Effects of platelet-derived growth factor-BB on the metabolic function and morphologic features of equine tendon in explant culture.
OBJECTIVE
To evaluate the effects of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) on the metabolic function and morphologic features of equine superficial digital flexor tendon (SDFT) in explant culture. Animals-6 euthanized horses (2 to 5 years old).


METHODS
Forelimb SDFT explants were cultured for 6 days as untreated control specimens or treated with rhPDGF-BB (1, 10, 50, or 100 ng/mL of medium). Treatment effects on explant gene expression were evaluated via real-time PCR analysis of collagen type I, collagen type III, PDGF-A, and PDGF-B mRNA. Explants were assayed for total collagen, glycosaminoglycan, and DNA content; histologic changes were assessed via H and E staining and immunohistochemical localization of collagen types I and III.


RESULTS
No morphologic or proliferative changes were detected in tendon explant sections. After high-dose rhPDGF-BB treatment, gene expression of collagen types I and III was increased and decreased, respectively. Expression of PDGF-A and PDGF-B mRNA was significantly increased at 24 hours, but later decreased to have few or negative autoinductive effects. Although PDGF gene expression waned after 48 hours of culture, collagen type I gene expression was significantly increased at 48 hours and reached peak value on day 6. Glycosaminoglycan and DNA content of explants were unchanged with rhPDGF-BB treatment.


CONCLUSIONS
Results suggest that rhPDGF-BB use may be of benefit in the repair of equine tendon, particularly through induction of collagen type I mRNA. Positive autoinductive effects of PDGF-BB in equine SDFT explants were detected early following culture medium supplementation, but these diminished with time.
Haupt
Jennifer L
JL
Comparative Orthopaedics Laboratory, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Donnelly
Brandon P
BP
Nixon
Alan J
AJ
D000818:Animals; D000077214:Becaplermin; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D024061:Collagen Type III / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects; D006025:Glycosaminoglycans / Q000378:metabolism; D006736:Horses / Q000378:metabolism*; D007150:Immunohistochemistry / Q000662:veterinary; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D013710:Tendons / Q000187:drug effects* / Q000378:metabolism*; D046509:Tissue Culture Techniques
D024042:Collagen Type I; D024061:Collagen Type III; D006025:Glycosaminoglycans; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; C075278:platelet-derived growth factor A; D000077214:Becaplermin; D004247:DNA