Acoustic and Magnetic Stimuli-Based Three-Dimensional Cell Culture Platform for Tissue Engineering

In a conventional two-dimensional (2D) culture method, cells are attached to the bottom of the culture dish and grow into a monolayer. These 2D culture methods are easy to handle, cost-effective, reproducible, and adaptable to growing many different types of cells. However, monolayer 2D cell culture conditions are far from those of natural tissue, indicating the need for a three-dimensional (3D) culture system. Various methods, such as hanging drop, scaffolds, hydrogels, microfluid systems, and bioreactor systems, have been utilized for 3D cell culture. Recently, external physical stimulation-based 3D cell culture platforms, such as acoustic and magnetic forces, were introduced. Acoustic waves can establish acoustic radiation force, which can induce suspended objects to gather in the pressure node region and aggregate to form clusters. Magnetic targeting consists of two components, a magnetically responsive carrier and a magnetic field gradient source. In a magnetic-based 3D cell culture platform, cells are aggregated by changing the magnetic force. Magnetic fields can manipulate cells through two different methods: positive magnetophoresis and negative magnetophoresis. Positive magnetophoresis is a way of imparting magnetic properties to cells by labeling them with magnetic nanoparticles. Negative magnetophoresis is a label-free principle-based method. 3D cell structures, such as spheroids, 3D network structures, and cell sheets, have been successfully fabricated using this acoustic and magnetic stimuli-based 3D cell culture platform. Additionally, fabricated 3D cell structures showed enhanced cell behavior, such as differentiation potential and tissue regeneration. Therefore, physical stimuli-based 3D cell culture platforms could be promising tools for tissue engineering.

Mutation Analysis of the rpoB Gene in the Radiation-Resistant Bacterium Deinococcus radiodurans R1 Exposed to Space during the Tanpopo Experiment at the International Space Station

To investigate microbial viability and DNA damage, dried cell pellets of the radiation-resistant bacterium Deinococcus radiodurans were exposed to various space environmental conditions at the Exposure Facility of the International Space Station (ISS) as part of the Tanpopo mission. Mutation analysis was done by sequencing the rpoB gene encoding RNA polymerase β-subunit of the rifampicin-resistant mutants. Samples included bacteria exposed to the space environment with and without exposure to UV radiation as well as control samples held in the ISS cabin and at ground. The mutation sites of the rpoB gene obtained from the space-exposed and ISS/ground control samples were similar to the rpoB mutation sites previously reported in D. radiodurans. Most mutations were found at or near the rifampicin binding site in the RNA polymerase β-subunit. Mutation sites found in UV-exposed samples were mostly shared with non-exposed and ISS/ground control samples. These results suggest that most mutations found in our experiments were induced during procedures that were applied across all treatments: preparation, transfer from our laboratory to the ISS, return from the ISS, and storage before analysis. Some mutations may be enhanced by specific factors in the space experiments, but the mutations were also found in the spontaneous and control samples. Our experiment suggests that the dried cells of the microorganism D. radiodurans can travel without space-specific deterioration that may induce excess mutations relative to travel at Earth's surface. However, upon arrival at a recipient location, they must still be able to survive and repair the general damage induced during travel.

Three-dimensional cellular aggregates formed by Beauveria pseudobassiana in liquid culture with potential for use as a biocontrol agent of the African black beetle (Heteronychus arator)

Beauveria pseudobassiana formed three-dimensional aggregates of cells (CAs) in liquid culture. CAs were formed mainly by blastospores and conidia, distinct from microsclerotia formed through adhesion of hyphae. The formation, germination and sporulation of CAs were studied, as well as the pathogenicity of conidia produced from them against adults of black beetle. After 4 days of culture, CAs were formed, becoming compact and melanised after 10 days of incubation. Electron microscopy showed three-dimensional CAs averaging 431.65 µm in length with irregular shapes and rough surfaces, where cells were trapped within an extracellular matrix. CAs germinated after 2 days of incubation on agar-plates producing hyphae and forming phialides and conidia after 4 days. Produced conidia caused 45% mortality of black beetle adults. CAs germination and sporulation on soil were directly correlated with soil moisture, reaching 80% and 100% germination on the surface of soil with 17% and 30% moisture, respectively. CAs maintained 100% germination after 2 years of storage under refrigeration. These CAs could have a similar function as microsclerotia in nature, acting as resistant structures able to protect internal cells and their ability to sporulate producing infective conidia, suggesting their potential to be used as bioinsecticides to control soil-dwelling insects.

A basic study on self-reconstitution of alveolar epithelium-like cells by tissue stem cells in mouse lung

In recent research on regenerative medicine, three-dimensional (3D) tissue reconstruction using the induced pluripotent stem cell (iPS cell) differentiated cells has attracted attention. In this study, mouse lungs at 1.5, 10, and 20 d old were subjected to enzyme treatment, and aggregates formed in serum-free suspension culture (3D-culture) were observed. The number of aggregates formed was the highest in 1.5 d. The cell aggregates in which the interior of the aggregate is filled and form small vacuoles and the organoid-like aggregates having a relatively large vacuole inside and forming the alveolar-like structure were observed. At 1.5 d, the formation ratio of the organoid-like aggregates was the highest and aggregate size was small at 20 d. For the cell aggregates derived from 1.5 d, positive cells of SSEA-1, CD29, CD90, CD105, alveolar epithelial stem cell marker of SP-C, and Sca-1 were observed in the center. In the cell aggregates derived from 10 d, the expression level of 1.5 d each protein markers and OCT4 gene of transcription factor was decreased, and furthermore, markers were hardly observed in the organoid-like aggregates derived from 10 d. In addition, cells surrounding the vacuole of organoid-like aggregate obtained over 10 d differentiated into periodic acid-Schiff (PAS), podoplanin-positive cells. When the formed cell aggregates were dispersed, cell aggregates and organoid-like aggregates were reformed. Comparing 3D-culture and adhesion culture (2D-culture), SP-C expression of 10 d of cells was maintained. Expression of markers of undifferentiated markers and alveolar tissue stem cells decreased when cell aggregates were cultured with the addition of fetal bovine serum.

Reconstruction of Regenerative Stem Cell Niche by Cell Aggregate Engineering

The niche plays critical roles in regulating functionality and determining regenerative outcomes of stem cells, for which establishment of favorable microenvironments is in demand in translational medicine. In recent years, the cell aggregate technology has shown immense potential to reconstruct a beneficial topical niche for stem cell-mediated regeneration, which has been recognized as a promising concept for high-density stem cell delivery with preservation of the self-produced, tissue-specific extracellular matrix microenvironments. Here, we describe the basic methodology of stem cell aggregate-based niche engineering and quality check indexes prior to application.

Performing Axon Orientation Assays with Secreted Semaphorins and Other Guidance Cues

The guidance of axons within the developing nervous system is orchestrated by a variety of cues that successively and complementary attract or repel axons to achieve a stereotyped wiring of neural circuits. Here we present a version of a method that has been widely used to identify and characterize the effect of guidance cues on the orientation of axons. We describe the coculture, within a three-dimensional environment, of dorsal spinal cord explants together with a cell aggregate secreting a candidate cue and the method to quantify the effect of this cue on axon orientation.

An in vitro model for hepatocyte-like cell differentiation from Wharton's jelly derived-mesenchymal stem cells by cell-base aggregates

AIM

The present study investigated the differentiation potential of human Umbilical Cord Mesenchymal Stem Cells (UCMSCs) into hepatic lineage through embryonic body-like aggregate formation in the presence of IGF-1.

BACKGROUND

Cells derived from Wharton's jelly have been reported to display a wide multilineage differentiation potential, showing some similarities to both embryonic (ESC) and mesenchymal stem cells (MSCs).

PATIENTS AND METHODS

Human MSCs isolated from the umbilical cord were plated in 20 μL micro drops. A two-step differentiation protocol was used and the cell aggregates were exposed to the media supplemented with IGF, HGF, oncostatin M, and dexamethasone for 21 days. Immunoperoxidase and immuno-fluorescence were performed for cyrokeratins 18, 19 and albumin. Functional assays were done by periodic acid Schiff (PAS) and indocyanine green.

RESULTS

The expression of cytokeratin 19 was shown to be higher in the cells derived from 3D spheroids compared to those cultured in conventional protocol. They showed a polygonal shape after being exposed to hepatogenic media. Immunostaining demonstrated the expression of cytokeratin-18, 19 and albumin by the differentiated cells. Besides, PAS staining revealed glycogen storage in differentiated cells. Also, a greater number of large size differentiated cells were found at the periphery of the expanded cell aggregates.

CONCLUSION

We established a protocol for UCMSC differentiation into hepatocytes and these cells were morphologically and functionally similar to hepatocytes. Thus, hepatocyte differentiation may be facilitated by the UCMSCs aggregate formation before administration of the differentiation protocols.