Cloning and expression of type III collagen in normal and injured tendons of horses.
OBJECTIVE
To clone the 5' end of type III collagen and describe its pattern of mRNA and protein expression in normal and healing tendons in horses.


METHODS
14 healthy adult horses.


METHODS
The tensile region of collagenase-injured superficial digital flexor tendons was harvested at intervals from 1 to 24 weeks after injury. Total RNA was reverse-transcribed into cDNA for cloning and sequencing of type III collagen. Equine-specific nucleic acid probes were developed and used for northern blot analysis and in situ hybridization. Type III collagen protein and cyanogen bromide-cleaved collagen peptides were assessedby gel electrophresis.


RESULTS
Type III collagen mRNA expression and protein content increased immediately after injury and remained increased. Type III collagen was localized to the endotenon in normal tendon and in injured tendon at 1 week. At 8 and 24 weeks, expression became more widely distributed throughout the tendon parenchyma. Injured tendon contained 6 times more type I than type III collagen mRNA. Quantities of type III collagen protein were maximal in the first 4 weeks after injury (approx 33%) and then began to decrease.


CONCLUSIONS
Type III collagen expression is increased initially in endotenon and subsequently in parenchyma of healing tendon; however, type III remains the minor collagen throughout the healing process. The role of type III collagen in tendon healing is not fully elucidated.
Dahlgren
Linda A
LA
Comparative Orthopaedics Laboratory, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Brower-Toland
Brent D
BD
Nixon
Alan J
AJ
D000818:Animals; D015152:Blotting, Northern / Q000662:veterinary; D003001:Cloning, Molecular; D024061:Collagen Type III / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression; D006734:Horse Diseases / Q000378:metabolism*; D006736:Horses / Q000293:injuries*; D007150:Immunohistochemistry / Q000662:veterinary; D017403:In Situ Hybridization / Q000662:veterinary; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012333:RNA, Messenger / Q000378:metabolism; D013708:Tendon Injuries / Q000378:metabolism / Q000662:veterinary*; D013710:Tendons / Q000378:metabolism*; D014945:Wound Healing
D024061:Collagen Type III; D012333:RNA, Messenger