Pulp bioengineering: tracking of implanted stem cells by nuclear imaging

Endodontic treatment as current therapeutic may occurred when tooth is exposed to severe injuries from caries or traumatic fractures.  Such treatment does not exploit the high regenerative cellular potential of the pulp. The present study is part of a research project aimed to develop a pulp equivalent implantable in the injured dental pulp based on the use of mesenchymal pulp stem cells. Here the specific objective is to track the implanted cells by Nuclear Imaging to determine their behavior and fate in a living organism.

Methods:

Rat pulp cells were radio-labeled with ¹¹¹indium-oxine. Labeled cells were added to polymerizing type I collagen matrix in order to obtain a pulp equivalent. This cellular matrix was implanted in the emptied pulp chamber space in the first upper rat molar, after pulpotomy. Labeled cells were detected by Nuclear Imaging (Nano SPECT/CT plus, Bioscan®) for 4 weeks.  Negative controls were also performed using lysates from radiolabeled cells.

Treated rats were sacrified 1 week, 1 month and 2 months after implantation step. Maxillary were isolated, demineralized before embedded in paraffin for histological staining and immunohistochemistry studies.

Results:

In vitro studies showed that ¹¹¹In-labelled pulp cells viability and cell proliferation were similar to unlabeled cells.  

In vivo imaging performed sequentially over a month showed a significant increased radioactivity level from labeled pulp equivalent into the pulp chamber, compared to controls. Full-body imaging indicated no spreading cells out of implantation site.

Histological and immunochemistry studies showed angiogenesis near the implanted matrix and limited inflammation.

Conclusions:

Our data show that nuclear imaging is a high sensitive method for tracking implanted cells into the animal tooth. These results may open a promising way in human dental diseases.