ABSTRACT
Bioactive growth factors identified within the extracellular matrix of dentine have been proposed roles in regulating the naturally inherent regenerative dentine formation seen in teeth in response to trauma and infection, which may also be harnessed for novel clinical treatments in augmenting mineralised tissue repair. This study examined the specific biological action of demineralised dentine matrix extract on a clonal population of dental pulp stem cells in stimulating the prerequisite stages of wound healing associated with mineralised tissue repair. A clonal dental pulp stem cell population with sustained proliferative capacity and multi-potentiality towards osteogenic, adipogenic and chondrogenic lineages was isolated from the pulp of human third molars. Dentine was collected from human healthy teeth, powdered and treated with ethylenediaminetetraacetic acid to obtain a solubilised DDM protein extract. The influence of DDM on the DPSC clonal population was assessed in vitro. Exposure of cells to proteolytically degraded DDM or unsupplemented media served as controls. Compared to controls, DDM stimulated cell expansion, reduced apoptotic marker caspase 3, increased cell survival marker Akt1 and enhanced mineralised matrix deposition as determined by mineral deposition and increased expression of bone-related markers, alkaline phosphatase and osteopontin. Dental pulp stem cells successfully migrated into collagen gels supplemented with demineralised dentine matrix, with cells remaining viable and expanding in numbers over a 3-day period. Collectively, the results provide evidence that soluble proteins extracted from dentine matrix are able to exert a direct biological effect on dental pulp stem cells in promoting mineralised tissue repair mechanisms.
ABSTRACT
The present study compared the cellular characteristics of progenitor stem cell populations present in adult dental pulp, isolated by different methods utilizing 2 different features of stem cell biology. One population expressing high levels of beta1 integrin was isolated by preferential selection of adherent cells to fibronectin over 20 min. In an alternative approach, cells expressing the embryonic neural crest cell marker, low-affinity nerve growth factor receptor (LANGFR), were selected by magnetic-activated cell sorting. For each method, clonal cell lines were established and expanded in culture. One clone derived via the respective methods was examined for embryonic/progenitor cell markers by immunocytochemistry and RT-PCR. Both clonal populations demonstrated the expression of stro-1 and stained positive for vimentin, demonstrating mesenchymal lineage. Of note, cells selected for LANGFR cells demonstrated the additional expression of CD105 and Notch 2. For both clonal populations, expanded cultures demonstrated the ability to differentiate into osteoblasts, adipocytes and chondrocytes. These results would suggest the potential isolation of 2 progenitor cell populations exhibiting different cellular characteristics in terms of their embryonic nature. The potential for both cell populations to derive from a common origin is discussed.
