Isolation and characterization of cells derived from human epithelial rests of Malassez

Epithelial Cell Rests of Malassez Provide a Favorable Microenvironment for Ameliorating the Impaired Osteogenic Potential of Human Periodontal Ligament Stem Cells

Human periodontal ligament stromal/stem cells (PDLSCs) are ideal candidates for periodontal regeneration and are of significant importance in clinical practice. However, PDLSCs derived from diseased microenvironments exert impaired behavior, which leads to the failure of periodontal regeneration. The epithelial cell rests of Malassez (ERM), which are involved in periodontal homeostasis, are residual cells from Hertwig's epithelial root sheath (HERS). However, the function of ERM remains largely unknown. Therefore, the aim of this study was to evaluate the effect of ERM on the osteogenic potential of PDLSCs from an impaired microenvironment. PDLSCs from healthy donors (H-PDLSCs), periodontitis donors (P-PDLSCs) and human ERM were harvested. Osteogenic evaluation showed a lower osteogenic potential of P-PDLSCs compared to that of H-PDLSCs. Then, we co-cultured ERM with P-PDLSCs, and the data showed that ERM promoted the expression of osteogenic genes and proteins in P-PDLSCs. In addition, we collected the PDLSCs from aged donors (A-PDLSCs) and analyzed the osteogenesis capacity of the A-PDLSCs and A-PDLSCs + ERM groups, which displayed similar results to P-PDLSCs. Finally, we evaluated the Wnt pathway, which is associated with osteogenic differentiation of stromal/stem cells, in A-PDLSCs + ERM and P-PDLSCs + ERM groups, which indicated that suppression of the Wnt pathway may result in an increase in the osteogenic properties of A-PDLSCs + ERM and P-PDLSCs + ERM groups. Taken together, the above findings shed new light on the function of ERM and provide a novel therapeutic for optimizing PDLSCs-based periodontal regeneration.

Periapical Cyst and Odontogenic Remnants on Osseous Mandibulectomy Margins: Two Diagnostic Pitfalls

In this article, we describe 2 high-stake diagnostic pitfalls that occurred in a single patient having undergone partial glossectomy and marginal mandibulectomy for invasive squamous cell carcinoma. Margins were grossly uninvolved. Histopathology showed a moderately differentiated squamous cell carcinoma. Microscopic evaluation of margins was challenging, as the inferior osseous margin submitted en face showed spongiotic epithelium with mixed chronic and acute inflammation, representing a periapical cyst after correlation with the gross examination. Another section of the osseous margin showed a small non-atypical epithelial nest, consistent with an odontogenic epithelial rest. We wish to raise awareness of these diagnostic pitfalls as a bone margin with such epithelial foci could be misinterpreted as positive, with serious therapeutic consequences.