Modulation of digital flexor tendon healing by vascular endothelial growth factor gene transfection in a chicken model.

A major challenge in tendon injury is the weak intrinsic healing capacity of tendon that may cause rupture of the repair after surgery. Growth factors are believed to be critical during tendon healing. This study aimed to investigate the effects of vascular endothelial growth factor (VEGF) genes delivered by adeno-associated virus (AAV) vectors on tendon healing and molecular events involved in a chicken model. A total of 128 deep flexor tendons in the long toes of chickens were completely transected and injected with 2 × 109 particles of AAV2-VEGF or saline before surgically repaired. At postoperative 4, 6 and 8 weeks, the gliding excursions of tendon were recorded and adhesions around the repair site scored. At 2, 4, 6 and 8 weeks, the ultimate strengths of the healing tendons were tested. Terminal deoxynucleotide transferase dUTP nick end labeling assay were performed to detect cellular apoptosis and immunofluorescence staining to detect type III collagen and matrix metalloprotease-2 (MMP2) expression in tendon tissues. The gliding excursion and adhesion score were similar between AAV2-VEGF-treated tendons and the control tendons. Delivery of AAV2-VEGF significantly increased ultimate strength of the healing tendons at postoperative 4, 6 and 8 weeks (P<0.05). Apoptotic reaction was inhibited from postoperative 2 to 8 weeks in tendon core area or surface area. Type III collagen expression was enhanced at 2, 4, 6 and 8 weeks and MMP2 expression enhanced at 2 and 4 weeks after AAV2-VEGF transfection. The current study confirms the therapeutic efficacy of AAV2-VEGF in improving healing strength of tendon without aggravating adhesion formation after tendon injury, shedding light on the application of molecular therapy in modulating tendon healing.

Adeno-associated virus-2-mediated TGF-ß1 microRNA transfection inhibits adhesion formation after digital flexor tendon injury.

Adhesion formation after digital flexor tendon injury greatly affects gliding function of the tendon, which is a major clinical complication after hand surgery. Transforming growth factor beta 1 (TGF-ß1) has a critical role in adhesion formation during tendon healing. Persistent regulation of TGF-ß1 through application of microRNA (miRNA) specifically inhibiting the function of TGF-ß1 (TGF-ß1-miRNA) holds promise for treatment of such a complication. Adeno-associated virus (AAV) was used to transfer TGF-ß1-miRNA to the chicken digital flexor tendons, which had been injured and surgically repaired. Four doses of AAV2-TGF-ß1-miRNA (2 × 10¹¹, 2 × 10¹°, 2 × 109 and 2 × 108 vector genomes (vg)) were used to determine the transfection efficiency. At postoperative 3 weeks, we found a positive correlation between the administered AAV2-TGF-ß1-miRNA doses and transfection efficiency. The transfection rate ranged from 10% to 77% as the doses increased. Production of TGF-ß1 protein in the tendons decreased on increasing vector dosage. When 2 × 10¹¹ and 2 × 10¹°) vg were injected into the tendon, gliding excursion of the repaired tendon and work of flexion of chicken toes were significantly increased and adhesion score decreased 6 and 8 weeks later, indicating the improvement of tendon gliding and decreases in adhesion formations. However, the ultimate strength of the tendons transfected at the dose of 2 × 10¹° vg was 12-24% lower than that of the control tendons. The results of this study demonstrate that application of TGF-ß1-miRNA had a mixed impact on tendon healing: adhesion around the tendon is reduced but strength of the tendon healing is adversely affected. Future studies should aim at maintaining the beneficial effects of reducing tendon adhesions, while eliminating the adverse effects of decreasing the healing strength.

[Investigation on prevalence of Schistosoma japonicum infections in wild mice in Shitai County, Anhui Province, 2018].

OBJECTIVE: To investigate the prevalence of Schistosoma japonicum infection in wild mice in Shitai County, Anhui Province, so as to provide insights into precise control of the source of S. japonicum infections. METHODS: Wild mice were captured using the trapping method for three successive nights at snail-infested settings from Jitan Village of Jitan Township, and Shiquan Village and Xibai Village of Dingxiang Township, Shitai County, Anhui Province in June and October, 2018. All trapped wild mice were sacrificed and liver and mesenteric vein specimens were collected for detection of S. japonicum eggs using microscopy, while the fecal samples in mouse intestines were collected for identification of S. japonicum infections using Kato-Katz technique. In addition, the population density of trapped wild mice was estimated and the prevalence of S. japonicum infection was calculated in trapped wild mice. RESULTS: A total of 376 wild mice were trapped from three villages in Shitai County. The population density of trapped wild mice was 9.1% (376/4 124), and the prevalence of S. japonicum infection was 24.2% (91/376) in trapped wild mice. The highest prevalence of S. japonicum infection was detected in Shiquan Village of Dingxiang Township (30.1%), and the lowest prevalence was seen in Xibai Village of Dingxiang Township; however, there was no significant difference in the prevalence of S. japonicum infection in trapped wild mice among three villages (χ2= 4.111, P > 0.05). In addition, there was no significant difference in the prevalence of S. japonicum infection in wild mice captured between on June (26.8%, 34/127) and October (22.9%, 57/249) (χ2 = 0.690, P = 0.406). The trapped wild mice included 6 species, including Rattus norvegicus, Niviventer niviventer, R. losea, Apodemus agrarius, Mus musculus and N. coning, and the two highest prevalence of S. japonicum infection was detected in R. losea (34.9%, 22/63) and R. norvegicus (31.2%, 44/141). CONCLUSIONS: The prevalence of S. japonicum infections is high in wild mice in Shitai County, and there is a natural focus of schistosomiasis transmission in Shitai County.

A study of the anatomy and repair strengths of porcine flexor and extensor tendons: are they appropriate experimental models?

Although both porcine flexor and extensor tendons have been used in tendon repair research, no studies have specifically studied the anatomical differences and repair strengths in both types of tendons. We used 12 pig trotters to observe the anatomy of these tendons and compared the 2 mm gap and ultimate strengths of flexor and extensor tendons. There were four annular (A1, A2, A3, and A4) pulleys and one oblique pulley, which form a fibro-osseous tunnel for the flexor tendons, but the anatomy of the porcine extensor tendons was markedly different from the human flexor or extensor tendons. The diameter of flexor tendons was significantly greater than that of the extensors. The 2 mm gap and ultimate strengths of the flexor tendon with either two-strand or four-strand repairs were significantly greater than those of the extensor tendon. We conclude that the porcine flexor tendon systems are similar to those in the human, but the extensor tendons are not similar to either the flexor or extensor tendons in humans. Flexor and extensor tendons have different repair strengths which should be taken into account when interpreting findings from investigations using these tendons.