FIG. 1.

Effect of tooth root surface topography on initial attachment and spreading of mPDLPs. Under the scanning electron microscope the natural root surface of a rat mandibular first molar exhibits an intricate, heavily grooved topography. The microporous topography of a ethylenediaminetetraacetic acid-etched root surface (a, f) had a significantly more pronounced surface relief than a nanostructured, nano-HA apatite surface (b) or a smoothened and polished root surface (d). Differences in surface topography resulted in significant changes in cell shape and attachment when apatite surfaces were seeded with mouse periodontal progenitor cells. On nano-HA, cells were flattened and spread out (c), on smoothened root surface apatite there was little or no attachment of cells (e), and on a microporous root surface, cells demonstrated an elongated, fibroblast-like morphology (g). Compared to mPDLPs grown on smooth or nano-HA surfaces, mPDLPs grown on microporous root surface apatite were significantly more elongated (h). Western blots demonstrated that the two early attachment focal adhesion proteins phospho-paxillin Y31 and phospho-focal adhesion kinase Y397 were highly expressed on cells attached to microporous root surfaces, whereas expression of these adhesion proteins was reduced in cells on nano-HA surfaces and almost absent in cells cultured on smoothened apatite surfaces (i). Changes in gene expression as a result of surface topography were not unique to native rat molar tooth roots but also occurred on smoothened or roughened apatite surfaces of identical chemical composition (j–l). (m–r) Images document the multipotency of mPLDPs to differentiate toward adipogenic (n), osteogenic (p), and chondrogenic (r) lineages compared to noninduced negative controls (m, o, q). mPDLP, mouse periodontal ligament progenitor cell; nano-HA, nano-hydroxyapatite; PAX, paxillin; FAK, focal adhesion kinase.