Molecular events surrounding collagen fibril assembly in the early healing rabbit medial collateral ligament—failure to recapitulate normal ligament development

Abstract

??Although injuries to the medial collateral ligament (MCL) can heal functionally without surgical intervention, the collagen fibers in the healing tissue remain compromised. The molecular basis for this poor healing potential was investigated by examining extracellular matrix-modifying molecules such as bone morphogenetic protein 1 (BMP-1), procollagen C proteinase enhancer (PCOLCE), lysyl oxidase (LOX), and transforming growth factor beta 1 (TGF-β1) involved in collagen fibrillogenesis during normal early postnatal ligament maturation and at comparable intervals after MCL injury. Samples of midsections of rabbit MCLs were collected from 3-, 6-, 14-, and 52-week-old normal animals and at 3, 6, and 14 weeks postinjury. Harvested midsubstance tissues were analyzed for collagen fibril diameter by transmission electron microscopy (TEM), and mRNA levels were assessed by reverse transcription-polymerase chain reaction (RT-PCR). Results showed different patterns of expression between normal MCL maturation and during scar maturation. BMP-1 and PCOLCE mRNA levels were upregulated in the 3?14-week period during maturation of normal ligaments but decreased at skeletal maturity. The scar tissue exhibited a 3.5-fold increase in PCOLCE mRNA levels during the early healing phase, but these decreased with time. After injury, BMP-1 mRNA levels in scars were low and did not change during healing. Both LOX and TGF-β1 mRNA levels were low during normal MCL development compared with levels at maturity and exhibited elevated mRNA levels during early healing that decreased with time postinjury. These results suggest that gene expression in scars during MCL healing does not recapitulate expression in normal ligament fibroblasts during maturation.

Comparative transcriptional analysis of three human ligaments with distinct biomechanical properties

“…Decorin, Biglycan and Fibromodulin all bind TGFb1, and they modulate its function in association with enzymatic processing (Hausser et al 1994;Hildebrand et al 1994). TGFb1 has been involved in ligament development, homeostasis and healing, in turn regulating fibroblast differentiation, proliferation, adhesion and migration; furthermore, it promotes ECM synthesis and inhibits enzymatic degradation (Peltonen et al 1991;Ghahary et al 1993;Mauviel, 1993;Scherping et al 1997;Uria et al 1998;Evans, 1999;Lorda-Diez et al 2009;Ferdous et al 2010;Achari et al 2011;Wang et al 2011a). TGFb1 also promotes collagen cross-linking, thereby contributing to ligament stiffness (Eleswarapu et al 2011).…”

Transcriptional Profiling of Rapamycin-Treated Fibroblasts From Hypertrophic and Keloid Scars

“…PCOLCE1 has been linked to fibroblast production of stiffer collagen matrix in vitro, 43 and PCOLCE knockout mice exhibit impaired matrix biomechanical properties in bone and tendon because of disrupted collagen fibril morphology. 44 PCOLCE is also thought to induce collagen synthesis in ligament, liver, and cardiac fibroblasts, 45–47 highlighting its potential role in scar formation across organ systems. Interestingly, PCOLCE proteins may also regulate metalloproteinase activity, suggesting a dual role in scar formation through regulation of synthesis and degradation pathways.…”

The 3D-Printed PLGA Scaffolds Loaded with Bone Marrow-Derived Mesenchymal Stem Cells Augment the Healing of Rotator Cuff Repair in the Rabbits

“…The diameters of collagen fibrils were determined using transmission electron micrographs according to previously reported methods 22 . A minimum of 1,000 fibrils were analyzed from each sample.…”