Anti-angiogenic rAAV-Vastatin gene transduction retarded mandibular condylar growth

Objectives: To investigate whether the novel anti-angiogenic gene vastatin could inhibit

neovascularization in condylar cartilage and thus cause reduction of mandibular condylar growth.

Methods: rAAV-Vastatin vector was constructed to mediate secreted vastatin by two plasmid

packaging system. 2x10¹¹ genome copies of rAAV-Vastatin and rAAV-eGFP were injected into

each side of temporal mandibular joint(TMJ) of 30-day-old, female, 100±5g SD rats in

experimental group and control group respectively. 8 rats were sacrificed at day 7, day 14,

day 21, day 30 and day 60 respectively in both groups. The lengths of right condyles were

measured. Tissue processing was carried out for further stainings. Von Willbrand Factor

VIII and Vastatin immunohistochemical staining were carried out to identify the distribution

of angiogenesis sites and microvessel density (MVD) as well as the expression layer of

vastatin at different time points. PAS and TRAP staining were carried out to study the

osteogenesis and osteoclastgenesis. Left condylar cartilages were collected and total RNA

was extracted. The expression level of a series of angiogenesis related genes,

osteogenesis related genes, and chondrogenesis related genes were quantified by real-time

PCR. Fold changes were calculated with comparative CT method. All the statistical

analyses were processed with SPSS for Windows.

Results: Mandibular condyalr growth was retarded at day 21 in AAV-Vastatin injection

group. MVD was decreased and angiogenesis related genes were down-regulated, with lowered

percentage of new bone formation, less number of TRAP positive cells and decreased

expression of Cbfa1. The changes of chondrogenesis related genes indicated delayed

transformation from cartilage to bone.

Conclusion: Vastatin inhibited neovascularisation and further retarded condylar

growth. Vastatin may also have direct effect on chondrocytes differentiation and

maturation which helped to trigger the anti-angiogenic effect.