Studies on the importance of sympathetic innervation, adrenergic receptors, and a possible local catecholamine production in the development of patellar tendinopathy (tendinosis) in man |
Patrik Danielson 1 *, Håkan Alfredson 2, Sture Forsgren 1 |
1Department of Integrative Medical Biology, Section for Anatomy, Umeå University, Umeå, Sweden 2Department of Surgical and Perioperative Science, Sports Medicine, Umeå University, Umeå, Sweden |
email: Patrik Danielson (patrik.danielson@anatomy.umu.se) |
*Correspondence to Patrik Danielson, Department of Integrative Medical Biology, Section for Anatomy, Umeå University, SE-901 87 Umeå, Sweden
Funded by:
Faculty of Medicine at Umeå University
The Swedish National Centre for Research in Sports
The County Council of Västerbotten
The Arnerska Research Foundation
Keywords |
tyrosine hydroxylase • (alpha)-1 • (alpha)-2A • (beta)-1 • adrenoreceptors • tenocytes |
Abstract |
Changes in the patterns of production and in the effects of signal substances may be involved in the development of tendinosis, a chronic condition of pain in human tendons. There is no previous information concerning the patterns of sympathetic innervation in the human patellar tendon. In this study, biopsies of normal and tendinosis patellar tendons were investigated with immunohistochemical methods, including the use of antibodies against tyrosine hydroxylase (TH) and neuropeptide Y, and against 1-, 2A-, and 1-adrenoreceptors. It was noticed that most of the sympathetic innervation was detected in the walls of the blood vessels entering the tendon through the paratendinous tissue, and that the tendon tissue proper of the normal and tendinosis tendons was very scarcely innervated. Immunoreactions for adrenergic receptors were noticed in nerve fascicles containing both sensory and sympathetic nerve fibers. High levels of these receptors were also detected in the blood vessel walls; 1-adrenoreceptor immunoreactions being clearly more pronounced in the tendinosis tendons than in the tendons of controls. Interestingly, immunoreactions for adrenergic receptors and TH were noted for the tendon cells (tenocytes), especially in tendinosis tendons. The findings give a morphological correlate for the occurrence of sympathetically mediated effects in the patellar tendon and autocrine/paracrine catecholamine mechanisms for the tenocytes, particularly, in tendinosis. The observation of adrenergic receptors on tenocytes is interesting, as stimulation of these receptors can lead to cell proliferation, degeneration, and apoptosis, events which are all known to occur in tendinosis. Furthermore, the results imply that a possible source of catecholamine production might be the tenocytes themselves. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. |
Received: 4 July 2006; Accepted: 26 October 2006