Introduction: Focused ultrasound can stimulate a specific point of tissue and can be a noninvasive method for acupoint stimulation. The aim of this study was to clarify the effects of acupoint stimulation by focused ultrasound on blood flow volume and coldness of the fingers and toes. Materials and Methods: Forty healthy volunteers were included in this experiment. The blood flow volume and the skin temperature of a finger and toe were measured before and after stimulation of the pericardium 6 acupuncture point (PC-6) by focused ultrasound. Subjective coldness of the fingers and toes was also assessed using a visual analog scale (VAS) before and after stimulation. Results: The maximum blood flow volumes of the finger and toe were significantly larger (p < 0.01) than those before stimulation. The maximum skin surface temperatures of the fingers were significantly higher (p < 0.01) than those before stimulation. The VAS scores for subjective coldness of the toes after stimulation were significantly higher (p < 0.01). Conclusion: The blood flow volume and skin temperature tended to increase after PC-6 stimulation. The VAS scores also indicated a tendency toward a warmer sensation in the toes after stimulation.
When ligaments are injured, reconstructive surgery is sometimes required to restore function. Methods of reconstructive surgery include transplantation of an artificial ligament and autotransplantation of a tendon. However, these methods have limitations related to the strength of the bone-ligament insertion and biocompatibility of the transplanted tissue after surgery. Therefore, it is necessary to develop new reconstruction methods and pursue the development of artificial ligaments. Elastin is a major component of elastic fibers and ligaments. However, the role of elastin in ligament regeneration has not been described. Here, we developed a rabbit model of a medial collateral ligament (MCL) rupture and treated animal knees with exogenous elastin [100 µg/(0.5 mL·week)] for 6 or 12 weeks. Elastin treatment increased gene expression and protein content of collagen and elastin (gene expression, 6-fold and 42-fold, respectively; protein content, 1.6-fold and 1.9-fold, respectively), and also increased the elastic modulus of MCL increased with elastin treatment (2-fold) compared with the controls. Our data suggest that elastin is involved in the regeneration of damaged ligaments.
Ligament reconstruction using a tissue-engineered artificial ligament (TEAL) requires regeneration of the ligament-bone junction such that fixation devices such as screws and end buttons do not have to be used. The objective of this study was to develop a TEAL consisting of elastin-coated polydioxanone (PDS) sutures covered with elastin and collagen fibers preseeded with ligament cells. In a pilot study, a ring-type PDS suture with a 2.5 mm (width) bone insertion was constructed with/without elastin coating (Ela-coat and Non-coat) and implanted into two bone tunnels, diameter 2.4 mm, in the rabbit tibia (6 cases each) to access the effect of elastin on the bond strength. PDS specimens taken together with the tibia at 6 weeks after implantation indicated growth of bone-like hard tissues around bone tunnels accompanied with narrowing of the tunnels in the Ela-coat group and not in the Non-coat group. The drawout load of the Ela-coat group was significantly higher (28.0 ± 15.1 N, n = 4) than that of the Non-coat group (7.6 ± 4.6 N, n = 5). These data can improve the mechanical bulk property of TEAL through extracellular matrix formation. To achieve this TEAL model, 4.5 × 10 ligament cells were seeded on elastin and collagen fibers (2.5 cm × 2.5 cm × 80 µm) prior to coil formation around the elastin-coated PDS core sutures having ball-shape ends with a diameter of 2.5 mm. Cell-seeded and cell-free TEALs were implanted across the femur and the tibia through bone tunnels with a diameter of 2.4 mm (6 cases each). There was no incidence of TEAL being pulled in 6 weeks. Regardless of the remarkable degradation of PDS observed in the cell-seeded group, both the elastic modulus and breaking load of the cell-seeded group (n = 3) were comparable to those of the sham-operation group (n = 8) (elastic modulus: 15.4 ± 1.3 MPa and 18.5 ± 5.7 MPa; breaking load: 73.0 ± 23.4 N and 104.8 ± 21.8 N, respectively) and higher than those of the cell-free group (n = 5) (elastic modulus: 5.7 ± 3.6 MPa; breaking load: 48.1 ± 11.3 N) accompanied with narrowed bone tunnels and cartilage matrix formation. These data suggest that elastin increased the bond strength of TEAL and bone. Furthermore, our newly developed TEAL from elastin, collagen, and ligament cells maintained the strength of the TEAL even if PDS was degraded.
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