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

用Waldo法观察注射EGF或PGE2或牙齿移动6 d后大鼠静脉注射微量过氧化酶（MP，肽示踪剂）或抗酒石酸磷酸酶（TRAP）染色。第一磨牙根间隔远端骨面出现骨吸收，上磨牙远端根近中、远端根面出现牙根吸收。破牙细胞具有与破骨细胞相同的细胞器（多核，发育良好的皱边（RB），透明带，空泡，线粒体和特定颗粒）。透明区没有阻止任何MP，因此MP通过透明区沉积在吸收区，并仅沿着RB的通道运输到液泡中。此外，胶原原纤维位于RB的通道中，但在液泡中未检测到。相反，在液泡中检测到丝状结构，并且非常靠近通道中的胶原原纤维。被吸收腔隙的成纤维细胞内吞胶原蛋白。相比之下，成纤维细胞和破牙细胞在腔隙中没有内吞任何胶原原纤维。与破骨细胞相比，破牙细胞对MP的摄取很少，这也是一个特征。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，被吸收的区域与细胞外间隙相连，而没有被透明区封闭；第三，牙本质或牙骨质的有机成分（如胶原原纤维）通过RB的通道内吞，与MP的内吞方式相同。虽然破牙细胞的内吞能力不如破骨细胞。

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.