Enhanced connexin 43 expression following neural stem cell transplantation in a rat model of traumatic brain injury

Abstract

Introduction: Reestablishment of functional networks after traumatic brain injury (TBI) has been proffered as one of the goals of neural stem cell (NSC) transplantation therapeutics. Gap junctions provide essential means for direct cellular communication by transferring small molecules and ions, which may provide insights into the interplay between grafted NSCs and host cells.

Material and methods: Thirty-six adult male Wister rats were used in this study. The controlled cortical impact (CCI) model of brain injury has been performed. Seventy-two hours after CCI injury, animals were randomly assigned to two groups: PBS- and NSC- transplanted group. NSCs-transplanted group received delivery of the NSCs suspension to the cortex below the injury cavity in the ipsilateral hemisphere. At 1, 2, and 4 weeks post-transplantation, we investigated the expression patterns of gap junction-associated connexin 43 (Cx43) in the transplant site and the border of CCI by immunohistochemistry, Western blot and RT-PCR.

Results: Our findings showed that Cx43 staining was significantly greater in the transplant site and the border of CCI in the NSCs-transplanted rats compared to the control rats at different time points (p < 0.01 at 1 week, p < 0.05 at 2 and 4 weeks). Significantly higher gene and protein expression of Cx43 was found in NSCs-transplanted rats compared to the control rats in the period of 4 weeks post-transplantation (p < 0.01), and remained at a higher level until 2 weeks with or without NSC transplantation.

Conclusions: It is proposed that gap junction-associated Cx43 might participate in NSCs' beneficial effects via gap-junctional coupling by which grafted NSCs integrate into host neural tissue following transplantation after TBI.

Keywords: connexin43; neural stem cell; transplantation; traumatic brain injury.

Figure 1

The immunoreactivity of Cx43 in the transplant core and the border of CCI at 1, 2 and 4 weeks post-transplantation. (A and B) Cx43-positive staining in 16-m sections from the brains of the NSCs-transplanted and the control rats at 1, 2 and 4 weeks. Immunoreactivity of Cx43 was significantly increased in the brains of the NSCs-transplanted rats compared to the control rats at different time points (C). The scale bar represents 30 m * and ** indicate p < 0.05 and p < 0.01 vs. the control group at different time points

Figure 2

Gene and protein expression of Cx43 in the injured brain. In (A) and (C), lanes 1, 2 and 3 are from control rats and lanes 4, 5 and 6 are from NSCs-transplanted rats. Lanes 1 and 4, 2 and 5, and 3 and 6 are derived from rats at 1, 2 and 4 weeks post-transplantation, respectively. Representative results from semi-quantitative RT-PCR for Cx43 (A) and densitometric analysis of these bands (B). The intensity of each band was standardized to the band intensity of β-actin. Representative Western blots for Cx43 (C) and densitometric analysis of protein bands (D). The intensity of each band was standardized to the band intensity of GAPDH. Data are expressed as the mean ± SD (n = 3 in each group) * and ** indicate p < 0.05 and p < 0.01 vs. the control group at different time points