Search

Application of tissue engineering currently provides promising therapeutic options in the fields of plastic surgery and wound management. The ability of scaffold material for cell proliferation and differentiation is the key for tissue engineering. This study has developed a novel nanofibre composed of poly glycolic acid (PGA) and collagen, both of which have their own respective beneficial properties. This study aimed to estimate the in vivo efficiency of the PGA/collagen nanofibre on granulation histology and its ability to induce neovascularisation. The electrospinning technique produced the PGA/collagen nanofiber with a diameter of 500 nm and weight mixing ratio of 40%. The skin defects on the mouse model were covered with PGA/collagen or a commercially available collagen matrix (n = 9). The PGA/collagen group histologically showed significantly higher cell density and a fine microstructure with greater number of migrating cells as compared to collagen matrix. Then, both materials were applied to the microcirculatory angiogenesis model. The PGA/collagen group (n = 8) revealed significantly higher functional capillary density on days 5 and 7 after application. The findings substantiated the fact that our material had a superior ability regarding cellular migration and induction of neovascularisation compared with the elementary collagen matrix product. This better result might be attributed to the nano-size effect of fine structure and the incorporation of PGA, which has been associated with enhanced angiogenesis.

Experimental results have previously been reported for a new biological dressing consisting of concentrated plasma proteins and platelet-rich plasma (PRP), which is named Platelet-Protein film (PPF). Based on the results of this experimental study, a clinical trial was begun to examine the usefulness of PPF. Although fresh autologous PPF is being used in the clinical trial, it is considered that the use of a preserved material prepared in advance would enable more convenient application. To verify the usefulness of preserved PPF, this preliminary study was conducted to examine the effects of fresh PPF, preserved PPF or blood clot, as control, applied to excisional skin defects in healing-impaired mice. The wound area and vascular density were analysed on day 9 after wound creation. Significant decrease of the wound size was observed in the preserved PPF and fresh PPF groups (4.2 (3.7), 2.2 (0.53)%) in comparison with that in the control group (38.5 (18.6)%, p < 0.05). Furthermore, a significant increase of the vascular density was also observed in the preserved PPF and fresh PPF groups (0.055 (0.021), 0.050 (0.019) mm(2)/mm(2)) as compared with that in the control group (0.016 (0.010) mm(2), p < 0.01). There was no significant difference in the effect on the wound size or vascular density between the preserved PPF and fresh PPF groups. The results showed that the properties of PPFs could be maintained for at least 1 week under appropriate storage conditions. The possibility of preservation of PPF for future use could be of practical advantage in actual clinical situations.

Studies in healthy volunteers and patients with renal failure have shown that vibration, applied with a frequency of 47 Hz and a vibrational intensity of 600 mVpp, increases microcirculation of blood in the skin. This controlled, in vivo, experimental study was conducted to further evaluate the effect of vibration on skin microcirculation and to ascertain whether administration of a nitric oxide (NO) synthase inhibitor (NG-nitro-L-arginine methyl ester [L-NAME]) diminishes the effect of vibration on skin blood flow. Using a mouse microcirculatory model, 12 animals were prepared for study (six in the control and six in the experimental group). In the experimental group, vibrations were applied horizontally for 15 minutes. The control group received no vibration. Venular blood flow was measured using intravital videomicroscopy at baseline and at 0, 5, and 15 minutes after the application of vibration. Vibration significantly increased the blood flow at 5 and 15 minutes after application (P = 0.002 and P = 0.046, respectively). Differences between the control and experimental group also were statistically significant (P = 0.0017 and P = 0.046, respectively). In the second study, all animals (seven in each group) received an intraperitoneal injection of NO synthase inhibitor L-NAME before vibration application. When NO synthase inhibitor L-NAME was administered, the increase in blood flow in the vibration group was minimal after 5 and 10 minutes, and nonexistent after 15 minutes. No significant differences between the control and experimental group were observed. Because NO synthase inhibitor L-NAME inhibits NO production in vivo, these findings imply the involvement of NO in the observed blood flow increase during vibration. Future clinical trials to establish evidence as to the beneficial effects of vibration are warranted.

Although previous studies have proved that subatmospheric pressure in vacuum assisted closure therapy increased blood flow at the wound edge, no reports have presented data on blood flow in the wound bed. This study examined a technique that visualized microcirculation of the wound bed and estimated the acute effect of negative pressure. The superficial stratum of the mouse gluteal skin was microsurgically excised preserving the subdermal vascular plexus. The preserved vessels were visualized as the wound bed microcirculation using an intravital microscope-video-computer system. Three levels of negative pressure (-125 mmHg [n=12], -500 mmHg [n=12], 0 mmHg [n=8]) were applied to the wound. Our experimental model successfully and quantitatively visualized wound bed microcirculation under negative pressure application. A negative pressure of -125 mmHg significantly increased wound bed blood flow immediately after pressure application, maintained for 1 minute after pressure release, whereas in the -500 mmHg group blood flow decreased with time and reached a statistically significant level 5 minutes after pressure application. These findings reinforce the hypothesis that enhanced blood flow in the wound bed as well as at the wound edge may contribute to the beneficial effects of certain levels of negative pressure therapy for wound perfusion.

The effect of vibration on skin microcirculation was studied to investigate the possibility of clinical use of vibration to prevent and treat pressure ulcers. Vibrations at a vibrational intensity of 600, 800, or 1,000 mVpp with a fixed frequency of 47 Hz were applied horizontally to the ear of male hairless mice (n = 6 for each group) under inhalation anesthesia. The control group (n = 6) received no vibrations. Venular blood flow was measured by an intravital videomicroscope at the baseline and at 0, 5, and 15 min after the application of vibrations. A significant increase was observed in the 600 mVpp group 5 and 15 min after vibration in comparison to the control group (P = 0.002 and P = 0.046, respectively). We also detected increased blood flow in the 800 mVpp group (P = 0.028) and the 1,000 mVpp group (P = 0.012) 5 min after vibration; however, these increases attenuated after 15 min. These results indicate that direct skin vibration at a frequency of 47 Hz improves skin blood flow. The present study gives further support to the role of vibration on a short-term increase in skin blood flow.

Background and Objectives: The growth factors derived from platelets and plasma proteins mediate the wound-healing process that is characterized by the sequential migration and differentiation of several cell populations that give rise to angiogenesis, collagen synthesis, wound contraction, and re-epithelialization. To evaluate the efficacy of the blood-derived factors in wound healing, we examined a novel wound dressing consisting of concentrated human plasma proteins and platelet releasate (CPPP)., Materials and Methods: To generate CPPP, plasma proteins and platelets in the peripheral blood (n = 5) were concentrated with the cold ethanol precipitation method. The thrombin obtained from the same blood unit and calcium chloride (CaCl(2)) were mixed to a concentrate. The CPPP has enough strength to dress cutaneous wounds and contains large amounts of cytokines and fibronectin. We applied the CPPP to excisional skin wounds in genetically healing-impaired model mice (n= 5) and the wounds were evaluated 10 days after the operation., Results: The area of CPPP-treated wounds decreased significantly compared with that of the control wounds (65% vs. 94% of the original size, respectively, P= 0.032). The immunostained section revealed a striking effect of CPPP on vascularization compared with the control wounds (13.2 vs. 2.7 vessels per mm(2) as mean vascular density observed in the sections, respectively, P= 0.013)., Conclusions: Our results suggest that CPPP is a promising biologically active dressing for full-thickness skin wounds. CPPP can be an entirely autologous biological dressing, suggesting that it is free from the risk of transmission of pathogens through blood products.

To investigate whether hyperthermic preconditioning can actually protect skin flaps against ischemia/reperfusion injury, the authors first developed a new skin-flap model in 15 mice, a dorsal bipedicle island skin-flap model. Then, another 75 mice were separated into five groups. Mice in Groups 1 to 4 received the same hyperthermic preconditioning, but had different recovery times of 6 hr, 24 hr, 48 hr, and 72 hr, respectively. Mice in Group 5 served as control. Island skin flaps were elevated in all groups, and then were subjected to 8 hr of ischemia and subsequent reperfusion. Flap survival was statistically significantly higher than in controls in animals in Groups 1 and 3, with recovery times of 6 hr and 48 hr, respectively. Mice in Groups 2 and 4 had recovery times of 24 hr and 72 hr, respectively. Hyperthermic preconditioning could thus protect skin flaps against ischemia/reperfusion injury, and there were two optimal periods for such a protective effect.

Mice are popular animals for biomedical studies, but few skin flap models have been reported in them. To investigate the ischaemia/reperfusion phenomenon in skin flaps, we first investigated the vascular anatomy of murine dorsal skin and then designed a suitable murine dorsal skin flap model. In 120 mice, six distinct vascular patterns were identified, one being seen in 111 mice (93%). Based on this finding, in Part 2 of the study, 15 mice had flaps (4 x 4 cm) raised based on the two caudal vascular pedicles of the left and right deep circumflex iliac vessels as a bipedicled flap in which the mean (SD) survival was 96 (5)%. In a further 10 mice, flaps were raised based on a single pedicle, the left deep circumflex iliac vessel, as a monopedicled flap, in which the mean (SD) survival was 71 (12)%. The bipedicled flap model was then used to study ischaemia/reperfusion injury. Twenty flaps were subjected to eight hours of ischaemia and subsequent reperfusion, and their mean (SD) survival was 43 (26)%. Histological assessments were also carried out using neutrophil and leucocyte counts, and significant differences between groups were observed.

We investigated the acute effect of static magnetic fields of up to 8 T on skin blood flow and body temperature in anesthetized rats. These variables were measured prior to, during, and following exposure to a magnetic field in a superconducting magnet with a horizontal bore. The dorsal skin was transversely incised for 1 cm to make a subcutaneous pocket. Probes of a laser Doppler flowmeter and a thermistor were inserted into the pocket and positioned at mid-dorsum to measure skin blood flow and temperature. Another thermistor probe was put into the rectum to monitor rectal temperature. After baseline measurement outside the magnet, the rat was inserted into the bore for 20 min so that mid-dorsum was exactly positioned at the center, where the magnetic field was nearly homogeneous. Post-exposure changes were then recorded for 20 min outside the bore. Sham-exposed animals were submitted to exactly the same conditions, except that the superconducting magnet was not energized. Skin blood flow and temperature decreased significantly during magnetic field exposure and recovered after removal of the animal from the magnet. The rectal temperature showed a tendency to decrease while the animal was in the magnet. The microcirculatory and thermal reactions in the present study were consistent and agreed with some of the predictions based on mathematical simulations and model experiments., (Copyright 2000 Wiley-Liss, Inc.)