Therapeutic effect of dental pulp stem cell transplantation on a rat model of radioactivity-induced esophageal injury

Abstract

Dental pulp stem cell (DPSC) transplantation has been demonstrated to promote the regeneration and repair of tissues and organs and is a potentially effective treatment for radioactive esophageal injury. In this study, to explore the therapeutic effects of DPSCs on acute radiation-induced esophageal injury, DPSCs were cultured and transplanted into rats with acute radioactive esophageal injuries induced by radioactive ¹²⁵I seeds in vivo. In the injured esophagus, PKH26-labeled DPSCs co-localized with PCNA, CK14, CD71, and integrin α6, and the expression levels of these four makers of esophageal stem cells were significantly increased. After DPSC transplantation, the injured esophagus exhibited a greater thickness. In addition, the esophageal function and inflammation recovered faster. The results demonstrated that transplanted DPSCs, which trans-differentiated into esophageal stem cells in vivo, could repair the damaged esophageal tissue.

Fig. 1. Evaluation of the model.

a X-ray revealed that the ¹²⁵I seed strain lined up in the esophageal lumen from the prone and lateral position. b Histological images showing esophageal tissue from the model, sham-operated and normal groups. The polygon cells and basal cells of the mucosa were arranged in a disorderly manner. Moreover, fractures, defects. and blood vessel congestion were observed. The lamina propria and submucosa were infiltrated by neutrophils and lymphocytes in the model group. However, the esophageal epithelium was well organized in the sham-operated and control groups (×100). c TNF-α, IL-1β, and IL-8 concentrations were significantly increased in the model group compared with those in the control and sham-operated groups on the fourth day after radiation (P < 0.0001). Moreover, there were no significant differences between the control and sham-operated groups (P > 0.05). *P < 0.05, **P < 0.001, ***P < 0.0001, the model group compared with the sham-operated group. ^#P < 0.05, ^##P < 0.001, ^###P < 0.0001, the model group compared with the normal group

Fig. 2. Morphological features of DPSC growth and flow cytometric analyses with DPSC markers.

a Primary DPSCs assumed a fibroblast-like appearance on the first day (×40). b A large number of spindle cells attached to the culture dish on the fourth day (×40). c The majority (80–90%) of the DPSCs were confluent after 2 weeks (×40). d On days 1–3, the P1, P3, and P4 DPSCs proliferated slowly, and the cells appeared to proliferate rapidly from day 4, entering the logarithmic phase. The increase in the number of cells then slowed gradually, reaching the plateau phase on day 8. e, f The DPSCs differentiated into the osteogenic and adipogenic lineages (×100). g A total of 99.85% of the cells reacted with anti-rat CD29; 89.08% of the cells reacted with anti-rat CD90; 1.42% of the cells reacted with anti-rat CD45; and 0.12% of the cells reacted with anti-rat CD34

Fig. 3. Colocalization of the transplanted DPSCs in the esophagus.

a PKH26-labeled cells (red) co-localized with CD71, CK14, integrin α6, and PCNA (green) in the esophageal epithelium after transplantation. The cell nuclei were labeled with DAPI (blue) (×400 and ×800). b, c Few PKH26-positive cells were found in the control group, sham-operated group, and other organs, including spleen, lung, and liver, in the DPSC group (×100)

Fig. 4. Protein expression levels of proliferative and trans-differentiated cell markers.

The protein expression levels of CD71, CK14, integrin α6, and PCNA significantly increased in the DPSC group compared with those in the control and sham-operated groups. *P < 0.05, **P < 0.001, ***P < 0.0001, the DPSC group compared with the control group. ^#P < 0.05, ^##P < 0.001, ^###P < 0.0001, the DPSC group compared with the sham-operated group

Fig. 5. The MODs of the AOIs of proliferative and trans-differentiated cell markers.

The MODs of the AOIs of CD71, CK14, integrin α6, and PCNA in the DPSC group were significantly higher than those in the control and sham-operated groups (×400)

Fig. 6. Histological and inflammatory improvements in radioactive esophageal injury with infused DPSCs.

a, b The histological images of the esophagus revealed that the thickness of the epithelium in the DPSC group was significantly increased compared with those in the control and sham-operated groups (×400). c The TNF-α, IL-1β, and IL-8 concentrations in the DPSC group were not significantly different from those in the sham-operated group (P > 0.05). The TNF-α, IL-1β, and IL-8 concentrations in the control group were higher than those in the DPSC and sham-operated groups (P < 0.0001). *P < 0.05, **P < 0.001, and ***P < 0.0001, the DPSC group compared with the control group. ^#P < 0.05, ^##P < 0.001, and ^###P < 0.0001, the DPSC group compared with the sham-operated group

Fig. 7. Average daily food intake levels of rats in all groups.

The rats with DPSC treatment showed better food intake recovery; the food intake in the DPSC group was significantly higher than that in the control group from the sixth day forward, and the food intake in the DPSC group gradually approached the normal level

Fig. 8. The steps to produce an in vivo model.

a Five ¹²⁵I seeds were placed close together in a disposable ureteral catheter, and the end of the catheter was stitched with a suture to secure the ¹²⁵I. b The disposable ureteral catheter including the ¹²⁵I seeds was fixed in the oral cavity. c The rats were administered food and estazolam through a disposable ureteral catheter when they were irradiated. d The flow chart of this study