Nitric oxide enhances collagen synthesis in cultured human tendon cells

Abstract

Collagen deposition is an important process that occurs during wound healing. We and others have shown that nitric oxide (NO) is important in tendon healing. The mechanisms whereby healing is enhanced are, however, undetermined. The aim of this study was to investigate whether NO could enhance collagen synthesis in cultured human tendon cells via exogenous NO and via an adenovirus containing the gene for inducible nitric oxide synthase (Ad-iNOS). Tendon cells from the torn edge of the tendons of patients undergoing rotator cuff repair surgery were cultured following collagenase digestion, and stimulated with exogenous NO (SNAP), transfected with Ad-iNOS, and treated with the NOS inhibitor, L-NMMA. Total protein and collagen synthesis were evaluated by 3 H-proline and collagenase sensitive 3 H-proline incorporation in human tendon cells. High doses of exogenous NO (SNAP) inhibited collagen synthesis. Lower doses enhanced total protein and collagen synthesis of the tendon cells. Ad-iNOS successfully transfected active iNOS into human tendon cells in vitro and also enhanced total protein and collagen synthesis of the tendon cells. The NOS inhibitor, L-NMMA, inhibited the effects of iNOS on the cells. Our studies show for first time that nitric oxide can enhance collagen synthesis in human tendon cells in vitro. These results may explain, in part, at least, the beneficial effects of NO donors in animal models and during the treatment of tendonopathies in human clinical trials. ß

Reduced Renal Methylarginine Metabolism Protects against Progressive Kidney Damage

“…A stimulatory role of NO activity upon collagen deposition and wound-healing in skin and tendon tissue has been shown in in vitro and in vivo studies using exogenous NO donors, 31 iNOS overexpression 32 and even dietary L-arginine supplementation. 33 Published literature confirms NO as a pleiotropic molecule in the kidney as well as other systems 34 with both protective and deleterious effects exerted by NO upon collagen deposition and fibrosis in renal disease.…”

Endothelial dysfunction and tendinopathy: how far have we come?

“…In 14 patients undergoing rotator cuff repair, the stimulation of the tendon cells in culture with exogenous NO (SNAP) and iNOS gene carrier followed by enzymatic inhibition showed that low doses of NO positively influence the fibroblastic synthesis of collagen, while high doses inhibit it [38]. Murrel et al [19] demonstrated that oxygen free radicals, whose values are strictly modulated by concentration of NO, may modulate the growth of fibroblasts in vitro, with increased cell density and cell size when the concentration of free radicals is low, and evidence of cellular damage when the concentration is high.…”

“…Authors [38] reported that low doses of NO increase the synthesis of collagen in cultured human tendon cells. Paoloni et al [26] showed that topical glyceryl trinitrate (GTN) application reduces pain and improves range of motion, force, and symptoms of shoulder impingement after 6 months of treatment, improving the outcomes of patients with chronic tendinopathy when combined with rehabilitation.…”

“…At high concentrations, it is cause of tissue damage mediated by reactive oxygen species, activating specific molecular pathways [19,38]. Therefore, NO could be a marker to quantify the response of the endothelium to mechanical stress or hypoxia indicating the final balance between vasodilatating and vasoconstricting factors and their effects, but more ad stronger evidence is still needed to fully support this practice.…”

Healing of subcutaneous tendons: Influence of the mechanical environment at the suture line on the healing process

“…If such effects also occur in vivo, then this may explain why the integrity of the tendon as a whole may be affected by corticosteroid treatment. In contrast to corticosteroids, nitric oxide generally benefits tendon healing and enhances collagen synthesis [57] . Nitric oxide synthetases are normally expressed at low levels and are up regulated by mechanical stimuli [58,59] .…”