Growing back brain cells

The loss of brain cells is a serious issue in many neurodegenerative diseases and brain injuries associated with accidents. Loss of neuronal tissue affects optimal function of the central nervous system (CNS) as neurons have a very low regeneration potential.

To hasten the process of regeneration of tissues in the CNS, scientists are harnessing the power of emerging tissue engineering technologies. A team of researchers at the Indian Institute of Technology (IIT) Roorkee has devised a technique for doing so using an electro-conductive scaffold made of chitosan polymer and graphene nano platelets (GNPs).

Conventional tissue-engineering techniques which are commonly used for the regeneration of bones and other skeletal organs are not suitable for CNS tissue regeneration. The scaffolds required for neuronal regeneration must be soft, mechanically strong, biodegradable, biocompatible and, moreover, electro-conductive.

"Neural tissues do regenerate on their own. But the process is slow," says Debrupa Lahiri, Associate Professor at IIT Roorkee. Neural tissue engineering can speed up the process, but the regenerated neurons need to be guided properly. "If we don't properly guide them, they get oriented in different directions and this defeats the purpose. For regeneration of the bones and muscles, the orientation of the cells is not that important," she says.

Natural and synthetic polymers are ideal for regenerating neural tissues, but polymers are conventionally insulators. The scaffolds used for neural tissue regeneration have to be conductive for the orientation of neurons. The scientists found that incorporating GNPs in the chitosan matrix and aligning them properly improved all physical and biological properties required for growing HT22 cells, neurons found in the hippocampus of the mouse brain. The reinforcement of GNPs also enhanced surface roughness and protein adsorption capability of the scaffolds, which are prerequisites for cellular adhesion and proliferation. The study was published online in Biomaterials Advances (bit.ly/CNS-tissue).

Lahiri's team had earlier used a similar tissue-engineering approach to grow peripheral nervous system (PNS) tissues. The technique that they developed for PNS tissue regeneration is fairly advanced and they had successfully tested the reinforced scaffold in mice. The material they incorporated in the scaffold for PNS tissue regeneration was carbon nanotubes (CNTs). Because the conductivity required by the scaffold was unidirectional, CNTs were a good material to provide that. But, as the CNS tissue requires bi-directional conductivity, the scientists used GNPs instead of CNTs.

"This work is useful and interesting as it presents a promising strategy to prepare nerve conduits where they use conducting nanoparticles that are aligned to help make better conduits," says Kaushik Chatterjee, Professor at the Indian Institute of Science in Bengaluru, who was not involved in the study.