Creating and Transferring an Innervated, Vascularized Muscle Flap Made from an Elastic, Cellularized Tissue Construct Developed In Situ

Reanimating facial structures following paralysis and muscle loss is a surgical objective that would benefit from improved options for harvesting appropriately sized muscle flaps. The objective of this study is to apply electrohydrodynamic processing to generate a cellularized, elastic, biocomposite scaffold that could develop and mature as muscle in a prepared donor site in vivo, and then be transferred as a thin muscle flap with a vascular and neural pedicle. First, an effective extracellular matrix (ECM) gel type is selected for the biocomposite scaffold from three types of ECM combined with poly(ester urethane)urea microfibers and evaluated in rat abdominal wall defects. Next, two types of precursor cells (muscle-derived and adipose-derived) are compared in constructs placed in rat hind limb defects for muscle regeneration capacity. Finally, with a construct made from dermal ECM and muscle-derived stem cells, protoflaps are implanted in one hindlimb for development and then microsurgically transferred as a free flap to the contralateral limb where stimulated muscle function is confirmed. This construct generation and in vivo incubation procedure may allow the generation of small-scale muscle flaps appropriate for transfer to the face, offering a new strategy for facial reanimation.

Correlation between blood flow, tissue volume and microvessel density in the flap

The purpose of this study was to assess the correlation between tissue volume and blood flow of the flap in an animal model. Using animal model, tissue volume can be attenuated, and precise change of blood flow could be evaluated. We further investigate the relationship between blood flow and vascular density in the tissue. In this study, we assessed flap conductance (ml/min/mm Hg) as to evaluate the conductivity of blood flow into the flap. Japanese white rabbit was used (n = 7) for this study. The amount of blood flow of jejunal and latissimus dorsi muscle (LD) flaps was measured while removing the distal portion of the flap sequentially. Conductance at each time was calculated from blood pressure and blood flow volume. The tissue volume at each time was also measured. The correlation between conductance and volume was analyzed using a linear mixed model. Immunohistochemical evaluation of microvessel densities (MVD) in these tissues was also performed for CD31/PECAM1 positive area. Conductance and tissue volume were significantly correlated in both jejunal and LD flaps. As the volume increases by 1 cm³, the conductance increased significantly by 0.012 ml/min/mm Hg in jejunum, and by 0.0047 ml/min/mm Hg in LD. Mean MVD was 1.15 ± 0.52% in the jejunum and 0.37 ± 0.29% in the LD muscle. In this study, we revealed that flap conductance is proportional to volume and proportional constant is different between the type of tissue. It suggests that the difference of MVD creates the unique conductance of each tissue.

Nuss procedure for patients with pectus excavatum with a history of intrathoracic surgery

BACKGROUND

The aim of this study was to demonstrate the feasibility and safety of the Nuss procedure for patients with pectus excavatum (PE) with a history of intrathoracic surgery.

PATIENTS

From April 2010 to December 2013, we performed 6 cases of PE repair in patients with a history of intrathoracic surgery. The causes of previous operations were congenital cystic adenomatoid malformation in 4 patients and congenital diaphragmatic hernia in 2. The patients' median age was 5 years (range, 4-9 years) and median preoperative pectus severity index was 4.63 (range, 3.42-10.03). Their intraoperative and postoperative courses were reviewed retrospectively.

RESULTS

The mean overall operation time was 127.5 ± 17.0 minutes, and the mean operation time for endoscopic pneumolysis was 28.8 ± 12.3 minutes. Intraoperative exploration for pleural adhesion revealed that the endoscopic approach in the previous operation was associated with low pleural adhesion, and the open thoracotomy or laparotomy approach was associated with low to high pleural adhesion. One patient developed a pneumothorax on the first postoperative day. All the other patients had uneventful postoperative courses. All the patients received bar removal 2-3 years after bar insertion. One patient developed atelectasis after bar removal. All the other patients had an uneventful postoperative course. The mean postoperative follow-up time after bar removal was 20.1 ± 14.7 months.

CONCLUSIONS

History of intrathoracic surgery seems not a contraindication for the Nuss procedure. However, perioperative complications should be carefully monitored in both the bar insertion and removal operations.

Use of a pedicled omental flap to reduce inflammation and vascularize an abdominal wall patch

BACKGROUND

Although a variety of synthetic materials have been used to reconstruct tissue defects, these materials are associated with complications such as seromas, fistulas, chronic patient discomfort, and surgical site infection. While alternative, degradable materials that facilitate tissue growth have been examined. These materials can still trigger a foreign body inflammatory response that can lead to complications and discomfort.

MATERIALS AND METHODS

In this report, our objective was to determine the effect of placing a pedicled omental flap under a biodegradable, microfibrous polyurethane scaffold serving as a full-wall thickness replacement of the rat abdominal wall. It was hypothesized that the presence of the omental tissue would stimulate greater vascularization of the scaffold and act to reduce markers of elevated inflammation in the patch vicinity. For control purposes, a polydimethylsiloxane sheet was placed as a barrier between the omental tissue and the overlying microfibrous scaffold. Both groups were sacrificed 8 wk after the implantation, and immunohistological and reverse transcription polymerase chain reaction (RT-PCR) assessments were performed.

RESULTS

The data showed omental tissue placement to be associated with increased vascularization, a greater local M2/M1 macrophage phenotype response, and mRNA levels reduced for inflammatory markers but increased for angiogenic and antiinflammatory factors.

CONCLUSIONS

From a clinical perspective, the familiarity with utilizing omental flaps for an improved healing response and infection resistance should naturally be considered as new tissue engineering approaches that are translated to tissue beds where omental flap application is practical. This report provides data in support of this concept in a small animal model.

Design of a Coupled Thermoresponsive Hydrogel and Robotic System for Postinfarct Biomaterial Injection Therapy

BACKGROUND

In preclinical testing, ventricular wall injection of hydrogels has been shown to be effective in modulating ventricular remodeling and preserving cardiac function. For some approaches, early-stage clinical trials are under way. The hydrogel delivery method varies, with minimally invasive approaches being preferred. Endocardial injections carry a risk of hydrogel regurgitation into the circulation, and precise injection patterning is a challenge. An epicardial approach with a thermally gelling hydrogel through the subxiphoid pathway overcomes these disadvantages.

METHODS

A relatively stiff, thermally responsive, injectable hydrogel based on N-isopropylacrylamide and N-vinylpyrrolidone (VP gel) was synthesized and characterized. VP gel thermal behavior was tuned to couple with a transepicardial injection robot, incorporating a cooling feature to achieve injectability. Ventricular wall injections of the optimized VP gel have been performed ex vivo and on beating porcine hearts.

RESULTS

Thermal transition temperature, viscosity, and gelling time for the VP gel were manipulated by altering N-vinylpyrrolidone content. The target parameters for cooling in the robotic system were chosen by thermal modeling to support smooth, repeated injections on an ex vivo heart. Injections at predefined locations and depth were confirmed in an infarcted porcine model.

CONCLUSIONS

A coupled thermoresponsive hydrogel and robotic injection system incorporating a temperature-controlled injectate line was capable of targeted injections and amenable to use with a subxiphoid transepicardial approach for hydrogel injection after myocardial infarction. The confirmation of precise location and depth injections would facilitate a patient-specific planning strategy to optimize injection patterning to maximize the mechanical benefits of hydrogel placement.

Adenosine A2A receptor mediated protective effect of 2-(6-cyano-1-hexyn-1-yl)adenosine on retinal ischaemia/reperfusion damage in rats

AIMS

To determine the effect of 2-(6-cyano-1-hexyn-1-yl)adenosine (2-CN-Ado), an adenosine A2A receptor agonist, on retinal ischaemia/reperfusion damage in rats.

METHODS

Retinal ischaemia/reperfusion damage was induced by elevating the intraocular pressure of one eye to 130 mm Hg for 60 minutes and returning it to normal. 7 days later, retinal ischaemia/reperfusion damage was histologically quantified by measuring the thickness of retinal layers. Intraocular pressure was measured by pressure transducer.

RESULTS

Retinal ischaemia/reperfusion caused cell loss in the ganglion cell layer and thinning of the inner plexiform and nuclear layer. Both ocular topical and intravenous administration of 2-CN-Ado caused a reduction of retinal ischaemia/reperfusion damage. A selective A2A receptor antagonist, 1,3,7-trimethyl-8-(3-chlorostyryl) xanthine (CSC), but not a selective A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), or a selective A2B receptor antagonist, alloxazine, reduced the protective effect of 2-CN-Ado. While ocular topical administration of 2-CN-Ado caused a sustained reduction of intraocular pressure, intravenous administration of 2-CN-Ado showed a transient ocular hypotensive effect.

CONCLUSIONS

These results suggest that 2-CN-Ado attenuates retinal ischaemia/reperfusion damage, and at least some of this protective effect of 2-CN-Ado might be mediated via activation of the adenosine A2A receptor.

New color Doppler technique for detecting turbulent tumor blood flow: a possible aid to hepatocellular carcinoma diagnosis

We created a new imaging technique that detects and emphasizes turbulence, which is a characteristic of blood flow in hepatocellular carcinoma. We devised two indices that determine a characteristic tumor flow, the bi-directional and low-peak indices. In the phantom study, both indices of turbulence caused by a stenosis were much higher. In the clinical study, both indices were significantly higher in tumors than in the portal vein or hepatic vein. A turbulent blood flow was detected in 77% of tumors, whereas such detection seldom occurred in the portal or hepatic vein. This technique has the potential to distinguish turbulence in hepatocellular carcinoma.

Effect of a prenylamine analog (MG8926) on spontaneous action potentials in isolated rabbit sinoatrial node

Effects of verapamil, prenylamine and a prenylamine analog, MG8926 on the intracellular spontaneous action potentials recorded from the isolated rabbit sinoatrial (SA) node were studied. Verapamil (1 microM), a selective inhibitor for slow Ca2+ channels, prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential, the amplitude of action potential and the maximal diastolic potential, and usually arrested showing subthreshold fluctuation of the membrane potential within several ten min. Prenylamine (10 microM), a nonselective inhibitor for slow Ca2+ channels, tended to prolong the cycle length to decrease the diastolic depolarization, the rate of rise of action potential, the amplitude of action potential. However, these changes were statistically insignificant. Prenylamine at the concentration of 10 microM had no effect on the maximal diastolic potential. MG8926 (10 microM) prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential and tended to decrease the amplitude of action potential. MG8926 at the concentration of 10 microM had almost no effect on the maximal diastolic potential. The present findings may indicate that replacement of phenyl residue of prenylamine by cyclohexyl residue increases the inhibitory action on the slow Ca2+ channels in rabbit SA node.

Identification of adenosine A2 receptor-cAMP system in human aortic endothelial cells

The involvement of endothelial adenosine A2 receptor-cAMP system in A2 receptor-mediated vasodilation in human aortic endothelial cells (HAEC) was investigated. Reverse transcription-polymerase chain reaction (RT-PCR) revealed the expression of both A2a and A2b receptors mRNA in HAEC. In HAEC, YT-146 (selective A2 receptor-agonist) produced a dose-dependent increase of cAMP production. This increase was inhibited by theophylline. YT-146 also showed a vasodilatory action in isolated rat aorta. The removal of endothelium significantly attenuated this vasodilatory effect. Our results provide the first evidence for the expression of both subtypes of the A2a and A2b receptors which regulate cAMP production in human endothelial cells. The present results also suggest that A2 receptor-cAMP system was involved in the endothelium-dependent vasodilatory actions and may play important roles in regulating vascular functions of HAEC.

[Synthesis and antimicrobial properties of methyl 3-O-alkyl-glucopyranosides]

A new type of nonionic surface-active agents containing sugars as the hydrophilic group were synthesized and evaluated for their antimicrobial activity. Methyl 6-deoxy-3-O-dodecyl-6-halo-D-glucopyranoside derivatives showed powerful antimicrobial activity, but no significant differences were observed on the activity with regard to the kinds of anomers as well as halogen atoms.

[Synthesis and antibacterial properties of 3-O-alkyl-D-glucose derivatives]

A series of 3-O-alkyl-1,2-O-isopropylidene-alpha-D-glucofuranoses (3-7), 6-deoxy-3-O-dodecyl-6-halo-1,2-O-isopropylidene-alpha-D-glucofuranose s (9-11), and 6-deoxy-3-O-dodecyl-6-halo-D-glucopyranoses (12-14) were prepared from 1,2; 5,6-di-O-isopropyridene-alpha-D-glucofuranose and their antibacterial activities were evaluated. The compounds having C12 and C14 alkylchains at C-3 of 1,2-O-isopropylidene glucoses were the most effective in vitro antibacterial screening, of which the structure-activity relationships are also discussed.

[Synthesis and antimicrobial properties of 3-O-alkyl and 3-O-haloalkyl-D-glucoses]

A series of 3-O-alkyl and 3-O-haloalkyl-D-glucoses were prepared from 1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose and their antibacterial activities were evaluated. The compounds with C12 and C14-alkyl chains were the most effective in vitro antibacterial screening, among 3-O-alkyl and 3-O-haloalkyl derivatives. The 3-O-alkyl derivatives were more effective than 3-O-haloalkyl derivatives.

Pharmacological profile of the 2-alkynyladenosine derivative 2-octynyladenosine (YT-146) in the cardiovascular system

We investigated the cardiovascular effects of 2-octynyladenosine (YT-146), an adenosine A2 agonist, in various mammalian preparations in comparison with adenosine and 2-chloroadenosine. YT-146, when intravenously administered, caused a dose-dependent decrease of blood pressure in anesthetized normotensive rats (with ED30 values of 0.4 micrograms/kg), and YT-146 was 250 times more potent than adenosine. Whereas adenosine and 2-chloroadenosine decreased heart rate at approximately equihypotensive doses, YT-146 had no negative chronotropic effects at h hypotensive doses. Orally given YT-146 (0.1 - 1 mg/kg) produced a potent and long-lasting antihypertensive effect in spontaneously hypertensive rats. YT-146 was 15.9 and 12.5 times more potent than adenosine in producing relaxation of isolated porcine coronary arteries and in increasing dog coronary blood flow, respectively. Although YT-146 was equipotent to adenosine in causing a negative inotropic effect in isolated guinea pig atria, it was less potent than adenosine in producing atrioventricular conduction block in guinea pigs. On the other hand, 2-chloroadenosine was 9.1, 1.8 and 2.4 times more potent than adenosine in lowering blood pressure, relaxing isolated porcine coronary arteries and increasing dog coronary blood flow, respectively. 2-Chloroadenosine was the most potent in producing cardiodepression, i.e., negative inotropy and atrioventricular conduction block in guinea pigs. From these results, we concluded that YT-146 is a potent coronary vasodilator and also a potent, orally active and long-acting hypotensive agent having less cardiac depressant activity.