Influence of the extracellular matrix on endogenous and transplanted stem cells after brain damage

Abstract

The limited regeneration capacity of the adult central nervous system (CNS) requires strategies to improve recovery of patients. In this context, the interaction of endogenous as well as transplanted stem cells with their environment is crucial. An understanding of the molecular mechanisms could help to improve regeneration by targeted manipulation. In the course of reactive gliosis, astrocytes upregulate Glial fibrillary acidic protein (GFAP) and start, in many cases, to proliferate. Beside GFAP, subpopulations of these astroglial cells coexpress neural progenitor markers like Nestin. Although cells express these markers, the proportion of cells that eventually give rise to neurons is limited in many cases in vivo compared to the situation in vitro. In the first section, we present the characteristics of endogenous progenitor-like cells and discuss the differences in their neurogenic potential in vitro and in vivo. As the environment plays an important role for survival, proliferation, migration, and other processes, the second section of the review describes changes in the extracellular matrix (ECM), a complex network that contains numerous signaling molecules. It appears that signals in the damaged CNS lead to an activation and de-differentiation of astrocytes, but do not effectively promote neuronal differentiation of these cells. Factors that influence stem cells during development are upregulated in the damaged brain as part of an environment resembling a stem cell niche. We give a general description of the ECM composition, with focus on stem cell-associated factors like the glycoprotein Tenascin-C (TN-C). Stem cell transplantation is considered as potential treatment strategy. Interaction of transplanted stem cells with the host environment is critical for the outcome of stem cell-based therapies. Possible mechanisms involving the ECM by which transplanted stem cells might improve recovery are discussed in the last section.

Mifepristone-inducible transgene expression in neural progenitor cells in vitro and in vivo

“…Histological inspection of the brains revealed that DsRed was easily observable without immunocytochemistry, whereas eGFP required anti-GFP immunocytochemistry for visualization (data not shown; there were also no overt tumors). Because of this pattern, we could use an anti-nestin primary antibody conjugated to a green fluorophore (results are shown as a white channel) to detect the grafts in all rats, as this coreacted with both infiltrating endogenous nestin-positive reactive cells around the graft 24,25 and (to a lesser extent) the transplanted 6B6D-NPCs. Conversely, an anti-DsRed antibody was used to further amplify and analyze the MFP-inducible transgene expression of our cells in vivo (Figures 6–8).…”

“…Finally, CellProfiler 26 was used to quantitate the number of DsRed-positive mNPCs in regions with a large cluster of endogenous nestin-positive reactive cells 24,25 (Supplementary Figure S2). By quantifying the nestin and DsRed signals adjacent to the transplant site, this analysis allowed for single-cell identification as well as eliminating potential concerns associated with autofluorescent material within the graft cores.…”

“…These grayscale images were then analyzed for the average fluorescence intensity across the x axis, and as such, the relative intensity of the left versus right side of the image could be compared and display any difference between the treatment groups. This analysis was performed for the Nestin (white channel) image, 24,25 in order to confirm the same graft region was selected for both groups, as well as the DsRed (red channel) image, to evaluate the relative level of transgene expression. In addition, grayscale images were transformed into a spectral color scale using the Thermal LUT reference file; a surface plot of this Thermal LUT image was also generated in ImageJ (Figure 7).…”

“…This analysis used the presence of endogenous Nestin-positive reactive cells adjacent to the grafts, 24,25 but did not include the possible confounding influence of autofluorescent material (i.e., dead cells) at the transplant sites themselves. 27 DsRed-positive cells that had migrated to this region were counted and analyzed.…”

The Role of the Brain Extracellular Matrix in Synaptic Plasticity After Brain Injuries (Review)

“…Notably, the enzymatic removal of CSPGs by chondroitinase ABC at the damage site leads to significant improvements in the connections reestablishment, and more important, to functional recovery of motor functions [20,21,53,90,91]. One possible mechanism for it could be facilitation of oligodendrocytic migration, and, therefore, promoting remyelination [5,55,92,93]. Moreover this positive effect of chondroitinase ABC treatment remains sufficient to promote motor recovery on day 2, 4 and 7 following injury [20].…”