Positive and Negative Feedback Dynamics in Mixed Brain Cell Cultures

Elnaz Khezerlou, Louisiana Tech University


The aim of this project is to provide a better understanding of the brain in normal and epileptic conditions by studying the neuronal networks in vitro. The brain contains glial cells which provide negative feedback to maintain neuronal homeostasis. In the central nervous system (CNS), lack of negative feedback makes local neuronal circuits more excitable, potentially contributing to epileptogenic phenomena. To accomplish the goal of this project, different models of the brain cells in tissue engineered microenvironments are imaged for intracellular calcium concentration ([Ca2+]i). Here, we are mainly concerned about the positive, and negative feedback signals as key regulatory mechanisms underlying neuronal excitation. To investigate the role of glial cells in providing negative feedback we added nanomolar concentrations of glutamate (Glu) and other materials on neuronal cultures with both high glial content and depleted glial content during calcium imaging. We found that glial cells have effective roles in balancing the activity in the brain cell networks in high negative feedback cultures, where more astrocytes are present. Also, the low glial content cultures are more complex and less predictable.

In this project, we will discuss various conditions that affects neuronal excitation and inhibition. Understanding the role of each individual cell in its network could help us control the excitation of the neuronal networks as a result. We used a new method in analyzing calcium results to study the individual cells in their network. We showed that using these methods allowed us to gain a better understanding about the roles that each cell can play in its network.

The brain tumors can cause seizures in patients with glioma. Patients need medication for related neurologic symptoms, such as seizures, in addition to treatment for the tumor itself. We studied role of glial cells in providing negative feedback to the brain tumor cells in mixed cultures of astrocytes and glioma cells (CRL-2303 cells). We found that mixed cultures in which glial cells were present, were less responsive to the stimulations. This proves the effects of glial cells in providing negative feedback to the brain tumor cells.

We anticipate that this study may shed light on the important balancing effects of astrocytes in providing negative feedback to help prevent epileptogenesis. Using the new information about the neuronal networks, we can expand this approach to other cell types and study the effects of other excitatory and inhibitory neurotransmitters such as dopamine and GABA on cellular responses.