Temporal expression of growth factors and matrix molecules in healing tendon lesions

Abstract

Overuse tendon injuries are common among elite and recreational athletes. Tendon healing may be enhanced a t the cellular level through the use of exogenous growth factors; however, little is known about the endogenous expression of growth factors in healing tendon. This study describes the temporal expression of insulin-like growth factor-I (IGF-I), transforming growth factor-(31 (TGF-PI), and collagen types I and 111 in healing tendon lesions. Collagenase-induced lesions were created in the tensile region of theflexor digitorurn superJicialis tendon of both forelimbs of 14 horses. Tendons were harvested from euthanatized horses 1,2,4, 8 or 24 weeks following injury. Gene expression was evaluated using Northern blot analysis (collagen types I and HI), real time PCR (IGF-I and TGF-PI), and in situ hybridization. Protein content was assayed by dye-binding assay (collagen types I and HI), radioimmunoassay (IGF-I), ELISA (TGF-Pl), and immunohistochemistry. Samples were also processed for differential collagen typing, DNA and glycosaminoglycan content, and routine H&E staining. Microscopically, lesions progressed from an amorphous, acellular lesion soon after injury to scar tissue filled with collagen fibers and mature fibroblasts organized along lines of tension. Early lesions were characterized by immediate increases in expression of growth factors and collagen. Message levels for TGF-PI peaked early in the wound healing process (1 week), while IGF-I peaked later (4 weeks), as the regenerative phase of healing was progressing. In the first 2 weeks after lesion induction, tissue levels of IGF-I protein actually decreased approximately 40% compared to normal tendon. By 4 weeks, these levels had exceeded those of normal tendon and remained elevated through 8 weeks. Message expression for collagen types I and 111 increased by 1 week following injury and remained elevated throughout the course of the study. Collagen type 1 represented the major type of collagen in healing tendon at all time points of the study. Based on these results, IGF-I, administered exogenously during the first 2 weeks following injury, may provide a therapeutic advantage by bolstering low endogenous tissue levels and enhancing the metabolic response of individual tendon fibroblasts.

Mesenchymal stem cells and insulin‐like growth factor‐I gene‐enhanced mesenchymal stem cells improve structural aspects of healing in equine flexor digitorum superficialis tendons

“…RNA was assessed by spectrophotometry at 260:280 nm and by 1% agarose gel electrophoresis. RNA was used for quantitative RT/PCR of collagen types I and III, 22,24 IGF-I, 25 and cartilage oligomeric matrix protein (COMP), [26][27][28] as indicators of tendon matrix synthesis, and matrix metalloproteinase-3 (MMP-3), [29][30][31] matrix metalloproteinase-13 (MMP-13), 24,29,32 and aggrecanase (ADAMTS-4) 30,33 as indicators of tendon catabolism.…”

Spatiotemporal protein distribution of TGF‐βs, their receptors, and extracellular matrix molecules during embryonic tendon development

“…In contrast, most studies have focused mainly on the role of TGF-␤s in adult tendon and ligament pathology and wound healing. Thus, elevated protein and mRNA levels of TGF-␤ have been demonstrated in pathological Achilles tendons and during healing of injured tendons and ligaments (Natsu-ume et al, 1997;Fenwick et al, 2001;Darmani et al, 2004;Tsubone et al, 2004;Dahlgren et al, 2005). Exogenous application of TGF-␤1 and -␤2 significantly increased expression of collagen types I and III, and improved the mechanical properties of healing tendons or ligaments (Spindler et al, 2003;Kashiwagi et al, 2004;Anaguchi et al, 2005).…”

Strategies in Biologic Augmentation of Rotator Cuff Repair: A Review

“…Seeherman et al [49] demonstrated in a full-thickness rotator cuff tear sheep model that delivery of rhBMP-12 in sponge carriers had the potential to accelerate healing of rotator cuff repairs when compared to untreated controls. Basic fibroblast growth factor (bFGF), which increases fibroblastic proliferation while suppressing collagen formation, is also present [13]. Insulin-like growth factor 1 (IGF-1), which stimulates protein synthesis and cell proliferation while decreasing swelling, has been observed in the healing bone-to-tendon junction [13].…”

“…Basic fibroblast growth factor (bFGF), which increases fibroblastic proliferation while suppressing collagen formation, is also present [13]. Insulin-like growth factor 1 (IGF-1), which stimulates protein synthesis and cell proliferation while decreasing swelling, has been observed in the healing bone-to-tendon junction [13]. Platelet-derived growth factor b (PDGF-b), correlated to increased levels of Type I collagen, is also present in low levels throughout the repair [32,52].…”