Article

Immunohistochemical and histochemical findings favoring the occurrence of autocrine/paracrine as well as nerve-related cholinergic effects in chronic painful patellar tendon tendinosis.

Department of Integrative Medical Biology, Section for Anatomy, Umeå University, SE-901 87 Umeå, Sweden.
Microscopy Research and Technique (impact factor: 1.79). 11/2006; 69(10):808-19. DOI:10.1002/jemt.20351 pp.808-19
Source: PubMed

ABSTRACT The pathogenesis of the pain in patellar tendon tendinosis ("jumper's knee") is unclear. We have recently presented new information about the sensory nervous system in the human patellar tendon, but there is very little information regarding the possible occurrence of a cholinergic system in this tendon. In the present study, specimens of pain-free normal tendons and chronically painful tendinosis tendons were examined by different immunohistochemical and histochemical methods. Antibodies against the M(2) receptor, choline acetyltransferase (ChAT), and vesicular acetylcholine transporter (VAChT) were applied, and staining for demonstration of activity of acetylcholinesterase (AChE) was also utilized. It was found that immunoreactions for the M(2) receptor could be detected intracellularly in both blood vessel cells and tenocytes, especially in tendinosis specimens. Furthermore, in the tendinosis specimens, some tenocytes were seen to exhibit immunoreaction for ChAT and VAChT. AChE reactions were seen in fine nerve fibers associated with small blood vessels in both the normal control tendons and the tendinosis tendons. The observations suggest that there is both a nerve related and a local cholinergic system in the human patellar tendon. As ChAT and VAChT immunoreactions were detected in tenocytes of tendinosis tendons, these cells might be a source of local acetylcholine (Ach) production. As both tenocytes and blood vessel cells were found to exhibit immunoreactions for the M(2) receptor, it is likely that both of these tissue cells may be influenced by ACh. Thus, in conclusion, there appears to be an upregulation of the cholinergic system, and an occurrence of autocrine/paracrine effects in this system, in the tendinosis patellar tendon.

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Keywords

acetylcholinesterase
 
AChE reactions
 
autocrine/paracrine effects
 
blood vessel cells
 
cholinergic system
 
chronically painful tendinosis tendons
 
fine nerve fibers
 
human patellar tendon
 
local acetylcholine
 
local cholinergic system
 
normal control tendons
 
pain-free normal tendons
 
patellar tendon tendinosis
 
possible occurrence
 
sensory nervous system
 
small blood vessels
 
tendinosis patellar tendon
 
tissue cells
 
VAChT immunoreactions
 
vesicular acetylcholine transporter
 

Patrik Danielson