Tsubone Tetsu, Moran Steven L, Subramaniam M, Amadio P C, Spelsberg T C, An K N
Orthopedic Biomechanics Laboratory, Division of Orthopedic Research, Mayo Clinic, Rochester, Minnesota, USA.
J Orthop Res. 2006 Mar;24(3):569-75. doi: 10.1002/jor.20101.
The role of transforming growth factor beta (TGF-beta) in tendon healing is still not clearly established. TGF-beta affects gene expression primarily through the activation of the Smad signaling pathway. The first step in the Smad pathway is the expression of TGF-beta inducible early gene (TIEG). Recently, a TIEG knockout mouse has been developed. The purpose of this study was to examine the healing potential of flexor tendons in mice lacking the TIEG gene, and to further examine what role the TIEG pathway plays in flexor tendon repair. Twenty-two mice, consisting of 11 normal wild-type mice and 11 TIEG knockout mice, were euthanized at 8 to 12 weeks of age. The second through fifth FDL tendons of both hind feet were transected and repaired in zone 2. The repaired tendons were removed from the mice and placed into tissue culture. Tendons were then examined at days 3, 7, 14, 21, and 42 after surgery. Hematoxylin and eosin (HE) staining and immunohistochemical staining for TGF-beta, collagen type I, and collagen type III were performed. Reverse transcriptase polymerase chain reaction (RT-PCR) was performed to examine expression of TGF-beta1, beta2, beta3, and collagen type I and III. At 42 days after surgery, HE staining showed coaptation of lacerated tendon ends in both groups. Both groups showed healing of the lacerated tendon, but the chronologic expression pattern of TGF-beta was different between the knockout and normal tendons. TIEG deficient tendons had delayed expression of TGF-beta when compared with control tendons. The collagen mRNA expression pattern was similar with both groups, but the expression level was different, with TIEG knockout tendons having a lower expression of collagen type I mRNA (p < 0.001). TGF-beta is thought to play a major role in tendon healing. Healing of tendons in the TIEG knockout mouse suggests the possibility of tendon healing in the absence of the Smad pathway. The knockout mouse model described in the present study provides a novel means for further understanding of the tendon healing process through isolated deletion of specific growth factors.
转化生长因子β（TGF-β）在肌腱愈合中的作用仍未明确。TGF-β主要通过激活Smad信号通路来影响基因表达。Smad通路的第一步是TGF-β诱导早期基因（TIEG）的表达。最近，已培育出TIEG基因敲除小鼠。本研究的目的是检测缺乏TIEG基因的小鼠屈肌腱的愈合潜能，并进一步研究TIEG通路在屈肌腱修复中所起的作用。22只小鼠，包括11只正常野生型小鼠和11只TIEG基因敲除小鼠，在8至12周龄时实施安乐死。切断并修复双后足的第二至第五趾长屈肌腱（FDL）的2区。将修复后的肌腱从小鼠体内取出并进行组织培养。然后在术后第3、7、14、21和42天对肌腱进行检查。进行苏木精-伊红（HE）染色以及TGF-β、I型胶原和III型胶原的免疫组化染色。采用逆转录聚合酶链反应（RT-PCR）检测TGF-β1、β2、β3以及I型和III型胶原的表达。术后42天，HE染色显示两组中撕裂的肌腱断端均已对接。两组均显示撕裂的肌腱愈合，但基因敲除肌腱与正常肌腱之间TGF-β的时序表达模式不同。与对照肌腱相比，TIEG缺陷肌腱的TGF-β表达延迟。两组的胶原mRNA表达模式相似，但表达水平不同，TIEG基因敲除肌腱的I型胶原mRNA表达较低（p<0.001）。TGF-β被认为在肌腱愈合中起主要作用。TIEG基因敲除小鼠的肌腱愈合提示在没有Smad通路的情况下肌腱仍有愈合的可能性。本研究中描述的基因敲除小鼠模型为通过特异性生长因子的单独缺失进一步了解肌腱愈合过程提供了一种新方法。
