In vitro and in vivo studies of osteoclasts by effect of EGF or PGE_2

注射EGF或PGE2后或牙齿移动6天后（Waldo法）的大鼠通过静脉注射微过氧化物酶（MP，肽示踪剂）或通过抗酒石酸酸性磷酸酶（TRAP）染色进行研究。在上颌第一磨牙的根间隔的远中骨表面处观察到骨吸收，并且沿着上述牙齿的远中牙根的近中和远中牙根表面发现牙根吸收。破牙细胞具有与破骨细胞相同的细胞器（多核、发达的皱边（RB）、透明区、液泡、线粒体和特定颗粒）。透明区不会阻止任何MP，因此MP通过透明区沉积在再吸收区域上，并且仅沿着RB的通道运输到液泡中。此外，胶原纤维位于 RB 通道中，但在液泡中未检测到。相反，在液泡中检测到丝状结构，并且其位置非常靠近通道中的胶原纤维。吸收的腔隙中的成纤维细胞内吞胶原蛋白。相反，腔隙中的成纤维细胞和破牙细胞不内吞任何胶原纤维。与破骨细胞相比，破牙细胞对MP的细胞摄取也很少。这些发现表明，首先，破牙细胞吸收牙根的牙本质（牙骨质），就像破骨细胞在骨吸收中所做的那样；其次，吸收区域与细胞外空间相连，没有被透明区封闭；第三，牙本质或牙骨质的有机成分（例如胶原纤维）被内吞。尽管破牙细胞的内吞能力不如破骨细胞，但以与 MP 相同的内吞方式通过 RB 通道。

Rats after injection of EGF or PGE2 or after 6 day tooth movement ( Waldo method ) were investigated by intravenous injection of microper-oxidase ( MP, peptide tracer ) or by tatrate-resistant acid phospha-tase(TRAP) staining. Bone resorption was observed at a distal bone surface of the interradicular septum of the upper first molar tooth, and tooth root resorption was found along mesial and distal root surfaces of the distal root of the above tooth. Odontoclasts had the same organellae ( multinuclear, well-developed ruffled border(RB), clear zone, vaculoes, mitochondria and specific granules ) that osteo-clasts possess. The clear zone did not stop any MP, therefore the MP deposited on the resorbed area through the clear zone and was transported into the vacuoles only along the channels of the RB. In addition, collagen fibrils localized in the channels of the RB but were not detected in the vacuoles. Instead, filament-like structures were detected in the vacuoles and were locating very near the collagen fibrils in the channels. Fibroblasts out of the resorbed lacunae endocytosed collagen. In contrast, the fibroblasts together with odontoclasts in the lacunae did not endocytose any collagen fibrils. It was also characteristic that little cellular uptake of MP by odontoclasts was observed, compared with that by osteoclasts.These findings suggested, first that odontoclasts resorb the dentin ( cementum ) of the tooth roots, just as osteoclasts do in bone resorption, second that the resorbed area connects with the extracellular spaces without sealing off by the clear zone, and third that the organic components( ex. collagen fibrils ) of dentin or cementum are endocytosed through the channels of the RB in the same endocytotic manner as that for MP, although the endocytotic ability of odontoclasts is inferior to that of osteoclasts.