Blockade of the sympathetic nervous system degrades ligament in a rat MCL model.
We hypothesize that blockade of the sympathetic nervous system degrades ligament. We tested this hypothesis in a rat medial collateral ligament (MCL) model. Fifteen animals were treated for 10 days with the sympathetic chemotoxin guanethidine using osmotic pumps, whereas 15 control rats received pumps containing saline. A reduction in plasma concentrations of norepinephrine in the guanethidine rats indicated a significant decrease in sympathetic nerve activity. Vasoactive intestinal peptide and neuropeptide Y were decreased in MCLs from guanethidine animals, as quantified by radioimmunoassays. Tissue vascularity was substantially increased in guanethidine MCLs, whereas mechanical properties were significantly decreased. Proteases, such as matrix metalloproteinases (MMP) and cysteine proteases, play a major role in ligament degradation. The proteases MMP-13, cathepsin K, and tartrate-resistant acid phosphatase (TRAP) have collagenolytic activity and have been shown in rat ligament tissues. To determine whether the degradation seen in this study was due to protease activity, we determined the expression of these enzymes in control and treated MCLs. Real-time quantitative PCR revealed that guanethidine treatment increased expression of MMP-13 and cathepsin K mRNAs, although overall expression levels of MMP-13 and TRAP were relatively low. Histology also identified increases in TRAP and cathepsin K, but not MMP-13, in guanethidine-treated tissues. Results support our hypothesis that blockade of the sympathetic nervous system substantially degrades ligament.
Dwyer
Kelley W
KW
Department of Orthopedics and Rehabilitation, University of Wisconsin, Madison, Wisconsin 53792, USA.
Provenzano
Paolo P
PP
Muir
Peter
P
Valhmu
Wilmot B
WB
Vanderby
Ray
R
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D056657:Cathepsin K; D002403:Cathepsins / Q000378:metabolism; D017364:Collagenases / Q000378:metabolism; D005260:Female; D006145:Guanethidine / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D053509:Matrix Metalloproteinase 13; D017888:Medial Collateral Ligament, Knee / Q000294:innervation* / Q000502:physiology*; D009478:Neuropeptide Y / Q000378:metabolism; D009638:Norepinephrine / Q000097:blood; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D013373:Substance P / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D013565:Sympatholytics / Q000494:pharmacology*; D000071681:Tartrate-Resistant Acid Phosphatase; D023822:Tissue Engineering; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D007527:Isoenzymes; D009478:Neuropeptide Y; D013565:Sympatholytics; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase; D002403:Cathepsins; D056657:Cathepsin K; C534133:Ctsk protein, rat; D017364:Collagenases; D053509:Matrix Metalloproteinase 13; C507083:Mmp13 protein, rat; D020781:Matrix Metalloproteinase 1; D015740:Calcitonin Gene-Related Peptide; D009638:Norepinephrine; D006145:Guanethidine