Distraction Osteogenesis-Induced Muscle Fibrosis May Not Be Associated With TGF-beta 1
ABSTRACT Transforming growth factor-β 1 (TGF-β1) participates in the synthesis and deposition of collagen. It has been implicated in fibrosis of tendons in wound-healing models but has never been studied in muscles with respect to distraction osteogenesis.
Using a rabbit model of distraction osteogenesis, we distracted the left tibias of 36 New Zealand white rabbits at 0.75 mm/d for 20 days. To determine whether suramin, an antagonist of TGF-β, could aid in the prevention of fibrosis, we injected it into the anterior tibialis muscle [12 rabbits received low-dose suramin (50 mg), 12 received high-dose suramin (100 mg), and 12 received sham injections]. Half of each group was killed at the end of distraction (day 24) and the other half at day 60. At the time of killing the rabbits, joint range of motion was measured, and strength and morphometric measures of the muscle were taken. Muscle was harvested and immunolabeled for TGF-β1. All findings were compared between study limbs and control (right) limbs.
The comparison failed to demonstrate improvements in the range of motion, and in strength or morphometric muscle development. Immunolabeling for TGF-β1 failed to show any staining in the intramuscular fibrosis. Paradoxically, muscle injected with high-dose suramin had the highest degree of fibrosis.
We conclude that TGF-β1 may not be the primary mediator of muscle fibrosis in distraction osteogenesis.
Injection of suramin may not prevent contracture formation after distraction osteogenesis.
[Show abstract] [Hide abstract]
ABSTRACT: The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that prevent normal range of motion. Recent studies using in situ hybridization techniques harle implicated transforming growth factor beta-1 (TGF-beta 1) in both intrinsic and extrinsic mechanisms of repair. TGF-beta 1 is a growth factor that plays multiple roles in wound healing and has also been implicated in the pathogenesis of excessive scar formation. The purpose of this study was to examine the effect of neutralizing antibody to TGF-beta 1 in a rabbit zone II flexor tendon wound-healing model. Twenty-two adult New Zealand White rabbits underwent complete transection of the middle digit flexor digitorum profundus tendon in zone II. The tendons were immediately repaired and received intraoperative infiltration of one of the following substances: (1) control phosphate-buffered saline; (2) 50 mu g neutralizing antibody to TGF-beta 1; (3) 50 mu g each of neutralizing antibody to TGF-beta 1 and to TGF-beta 2. Eight rabbit that had not been operated on underwent analysis for determination of normal flexion range of motion at their proximal and distal interphalangeal joints, using a 1.2-N axial load applied to the flexor digitorum profundus tendon. All rabbits that had been operated on were placed in casts for 8 weeks to allo iv maximal tendon adhesion and were then killed to determine their flexion range of motion. Statistical analysis was performed using the Student's unpaired t test. When a 1.2-N load was used on rabbit forepaws that had not been operated on, normal combined flexion range of motion at the proximal and distal interphalangeal joints was 93 +/- 0 degrees. Previous immobilization in casts did not reduce the range of motion in these forepaws (93 +/- 4 degrees). In the experimental groups, complete transection and repair of the flexor digitorum profundus tendon with infiltration of control phosphate-buffered saline solution resulted in significantly decreased range of motion between the proximal and distal phalanges [15 +/- 6 degrees (n = 8)]. However, in the tendon repairs infiltrated with neutralizing antibody to TGF-beta 1, flexion range of motion increased to 32 +/- 9 degrees (n = 7; p = 0.002). Interestingly, a combination of neutralizing antibody to TGF-beta 1 and that to TGF-beta 2 did not improve postoperative range of motion [18 +/- 4 degrees (n = 7; p = 0.234)]. These data demonstrate that (1) the rabbit flexor tendon repair model is useful for quantifying tendon scar formation on the basis of degrees of flexion between proximal and distal phalanges; (2) intraoperative infiltration of neutralizing antibody to TGF-beta 1 improves flexor tendon excursion; and (3) simultaneous infiltration of neutralizing antibody to TGF-beta 2 nullifies this effect. Because TGF-beta 1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that intraoperative biochemical modulation of TGF-beta 1 levels limits flexor tendon adhesion formation.Plastic & Reconstructive Surgery 01/2000; 105(1):148-155. DOI:10.1097/00006534-200001000-00025 · 3.33 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: The postoperative outcome of hand flexor tendon repair can be complicated by adhesions between the repair site and surrounding tissue. To date, the biology of hand flexor tendon wound healing remains controversial - both intrinsic (resident tenocyte) and extrinsic (tendon sheath fibroblast and inflammatory cell) processes may contribute to repair. Transforming growth factor beta-1 is a cytokine that plays multiple roles in wound healing bur is also implicated in the pathogenesis of excessive scar formation. This study examines the activation of transforming growth factor beta-1 mRNA in a rabbit zone II flexor tendon wound-healing model. Forty New Zealand White rabbit forepaws underwent complete transection and repair of the middle digit flexor digitorum profundus tendon in zone II. Tendons were harvested at increasing time intervals (1, 3, 7, 14, 28, and 56 days) and analyzed by in situ hybridization and immunohistochemistry to determine the expression patterns of transforming growth factor beta-1. A small number of tenocytes exhibited expression of transforming growth factor beta-1 mRNA at baseline in nonwounded control tendon specimens. The surrounding tendon sheath in these control specimens also revealed low numbers of fibroblasts and inflammatory cells expressing transforming growth factor beta-1 mRNA. In contrast, flexor-tendons subjected to transection and repair exhibited increased signal for transforming growth factor beta-1 mRNA in both resident tenocytes and infiltrating fibroblasts and inflammatory cells from the tendon sheath. These data demonstrate that (1) normal unwounded tenocytes and tendon sheath cells are capable of transforming growth factor beta-1 production, (2) this cytokine is activated in the tendon wound environment, as evidenced by mRNA upregulation, and (3) the upregulation of this cytokine in both ''intrinsic'' tenocytes and ''extrinsic'' tendon sheath fibroblasts and inflammatory cells supports dual mechanisms for tendon repair. Because transforming growth factor beta-1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that perioperative biochemical modulation of transforming growth factor beta-1 levels may help limit flexor tendon adhesion formation.Plastic & Reconstructive Surgery 09/1997; 100:937-944. DOI:10.1097/00006534-199709001-00016 · 3.33 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Flexor tendon healing is complicated by adhesions to the surrounding sheath. Transforming growth factor beta (TGF-β) is a cytokine with numerous activities related to wound healing. We examined the effects of TGF-β–1, –2 and –3 on tendon cell proliferation and collagen production. Three separate cell lines—sheath fibroblasts, epitenon and endotenon tenocytes—were isolated from rabbit flexor tendons and cultured separately. Cell culture media was supplemented with 1 or 5 ng/mL of TGF-β–1, –2, or –3. Cell number and collagen I and III production were measured and compared with unsupplemented control cultures. The addition of TGF-β to cell culture media resulted in a decrease in cell number in all 3 lines that did not reach statistical significance. There was a significant increase (pThe Journal Of Hand Surgery 07/2002; 27(4):615-620. DOI:10.1053/jhsu.2002.34004 · 1.66 Impact Factor