Selective differentiation of central nervous system–derived stem cells in response to cues from specific regions of the developing brain

Neural stem/progenitor cells derived from the embryonic dorsal telencephalon of D6/GFP mice differentiate primarily into neurons after transplantation into a cortical lesion

D6 is a promoter/enhancer of the mDach1 gene that is involved in the development of the neocortex and hippocampus. It is expressed by proliferating neural stem/progenitor cells (NSPCs) of the cortex at early stages of neurogenesis. The differentiation potential of NSPCs isolated from embryonic day 12 mouse embryos, in which the expression of green fluorescent protein (GFP) is driven by the D6 promoter/enhancer, has been studied in vitro and after transplantation into the intact adult rat brain as well as into the site of a photochemical lesion. The electrophysiological properties of D6/GFP-derived cells were studied using the whole-cell patch-clamp technique, and immunohistochemical analyses were carried out. D6/GFP-derived neurospheres expressed markers of radial glia and gave rise predominantly to immature neurons and GFAP-positive cells during in vitro differentiation. One week after transplantation into the intact brain or into the site of a photochemical lesion, transplanted cells expressed only neuronal markers. D6/GFP-derived neurons were characterised by the expression of tetrodotoxin-sensitive Na(+)-currents and K (A)- and K (DR) currents sensitive to 4-aminopyridine. They were able to fire repetitive action potentials and responded to the application of GABA. Our results indicate that after transplantation into the site of a photochemical lesion, D6/GFP-derived NSPCs survive and differentiate into neurons, and their membrane properties are comparable to those transplanted into the non-injured cortex. Therefore, region-specific D6/GFP-derived NSPCs represent a promising tool for studying neurogenesis and cell replacement in a damaged cellular environment.

Transdifferentiation of rat fetal brain stem cells into penile smooth muscle cells

OBJECTIVES

To evaluate whether rat fetal brain stem cells can be induced to acquire cell fates outside the nervous system, hypothesising that cell-based replacement therapy with stem cells can aid in the regeneration of penile smooth musculature and might help to attenuate organic erectile dysfunction (ED), as the degeneration of penile smooth muscle cells leading to subsequent impairment of function is important in organic ED.

MATERIALS AND METHODS

Fetal brain stem cells (FBSCs) from embryonal 12-day Fisher 344 rats were isolated and characterized. For in vitro studies, undifferentiated FBSCs were cultured for 21 days in either N2 media (control) or N2 media conditioned in rat penile smooth muscle cell culture. These were then subjected to immunocytochemistry for specific markers of neural stem cells (nestin) and penile smooth muscle cells, i.e. alpha-smooth muscle actin (alphaSMA), penis-specific myosin light chain (MLC) desmin, calponin, vimentin, phosphodiesterase-5 (PDE5) and connexin. For in vivo studies, male adult Fisher 344 rats had an intracavernous injection with saline (five rats, control) or FBSCs that were labelled genetically by an expression construct for green fluorescent protein (GFP, nine rats, experimental) and maintained for 6 weeks. The rats were then killed and penile tissue was harvested and subjected to immunocytochemistry for markers of neural stem cells, smooth muscle cells, and sinusoidal endothelium (vascular endothelial growth factor, VEGF).

RESULTS

Undifferentiated cells exposed to N2 media continued to maintain the characteristic morphological and protein marker features of FBSCs, while the cells exposed to the conditioned media acquired the morphological features of smooth muscle cells. In addition, the differentiated cells (30-40%) expressed smooth muscle markers. Rats implanted with FBSCs had cells that showed double-labelling for GFP/alphaSMA, GFP/calponin and GFP/VEGF. The control group had no evidence of such double-labelling.

CONCLUSIONS

These results suggest the transdifferentiation of FBSCs into penile smooth muscle cells. Such transdifferentiated cells showed long-term survival when injected into the cavernous tissue, thus raising the possibility of a novel therapeutic option for organic ED.