There is an elaborate system of a slew of cells associated with each other directly and indirectly in the human brain. Each of these cells is targeted differently by both diseases and drugs. According to the World Health Organization, many diseases target the central nervous system such as Parkinson’s disease, Alzheimer’s disease, dementia, brain tumours, stroke, migraine to name a few. 47.5 million people are estimated to have dementia across the world with 7.7 million new cases each year! Stroke claims 6 million people each year! According to the GBD 2015 Neurological Disorders Collaborator Group, the year 2015 saw neurological diseases rank first in causing disability-adjusted life-years (DALYs). Though stroke mortality has reduced, the last 25 years have seen an increase in the burden of neurological diseases.
Given these dismal statistics, studies for understanding the nervous system diseases and effects of drugs in the lab are required. The variability in cell types and effects can be studied using single-cell studies. Such studies at the level of transcriptomics have been performed using rodents, Cancer Cell Line and post-mortem samples. Yet, these sources cannot account for long term studies of morphology and functions given the species difference in the case of rodents, transformation in the case of cancer cells and the viability cells from post mortem samples. While there have been studies using neurons derived from induced pluripotent stem cells (iPSC), the effect of the transcription factors become a question.
Thus, a model system is required to examine the roles and effects of drugs on the different cells of the brain. One such option is the culture of the adult human brain that can present the picture of the nervous system. This can address the issues of using another species in animal studies or the effects of differentiation seen with induced stem cells.
A team led by Spaethling published research in 2017 in Cell Reports reporting the culture of healthy adult human brain cells. Brain tissue was obtained from patients undergoing surgery and collected in a CSF solution and sent to the lab within 10 minutes. Digestion of the tissue was done using papain after which the samples were centrifuged and dissociated gently with a pipette. Live cells were plated on 12-mm coverslips coated with lysine in Neurobasal B medium with penicillin/streptomycin.
The cells could be cultured to 84 days in vitro that were subjected to analysis to get the individual RNA profiles using deep sequencing. This was reported as the first to culture adult and healthy brain cells for this long a timeframe. The wear and tear seen in rodent brain cultures were not reported here. The expression of RNA markers and morphology were as expected.
Many primary micro RNA (pri-miRNA), long noncoding RNA (lncRNA) and transcription factors were identified that were specific for each cell type. The range and variance of important genes were measured using the single-cell resolution. The use of statistics and bioinformatics allowed the identification of cells and their types that were as predicted. Neuronal sub-classes were predicted with the mRNA profile. Additionally, miRNAs and transcription factors specific to patient diseases could be identified.
Of interest is that changes in gene profiles due to drugs over the long term could be detected in the culture that opens up the possibility of using this culture to assess the effect of drugs, their safety and the much sought after field of personalized medicine. The primary culture could be established irrespective of the sample age and could be used with ease. Thus, cells can be tested at the single-cell level to ascertain the effect on multiple cells that make up the brain.
GBD 2015 Neurological Disorders Collaborator Group (2017) Global, regional, and national burden of neurological disorders during 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015. Global Health Metrics 16 (11): P877-897.
Spaethling et al., Primary Cell Culture of Live Neurosurgically Resected Aged Adult Human Brain Cells and Single Cell Transcriptomics, Cell Reports, 2017; 18, 791–803.