Healing of Periodontal Tissues Following Transplantation of Cells in a Rat Orthodontic Tooth Movement Model

Abstract

To determine the fate and differentiation of transplanted periodontal ligament (PL) precursor cells and mouse embryonic stem (ES) cells and their relative capacity to regenerate wounded periodontium. Orthodontic tooth movement was introduced 24 hours before transplantation of PL or ES cells, and rats were euthanized either 24 hours or 72 hours after cell transplantation. The control rats received either no tooth movement and no cell transplantation or tooth movement and no cell transplantation. Differentiation of transplanted cells was assessed from mandibular periodontal histological tissue sections by immunohistochemical methods using monoclonal antibodies against PL cell differentiation markers. Data were analyzed using Student's t-test at a significance level of P = .05. Transplantation of PL and ES cells resulted in a higher number of osteopontin, bone sialoprotein, and alpha-smooth muscle actin labeled transplanted cells, predominantly around the blood vessels of the periodontium in study rats compared with control rats (cell transplantation but no orthodontic tooth movement, P = .05). Combined treatments of tooth movement and cell transplantation resulted in enhanced regeneration of the periodontium as a result of tooth movement. Transplantation of PL cells induced a higher number of differentiating cells in the PL and alveolar bone than did transplantation of ES cells. Orthodontic tooth movement promotes the differentiation of transplanted cells, and the differentiation occurs predominantly in the paravascular areas of the periodontium. In terms of regeneration of wounded periodontium, transplantation of PL cells produced a higher level of regeneration than ES cells, possibly because of PL cell plasticity and the capacity to undergo effective differentiation in the periodontal cellular microenvironment.