A new synthetic matrix to grow mature neurons and study neurodegenerative diseases

A team of researchers from the University of Barcelona, the UB Institute of Neurosciences (UBneuro) and the Institute for Bioengineering of Catalonia (IBEC) has created the first highly mature neurons from human induced pluripotent stem cells (iPSCs) using a synthetic material. This finding opens up new opportunities for medical research and potential therapies for neurodegenerative diseases and traumatic injuries.

The paper, published in the journal Cell Stem Cell, is co-authored by experts Alberto Ortega, Ramón y Cajal researcher at the UB Faculty of Medicine and Health Sciences and member of UBNeuro, and Zaida Álvarez, Ramón y Cajal researcher at the Institute for Bioengineering of Catalonia (IBEC).

“In this project, we have developed a new synthetic matrix that imitates different aspects of the extracellular matrix of the mammalian spinal cord, including topography, chemical composition and, above all, high molecular dynamism. This last feature has never been tested before due to the high technical complexity required to analyse it, and it seems to be very important for regulating multiple functions of human neurons in vitro, including adhesion, migration, survival and functional maturation”, says Professor Alberto Ortega, from the UB Department of Pathology and Experimental Therapeutics.

This is the first time that neurons derived from human iPSCs have been matured with a synthetic matrix.

“These matrices can help to solve historical limitations in moulding neurodegenerative diseases from human neurons derived from stem cells, as these systems normally present limited levels of maturation that do not go beyond the fetal and infant phases,” says the UB researcher.

Zaida Álvarez points out that this is the first time “that neurons derived from human iPSCs have been matured with a synthetic matrix”. “This platform —notes the researcher— will allow laboratories to have mature human neurons to study multiple neurological diseases and develop new therapies”.

To date, neurons had been generated from induced pluripotent stem cells, but these neurons had insufficient functional maturity, similar to neurons in the early stages of the development. This limited their ability to study neurodegenerative diseases, as it is the adult neurons that degenerate. The inefficient maturation of neurons differentiated from iPSCs was due, in part, to the lack of signals found in the neurons’ environment, the extracellular matrix.

The extracellular matrix and the dancing molecules

The extracellular matrix is essential for cell development in the laboratory, as it provides structural support, regulates cell signalling and differentiation, maintains cell integrity and provides a suitable environment for cell growth.

To recreate the extracellular matrix and achieve maturation and functionality similar to neurons in the nervous system under physiological conditions, the researchers used so-called dancer molecules, a revolutionary technique introduced last year by Zaida Álvarez and Samuel I. Stupp, professor at Northwestern University (United States).

The first step was to differentiate human iPSCs into motor and cortical neurons and then put them on nanofibres made of dancing molecules. The experts observed that the signalling and branching capacity of the neurons had improved, allowing them to make better synaptic contacts with each other.

The researchers believe that by advancing the age of neurons in cell cultures, they will be able to improve experiments to better understand late-onset diseases. “Having mature neurons in the lab is essential to advance our understanding of neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease and ALS, and to develop effective and safe therapies”, says Alberto Ortega.

Synchronised dance skills

To develop the mature neurons, the researchers used nanofibres composed of dancing molecules, a material that Zaida Alvarez developed in Stupp’s lab as a potential treatment for acute spinal cord injuries. In previous research published in the journal Science, Zaida Alvarez discovered how to change the movement of the molecules so that they can more efficiently find and connect to cell receptors that are constantly moving.

In the new study, Zaida Álvarez and Alberto Ortega observed that nanofibres with higher molecular motion led to improvements in human neuron cultures. In other words, neurons cultured on these more dynamic synthetic materials showed greater maturity, with less aggregation and more intense signalling.

“We think this works because the receptors move very fast in the cell membrane and the signalling molecules in our scaffolds also move very fast”, states Samuel I. Stupp, director of the Simpson Querrey Institute for BioNanotechnology (SQI) and Severo Ochoa Distinguished Professor at IBEC.

As part of the study, skin cells were taken from an ALS patients and converted into patient-specific motor neurons, the cell type affected in this neurodegenerative disease. These neurons were cultured for two months in the synthetic materials to develop characteristics characteristic of the ALS disease. “Not only has this provided a new window to study ALS, but this system can also be used to study and test potential therapies for other neurological diseases”, says Evangelos Kiskinis, professor of neurology and neuroscience at Northwestern University’s Feinberg School of Medicine and Robertson Investigator at the New York Stem Cell Foundation.

Searching for new therapeutic strategies

Thanks to the synthetic material, these highly functional neurons could be transplanted into patients with neuron loss —through injury or disease— which could restore lost cognition or sensation. As the initial cells could come from the same patient, the derived and transplanted neurons would not generate rejection.

The study also involved Kohei Sato, researcher at the School of Life Sciences and Technology at the Tokyo Institute of Technology, and Elisabeth Engel, senior researcher at the IBEC Biomaterials for Regenerative Therapies group.

Reference article:

Álvarez, Z.; Ortega, J. A. et al. «Artificial extracellular matrix scaffolds of mobile molecules enhance maturation of human stem cell-derived neurons». Stem Cell Stem, January 2023. Doi: 10.1016/j.stem.2022.12.010