Cell therapy in experimental TBI

Abstract

The review of the literature deals with the results of the use of cell therapy in experimental TBI in animals, which analyses stem cells of different origin and degree of differentiation — neuronal embryonic, mesenchymal multipotent, totipotent blastogenic, endothelial cells and others.

The very first studies were conducted with neurogenic (nerve) stem cells (NSCs) and their progenitors, which were received from various brain structures of the embryo or adult animal. Most studies have been conducted using the mesenchymal stem cells (MSCs), due to the capacity of these cells to transform into nerve cells and endothelial cells. MSCs were obtained from various sources — adipose and bone tissue, placenta, umbilical cord or amniotic membrane and others.

The primary hypothesis was that transplanted stem cells were able to transform into neurons. Eventually, they were found to only secrete paracrine humoral factors that stimulate neuronal regeneration. It was established that the more stells were administered the more effective neuron restoration was. The stem cells were injected in various ways, mostly through stereotaxic or intravenous administration, although other methods were described, and cell introduction was either immediately after TBI or after 24 hours or several days. The accumulation of MSCs in the injured brain when administered intravenously was slight ranging from 1.4 % to 0.01  %, survival was short, regardless of the route of administration — to 14  % of cells within the week and only 0.6 % within a month. Today, there is no consensus about the mechanism of action of stem cells in TBI and there are at least six different hypotheses on this issue. The review also focuses on adult stem cells and the search for ways to activate and migrate them to the TBI injury zone, which may serve as one of the new approaches to treating the effects of TBI in humans.