On the Functional Role of Valve Interstitial Cell Stress Fibers: A Continuum Modeling Approach.

The function of the heart valve interstitial cells (VICs) is intimately connected to heart valve tissue remodeling and repair, as well as the onset and progression of valvular pathological processes. There is yet only very limited knowledge and extant models for the complex three-dimensional VIC internal stress-bearing structures, the associated cell-level biomechanical behaviors, and how they change under varying activation levels. Importantly, VICs are known to exist and function within the highly dynamic valve tissue environment, including very high physiological loading rates. Yet we have no knowledge on how these factors affect VIC function. To this end, we extended our previous VIC computational continuum mechanics model (Sakamoto, et al., 2016, "On Intrinsic Stress Fiber Contractile Forces in Semilunar Heart Valve Interstitial Cells Using a Continuum Mixture Model," J. Mech. Behav. Biomed. Mater., 54(244-258)). to incorporate realistic stress-fiber geometries, force-length relations (Hill model for active contraction), explicit α-smooth muscle actin (α-SMA) and F-actin expression levels, and strain rate. Novel micro-indentation measurements were then performed using cytochalasin D (CytoD), variable KCl molar concentrations, both alone and with transforming growth factor ß1 (TGF-ß1) (which emulates certain valvular pathological processes) to explore how α-SMA and F-actin expression levels influenced stress fiber responses under quasi-static and physiological loading rates. Simulation results indicated that both F-actin and α-SMA contributed substantially to stress fiber force generation, with the highest activation state (90 mM KCL + TGF-ß1) inducing the largest α-SMA levels and associated force generation. Validation was performed by comparisons to traction force microscopy studies, which showed very good agreement. Interestingly, only in the highest activation state was strain rate sensitivity observed, which was captured successfully in the simulations. These unique findings demonstrated that only VICs with high levels of αSMA expression exhibited significant viscoelastic effects. Implications of this study include greater insight into the functional role of α-SMA and F-actin in VIC stress fiber function, and the potential for strain rate-dependent effects in pathological states where high levels of α-SMA occur, which appear to be unique to the valvular cellular in vivo microenvironment.

On intrinsic stress fiber contractile forces in semilunar heart valve interstitial cells using a continuum mixture model.

Heart valve interstitial cells (VICs) play a critical role in the maintenance and pathophysiology of heart valve tissues. Normally quiescent in the adult, VICs can become activated in periods of growth and disease. When activated, VICs exhibit increased levels of cytokines and extracellular matrix (ECM) synthesis, and upregulated expression and strong contraction of α-smooth muscle actin (α-SMA) fibers. However, it remains unknown how expression and contraction of the α-SMA fibers, which vary among different VIC types, contribute to the overall VIC mechanical responses, including the nucleus and cytoskeleton contributions. In the present study, we developed a novel solid-mixture model for VIC biomechanical behavior that incorporated 1) the underlying cytoskeletal network, 2) the oriented α-SMA stress fibers with passive elastic and active contractile responses, 3) a finite deformable elastic nucleus. We implemented the model in a full 3D finite element simulation of a VIC based on known geometry. Moreover, we examined the respective mechanical responses of aortic and pulmonary VICs (AVICs and PVICs, respectively), which are known to have different levels of α-SMA expression levels and contractile behaviors. To calibrate the model, we simulated the combined mechanical responses of VICs in both micropipette aspiration (MA) and atomic force microscopy (AFM) experiments. These two states were chosen as the VICs were under significantly different mechanical loading conditions and activation states, with the α-SMA fibers inactivated in the MA studies while fully activated in the AFM studies. We also used the AFM to study the mechanical property of the nucleus. Our model predicted that the substantial differences found in stiffening of the AVIC compared to the PVICs was due to a 9 to 16 times stronger intrinsic AVIC α-SMA stress fiber contractile force. Model validation was done by simulating a traction force microscopy experiment to estimate the forces the VICs exert on the underlying substrate, and found good agreement with reported traction force microscopy results. Further, estimated nuclear stiffness for both AVICs and PVICs were similar and comparable to the literature, and were both unaffected by VIC activation level. These results suggest substantial functional differences between AVICs and PVICs at the subcellular level. Moreover, this first VIC computational biomechanical model is but a first step in developing a comprehensive, integrated view of the VIC pathophysiology and interactions with the valve ECM micro-environment based on simulation technologies.

Assessment of vaccination-related information for consumers available on Facebook.

OBJECTIVES: To assess the magnitude, interest, purpose and validity of vaccination-related information on Facebook and to determine whether information varies by site viewpoint. METHODS: The 10 largest vaccination-focused Facebook pages, groups and places in each category were identified and classified by viewpoint (i.e. anti-, pro-, neutral) and purpose. Number of members, posts per week, likes, comments and shares per post were recorded. Posts were assessed for concordance with CDC and FDA recommendations. RESULTS: Of 30 sites, 43% (n = 13) were anti-vaccination, 7% (n = 2) neutral and 50% (n = 15) pro-vaccination. Most sites were most popular with American users. Median members were similar between anti-vaccination (2703 members, range 337-33 631 members) and pro-vaccination sites (2142 members, range 456-61,565 members, P = 0.262); however, anti-vaccination sites accumulated more posts per week by authors (median 15 vs. 3, P = 0.031) and members (median 33 vs. 1, P < 0.001). Pro-vaccination sites more commonly had commercial purpose (53% [n = 8] vs. 8% [n = 1], P = 0.02). Anti-vaccination sites more commonly gave medical advice (54% [n = 7] vs. 0%, P = 0.004). Overall, 48% (n = 22) of author posts were concordant with regulatory recommendations; concordance was more common on pro-vaccination sites (78% [n = 21] vs. 5% [n = 1], P = 0.0002). CONCLUSION: Vaccination-related information is prevalent on Facebook regardless of viewpoint; however, anti-vaccination information generates more interest. Anti-vaccination sites were likely to provide medical advice and disagree with regulatory bodies.

Extensive scalp angioedema following high-dose diphenylcyclopropenone for alopecia areata.

OBJECTIVE: To describe a case of an unusual adverse drug reaction to diphenylcyclopropenone for the treatment of alopecia areata. CASE SUMMARY: A 31-year-old Caucasian male presented with extensive angioedema to the head with neck involvement 10 days following treatment with diphenylcyclopropenone 2% solution in acetone topically on his scalp to treat alopecia areata. Findings on patient presentation included edema of the soft tissues (deeper dermis and subcutaneous tissue) of the head and face with mild neck involvement, acute inflammatory changes from chemical-induced irritation, scalp erythema, and serous fluid drainage from inflamed and fissured edematous scalp. Acute treatments used for control of the reaction included intravenous steroids and antihistamines during hospitalization followed by oral steroids and antihistamines for maintenance during outpatient treatment of the resolving condition. DISCUSSION: The role of topical diphenylcyclopropenone in this case of alopecia areata is probable according to the Naranjo criteria, with a score of 8. Diphenylcyclopropenone is not approved by the US Food and Drug Administration, but it has been used by many clinicians for the treatment of alopecia areata. Diphenylcyclopropenone causes an allergic contact dermatitis in the area of hair loss. In general, diphenylcyclopropenone is applied at a high concentration of 2% once and then at lower concentrations once weekly after the sensitization dose. This patient applied the 2% concentration on multiple consecutive days. CONCLUSION: Frequent use of topical diphenylcyclopropenone 2% applied to the scalp may cause scalp angioedema.

Interlayer micromechanics of the aortic heart valve leaflet.

While the mechanical behaviors of the fibrosa and ventricularis layers of the aortic valve (AV) leaflet are understood, little information exists on their mechanical interactions mediated by the GAG-rich central spongiosa layer. Parametric simulations of the interlayer interactions of the AV leaflets in flexure utilized a tri-layered finite element (FE) model of circumferentially oriented tissue sections to investigate inter-layer sliding hypothesized to occur. Simulation results indicated that the leaflet tissue functions as a tightly bonded structure when the spongiosa effective modulus was at least 25 % that of the fibrosa and ventricularis layers. Novel studies that directly measured transmural strain in flexure of AV leaflet tissue specimens validated these findings. Interestingly, a smooth transmural strain distribution indicated that the layers of the leaflet indeed act as a bonded unit, consistent with our previous observations (Stella and Sacks in J Biomech Eng 129:757-766, 2007) of a large number of transverse collagen fibers interconnecting the fibrosa and ventricularis layers. Additionally, when the tri-layered FE model was refined to match the transmural deformations, a layer-specific bimodular material model (resulting in four total moduli) accurately matched the transmural strain and moment-curvature relations simultaneously. Collectively, these results provide evidence, contrary to previous assumptions, that the valve layers function as a bonded structure in the low-strain flexure deformation mode. Most likely, this results directly from the transverse collagen fibers that bind the layers together to disable physical sliding and maintain layer residual stresses. Further, the spongiosa may function as a general dampening layer while the AV leaflets deforms as a homogenous structure despite its heterogeneous architecture.

Adult and umbilical cord blood-derived platelet-rich plasma for mesenchymal stem cell proliferation, chemotaxis, and cryo-preservation.

Platelet-rich plasma (PRP) was prepared from human adult peripheral blood and from human umbilical cord (uc) blood and the properties were compared in a series of in vitro bioassays. Quantification of growth factors in PRP and platelet-poor plasma (PPP) fractions revealed increased levels of mitogenic growth factors PDGF-AB, PDGF-BB, and FGF-2, the angiogenic agent VEGF and the chemokine RANTES in ucPRP compared to adult PRP (aPRP) and PPP. To compare the ability of the various PRP products to stimulate proliferation of human bone marrow (BM), rat BM and compact bone (CB)-derived mesenchymal stem cells (MSC), cells were cultured in serum-free media for 4 and 7 days with varying concentrations of PRP, PPP, or combinations of recombinant mitogens. It was found that while all forms of PRP and PPP were more mitogenic than fetal bovine serum, ucPRP resulted in significantly higher proliferation by 7 days than adult PRP and PPP. We observed that addition of as little as 0.1% ucPRP caused greater proliferation of MSC effects than the most potent combination of recombinant growth factors tested, namely PDGF-AB + PDGF-BB + FGF-2, each at 10 ng/mL. Similarly, in chemotaxis assays, ucPRP showed greater potency than adult PRP, PPP from either source, or indeed than combinations of either recombinant growth factors (PDGF, FGF, and TGF-ß1) or chemokines previously shown to stimulate chemotactic migration of MSC. Lastly, we successfully demonstrated that PRP and PPP represented a viable alternative to FBS containing media for the cryo-preservation of MSC from human and rat BM.

Multi-composite bioactive osteogenic sponges featuring mesenchymal stem cells, platelet-rich plasma, nanoporous silicon enclosures, and Peptide amphiphiles for rapid bone regeneration.

A novel bioactive sponge was created with a composite of type I collagen sponges or porous poly(e-caprolactone) (PCL) scaffolds, platelet-rich plasma (PRP), BMP2-loaded nanoporous silicon enclosure (NSE) microparticles, mineralizing peptide amphiphiles (PA), and mesenchymal stem cells (MSC). Primary MSC from cortical bone (CB)  tissue proved to form more and larger colony units, as well as produce more mineral matrix under osteogenic differentiation, than MSC from bone marrow (BM). Coating pre-treatments were optimized for maximum cell adhesion and mineralization, while a PRP-based gel carrier was created to efficiently deliver and retain MSC and  microparticles within a porous scaffold while simultaneously promoting cell recruitment, proliferation, and angiogenesis. Components and composite sponges were evaluated for osteogenic differentiation in vitro. Osteogenic sponges were loaded with MSC, PRP, PA, and NSE and implanted subcutaneously in rats to evaluate the formation of bone tissue and angiogenesis in vivo. It was found that the combination of a collagen sponge with CB MSC, PRP, PA, and the BMP2-releasing NSE formed the most bone and was most vascularized by four weeks compared to analogous composites featuring BM MSC or PCL or lacking PRP, PA, and NSE. This study indicates that CB MSC should be considered as an alternative to marrow as a source of stem cells, while the PRP-PA cell and microparticle delivery system may be utilized for diverse tissue engineering applications.

Enabling individualized therapy through nanotechnology.

Individualized medicine is the healthcare strategy that rebukes the idiomatic dogma of 'losing sight of the forest for the trees'. We are entering a new era of healthcare where it is no longer acceptable to develop and market a drug that is effective for only 80% of the patient population. The emergence of "-omic" technologies (e.g. genomics, transcriptomics, proteomics, metabolomics) and advances in systems biology are magnifying the deficiencies of standardized therapy, which often provide little treatment latitude for accommodating patient physiologic idiosyncrasies. A personalized approach to medicine is not a novel concept. Ever since the scientific community began unraveling the mysteries of the genome, the promise of discarding generic treatment regimens in favor of patient-specific therapies became more feasible and realistic. One of the major scientific impediments of this movement towards personalized medicine has been the need for technological enablement. Nanotechnology is projected to play a critical role in patient-specific therapy; however, this transition will depend heavily upon the evolutionary development of a systems biology approach to clinical medicine based upon "-omic" technology analysis and integration. This manuscript provides a forward looking assessment of the promise of nanomedicine as it pertains to individualized medicine and establishes a technology "snapshot" of the current state of nano-based products over a vast array of clinical indications and range of patient specificity. Other issues such as market driven hurdles and regulatory compliance reform are anticipated to "self-correct" in accordance to scientific advancement and healthcare demand. These peripheral, non-scientific concerns are not addressed at length in this manuscript; however they do exist, and their impact to the paradigm shifting healthcare transformation towards individualized medicine will be critical for its success.

Acculturation and adjustment in Latino adolescents: how cultural risk factors and assets influence multiple domains of adolescent mental health.

The purpose of this study was to examine the relationships among risk factors, cultural assets, and Latino adolescent mental health outcomes. We extend past research by using a longitudinal design and evaluating direct and moderated acculturation effects across a range of internalizing, externalizing, and academic engagement outcomes. The sample consisted of 281 Latino/a youths and one of their parents in metropolitan, small town, and rural areas within North Carolina and Arizona. The length of time the adolescent was in the U.S. was positively related to humiliation, aggression, and school bonding. Adolescent U.S. cultural involvement and parent culture of origin involvement were not significantly related to adolescent mental health or school bonding. Parent U.S. involvement had an inverse association with adolescent social problems, aggression, and anxiety. Adolescent culture of origin involvement was positively related to adolescent self-esteem 1 year later. Inverse relationships were found for the link between adolescent culture of origin involvement and hopelessness, social problems, and aggression 1 year later. Implications for prevention programming and policy development are discussed.

Pathways from acculturation stress to substance use among latino adolescents.

The purpose of this study was to examine the link between acculturation stress and substance use among Latino adolescents. In-home interviews were completed with the participants at four time-points between 2005 and 2007. Path analysis was completed using longitudinal data from 286 Latino adolescents living in North Carolina and Arizona (65% foreign-born). Results indicate that acculturation stress influences family and friend relationships, which in turn affect adolescent mental health problems, and finally, substance use. Key mediators in the pathway from acculturation stress to substance use were parent-adolescent conflict, internalizing, and externalizing problems. Implications for practice and research have been discussed here.