title: TGIF1 Gene Silencing in Tendon-Derived Stem Cells Improves the Tendon-to-Bone Insertion Site Regeneration.
abstract: OBJECTIVE
  The slow healing process of tendon-to-bone junctions can be accelerated via implanted tendon-derived stem cells (TDSCs) with silenced transforming growth interacting factor 1 (TGIF1) gene. Tendon-to-bone insertion site is the special form of connective tissues derivatives of common connective progenitors, where TGF-β plays bidirectional effects (chondrogenic or fibrogenic) through different signaling pathways at different stages. A recent study revealed that TGF-β directly induces the chondrogenic gene Sox9. However, TGIF1 represses the expression of the cartilage master Sox9 gene and changes its expression rate against the fibrogenesis gene Scleraxis (Scx).
  
  
  METHODS
  TGIF1 siRNA was transduced or TGIF1 was over-expressed in tendon-derived stem cells. Following suprapinatus tendon repair, rats were either treated with transduced TDSCs or nontransduced TDSCs. Histologic examination and Western blot were performed in both groups.
  
  
  RESULTS
  In this study, the silencing of TGIF1 significantly upregulated the chondrogenic genes and markers. Similarly, TGIF1 inhibited TDSC differentiation into cartilage via interactions with TGF-β-activated Smad2 and suppressed the phosphorylation of Smad2. The area of fibrocartilage at the tendon-bone interface was significantly increased in the TGIF1 (-) group compared with the control and TGIF1-overexpressing groups in the early stages of the animal model. The interface between the tendon and bone showed a increase of new bone and fibrocartilage in the TGIF1 (-) group at 4 weeks. Fibrovascular scar tissue was observed in the TGIF1-overexpressing group and the fibrin glue only group. Low levels of fibrocartilage and fibrovascular scar tissue were found in the TDSCs group.
  
  
  CONCLUSIONS
  Collectively, this study shows that the tendon-derived stem cell modified with TGIF1 gene silencing has promising effects on tendon-to-bone healing which can be further explored as a therapeutic tool in regenerative medicine.
authors.forename: Liyang
authors.initials: L
authors.lastname: Chen
authors.forename: Chaoyin
authors.initials: C
authors.lastname: Jiang
authors.forename: Shashi Ranjan
authors.initials: SR
authors.lastname: Tiwari
authors.forename: Amrit
authors.initials: A
authors.lastname: Shrestha
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Xu
authors.forename: Wenqing
authors.initials: W
authors.lastname: Liang
authors.forename: Yeqing
authors.initials: Y
authors.lastname: Sun
authors.forename: Shisheng
authors.initials: S
authors.lastname: He
authors.forename: Biao
authors.initials: B
authors.lastname: Cheng
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001842:Bone and Bones / Q000502:physiology*; D015536:Down-Regulation; D020868:Gene Silencing; D018398:Homeodomain Proteins / Q000235:genetics*; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012097:Repressor Proteins / Q000235:genetics*; D051899:Smad2 Protein / Q000378:metabolism; D013710:Tendons / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; D018398:Homeodomain Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D051899:Smad2 Protein; C497784:Smad2 protein, rat; C000605833:TGIF1 protein, rat; D016212:Transforming Growth Factor beta