Comparison of Biomaterial-Dependent and -Independent Bioprinting Methods for Cardiovascular Medicine

There is an increasing need of human organs for transplantation, of alternatives to animal experimentation, and of better in vitro tissue models for drug testing. All these needs create unique opportunities for the development of novel and powerful tissue engineering methods, among which the 3D bioprinting is one of the most promising. However, after decades of incubation, ingenuous efforts, early success and much anticipation, biomaterial-dependent 3D bioprinting, although shows steady progress, is slow to deliver the expected clinical results. For this reason, alternative ‘scaffold-free’ 3D bioprinting methods are developing in parallel at an accelerated pace. In this opinion paper we discuss comparatively the two approaches, with specific examples drawn from the cardiovascular field. Moving the emphasis away from competition, we show that the two platforms have similar goals but evolve in complementary technological niches. We conclude that the biomaterial-dependent bioprinting is better suited for tasks requiring faster, larger, anatomically-true, cell-homogenous and matrix-rich constructs, while the scaffold-free biofabrication is more adequate for cell-heterogeneous, matrix-poor, complex and smaller constructs, but requiring longer preparation time

Progress in scaffold-free bioprinting for cardiovascular medicine

Biofabrication of tissue analogues is aspiring to become a disruptive technology capable to solve standing biomedical problems, from generation of improved tissue models for drug testing to alleviation of the shortage of organs for transplantation. Arguably, the most powerful tool of this revolution is bioprinting, understood as the assembling of cells with biomaterials in three-dimensional structures. It is less appreciated, however, that bioprinting is not a uniform methodology, but comprises a variety of approaches. These can be broadly classified in two categories, based on the use or not of supporting biomaterials (known as "scaffolds," usually printable hydrogels also called "bioinks"). Importantly, several limitations of scaffold-dependent bioprinting can be avoided by the "scaffold-free" methods. In this overview, we comparatively present these approaches and highlight the rapidly evolving scaffold-free bioprinting, as applied to cardiovascular tissue engineering

Modeling Stem/Progenitor Cell-Induced Neovascularization and\ud Oxygenation around Solid Implants

Tissue engineering constructs and other solid implants with biomedical applications, such as drug delivery devices or bioartificial organs, need oxygen (O2) to function properly. To understand better the vascular integration of such devices, we recently developed a novel model sensor containing O2-sensitive crystals, consisting of a polymeric capsule limited by a nano-porous filter. The sensor was implanted in mice with hydrogel alone (control) or hydrogel embedded with mouse CD117/c-kit+ bone marrow progenitor cells (BMPC) in order to stimulate peri-implant neovascularization. The sensor provided local partial O2 pressure (pO2) using non-invasive electron paramagnetic resonance (EPR) signal measurements. A consistently higher level of per-implant oxygenation was observed in the cell-treatment case as compared to the control over a 10-week period. In order to provide a mechanistic explanation of these experimental observations, we present in this paper a mathematical model, formulated as a system of coupled partial differential equations, that simulates peri-implant vascularization. In the control case, vascularization is considered to be the result of a Foreign Body Reaction (FBR) while in the cell-treatment case, adipogenesis in response to paracrine stimuli produced by the stem cells is assumed to induce neovascularization. The model is validated by fitting numerical predictions of local pO2 to measurements from the implanted sensor. The model is then used to investigate further the potential for using stem cell treatment to enhance the vascular integration of biomedical implants. We thus demonstrate how mathematical modeling combined with experimentation can be used to infer how vasculature develops around biomedical implants in control and stem celltreated cases

Present status and preliminary results of the VLF/LF radio recording European network installed in 2009.

In January 2009 a European network of receivers able to measure the electric field intensity from various VLF/LF broadcasting stations located throughout Europe, was installed. Five new receivers constructed by an Italian enterprise have been delivered to Greece, Romania, Turkey and to the Italian team. The motivation of this effort is to study the possible connections between the preparatory phase of earthquakes and perturbations in the transmitted radio signals. The receivers can be reached via ftp and gsm mobile connection, thus allowing a real time data collection. We present here the status of the network and the various testing steps performed in order to achieve a correct set up. We show how antennas variations, receivers locations and changes of selected frequencies affect the performances of the whole network. After this necessary testing period, several LF/VLF radio signals are now simultaneously and continuously being sampled by the five receivers. As a preliminary result we inspect also specific cases in which an anomaly in the radio signals is clearly related to the transmitter or to the receiver (e.g. meteorological conditions around the sampling site). At a basic level, the analysis adopted consists in a simple statistical evaluation of the signals by comparing the instantaneous values to the trend of the signal

Crystallographic Structure, Intermolecular Packing Energetics, Crystal Morphology and Surface Chemistry of Salmeterol Xinafoate (Form I).

Single crystals of salmeterol xinafoate (form I), prepared from slow cooled supersaturated propan-2-ol solutions, crystallise in a triclinic P‾1 symmetry with two closely related independent salt pairs within the asymmetric unit, with an approximately double unit cell volume compared to the previously published crystal structure(1). Synthonic analysis of the bulk intermolecular packing confirms the similarity in packing energetics between the two salt pairs. The strongest synthons, as expected, are dominated by coulombic interactions. Morphological prediction reveals a plate-like morphology, dominated by the {001}, {010} and {100} surfaces, consistent with experimentally grown crystals. Though surface chemistry of the slow growing {001} face comprises of large sterically hindering phenyl groups, weaker coulombic interactions still prevail from the alcohol group present on the phenyl and hydroxymethyl groups. The surface chemistry of the faster growing {010} and {100} faces are dominated by the significantly stronger cation/anion interactions occurring between the carboxylate and protonated secondary ammonium ion groups. The importance of understanding the cohesive/adhesive nature of the crystal surfaces of an API, with respect to their interaction with other API crystals and excipients and how that may impact formulation design is highlighted

iPSC-Derived Vascular Cell Spheroids as Building Blocks for Scaffold-Free Biofabrication

Recently a protocol is established to obtain large quantities of human induced pluripotent stem cells (iPSC)-derived endothelial progenitors, called endothelial colony forming cells (ECFC), and of candidate smooth-muscle forming cells (SMFC). Here, the suitability for assembling in spheroids, and in larger 3D cell constructs is tested. iPSC-derived ECFC and SMFC are labeled with tdTomato and eGFP, respectively. Spheroids are formed in ultra-low adhesive wells, and their dynamic proprieties are studied by time-lapse microscopy, or by confocal microscopy. Spheroids are also tested for fusion ability either in the wells, or assembled on the Regenova 3D bioprinter which laces them in stainless steel micro-needles (the “Kenzan” method). It is found that both ECFC and SMFC formed spheroids in about 24 h. Fluorescence monitoring indicated a continuous compaction of ECFC spheroids, but stabilization in those prepared from SMFC. In mixed spheroids, the cell distribution changed continuously, with ECFC relocating to the core, and showing pre-vascular organization. All spheroids have the ability of in-well fusion, but only those containing SMFC are robust enough to sustain assembling in tubular structures. In these constructs a layered distribution of alpha smooth muscle actin-positive cells and extracellular matrix deposition is found. In conclusion, iPSC-derived vascular cell spheroids represent a promising new cellular material for scaffold-free biofabrication

Of balls, inks and cages: Hybrid biofabrication of 3D tissue analogs

The overarching principle of three-dimensional (3D) bioprinting is the placing of cells or cell clusters in the 3D space to generate a cohesive tissue microarchitecture that comes close to in vivo characteristics. To achieve this goal, several technical solutions are available, generating considerable combinatorial bandwidth: (i) Support structures are generated first, and cells are seeded subsequently; (ii) alternatively, cells are delivered in a printing medium, so-called “bioink,” that contains them during the printing process and ensures shape fidelity of the generated structure; and (iii) a “scaffold-free” version of bioprinting, where only cells are used and the extracellular matrix is produced by the cells themselves, also recently entered a phase of accelerated development and successful applications. However, the scaffold-free approaches may still benefit from secondary incorporation of scaffolding materials, thus expanding their versatility. Reversibly, the bioink-based bioprinting could also be improved by adopting some of the principles and practices of scaffold-free biofabrication. Collectively, we anticipate that combinations of these complementary methods in a “hybrid” approach, rather than their development in separate technological niches, will largely increase their efficiency and applicability in tissue engineering

Of balls, inks and cages: Hybrid biofabrication of 3D tissue analogs

The overarching principle of three-dimensional (3D) bioprinting is the placing of cells or cell clusters in the 3D space to generate a cohesive tissue microarchitecture that comes close to in vivo characteristics. To achieve this goal, several technical solutions are available, generating considerable combinatorial bandwidth: (i) Support structures are generated first, and cells are seeded subsequently; (ii) alternatively, cells are delivered in a printing medium, so-called “bioink,” that contains them during the printing process and ensures shape fidelity of the generated structure; and (iii) a “scaffold-free” version of bioprinting, where only cells are used and the extracellular matrix is produced by the cells themselves, also recently entered a phase of accelerated development and successful applications. However, the scaffold-free approaches may still benefit from secondary incorporation of scaffolding materials, thus expanding their versatility. Reversibly, the bioink-based bioprinting could also be improved by adopting some of the principles and practices of scaffold-free biofabrication. Collectively, we anticipate that combinations of these complementary methods in a “hybrid” approach, rather than their development in separate technological niches, will largely increase their efficiency and applicability in tissue engineering

EMBODYING INEQUALITY: THREE PAPERS ON THE ROLE OF GENDER AND DISCRIMINATION IN THE LIVES OF WOMEN

Women experience different forms of discrimination throughout their lives such as unfair treatment in interpersonal interactions in the public spheres and in the private sphere, as prescribed by societal gender roles, women can also experience inequality and discrimination as a disproportionate share of household work and caregiving, limited participation in decision making, unequal access and share of financial resources and leisure, and as well as in cases, of emotional, and physical, or sexual abuse. Limited research explored the potential joint effect of these forms of discrimination. The questions explored in this dissertation were: (1) How does gendered intra-household inequality, experienced as a constraint to women’s agency, interact with post-migration factors like interpersonal discrimination and how does the combination of factors affect the mental health of immigrant women? (2) how does gendered intra-household inequality and discrimination interact to affect mental health among women and men in the U.S? And lastly, how do major stressful and traumatic events and discrimination interact to affect mental health among women and men in the U.S? In the first paper, I analysed data from the National Latino and Asian American Study and I found that first- and second-generation immigrant and refugee women experience intra-household inequality such as having no say in final decisions, experiencing excessive demands from their spouse and moderate or severe violence and that both discrimination and intrahousehold inequality made a separate and a significant contribution to increasing women’s risk for meeting criteria for depression and PTSD. The second paper had two small substudies. In the first I analyzed data from the 2011-2014 MIDUS Refresher study, and I examined the relationship between perceived everyday discrimination, intrahousehold inequality, and depression and anxiety among women and men. I found that everyday discrimination was associated with depression and perceived role strain with both health outcomes. In the second substudy I analyzed data from the 2012-2016 MIDUS Refresher Biomarker to explore a potential pathway between role strain and depression and anxiety symptoms and whether these processes were contingent upon the perception of discrimination in social interactions. I found that perceived stress mediated the relationship between role strain and depression and anxiety and that discrimination moderated that relationship such that in the presence of perceived discrimination in interpersonal interactions, intrahousehold inequality was associated with more psychological distress and more severe symptoms of depression and anxiety. In the last paper, I used data from the 2012-2016 MIDUS Refresher Biomarker and I examined the association between major stressful and traumatic events, perceived discrimination and perceived multiple reasons for discrimination and anxiety and depression among women and men. I first examined a potential pathway between adverse experiences and depression and anxiety symptoms, and I found that perceived stress mediates these relationships. In the second part, I tested the moderating role of discrimination and of perceived multiple forms of discrimination and found that individuals who reported a greater number of major stressful events reported higher levels of stress if they perceive higher levels of discrimination and, further, that higher levels of stress predicted higher levels of depressive symptoms if they perceive higher levels of discrimination. Perception of multiple forms of discrimination (two forms or there or more) was also associated with higher levels of perceived stress. The concluding chapter presents the main findings of these studies and recommendations for social work practice and future research