Long-term cultures of human pancreatic islets in self-assembling peptides hydrogels

Human pancreatic islets transplantation is an experimental therapeutic treatment for Type I Diabetes. Limited islets lifespan in culture remains the main drawback, due to the absence of native extracellular matrix as mechanical support after their enzymatic and mechanical isolation procedure. Extending the limited islets lifespan by creating a long-term in vitro culture remains a challenge. In this study, three biomimetic self-assembling peptides were proposed as potential candidates to recreate in vitro a pancreatic extracellular matrix, with the aim to mechanically and biologically support human pancreatic islets, by creating a three-dimensional culture system. The embedded human islets were analyzed for morphology and functionality in long-term cultures (14-and 28-days), by evaluating β-cells content, endocrine component, and extracellular matrix constituents. The three-dimensional support provided by HYDROSAP scaffold, and cultured into MIAMI medium, displayed a preserved islets functionality, a maintained rounded islets morphology and an invariable islets diameter up to 4 weeks, with results analogues to freshly-isolated islets. In vivo efficacy studies of the in vitro 3D cell culture system are ongoing; however, preliminary data suggest that human pancreatic islets pre-cultured for 2 weeks in HYDROSAP hydrogels and transplanted under subrenal capsule may restore normoglycemia in diabetic mice. Therefore, engineered self-assembling peptide scaffolds may provide a useful platform for long-term maintenance and preservation of functional human pancreatic islets in vitro.

Ultrasound Triggers Hypericin Activation Leading to Multifaceted Anticancer Activity

The use of ultrasound (US) in combination with a responsive chemical agent (sonosensitizer) can selectively trigger the agent's anticancer activity in a process called sonodynamic therapy (SDT). SDT shares some properties with photodynamic therapy (PDT), which has been clinically approved, but sets itself apart because of its use of US rather than light to achieve better tissue penetration. SDT provides anticancer effects mainly via the sonosensitizer-mediated generation of reactive oxygen species (ROS), although the precise nature of the underpinning mechanism is still under debate. This work investigates the SDT anticancer activity of hypericin (Hyp) in vitro in two- (2D) and three-dimensional (3D) HT-29 colon cancer models, and uses PDT as a yardstick due to its well-known Hyp phototoxicity. The cancer cell uptake and cellular localization of Hyp were investigated first to determine the proper noncytotoxic concentration and incubation time of Hyp for SDT. Furthermore, ROS production, cell proliferation, and cell death were evaluated after Hyp was exposed to US. Since cancer relapse and transporter-mediated multidrug resistance (MDR) are important causes of cancer treatment failure, the US-mediated ability of Hyp to elicit immunogenic cell death (ICD) and overcome MDR was also investigated. SDT showed strong ROS-mediated anticancer activity 48 h after treatment in both the HT-29 models. Specific damage-associated molecular patterns that are consistent with ICD, such as calreticulin (CRT) exposure and high-mobility group box 1 protein (HMGB1) release, were observed after SDT with Hyp. Moreover, the expression of the ABC transporter, P-glycoprotein (P-gp), in HT-29/MDR cells was not able to hinder cancer cell responsiveness to SDT with Hyp. This work reveals, for the first time, the US responsiveness of Hyp with significant anticancer activity being displayed, making it a full-fledged sonosensitizer for the SDT of cancer.

Multi-Functionalized Self-Assembling Peptides as Reproducible 3D Cell Culture Systems Enabling Differentiation and Survival of Various Human Neural Stem Cell Lines

Neural stem cells-based therapies have shown great potential for central nervous system regeneration, with three-dimensional (3D) culture systems representing a key technique for tissue engineering applications, as well as disease modeling and drug screenings. Self-assembling peptides (SAPs), providing biomimetic synthetic micro-environments regulating cellular functionality and tissue repair, constitute a suitable tool for the production of complex tissue-like structures in vitro. However, one of the most important drawbacks in 3D cultures, obtained via animal-derived substrates and serum-rich media, is the reproducibility and tunability of a standardized methodology capable to coax neural differentiation of different human cell lines. In this work we cultured four distinct human neural stem cell (hNSC) lines in 3D synthetic multifunctionalized hydrogel (named HYDROSAP) for up to 6 weeks. Three-dimensional cultures of differentiating hNSCs exhibited a progressive differentiation and maturation over time. All hNSCs-derived neurons in 3D culture system exhibited randomly organized entangled networks with increasing expression of GABAergic and glutamatergic phenotypes and presence of cholinergic ones. Oligodendrocytes formed insulating myelin sheaths positive for myelin basic protein (MBP). In summary, results demonstrated a successfully standardized and reproducible 3D cell culture system for hNSC differentiation and maturation in serum-free conditions useful for future therapies.

Three-dimensional cell culture models for anticancer drug screening: Worth the effort?

High attrition of new oncology drug candidates in clinical trials is partially caused by the poor predictive capacity of artificial monolayer cell culture assays early in drug discovery. Monolayer assays do not take the natural three-dimensional (3D) microenvironment of cells into account. As a result, false positive compounds often enter clinical trials, leading to high dropout rates and a waste of time and money. Over the past 2 decades, tissue engineers and cell biologists have developed a broad range of 3D in vitro culturing tools that better represent in vivo cell biology. These tools preserve the 3D architecture of cells and can be used to predict toxicity of and resistance against antitumor agents. Recent progress in tissue engineering further improves 3D models by taking into account the tumor microenvironment, which is important for metastatic progression and vascularization. However, the widespread implementation of 3D cell cultures into cell-based research programs has been limited by various factors, including their cost and reproducibility. In addition, different 3D cell culture techniques often produce spheroids of different size and shape, which can strongly influence drug efficacy and toxicity. Hence, it is imperative to morphometrically characterize multicellular spheroids to avoid generalizations among different spheroid types. Standardized 3D culturing procedures could further reduce data variability and enhance biological relevance. Here, we critically evaluate the benefits and challenges inherent to growing cells in 3D, along with an overview of the techniques used to form spheroids. This is done with a specific focus on antitumor drug screening.

[Self-assembling peptide GFS-4 nanofiber scaffolds for three-dimensional cell cultures and myocardial infarction repair]

The purpose of this study is to investigate the effects of self-assembling peptide GFS-4 on three-dimen-sional myocardial cell culture and tissue repair of myocardial infarction. The circular dichroism (CD) spectrum was used to detect secondary structure of GFS-4, and atomic force microscope (AFM) was used to analyze the microstructure of self-assembly. The nanofiber scaffolds self-assembled by GFS-4 were used as the three-dimensional culture material to observe the growth effect of cardiomyocytes. The model of myocardial infarction was established and the effect of GFS-4 on myocardial infarction was studied. The results indicated that self-assembling peptide GFS-4 could form mainly β-sheet structure that can form dense nanofiber scaffolds after 24 hours' self-assembling. The myocardial cells had a favorable growth status in GFS-4 nanofiber scaffold hydrogel when cells treated in three-dimen-sional cell culture. The experiment of repairing myocardial infarction in vitro proved that peptide GFS-4 hydrogel scaffold could alleviate tissue necrosis in a myocardial infarction area. As a new nanofiber scaffold material, self-assembling peptide GFS-4 can be used for three-dimensional cell culture and tissue repairing in myocardial infarction area.

Cytotoxicity evaluation of self-etching dentine bonding agents in a cell culture perfusion condition

OBJECTIVE

The aim of this study was to evaluate the cytotoxicity of three dentine bonding agents (G-Bond, Clearfil S(3) Bond and Clearfil SE Bond X) in cell-culture perfusion.

METHODS

In this experiment, 8×10(4) TCPC SV40 cells (bovine-pulp-derived cells transfected with simian virus 40 large T-antigen) in MEM-alpha media, 20%FCS were seeded on mesh in a 6-well plate and incubated at 37 °C with 5% CO(2). After 2 days, the mesh inserts were transferred to a 24-well plate and incubated in MEM-alpha media, 20%FCS with 50 μg/ml of ascorbic acid at 37 °C with 5% CO(2) for 14 days. The test materials were applied to the dentine discs of dentine barrier models. Three-dimensional cell cultures in mesh and perfusion conditions were generated in this experiment. Each material, as well as the negative control (President) and the positive control (vitrebond), was tested in 5 models with the tests repeated in triplicate. The MTT assay was used to determine cell viability after the diffusion of leachable toxicity from the tested materials through the dentine discs.

RESULTS

The cell survival rate with G-Bond and Clearfil S(3) Bond was 113.03 and 90.98 percent, respectively, whereas that with Clearfil SE Bond X was 111.83 percent. All three dentine bonding agents had no toxicity compared with the negative control group (P>.05).

CONCLUSIONS

All three self-etching dentine-bonding agents are nontoxic. Pulp damage caused by these three bonding agents is unlikely to occur in the clinic.