Acute local inflammation elicits sprouting of sensory axons in the rat supraspinatus tendon
(English)Manuscript (preprint) (Other academic)
Inflammation activates nociceptive nerve endings and can elicit local sprouting of axons. We hypothesized that axon sprouting might be one factor behind the emergence of painful inflammatory conditions in the shoulder. Here we examine the distribution of sensory and sympathetic axons in the rat subacromial space under normal conditions and after local induction of inflammation with carrageenan. Furthermore, we measured the neuropeptide content in the supraspinatus tendon. In normal rats protein gene product 9.5- (POP 9.5-), substance P- (SP-), calcitonin gene related peptide- (CGRP-), neuropeptide Y- (NPY-) and tyrosine hydroxylase- (TH-) like immunoreactive (LI) axon profiles occurred in the subacromial space and around the glenohumeral joint. In the supraspinatus tendon axon profiles were limited to the tendon-muscle junction. After carrageenan injection inflammatory cells invaded the tendon and the subacromial bursa with a maximum at 2-3 weeks. Moreover, the tendon and the bursa showed signs of sprouting of PGP-9.5-, SP- and CGRP-LI axons, but not NPY- and TH-LI axons. The tendon was also invaded by blood vessels. The occurrence of axon profiles had a maximum at 2 weeks after injection and then subsided. Also, these axons were GAP-43-LI indicating collateral sprouting of nociceptive nerve fibres. There was no significant increase in the concentration of the neuropeptides SP and CGRP in the supraspinatus tendon. No inflammatory reaction or sprouting of nerve fibres was seen in saline-injected controls. We conclude that an acute inflammation in the subacromial space of the rat shoulder region can elicit a transient local sprouting of sensory axons in the tendon stroma and associated aberrant blood vessels.
inflanunation, carrageenan, protein gene product 9.5, calcitonin gene related peptide, neuropeptide Y, substance P, tyrosine hydroxylase, GAP-43, radioimmunoassay
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-80044OAI: oai:DiVA.org:liu-80044DiVA: diva2:545127