Injectable collagen implant improves survival, cardiac remodeling, and function in the early period after myocarditis in rats

Engineered Gold and Silica Nanoparticle-Incorporated Hydrogel Scaffolds for Human Stem Cell-Derived Cardiac Tissue Engineering

Electrically conductive biomaterials and nanomaterials have demonstrated great potential in the development of functional and mature cardiac tissues. In particular, gold nanomaterials have emerged as promising candidates due to their biocompatibility and ease of fabrication for cardiac tissue engineering utilizing rat- or stem cell-derived cardiomyocytes (CMs). However, despite significant advancements, it is still not clear whether the enhancement in cardiac tissue function is primarily due to the electroconductivity features of gold nanoparticles or the structural changes of the scaffold resulting from the addition of these nanoparticles. To address this question, we developed nanoengineered hydrogel scaffolds comprising gelatin methacrylate (GelMA) embedded with either electrically conductive gold nanorods (GNRs) or nonconductive silica nanoparticles (SNPs). This enabled us to simultaneously assess the roles of electrically conductive and nonconductive nanomaterials in the functionality and fate of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Our studies revealed that both GNR- and SNP-incorporated hydrogel scaffolds exhibited excellent biocompatibility and similar cardiac cell attachment. Although the expression of sarcomere alpha-actinin did not significantly differ among the conditions, a more organized sarcomere structure was observed within the GNR-embedded hydrogels compared to the nonconductive nanoengineered scaffolds. Furthermore, electrical coupling was notably improved in GNR-embedded scaffolds, as evidenced by the synchronous calcium flux and enhanced calcium transient intensity. While we did not observe a significant difference in the gene expression profile of human cardiac tissues formed on the conductive GNR- and nonconductive SNP-incorporated hydrogels, we noticed marginal improvements in the expression of some calcium and structural genes in the nanomaterial-embedded hydrogel groups as compared to the control condition. Given that the cardiac tissues formed atop the nonconductive SNP-based scaffolds (used as the control for conductivity) also displayed similar levels of gene expression as compared to the conductive hydrogels, it suggests that the electrical conductivity of nanomaterials (i.e., GNRs) may not be the sole factor influencing the function and fate of hiPSC-derived cardiac tissues when cells are cultured atop the scaffolds. Overall, our findings provide additional insights into the role of electrically conductive gold nanoparticles in regulating the functionalities of hiPSC-CMs.

Improving the development of human engineered cardiac tissue by gold nanorods embedded extracellular matrix for long-term viability

A myocardial infarction (MI), commonly called a heart attack, results in the death of cardiomyocytes (CMs) in the heart. Tissue engineering provides a promising strategy for the treatment of MI, but the maturation of human engineered cardiac tissue (hECT) still requires improvement. Conductive polymers and nanomaterials have been incorporated into the extracellular matrix to enhance the mechanical and electrical coupling between cardiac cells. Here we report a simple approach to incorporate gold nanorods (GNRs) into the fibrin hydrogel to form a GNR-fibrin matrix, which is used as the major component of the extracellular matrix for forming a 3D hECT construct suspended between two flexible posts. The hECTs made with GNR-fibrin hydrogel showed markers of maturation such as higher twitch force, synchronous beating activity, sarcomere maturation and alignment, t-tubule network development, and calcium handling improvement. Most importantly, the GNR-hECTs can survive over 9 months. We envision that the hECT with GNRs holds the potential to restore the functionality of the infarcted heart.

Preparation, characterization and biocompatibility of calcium peroxide-loaded polycaprolactone microparticles

OBJECTIVES

To explore the physicochemical characteristics and biocompatibility of calcium peroxide (CPO)-loaded polycaprolactone (PCL) microparticle.

METHODS

The CPO/PCL particles were prepared. The morphology and elemental distribution of CPO, PCL and CPO/PCL particles were observed with scanning electron microscopy and energy dispersive spectroscopy, respectively. Rat adipose mesenchymal stem cells were isolated and treated with different concentrations (0.10%, 0.25%, 0.50%, 1.00%) of CPO or CPO/PCL particles. The mesenchymal stem cells were cultured in normal media or osteogenic differentiation media under the hypoxia/normoxia conditions, and the amount of released O2 and H2O2 after CPO/PCL treatment were detected. The gene expressions of alkaline phosphatase (ALP), Runt-associated transcription factor 2 (RUNX2), osteopontin (OPN) and osteocalcin (OCN) were detected by realtime RT-PCR. SD rats were subcutaneously injected with 1.00% CPO/PCL particles and the pathological changes and infiltration of immune cells were observed with HE staining and immunohistochemistry at day 7 and day 14 after injection.

RESULTS

Scanning electron microscope showed that CPO particles had a polygonal structure, PCL particles were in a small spherical plastic particle state, and CPO/PCL particles had a block-like crystal structure. Energy dispersive spectroscopy revealed that PCL particles showed no calcium mapping, while CPO/PCL particles showed obvious and uniform calcium mapping. The concentrations of O2 and H2O2 released by CPO/PCL particles were lower than those of CPO group, and the oxygen release time was longer. The expressions of Alp, Runx2, Ocn and Opn increased with the higher content of CPO/PCL particles under hypoxia in osteogenic differentiation culture and normal culture, and the induction was more obvious under osteogenic differentiation conditions (all P<0.05). HE staining results showed that the muscle tissue fibers around the injection site were scattered and disorderly distributed, with varying sizes and thicknesses at day 7 after particle injection. Significant vascular congestion, widened gaps, mild interstitial congestion, local edema, inflammatory cell infiltration, and large area vacuolization were observed in some tissues of rats. At day 14 after microparticle injection, the muscle tissue around the injection site and the tissue fibers at the microparticle implantation site were arranged neatly, and the gap size was not thickened, the vascular congestion, local inflammatory cell infiltration, and vacuolization were significantly improved compared with those at day 7. The immunohistochemical staining results showed that the expressions of CD3 and CD68 positive cells significantly increased in the surrounding muscle tissue, and were densely distributed in a large area at day 7 after particle injection. At day 14 of microparticle injection, the numbers of CD3 and CD68 positive cells in peripheral muscle tissue and tissue at the site of particle implantation were lower than those at day 7 (all P<0.01).

CONCLUSIONS

CPO/PCL particles have good oxygen release activity, low damage to tissue, and excellent biocompatibility.

Electroconductive biomaterials for cardiac tissue engineering

Myocardial infarction (MI) is still the leading cause of mortality worldwide. The success of cell-based therapies and tissue engineering strategies for treatment of injured myocardium have been notably hindered due to the limitations associated with the selection of a proper cell source, lack of engraftment of engineered tissues and biomaterials with the host myocardium, limited vascularity, as well as immaturity of the injected cells. The first-generation approaches in cardiac tissue engineering (cTE) have mainly relied on the use of desired cells (e.g., stem cells) along with non-conductive natural or synthetic biomaterials for in vitro construction and maturation of functional cardiac tissues, followed by testing the efficacy of the engineered tissues in vivo. However, to better recapitulate the native characteristics and conductivity of the cardiac muscle, recent approaches have utilized electroconductive biomaterials or nanomaterial components within engineered cardiac tissues. This review article will cover the recent advancements in the use of electrically conductive biomaterials in cTE. The specific emphasis will be placed on the use of different types of nanomaterials such as gold nanoparticles (GNPs), silicon-derived nanomaterials, carbon-based nanomaterials (CBNs), as well as electroconductive polymers (ECPs) for engineering of functional and electrically conductive cardiac tissues. We will also cover the recent progress in the use of engineered electroconductive tissues for in vivo cardiac regeneration applications. We will discuss the opportunities and challenges of each approach and provide our perspectives on potential avenues for enhanced cTE. STATEMENT OF SIGNIFICANCE: Myocardial infarction (MI) is still the primary cause of death worldwide. Over the past decade, electroconductive biomaterials have increasingly been applied in the field of cardiac tissue engineering. This review article provides the readers with the leading advances in the in vitro applications of electroconductive biomaterials for cTE along with an in-depth discussion of injectable/transplantable electroconductive biomaterials and their delivery methods for in vivo MI treatment. The article also discusses the knowledge gaps in the field and offers possible novel avenues for improved cardiac tissue engineering.

Cardiac Morphology and Collagen Deposition in A Glucose-6-Phosphatase Catalytic Subunit 3 (G6PC3) Knockout Mouse model

Background

Glucose-6-phosphatase-- β (3), one of multiple isoforms of glucose-6-phosphatase, catalyzes the final step in gluconeogenesis. It is known that mutated G6P3 is associated with severe neutropenia in addition to congenital heart defects, but little is known about the histological changes in cardiac tissue as a result of mutated or deleted G6PC3⁴.

Objectives

We sought to further characterize the histological alterations caused by deleted G6PC3 and determine the role of collagen deposition, myocyte proliferation and apoptosis in these changes.

Methods

Cardiac tissue from G6PC3 knockout mice and WT mice were harvested, imbedded and stained for markers of collagen (Trichrome), proliferation (KI-67), apoptosis (caspase 3) and hematopoietic stem cells (CD34). Slides were digitally uploaded, and Leica stain quantification was calculated.

Results

We demonstrated that in G6PC3 knock out adult mice have significant differences in heart morphology including decreased left ventricular collagen, decreased cellular proliferation and increased apoptosis histologically.

Conclusions

As compared to wild type, the hearts of G6PC3 knockout mice demonstrated significantly decreased collagen globally, a crucial component for adequate strength and contractility of myocardial tissue. More investigation should be done to further explore the functional effects of such alterations via echocardiograms.

Cardio-supportive devices (VRD & DCC device) and patches for advanced heart failure: A review, summary of state of the art and future directions

Congestive heart failure (CHF) is a complicated pathophysiological syndrome, leading cause of hospitalization as well as mortalities in developed countries wherein an irregular function of the heart leads to the insufficient blood supply to the body organs. It is an accumulative slackening of various complications including myocardial infarction (MI), coronary heart disease (CAD), hypertension, valvular heart disease (VHD) and cardiomyopathy; its hallmarks include hypertrophy, increased interstitial fibrosis and loss of myocytes. The etiology of CHF is very complex and despite the rapid advancement in pharmacological and device-based interventional therapies still, a single therapy may not be sufficient to meet the demand for coping with the diseases. Total artificial hearts (TAH) and ventricular assist devices (VADs) have been widely used clinically to assist patients with severe HF. Unfortunately, direct contact between the patient's blood and device leads to thromboembolic events, and then coagulatory factors, as well as, infection contribute significantly to complicate the situation. There is no effective treatment of HF except cardiac transplantation, however, genetic variations, tissue mismatch; differences in certain immune response and socioeconomic crisis are an important concern with cardiac transplantation suggesting an alternate bridge to transplant (BTT) or destination therapies (DT). For these reasons, researchers have turned to mechanically driven compression devices, ventricular restraint devices (VRD) and heart patches. The ASD is a combination of all operational patches and cardiac support devices (CSD) by delivering biological agents and can restrain or compress the heart. Present study summarizes the accessible peer-reviewed literature focusing on the mechanism of Direct Cardiac Compression (DCC) devices, VRD and patches and their acquaintance to optimize the therapeutic efficacy in a synergistic way.

VA-086 methacrylate gelatine photopolymerizable hydrogels: A parametric study for highly biocompatible 3D cell embedding

The ability to replicate in vitro the native extracellular matrix (ECM) features and to control the three-dimensional (3D) cell organization plays a fundamental role in obtaining functional engineered bioconstructs. In tissue engineering (TE) applications, hydrogels have been successfully implied as biomatrices for 3D cell embedding, exhibiting high similarities to the natural ECM and holding easily tunable mechanical properties. In the present study, we characterized a promising photocrosslinking process to generate cell-laden methacrylate gelatin (GelMA) hydrogels in the presence of VA-086 photoinitiator using a ultraviolet LED source. We investigated the influence of prepolymer concentration and light irradiance on mechanical and biomimetic properties of resulting hydrogels. In details, the increasing of gelatin concentration resulted in enhanced rheological properties and shorter polymerization time. We then defined and validated a reliable photopolymerization protocol for cell embedding (1.5% VA-086, LED 2 mW/cm2) within GelMA hydrogels, which demonstrated to support bone marrow stromal cells viability when cultured up to 7 days. Moreover, we showed how different mechanical properties, derived from different crosslinking parameters, strongly influence cell behavior. In conclusion, this protocol can be considered a versatile tool to obtain biocompatible cell-laden hydrogels with properties easily adaptable for different TE applications.