Gene transfection to spheroid culture system on micropatterned culture plate by polyplex nanomicelle: a novel platform of genetically-modified cell transplantation

Sonoprinting nanoparticles on cellular spheroids via surface acoustic waves for enhanced nanotherapeutics delivery

Nanotherapeutics, on their path to the target tissues, face numerous physicochemical hindrances that affect their therapeutic efficacy. Physical barriers become more pronounced in pathological tissues, such as solid tumors, where they limit the penetration of nanocarriers into deeper regions, thereby preventing the efficient delivery of drug cargo. To address this challenge, we introduce a novel approach that employs surface acoustic wave (SAW) technology to sonoprint and enhance the delivery of nanoparticles onto and into cell spheroids. Our SAW platform is designed to generate focused and unidirectional acoustic waves for creating vigorous acoustic streaming while promoting Bjerknes forces. The effect of SAW excitation on cell viability, as well as the accumulation and penetration of nanoparticles on human breast cancer (MCF 7) and mouse melanoma (YUMM 1.7) cell spheroids were investigated. The high frequency, low input voltage, and contact-free nature of the proposed SAW system ensured over 92% cell viability for both cell lines after SAW exposure. SAW sonoprinting enhanced the accumulation of 100 nm polystyrene particles on the periphery of the spheroids to near four-fold, while the penetration of nanoparticles into the core regions of the spheroids was improved up to three times. To demonstrate the effectiveness of our SAW platform on the efficacy of nanotherapeutics, the platform was used to deliver nanoliposomes encapsulated with the anti-cancer metal compound copper diethyldithiocarbamate (CuET) to MCF 7 and YUMM 1.7 cell spheroids. A three-fold increase in the cytotoxic activity of the drug was observed in spheroids under the effect of SAW, compared to controls. The capacity of SAW-based devices to be manufactured as minuscule wearable patches can offer highly controllable, localized, and continuous acoustic waves to enhance drug delivery efficiency to target tissues.

Genetically modified cell spheroids for tissue engineering and regenerative medicine

Cell spheroids offer cell-to-cell interactions and show advantages in survival rate and paracrine effect to solve clinical and biomedical inquiries ranging from tissue engineering and regenerative medicine to disease pathophysiology. Therefore, cell spheroids are ideal vehicles for gene delivery. Genetically modified spheroids can enhance specific gene expression to promote tissue regeneration. Gene deliveries to cell spheroids are via viral vectors or non-viral vectors. Some new technologies like CRISPR/Cas9 also have been used in genetically modified methods to deliver exogenous gene to the host chromosome. It has been shown that genetically modified cell spheroids had the potential to differentiate into bone, cartilage, vascular, nerve, cardiomyocytes, skin, and skeletal muscle as well as organs like the liver to replace the diseased organ in the animal and pre-clinical trials. This article reviews the recent articles about genetically modified spheroid cells and explains the fabrication, applications, development timeline, limitations, and future directions of genetically modified cell spheroid.

Synthetic anti-angiogenic genomic therapeutics for treatment of neovascular age-related macular degeneration

In light of the intriguing potential of anti-angiogenic approach in suppressing choroidal neovascularization, we attempted to elaborate synthetic gene delivery systems encapsulating anti-angiogenic plasmid DNA as alternatives of clinical antibody-based therapeutics. Herein, block copolymer of cyclic Arg-Gly-Asp-poly(ethylene glycol)-poly(lysine-thiol) [RGD-PEG-PLys(thiol)] with multifunctional components was tailored in manufacture of core-shell DNA delivery nanoparticulates. Note that the polycationic PLys segments were electrostatically complexed with anionic plasmid DNA into nanoscaled core, and the tethered biocompatible PEG segments presented as the spatial shell (minimizing non-specific reactions in biological milieu). Furthermore, the aforementioned self-assembly was introduced with redox-responsive disulfide crosslinking due to the thiol coupling. Hence, reversible stabilities, namely stable in extracellular milieu but susceptible to disassemble for liberation of the DNA payloads in intracellular reducing microenvironment, were verified to facilitate transcellular gene transportation. In addition, RGD was installed onto the surface of the proposed self-assemblies with aim of targeted accumulation and internalization into angiogenic endothelial cells given that RGD receptors were specifically overexpressed on their cytomembrane surface. The proposed anti-angiogenic DNA therapeutics were validated to exert efficient expression of anti-angiogenic proteins in endothelial cells and elicit potent inhibition of ocular neovasculature post intravitreous administration. Hence, the present study approved the potential of gene therapy in treatment of choroidal neovascularization. In light of sustainable gene expression properties of DNA therapeutics, our proposed synthetic gene delivery system inspired prosperous potentials in long-term treatment of choroidal neovascularization, which should be emphasized to develop further towards clinical translations.

mRNA as a Tool for Gene Transfection in 3D Cell Culture for Future Regenerative Therapy

A combination of three-dimensional (3D) cell culturing and non-viral gene transfection is promising in improving outcomes of cell transplantation therapy. Herein, gene transfection profiles in 3D cell culture were compared between plasmid DNA (pDNA) and messenger RNA (mRNA) introduction, using mesenchymal stem cell (MSC) 3D spheroids. Green fluorescence protein (GFP) mRNA induced GFP protein expression in 77% of the cells in the spheroids, whereas only 34% of the cells became GFP positive following pDNA introduction. In mechanistic analyses, most of the cells in MSC spheroids were non-dividing, and pDNA failed to induce GFP expression in most of the non-dividing cells. In contrast, both dividing and non-dividing cells became GFP-positive after mRNA introduction, which led to a high overall percentage of GFP-positive cells in the spheroids. Consequently, mRNA encoding an osteogenic factor, runt-related transcription factor 2 (Runx2), allowed in vitro osteogenic differentiation of MSCs in spheroids more efficiently compared to Runx2 pDNA. Conclusively, mRNA exhibits high potential in gene transfection in 3D cell culture, in which the cell division rate is lower than that in monolayer culture, and the combination of mRNA introduction and 3D cell culture is a promising approach to improve outcomes of cell transplantation in future regenerative therapy.

Treatment of Bone Defects by Transplantation of Genetically Modified Mesenchymal Stem Cell Spheroids

Cell transplantation is promising for regenerative medicine. A combination of a three-dimensional spheroid culture system with gene transfection was developed to enhance the therapeutic effects of mesenchymal stem cell (MSC) transplantation. The spheroid cell culture system is based on micropatterned substrates composed of a regular array of 100-μm-diameter cell-adhesion areas coated with a temperature-responsive polymer, poly (N-isopropylacrylamide-co-methacrylic acid), which allows for spheroid detachment by simply cooling the plates. In this study, MSC spheroids were transfected with plasmid DNA encoding runt-related transcription factor 2 (Runx2) and tested for their ability to enhance bone regeneration. In vitro analyses revealed that osteogenic differentiation of the MSCs was enhanced by forming spheroids and was further promoted by Runx2 expression. The enhanced osteogenic differentiation was maintained under pathological conditions, such as hypoxia and inflammation. Transplanting Runx2-transfected MSC spheroids into bone defects on rat femurs induced significantly faster bone regeneration compared with nontransfected MSC spheroids or genetically modified MSCs from conventional monolayer culture. MSC migration into the bone defect area was enhanced by upregulation of cell-migration-related genes. In conclusion, genetically modified MSC spheroids are effective for enhancing bone regeneration, providing a promising option for cell transplantation therapy in the fields of regenerative medicine.

Multicellular Tumor Spheroids (MCTS) as a 3D In Vitro Evaluation Tool of Nanoparticles

Multicellular tumor spheroid models (MCTS) are often coined as 3D in vitro models that can mimic the microenvironment of tissues. MCTS have gained increasing interest in the nano-biotechnology field as they can provide easily accessible information on the performance of nanoparticles without using animal models. Considering that many countries have put restrictions on animals testing, which will only tighten in the future as seen by the recent developments in the Netherlands, 3D models will become an even more valuable tool. Here, an overview on MCTS is provided, focusing on their use in cancer research as most nanoparticles are tested in MCTS for treatment of primary tumors. Thereafter, various types of nanoparticles-from self-assembled block copolymers to inorganic nanoparticles, are discussed. A range of physicochemical parameters including the size, shape, surface chemistry, ligands attachment, stability, and stiffness are found to influence nanoparticles in MCTS. Some of these studies are complemented by animal studies confirming that lessons from MCTS can in part predict the behaviour in vivo. In summary, MCTS are suitable models to gain additional information on nanoparticles. While not being able to replace in vivo studies, they can bridge the gap between traditional 2D in vitro studies and in vivo models.

Gene Transfection toward Spheroid Cells on Micropatterned Culture Plates for Genetically-modified Cell Transplantation

To improve the therapeutic effectiveness of cell transplantation, a transplantation system of genetically modified, injectable spheroids was developed. The cell spheroids are prepared in a culture system on micropatterned plates coated with a thermosensitive polymer. A number of spheroids are formed on the plates, corresponding to the cell adhesion areas of 100 µm diameter that are regularly arrayed in a two-dimensional manner, surrounded by non-adhesive areas that are coated by a polyethylene glycol (PEG) matrix. The spheroids can be easily recovered as a liquid suspension by lowering the temperature of the plates, and their structure is well maintained by passing them through injection needles with a sufficiently large caliber (over 27 G). Genetic modification is achieved by gene transfection using the original non-viral gene carrier, polyplex nanomicelle, which is capable of introducing genes into cells without disrupting the spheroid structure. For primary hepatocyte spheroids transfected with a luciferase-expressing gene, the luciferase is sustainably obtained in transplanted animals, along with preserved hepatocyte function, as indicated by albumin expression. This system can be applied to a variety of cell types including mesenchymal stem cells.

An injectable spheroid system with genetic modification for cell transplantation therapy

The new methodology to increase a therapeutic potential of cell transplantation was developed here by the use of three-dimensional spheroids of transplanting cells subsequent to the genetic modification with non-viral DNA vectors, polyplex nanomicelles. Particularly, spheroids in regulated size of 100-μm of primary hepatocytes transfected with luciferase gene were formed on the micropatterned culture plates coated with thermosensitive polymer, and were recovered in the form of injectable liquid suspension simply by cooling the plates. After subcutaneously transplanting these hepatocyte spheroids, efficient transgene expression was observed in host tissue for more than a month, whereas transplantation of a single-cell suspension from a monolayer culture resulted in an only transient expression. The spheroid system contributed to the preservation of innate functions of transplanted hepatocytes in the host tissue, such as albumin expression, thereby possessing high potential for expressing transgene. Intravital observation of transplanted cells showed that those from spheroid cultures had a tendency to localize in the vicinity of blood vessels, making a favorable microenvironment for preserving cell functionality. Furthermore, spheroids transfected with erythropoietin-expressing DNA showed a significantly higher hematopoietic effect than that of cell suspensions from monolayer cultures, demonstrating high potential of this genetically-modified spheroid transplantation system for therapeutic applications.