3D Cell Culture
Although not a new trend, 3D culture is a growing concept in 2020. During 2019, 72,000 papers were published discussing 3D culture, in comparison to 46,000 papers in 2018. While the concept of 3D culture is not new, interesting developments and approaches are evolving.

Notorious for its high failure rate, drug development involves many promising candidates failing to live up to their expectations in clinical trials, resulting in a major source of financial loss for the industry.

Discussion within the pharmaceutical industry has highlighted hopes for better research in the early stages, which will be important in helping prevent costly losses in the future. Human primary cell culture plays a large role in this.

Although cell culture can be praised for its many scientific advances, 2D culture, unfortunately, has its disadvantages linked to the reflection of normal behavior of cells seen in living tissue. In comparison, 3D culture aims to reduce the restriction of growing on one flat surface, and presents the ability to stack up on top and around each other, as seen in tissue.

A common approach is to culture the cells on a 3D scaffold. Recent studies have researched what kind of scaffold should be used and how it is engineered. Further research has explored varied approaches, including graphene scaffolds, nanofibers, freeze-casting, 3D printing, and even utilizing natural marine collagen. Some researchers have investigated losing the scaffold altogether using magnetic levitation to give cells the ability to assemble in 3D.

Certainly, this area of cell culture is growing at a rapid rate and, in the process, demonstrates the full creativity of scientific research.

4D Cell Culture
With the increased interest in 3D cell culture, another dimension to cell culture could be added in the near future. 4D culture combines the benefits of 3D cell culture, with the addition of a culture medium that mimics the extracellular matrix (ECM) of native tissue more thoroughly.

Most 3D systems are static and, therefore, cannot capture the dynamic nature of the ECM. The ECM interacts with cells and includes a complex range of biochemical cues and physical properties that differ across space and time. In order to advance the study of fundamental cell biology and enhance human tissue engineering, this would need to be recreated.

Researchers have started to explore different ways to potentially modify cell culture on demand during an experiment, while avoiding damage to cells. One approach involves using light to modify the behavior of a photoresponsive hydrogel.

In a 2019 study, researchers produced a 4D cell culture, integrating a light-activated peptidomimetic into the hydrogel. They cultured human umbilical vein endothelial cells (HUVECs) in the presence of the growth factor VEGF, and activated the peptidomimetic using a laser.

Cells in light-exposed areas widely migrated and created a complex microvascular network within a week. Unilluminated HUVECs did not present these changes and became non-viable within three days, despite the presence of VEGF.

Researchers stated that the findings explain how the approach can control the culture environment in 3D space and time, giving the opportunity to control angiogenesis directly with the simple use of light.

Developments Closer to Biological Reality
In the future, there will undoubtedly be continued innovation in stem cell culture to aid in vitro experiments in mimicking biological reality more carefully.

In a recent study in 2020, a new approach was used involving a barrier substrate called the breath figure method. The method was used to mimic the blood-retinal barrier in the eye, which is known as a critical location in the disease pathology of macular degeneration.

On opposite sides of the barrier, they cultured hiPSC-derived retinal pigment epithelium and endothelial cells, and they were both coated with collagen using a technique known as the Langmuir-Schaefer technique. This process creates a highly porous film with a honeycomb-like surface.

Through this, a three-layered culture was created, in which both layers of cells could easily exchange substances through the barrier, while sustaining physical separation.

Researchers of the study note the technique results in the avoidance of the use of in vivoanimal models of the disease. In addition, they highlight the drawbacks of existing in vitromodels of the barrier, which have been too simple to reflect the function of this anatomy or the progression of the disease.

How Has Bioprinting Helped?
In the field of regenerative medicine, 3D bioprinting has been embraced due to its remarkable potential in the construction of complex functional tissues and organoids.

The value of 3D bioprinting is particularly noteworthy in the bioprinting of blood vessels. Vasculature formation has been an ongoing obstacle in tissue engineering because it needs to be both precise and complex on a tremendously small scale. These challenges can now be overcome with the tools that bioprinting offers.

Previously, fugitive bioinks have been successfully used to form tubular matrices for endothelial cells to be seeded. First, the hydrogel is cast around the bioink, and it is subsequently flushed away, leaving behind a surface on which the cells can form a lumen.

In a 2019 study, researchers investigated the combination of cellular self-assembly with 3D bioprinting using PromoCell HDMECs and HUVECs to escape the need for fugitive bioinks or preformed channels.

Investigations used a drop-on-demand method involving endothelial cells in a suspended or spheroid bioink, and it was possible to form a lumen positioned between two layers of hydrogel.

The bioprinting gave the opportunity to command several biologically relevant structures, and, after printing, cells displayed self-assembly, including undirected branching into lumens with smaller diameters, as seen in the human vascular system.

Simplifying Research with HLA-Typed Cells
Human leukocyte antigen (HLA) molecules play an important role in the human body. They allow the immune system to identify antigens and mount a response against invading pathogens.

In research, this role is vital in areas like organ transplantation, where donor and recipient HLA types need to be matched for the prevention of rejection, and in the development of cancer immunotherapy, a growing field with huge potential.

This kind of test can be slow, especially in research, with it taking up to several weeks to receive results from traditional HLA-typing. There is a unique inventory of more than 100 HLA-typed donor cells to streamline the process. These cells are received from a variety of human tissues, including the musculoskeletal system, kidney, peripheral blood cells, bone marrow, and more, and they are available to ship complete with their HLA-typing report.

A recent study in 2019 used HLA-typed cells to prove that HLA type II antibodies can induce necrotic cell death in endothelial cells through a complement-independent pathway. The endothelium is critical in antibody-mediated rejection development in solid organ transplantation, so this research could help inform about approaches to prevent or treat rejection.

What is in Store for the Future?
The steps researchers and scientists took in 2019 have positively contributed to improvements and advances in the types, throughput, and fundamental ideas in cell culture, giving way to new releases in the future.