眼球壁小梁网主要由平滑肌纤维构成且不存在内皮细胞

Histological structure of the trabecular meshwork in the eyeball:challenging the traditional concept and preliminary findings in rabbits,rats and mice

目的证明小梁网(TM)主要由平滑肌纤维而非胶原纤维构成,且不存在内皮细胞。方法选用家兔、SD大鼠、小鼠各3只,新鲜眼球共18只,沿矢状面对半切开眼球,石蜡包埋,常规组织切片,每个标本选取5片,分别采用HE染色、VG染色、Masson染色、α-SMA及CD31免疫组化法染色,显微镜下观察,并扫描成数字切片。将TM与巩膜胶原纤维、睫状肌(平滑肌)细胞、血管内皮细胞进行对比观察。结果 HE染色:3种动物TM呈紫红色粗丝状结构,交织成网,与睫状肌纤维胞质染色高度一致;TM表面附着的"细胞"界限不清,核扁,细长,呈深紫色,其"胞质"与TM无明显界限;睫状肌为典型的平滑肌,按不同方向成束排列,纵切的细胞呈扁平状,胞质紫红色,核扁,细长;巩膜内胶原纤维呈红色,深染;成纤维细胞少,依附于胶原纤维,其长轴与胶原纤维长轴一致,轮廓不清,核细长呈线样,深紫蓝色;血管内皮细胞胞质呈淡紫色,核深染,由于切面原因而呈不同的形状,突于腔内。VG染色:TM呈淡红色细丝状,胶原纤维呈亮红色粗条状。Masson染色:TM呈红绿相间网格状结构,其中以红色结构为主;巩膜胶原纤维呈绿色波浪状;血管内皮细胞呈绿色扁平状;睫状体的平滑肌纤维呈紫红色。α-SMA免疫组化:TM部分呈强阳性反应,胞质呈棕黄色颗粒;巩膜内胶原纤维及血管内皮细胞呈阴性;睫状体内的平滑肌纤维呈强阳性。CD31免疫组化:三种动物染色结果虽略有差异,但均为阴性。结论 TM主要由平滑肌纤维构成,外周包绕微量胶原纤维(肌内膜),不存在内皮细胞。

Objective To verify that the trabecular meshwork（TM） in the wall of the eyeball consists of smooth muscle fibers instead of collagen fibers or endothelial cells.Methods Eighteen fresh eyeballs from 3 rabbits,3 SD rats and 3 mice were sectioned along the sagittal plane and sliced after paraffin embedding for HE staining,VG staining,Masson staining,α-SMA immunohistochemistry or CD31 immunohistochemistry.These slices were observed under microscope and the structure of the TM was compared with those of scleral collagen fibers,ciliary muscles and endothelial cells.Results HE staining of the eyeball slices from the 3 animal species resulted in purplish red staining of the TM,which was highly consistent with ciliary muscle fibers.The cell-like structures on the surface of the TM were not clearly outlined,with flat nuclei showing a dark purple staining;these structures did not show obvious boundaries from the TM.Ciliary muscle fibers,which were smooth muscle cells in nature,were aligned in bundles in various directions.The longitudinally sectioned cells were flat and contained purplish cytoplasm and highly flattened nuclei.Scleral collagen fibers were stained dark red with a few fibroblasts sandwiched among them.The long axis of the fibroblasts was in parallel with that of the collagen fibers.The outline of the fibroblast was not clear and the nucleus was flat in dark blue.The vascular endothelial cells presented with different morphologies and contained light purplish cytoplasm and dark nuclei,protruding into the vascular cavity.VG staining of the TM revealed a pale red filamentous structure,and the collagen fibers were stained bright red.Masson staining of the TM showed a reticular structure consisting mainly of dark red fibers intermingled with thin green fibers.Scleral collagen fibers presented with a cord-like green wavy structure.The endothelial cells were green and flat,while the ciliary smooth muscle fibers were purple.In immunohistochemistry for α-SMA,the TM and the ciliary smooth muscle fibers showed a strong positivity in the cytoplasm,while the scleral collagen fibers and vascular endothelial cells showed negative staining;immunohistochemistry for CD31 showed no obvious positive staining in the TM,collagen fibers or ciliary smooth muscle cells from all the animals in spite of slight differences among them.Conclusion The TM consists mainly of smooth muscle fibers with a thin layer of peripheral endomysium without endothelial cells.