The cell specific temporal expression of nitric oxide synthase isoforms during achilles tendon healing.
OBJECTIVE
We have previously shown that nitric oxide synthase (NOS) activity is upregulated following tendon injury, and that this activity is important to Achilles tendon healing. The aim of this study was to identify the cellular distribution of nitric oxide synthase isoforms during tendon healing.


METHODS
Surgical division of the right Achilles tendon was performed in eighty-five male Sprague-Dawley rats. Healing Achilles tendons were harvested at 4, 7, 14 and 21 days following the surgery. The un-injured left Achilles tendons were used as controls. Using RNase protection assays, in situ hybridization and immunohistochemistry, mRNA and protein of NOS isoforms were evaluated.


RESULTS
Minimal NOS expression was found in un-injured tendon. A cell specific temporal pattern for the mRNA and protein for all three NOS isoforms was found following injury to the Achilles tendon. iNOS was maximal on day 4 in macrophages and fibroblasts. eNOS was maximal on day 4 in endothelial cells and fibroblasts. bNOS expression gradually increased up to day 21 and was found only in fibroblasts.


CONCLUSIONS
These results suggest that all three nitric oxide synthase isoforms are expressed by fibroblasts in a coordinated temporal sequence during tendon healing. The sequential pattern of NOS expression in healing fibroblasts suggests that each NOS isoform may play a different role in the healing process and provides opportunities to modify tendon healing in the clinical setting.
Lin
J
J
Orthopaedic Research Institute, University of New South Wales, Sydney, Australia.
Wang
M X
MX
Wei
A
A
Zhu
W
W
Murrell
G A
GA
D000125:Achilles Tendon / Q000201:enzymology* / Q000293:injuries* / Q000473:pathology; D000818:Animals; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007527:Isoenzymes / Q000096:biosynthesis / Q000737:chemistry; D008297:Male; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000737:chemistry; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D023282:Nuclease Protection Assays; D010641:Phenotype; D015347:RNA Probes; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley
D007527:Isoenzymes; D015347:RNA Probes; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat