) and comparing them to those cultured on tissue culture polystyrene (TCPS). Expression of the myofibroblast marker α-smooth muscle actin (αSMA), as well as by a global analysis of the transcriptional profiles1 demonstrated that TCPS caused significant perturbations in gene expression from the native VIC phenotype. The dimensionality of the hydrogel (2D vs 3D) was particularly influential in the regulation of genes related to cell structure and motility, developmental processes, proliferation and differentiation, and transport; these findings motivated the use of 3D cultures for the following experiments.
The effect of matrix modulus, particularly matrix stiffening, on encapsulated VICs was investigated2. To vary the matrix modulus without dramatic changes in VIC morphology, a method was developed for in situ stiffening of cell-laden hydrogels using sequential gelation steps. In contrast with prior findings in 2D, increased stiffness resulted in lower levels of myofibroblast activation, and suggested that stiffness alone was not sufficient to cause pathological activation of VICs to the myofibroblast phenotype in 3D. To facilitate the investigation of additional stimuli in a physiologically-relevant context, a high-throughput technique to encapsulate VICs within 3D hydrogels was developed and used to study VIC response to dynamic changes in matricellular signals3. A thiol-ene photoclick reaction provided temporal control over the presentation of peptide ligands to study their effects on VIC morphology and myofibroblast properties. Collectively, these studies demonstrate the ability to study and direct VIC phenotype through the temporal presentation of mechanical and biochemical cues in 3D polymer matrices. References 1. Mabry, K. M., Payne, S. Z. & Anseth, K. S. Microarray analyses to quantify advantages of 2D and 3D hydrogel culture systems in maintaining the native valvular interstitial cell phenotype. Submitted. 2. Mabry, K. M., Lawrence, R. L. & Anseth, K. S. Dynamic stiffening of poly(ethylene glycol)-based hydrogels to direct valvular interstitial cell phenotype in a three-dimensional environment. Biomaterials 49, 47–56 (2015). 3. Mabry, K. M., Schroeder, M. E., Payne, S. Z. & Anseth, K. S. Three-dimensional high-throughput cell encapsulation platform to</p
Postprandial cardiac hypertrophy is sustained by mechanics, epigenetic, and metabolic reprogramming in pythons
No full textConstricting pythons, known for their ability to consume infrequent, massive meals, exhibit rapid and reversible cardiac hypertrophy following feeding. Our primary goal was to investigate how python hearts achieve this adaptive response after feeding. Isolated myofibrils increased force after feeding without changes in sarcomere ultrastructure and without increasing energy cost. Ca2+ transients were prolonged after feeding with no changes in myofibril Ca2+ sensitivity. Feeding reduced titin-based tension, resulting in decreased cardiac tissue stiffness. Feeding also reduced the activity of sirtuins, a metabolically linked class of histone deacetylases, and increased chromatin accessibility. Transcription factor enrichment analysis on transposase-accessible chromatin with sequencing revealed the prominent role of transcription factors Yin Yang1 and NRF1 in postfeeding cardiac adaptation. Gene expression also changed with the enrichment of translation and metabolism. Finally, metabolomics analysis and adenosine triphosphate production demonstrated that cardiac adaptation after feeding not only increased energy demand but also energy production. These findings have broad implications for our understanding of cardiac adaptation across species and hold promise for the development of innovative approaches to address cardiovascular diseases. Copyright © 2024 the Author(s)
Nanoscale Stiffness Cues Influence Valvular Interstitial Cell Activation to Myofibroblasts
No full textSurgery is currently the primary treatment option for aortic valve stenosis (AVS) patients, many of whom are ineligible for surgery and are left untreated. AVS is progression is known to differ between males and females, and an understanding of sex-specific mechanisms of disease progression is imperative in developing accurate treatment options for men and women. The development of a nonsurgical therapy for AVS patients requires a deeper understanding of the molecular and cellular mechanisms of AVS progression. Currently, the role of calcium phosphate nanoparticles detected in the aortic valve during early stages of AVS in influencing disease progression and valvular interstitial cell (VIC) activation to myofibroblasts is unknown. Here, we sought to characterize the effects of nanoscale stiffness cues on VIC activation to myofibroblasts and hypothesized that alterations in nanoparticle stiffness and size would modulate sex-specific VIC activation and deactivation. Engineered hydrogel cell culture platforms embedded with polystyrene nanoparticles (PS-NPs) of varying size were employed to probe the role of nanoscale stiffness cues in modulating sex-specific VIC activation to the myofibroblast state, while poly(ethylene glycol) (PEG) nanogels of varying stiffness were synthesized and embedded in hydrogels or suspended in VIC media to gain a deeper understanding of VIC response to nanoscale stiffness cues. Analysis of alpha-smooth muscle actin (αSMA) expression and stress fiber formation in VICs in response to nanoscale stiffness cues revealed sex-specific VIC activation and deactivation in response to stiff PS-NPs and PEG nanogels of varying stiffness. Our results support the hypothesis that altering the stiffness and size of nanoparticles might influence sex-specific VIC activation
Nanoscale Stiffness Cues Influence Valvular Interstitial Cell Activation to Myofibroblasts
No full textSurgery is currently the primary treatment option for aortic valve stenosis (AVS) patients, many of whom are ineligible for surgery and are left untreated. AVS is progression is known to differ between males and females, and an understanding of sex-specific mechanisms of disease progression is imperative in developing accurate treatment options for men and women. The development of a nonsurgical therapy for AVS patients requires a deeper understanding of the molecular and cellular mechanisms of AVS progression. Currently, the role of calcium phosphate nanoparticles detected in the aortic valve during early stages of AVS in influencing disease progression and valvular interstitial cell (VIC) activation to myofibroblasts is unknown. Here, we sought to characterize the effects of nanoscale stiffness cues on VIC activation to myofibroblasts and hypothesized that alterations in nanoparticle stiffness and size would modulate sex-specific VIC activation and deactivation. Engineered hydrogel cell culture platforms embedded with polystyrene nanoparticles (PS-NPs) of varying size were employed to probe the role of nanoscale stiffness cues in modulating sex-specific VIC activation to the myofibroblast state, while poly(ethylene glycol) (PEG) nanogels of varying stiffness were synthesized and embedded in hydrogels or suspended in VIC media to gain a deeper understanding of VIC response to nanoscale stiffness cues. Analysis of alpha-smooth muscle actin (αSMA) expression and stress fiber formation in VICs in response to nanoscale stiffness cues revealed sex-specific VIC activation and deactivation in response to stiff PS-NPs and PEG nanogels of varying stiffness. Our results support the hypothesis that altering the stiffness and size of nanoparticles might influence sex-specific VIC activation
Design Of Novel Materials To Regulate Stem And Progenitor Cell Expansion And Differentiation
No full textCues from a cell’s microenvironment play a critical role in directing and maintaining cell fate in vivo. Misregulation within the extracellular space can cause cell death or other aberrant behaviors associated with developmental defects and diseases such as fibrosis and cancer. Thus, as one thinks about culturing stem cells or progenitor cells for functional studies or their delivery into patients for therapeutic purposes, it is prudent to consider the surrounding microenvironment, especially conditions that stimulate desired biological functions and/or integration with native tissue. In this regard, multicomponent biomaterials and their physicochemical manipulation can serve as in vitro platforms to decipher some of the complexities of dynamic cell-matrix signaling. This talk will focus on some of our recent efforts towards in situ hydrogel property manipulation with light, allowing intimate control of a cell’s microenvironment in both time and space
Determining the Molecular Mechanisms of Soluble TREM2 in Alzheimer’s Disease
No full textThe microglial surface protein Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) plays a critical role in mediating brain homeostasis and inflammatory responses in Alzheimer’s disease (AD). The soluble form of TREM2 (sTREM2) exhibits neuroprotective effects in AD, though the underlying mechanisms remain elusive. Moreover, differences in ligand binding between TREM2 and sTREM2, which have major implications for their roles in AD pathology, remain unexplained. To address these knowledge gaps, we conducted the most computationally intensive molecular dynamics simulations to date of (s)TREM2, exploring their interactions with key damage- and lipoprotein-associated phospholipids and the impact of the ADrisk mutation R47H. Additionally, we used MD simulations to characterize a newly proposed endogenous interaction between sTREM2 and neuronal receptor, TG2. This interaction is thought to attenuate tau hyperphosphorylation thereby slowing AD progression. Our results demonstrate that the flexible stalk domain of sTREM2 serves as the molecular basis for differential ligand binding between sTREM2 and TREM2, facilitated by its role in stabilizing the Ig-like domain and altering the accessibility of canonical ligand binding sites. We identified a novel ligand binding site on sTREM2, termed the ‘Expanded Surface 2’, which emerges due to competitive binding of the stalk with the Ig-like domain. Additionally, we observed that the stalk domain itself functions as a site for ligand binding, with increased binding in the presence of R47H. This suggests that iii sTREM2’s neuroprotective role in AD may, at least in part, arise from the stalk domain’s ability to rescue dysfunctional ligand binding caused by AD-risk mutations. Lastly, our findings indicate that R47H-induced dysfunction in membrane-bound TREM2 may result from both diminished ligand binding due to restricted complementarity-determining region 2 loop motions and an impaired ability to differentiate between ligands, proposing a novel mechanism for loss-offunction. Lastly, we found that sTREM2 interacted with TG2 in a pattern similar to that of phospholipids, however identified a need to further probe this interaction. In summary, these results provide valuable insights into the role of sTREM2 in AD pathology, laying the groundwork for the design of new therapeutic approaches targeting (s)TREM2 in AD.</p
The Power of Presence: Unlock Your Potential to Influence and Engage Others
No full textEveryone recognizes leaders with ôpresence.ö They stand out for their seemingly innate ability to command attention and inspire commitment. But what is this secret quality they exude, exactly? Executive and CEO coach Kristi Hedges demystifies this elusive trait, revealing that presence is the intersection of outward influencing skills and internal mental conditioning. Using her I-Presence model, the author shows how anyoneùregardless of position or personalityùcan strengthen their impact. Readers will learn how to build trust as the foundation for leadership, eschew perfectionism for authenti
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