Over the last decade, a number of hydrogels attracted great attention in the area of brain tissue engineering. The hydrogels are composed of hydrophilic polymers forming 3D network in water. Their function is promoting structural and functional restoration of damaged brain tissues by providing mechanical support and navigating cell fate. This paper reports on the neurocompatibility of chitosan- g -oligo(L,L-lactide) copolymer hydrogel with primary rat cortical neuron culture. The hydrogel was produced by a molding technique on the base of photocurable composition consisting of chitosan-g-oligo(L,L-lactide) copolymer, poly(ethylene glycol) diacrylate and photosensitizer Irgacure 2959. The influence of the hydrogel on cell viability, phenotype and calcium homeostasis, mitochondrial potential and oxygen consumption rate in glutamate excitotoxicity was analyzed using primary neuron cultures obtained from a neonatal rat cortex. This study revealed that the hydrogel is non-cytotoxic. Dissociated neonatal rat cortical cells were actively attaching to the hydrogel surface and exhibited the phenotype, calcium homeostasis and mitochondrial function in both standard conditions and glutamate excitotoxicity (100 μ M) similar to the control cells cultured without the hydrogel. To conclude, in this study we assessed the feasibility of the application of chitosan- g -oligo(L,L-lactide) copolymer hydrogel for tissue engineering therapy of brain injury in an in vitro model. The results support that the hydrogel is able to sustain realization of the functional metabolic activity of neonatal rat cortical cells in response to glutamate excitotoxicity.

A glutamate model of stroke was analyzed from the standpoint of the development of a typical pathological process that is thought to occur when major regulatory mechanisms are violated. The...

The brain and gastrointestinal tract are the most important organs responsible for detecting, transmitting, integrating, and responding to signals coming from the internal and external environment. A bidirectional system of neurohumoral communication (the “intestine–brain” axis) combines the activity of the intestine and brain (or brain and intestine) of a person. It affects human development and behavior. This paper analyzes the literature data on the existence of a relationship between the central and enteral nervous systems. Based on data on the number of neurons in the enteral nervous system (approximately 250 million nerve cells), the concept of a “second brain” in the intestine has been proposed in foreign literature, which, by its influence on the brain, can have a more powerful influence than the spinal cord (approximately 10 million neurons) with its autonomic nervous system. However, it turned out that Russian scientists, academicians of the Academy of Sciences of the Soviet Union I.P. Pavlov, K.M. Bykov, and A.M. Ugolev, analyzed cortical-visceral relationships in the 20th century and wrote about the existence of a connection between the central and enteral nervous systems. One of the urgent problems of modern physiology, pathophysiology, biophysics, biochemistry, and medicine is to clarify the causal relationship between the central and enteral nervous systems, as well as between neurological, mental, and gastrointestinal diseases in order to combine the efforts of specialists of various medical and biological profiles to solve urgent medical problems.

The scratch test is used as an experimental in vitro model of mechanical damage to primary neuronal cultures to study the mechanisms of cell death in damaged areas. The involvement of NMDA receptors in processes leading to delayed neuronal death, due to calcium dysregulation and synchronous mitochondrial depolarization, has been previously demonstrated. In this study, we explored the neuroregenerative potential of Pro-Gly-Pro (PGP)—an endogenous regulatory peptide with neuroprotective and anti-inflammatory properties and a mild chemoattractant effect. Mechanical injury to the primary neuroglial culture in the form of a scratch caused acute disruption of calcium homeostasis and mitochondrial functions. This was accompanied by neuronal death alongside changes in the profile of neuronal markers (BDNF, NSE and GFAP). In another series of experiments, under subtoxic doses of glutamate (Glu, 33 μM), delayed changes in [Ca²⁺]_i and ΔΨm, i.e., several days after scratch application, were more pronounced in cells in damaged neuroglial cultures. The percentage of cells that restored the initial level of [Ca²⁺]_i (p < 0.05) and the rate of recovery of ΔΨm (p < 0.01) were decreased compared with undamaged cells. Prophylactic application of PGP (100 μM, once) prevented the increase in [Ca²⁺]_i and the sharp drop in mitochondrial potential [ΔΨm] at the time of scratching. Treatment with PGP (30 μM, three or six days) reduced the delayed Glu-induced disturbances in calcium homeostasis and cell death. In the post-glutamate period, the surviving neurons more effectively restored the initial levels of [Ca²⁺]_i (p < 0.001) and Ψm (p < 0.0001). PGP also increased intracellular levels of BDNF and reduced extracellular NSE. In the context of the peptide’s therapeutic effect, the recovery of the damaged neuronal network occurred faster due to reduced astrogliosis and increased migration of neurons to the scratch area. Thus, the peptide PGP has a neuroprotective effect, increasing the survival of neuroglial cells after mechanical trauma in vitro by reducing cellular calcium overload and preventing mitochondrial dysfunction. Additionally, the tripeptide limits the post-traumatic consequences of mechanical damage: it reduces astrogliosis and promotes neuronal regeneration.