Decoding mechanism that regulate re-epithelialization

During normal wound healing, keratinocytes are the first dermal cell type to respond to the injury, covering the wound bed to establish a barrier for immune defense and provide structural and mechanical support for dermal regeneration. Failure of this re-epithelialization process results in the development of chronic wounds, which are associated with substantial medical costs. During re-epithelialization, keratinocytes can utilize multiple mechanisms to fill the space, including migration, proliferation, and hypertrophy. Additionally, individual keratinocytes are influenced by numerous factors in the wound microenvironment, including substrate mechanics and growth factors to direct these cellular decisions. To determine which individual cell behaviors represent the most promising targets to engineer re-epithelialization, we have examined collective and individual responses of HaCaT keratinocytes to changes in substrate mechanics and growth factors and utilized computational modeling to predict the hierarchy of factors driving wound closure. Our results suggest that migrational persistence is the key parameter for effective wound closure. We have further examined biomaterials-based methods to direct migrational persistence, and identified a mechanism by which immobilization of EGF induced strong migrational persistence through the activation of PLCg1 specifically in keratinocytes on the leading edge. Ongoing work is examining this process in more detail to determine the mechanism responsible for leading edge-specific activation of PLC

Identifying molecular and functional similarities and differences between human primary cardiac valve interstitial cells and ventricular fibroblasts

Introduction: Fibroblasts are mesenchymal cells that predominantly produce and maintain the extracellular matrix (ECM) and are critical mediators of injury response. In the heart, valve interstitial cells (VICs) are a population of fibroblasts responsible for maintaining the structure and function of heart valves. These cells are regionally distinct from myocardial fibroblasts, including left ventricular cardiac fibroblasts (LVCFBs), which are located in the myocardium in close vicinity to cardiomyocytes. Here, we hypothesize these subpopulations of fibroblasts are transcriptionally and functionally distinct.Methods: To compare these fibroblast subtypes, we collected patient-matched samples of human primary VICs and LVCFBs and performed bulk RNA sequencing, extracellular matrix profiling, and functional contraction and calcification assays.Results: Here, we identified combined expression of SUSD2 on a protein-level, and MEOX2, EBF2 and RHOU at a transcript-level to be differentially expressed in VICs compared to LVCFBs and demonstrated that expression of these genes can be used to distinguish between the two subpopulations. We found both VICs and LVCFBs expressed similar activation and contraction potential in vitro, but VICs showed an increase in ALP activity when activated and higher expression in matricellular proteins, including cartilage oligomeric protein and alpha 2-Heremans-Schmid glycoprotein, both of which are reported to be linked to calcification, compared to LVCFBs.Conclusion: These comparative transcriptomic, proteomic, and functional studies shed novel insight into the similarities and differences between valve interstitial cells and left ventricular cardiac fibroblasts and will aid in understanding region-specific cardiac pathologies, distinguishing between primary subpopulations of fibroblasts, and generating region-specific stem-cell derived cardiac fibroblasts

Engineered Collagen Matrices

Collagen is the most abundant protein in mammals, accounting for approximately one-third of the total protein in the human body. Thus, it is a logical choice for the creation of biomimetic environments, and there is a long history of using collagen matrices for various tissue engineering applications. However, from a biomaterial perspective, the use of collagen-only scaffolds is associated with many challenges. Namely, the mechanical properties of collagen matrices can be difficult to tune across a wide range of values, and collagen itself is not highly amenable to direct chemical modification without affecting its architecture or bioactivity. Thus, many approaches have been pursued to design scaffold environments that display critical features of collagen but enable improved tunability of physical and biological characteristics. This paper provides a brief overview of approaches that have been employed to create such engineered collagen matrices. Specifically, these approaches include blending of collagen with other natural or synthetic polymers, chemical modifications of denatured collagen, de novo creation of collagen-mimetic chains, and reductionist methods to incorporate collagen moieties into other materials. These advancements in the creation of tunable, engineered collagen matrices will continue to enable the interrogation of novel and increasingly complex biological questions

Multiscale Systems Biology Model of Calcific Aortic Valve Disease Progression.

Calcific aortic valve disease is a common cause of aortic stenosis, a life threatening condition. In this study, a mathematical model is developed to simulate the cascade of mechanosensitive biochemical events that occur upon damage to the endothelial layer, leading to calcification. The model contains two phases. In the initiation phase, the model accounts for low-density lipoprotein (LDL) penetration into the subendothelial space, oxidation of LDL, and monocyte penetration and differentiation to activated macrophages. In the calcification phase, transforming growth factor beta is secreted from macrophages, inducing differentiation of valvular interstitial cells into activated myofibroblasts that can enable calcium deposition. Wall shear stress and mechanical strain are taken into account with simplified models updated based on calcification progression. The model parameters are estimated based on experimental data. Next, a statin therapy simulation is performed to evaluate the effect of lipid lowering therapy on calcification progression, demonstrating an age-dependent effectiveness in statin therapy. A new potential therapy targeting transforming growth factor-β activation is proposed and simulated. The long-term evolution of calcification is compared to two sets of published longitudinal clinical data, showing promising agreement. The proposed model can provide clinically valuable data, potentially guiding surgeons in valve replacement decision makings

Ten simple rules for developing a mentor–mentee expectations document

<p>Ten simple rules for developing a mentor–mentee expectations document</p

Sex-Related Differences in Gene Expression by Porcine Aortic Valvular Interstitial Cells

<div><p>While many large-scale risk factors for calcific aortic valve disease (CAVD) have been identified, the molecular etiology and subsequent pathogenesis of CAVD have yet to be fully understood. Specifically, it is unclear what biological phenomena underlie the significantly higher occurrence of CAVD in the male population. We hypothesized the existence of intrinsic, cellular-scale differences between male and female valvular interstitial cells (VICs) that contribute to male sex being a risk factor for CAVD. Differences in gene expression profiles between healthy male and female porcine VICs were investigated via microarray analysis. Mean expression values of each probe set in the male samples were compared to the female samples, and biological processes were analyzed for overrepresentation using Gene Ontology term enrichment analysis. There were 183 genes identified as significantly (fold change>2; P<0.05) different in male versus female aortic valve leaflets. Within this significant gene list there were 298 overrepresented biological processes, several of which are relevant to pathways identified in CAVD pathogenesis. In particular, pathway analysis indicated that cellular proliferation, apoptosis, migration, ossification, angiogenesis, inflammation, and extracellular matrix reorganization were all significantly represented in the data set. These gene expression findings also translated into functional differences in VIC behavior in the <em>in vitro</em> environment, as sex-related differences in proliferation and apoptosis were confirmed in VIC populations cultured <em>in vitro</em>. These data suggest that a sex-related propensity for CAVD exists on the cellular level in healthy subjects, a phenomenon that could have significant clinical implications. These findings also strongly support discontinuing the use of mixed-sex VIC cultures, thereby changing the current standard in the field.</p> </div