The human brain is the least understood organ in the human body. The brain is difficult to access as it is encased by protective layers, is highly susceptible to damage and is intricate in structure and function. This deficiency is best demonstrated by the lack of comprehension of its function and the scarcity of effective treatments for various neurological disorders, i.e. Parkinson’s disease, Alzheimer’s disease and motor neuron disorders. Scientists remain in debate over the inadequacies of conventional approaches, such as culturing of the human somatic cells in flat, stiff, 2D environments; an approach that often results in an irregular morphology and develops unnatural cell-cell interactions. To address this shortfall, new methods for culturing human neural (neuronal and glial) cells, particularly in vitro three-dimensional (3D) culture, to more accurately reconstruct the complex in vivo structure and function of the human brain and provide more realistic in vitro models for disease interrogation and treatment studies, have been proposed.
Engineering neural tissue that is more closely representative of that found in the human brain and central nervous system typically requires a scaffold or matrix to recreate the 3D in vivo microenvironment or niche. To this end, porous polymeric materials, such as polymerized high internal phase emulsion (polyHIPE) materials, possess great potential as scaffolds for 3D cell culture and for applications in tissue engineering. Neural precursor cells (NPCs) are a valuable research tool for the study of mature human neural cells in vitro, given their proliferative capacity and potential to differentiate to all neural cell types.
At present, a variety of protocols have already been proposed to direct the differentiation of pluripotent stem cells (PSC)-derived NPCs (PSC-NPCs) to specialized neuronal and glial sub-types. However, 2D NPC differentiation techniques fail to produce a population of cells that realistically mimic the natural, 3D, complex networked nature of the human brain. To address this, a team of researchers from Monash University and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia: Dr. Ashley Murphy, Dr. John Haynes, Assoc. Prof. Andrew Laslett, Prof. Neil Cameron and Assoc. Prof. Carmel O’Brien, presented an in-depth investigation of the ability of a tailored polyethylene glycol-based polyHIPE scaffold to support the 3D expansion and long-term differentiation culture of human PSC-NPCs. Their work is currently published in the research journals, Polymer Chemistry and Acta Biomaterialia.
Generally, the interconnected porosity of polyHIPE scaffolds lends the ability to support three-dimensional neural cell network formation due to limited resistance to cellular migration and re-organization. The scaffold material displays mechanical properties akin to that of the mammalian brain. On this basis, the researchers employed the utility of pluripotent stem cell-derived neural cells which were of greater clinical relevance than primary neural cell lines, in their investigations.
Based on the phenotypic data and functional analyses, the authors reported that the investigated material could support terminal in vitro neural differentiation of PSC-NPCs to a mixed population of viable and mature human neuronal and glial cells, for periods of up to 49 days. Moreover, their analyses revealed spontaneously active, synchronous and rhythmic calcium flux, as well as response to the neurotransmitter glutamate.
In summary, the study explored the ability of tailored polyethylene glycol-based polyHIPE cell culture scaffolds to support the three-dimensional maintenance and neural specialisation of both induced pluripotent stem- and embryonic stem cell-hNPCs. It was shown that the polyethylene glycol-based polyHIPE scaffolds could support the attachment, migration and expansion of PSC-hNPCs over a 14-day period in NPC maintenance culture conditions. In a statement to Advances in Engineering, Assoc. Prof. Carmel O’Brien, the corresponding author highlighted that their work introduced a material that could provide an alternative to traditional hydrogel materials used to support 3D human neural cell cultures and potentially be used in high throughput drug screening. Furthermore, the tailored construct has potential to design an improved in vitro human neurogenesis model that can accelerate platform drug discovery programs.
Ashley R. Murphy, Irene Ghobrial, Pegah Jamshidi, Andrew L. Laslett, Carmel M. O’Brien, Neil R. Cameron. Tailored emulsion-templated porous polymer scaffolds for iPSC-derived human neural precursor cell culture. Polymer Chemistry, volume 43 (2017) page 6617–6627.
Ashley R. Murphy, John M. Haynes, Andrew L. Laslett, Neil R. Cameron, Carmel M. O’Brien. Three-dimensional differentiation of human pluripotent stem cell-derived neural precursor cells using tailored porous polymer scaffolds. Acta Biomaterialia, volume 101 (2020) page 102–116.