Evidence that cyclosporin A administration induces the formation of new cementum-like islets inside the gingival connective tissue

Two groups of 3 male Sprague-Dawley rats were given orally 30 mg/kg/d of vehicle (control group) or cyclosporin-A (experimental group) solution for 14 wk. The rats were anesthetized, tissues fixed by intracardiac perfusion of fixative solution and jaws dissected, demineralized, processed for Epon inclusion and cut by semi-thin serial sections. Histological examination revealed the presence of several islets located paravascularly inside the gingival connective tissue in the proximity of the root surfaces. The structure of these new cementum-like islets (NCLIs) was either compact and homogeneous or heterogeneous, but identical to that of the adjacent new cementum (NC) deposits. Histomorphometric evaluation indicated that the volume and the external surface of the NCLIs varied from 2354 to 679,497 μm³ and from 465 to 47,517 μm², respectively. These observations (a) suggest that CsA stimulates possibly paravascular progenitor cells which secrete in situ a NC-like material and (b) provides further evidence about the high potential of CsA to induce NC formation.