Influence of injectable microparticle size on cardiac progenitor cell response

Mending a broken heart by biomimetic 3D printed natural biomaterial-based cardiac patches: a review

Myocardial infarction is one of the major causes of mortality as well as morbidity around the world. Currently available treatment options face a number of drawbacks, hence cardiac tissue engineering, which aims to bioengineer functional cardiac tissue, for application in tissue repair, patient specific drug screening and disease modeling, is being explored as a viable alternative. To achieve this, an appropriate combination of cells, biomimetic scaffolds mimicking the structure and function of the native tissue, and signals, is necessary. Among scaffold fabrication techniques, three-dimensional printing, which is an additive manufacturing technique that enables to translate computer-aided designs into 3D objects, has emerged as a promising technique to develop cardiac patches with a highly defined architecture. As a further step toward the replication of complex tissues, such as cardiac tissue, more recently 3D bioprinting has emerged as a cutting-edge technology to print not only biomaterials, but also multiple cell types simultaneously. In terms of bioinks, biomaterials isolated from natural sources are advantageous, as they can provide exceptional biocompatibility and bioactivity, thus promoting desired cell responses. An ideal biomimetic cardiac patch should incorporate additional functional properties, which can be achieved by means of appropriate functionalization strategies. These are essential to replicate the native tissue, such as the release of biochemical signals, immunomodulatory properties, conductivity, enhanced vascularization and shape memory effects. The aim of the review is to present an overview of the current state of the art regarding the development of biomimetic 3D printed natural biomaterial-based cardiac patches, describing the 3D printing fabrication methods, the natural-biomaterial based bioinks, the functionalization strategies, as well as the in vitro and in vivo applications.

Injectable rBMSCs-laden hydrogel microspheres loaded with naringin for osteomyelitis treatment

Osteomyelitis, caused by purulent bacteria invading bone tissue, often occurs in long bones and seriously affects the physical and mental health and working ability of patients; it can even endanger life. However, due to bone cavity structure, osteomyelitis tends to occur inside the bone and thus lacks an effective treatment; anti-inflammatory treatment and repair of bone defects are necessary. Here, we developed injectable hydrogel microspheres loaded with naringin and bone marrow mesenchymal stem cells, which have anti-inflammatory and osteogenic properties. These homogeneous microspheres, ranging from 200 to 1000μm, can be rapidly fabricated using an electro-assisted bio-fabrication method. Interestingly, it was found that microspheres with relatively small diameters (200μm) were more conducive to the initial cell attachment, growth, spread, and later osteogenic differentiation. The developed microspheres can effectively treat tibial osteomyelitis in rats within six weeks, proving their prospects for clinical application.

Conductive and Semiconductive Nanocomposite-Based Hydrogels for Cardiac Tissue Engineering

Cardiovascular disease is the leading cause of death worldwide and the most common cause is myocardial infarction. Therefore, appropriate approaches should be used to repair damaged heart tissue. Recently, cardiac tissue engineering approaches have been extensively studied. Since the creation of the nature of cardiovascular tissue engineering, many advances have been made in cellular and scaffolding technologies. Due to the hydrated and porous structures of the hydrogel, they are used as a support matrix to deliver cells to the infarct tissue. In heart tissue regeneration, bioactive and biodegradable hydrogels are required by simulating native tissue microenvironments to support myocardial wall stress in addition to preserving cells. Recently, the use of nanostructured hydrogels has increased the use of nanocomposite hydrogels and has revolutionized the field of cardiac tissue engineering. Therefore, to overcome the limitation of the use of hydrogels due to their mechanical fragility, various nanoparticles of polymers, metal, and carbon are used in tissue engineering and create a new opportunity to provide hydrogels with excellent properties. Here, the types of synthetic and natural polymer hydrogels, nanocarbon-based hydrogels, and other nanoparticle-based materials used for cardiac tissue engineering with emphasis on conductive nanostructured hydrogels are briefly introduced.

Biomimetic Strategies to Develop Bioactive Scaffolds for Myocardial Tissue Engineering

The aim of this paper is to provide an overview of the results of the research activity carried out in our laboratories, over the last 10 years, in relation to the development of strategies for the production of biomimetic and bioactive scaffolds for myocardial tissue engineering. Biomimetic and bioactive polymeric scaffolds for cardiac regeneration were designed and manufactured in our laboratories and their morphological, physicochemical, mechanical and biological properties were investigated by different techniques, such as scanning electron microscopy, infrared chemical imaging, swelling test, in vitro degradation assessment, dynamic mechanical analysis, in vitro and in vivo biological tests. Biomimetic scaffolds, able to favor tissue regeneration by mimicking nature, were engineered by different strategies, comprising: (i) the imitation of the composition and interactions among components of the natural extracellular matrix (ECM), by mixing of proteins and polysaccharides; (ii) the material surface modification, using both traditional and innovative techniques, such as molecular imprinting; (iii) the incorporation and release of specific active agents and (iv) the production of scaffolds with a microarchitecture similar to that of native ECM. All the developed strategies were found to be effective in creating materials able to influence cellular behavior and therefore to favor the process of new tissue formation. In particular, the approach based on the combination of different strategies aimed at creating a system capable of communicating with the cells and promoting specific cellular responses, as the ECM does, has appeared particularly promising, in view to favor the formation of a tissue equivalent to the cardiac one.

Polymeric Biomaterials for the Treatment of Cardiac Post-Infarction Injuries

Cardiac regeneration aims to reconstruct the heart contractile mass, preventing the organ from a progressive functional deterioration, by delivering pro-regenerative cells, drugs, or growth factors to the site of injury. In recent years, scientific research focused the attention on tissue engineering for the regeneration of cardiac infarct tissue, and biomaterials able to anatomically and physiologically adapt to the heart muscle have been proposed as valuable tools for this purpose, providing the cells with the stimuli necessary to initiate a complete regenerative process. An ideal biomaterial for cardiac tissue regeneration should have a positive influence on the biomechanical, biochemical, and biological properties of tissues and cells; perfectly reflect the morphology and functionality of the native myocardium; and be mechanically stable, with a suitable thickness. Among others, engineered hydrogels, three-dimensional polymeric systems made from synthetic and natural biomaterials, have attracted much interest for cardiac post-infarction therapy. In addition, biocompatible nanosystems, and polymeric nanoparticles in particular, have been explored in preclinical studies as drug delivery and tissue engineering platforms for the treatment of cardiovascular diseases. This review focused on the most employed natural and synthetic biomaterials in cardiac regeneration, paying particular attention to the contribution of Italian research groups in this field, the fabrication techniques, and the current status of the clinical trials.

IGF-1 loaded injectable microspheres for potential repair of the infarcted myocardium

The use of injectable scaffolds to repair the infarcted heart is receiving great interest. Thermosensitive polymers, in situ polymerization, in situ cross-linking, and self-assembling peptides are the most investigated approaches to obtain injectability.Aim of the present work was the preparation and characterization of a novel bioactive scaffold, in form of injectable microspheres, for cardiac repair. Gellan/gelatin microspheres were prepared by a water-in-oil emulsion and loaded by adsorption with Insulin-like growth factor 1 to promote tissue regeneration. Obtained microspheres underwent morphological, physicochemical and biological characterization, including cell culture tests in static and dynamic conditions and in vivo tests. Morphological analysis of the microspheres showed a spherical shape, a microporous surface and an average diameter of 66 ± 17µm (under dry conditions) and 123 ± 24 µm (under wet conditions). Chemical Imaging analysis pointed out a homogeneous distribution of gellan, gelatin and Insulin-like growth factor-1 within the microsphere matrix. In vitro cell culture tests showed that the microspheres promoted rat cardiac progenitor cells adhesion, and cluster formation. After dynamic suspension culture within an impeller-free bioreactor, cells still adhered to microspheres, spreading their cytoplasm over microsphere surface. Intramyocardial administration of microspheres in a cryoinjury rat model attenuated chamber dilatation, myocardial damage and fibrosis and improved cell homing.Overall, the findings of this study confirm that the produced microspheres display morphological, physicochemical, functional and biological properties potentially adequate for future applications as injectable scaffold for cardiac tissue engineering.