Nucleotide structure of equine platelet-derived growth factor-A and -B and expression in horses with induced acute tendinitis.
OBJECTIVE
To characterize the nucleotide sequence of equine platelet-derived growth factor (PDGF)-A and -B and analyze temporal expression of these genes in equine tendon after induced tendinitis injury. Animals-18 mature horses.


METHODS
Genes for equine PDGF-A and -B were reverse transcribed and sequenced from synovial tissue mRNA obtained from a 3-year-old horse. Collagenase-induced lesions were created in the tensile region of the superficial digital flexor tendon in 14 horses; 3 horses served as uninjured control animals. Tendons were harvested and total RNA was isolated from experimental horses 1, 2, 4, 8, and 24 weeks after collagenase injection. Temporal gene expression for PDGF-A and -B was determined by use of quantitative PCR analysis.


RESULTS
Equine PDGF-A shared 83.8% sequence and 87.5% peptide homology with human PDGF-A, with a discrepancy of 70 bp from the human sequence. Equine PDGF-B was similar in length to the human gene, sharing 90.3% and 91.7% nucleotide and peptide identity, respectively. Expression of PDGF-A mRNA in collagenase-induced tendinitis lesions was unchanged, compared with expression for normal control tendon, and remained steady throughout the 24-week study. Expression of PDGF-B mRNA decreased over time, and the expression at 24 weeks was significantly reduced, compared with expression in normal and acutely injured tendon.


CONCLUSIONS
Injured tendon mounts a minimal constitutive PDGF-A or -B mRNA response. Serial exogenous treatment with either PDGF isoform within the first 2 to 4 weeks after tendon injury may bolster the meager PDGF paracrine-autocrine intrinsic response to injury.
Donnelly
Brandon P
BP
Comparative Orthopaedics Laboratory, Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Nixon
Alan J
AJ
Haupt
Jennifer L
JL
Dahlgren
Linda A
LA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017364:Collagenases; D005786:Gene Expression Regulation; D006734:Horse Diseases / Q000378:metabolism*; D006736:Horses; D008969:Molecular Sequence Data; D010982:Platelet-Derived Growth Factor / Q000737:chemistry* / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis / Q000737:chemistry* / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D052256:Tendinopathy / Q000139:chemically induced / Q000378:metabolism / Q000662:veterinary*
D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; C075278:platelet-derived growth factor A; D017364:Collagenases