A carbonized wormwood modified photothermal microneedle patch for the repair of damaged skeletal muscles

In this study, we aimed to achieve an efficient repair of damaged skeletal muscles using polyvinyl alcohol (PVA) soluble microneedle patches (MNP) loaded with carbonized wormwood and prostaglandin E2 (inflammatory factors). The introduction of carbonized wormwood imparted the MNP with near-infrared light heating characteristics that improved the efficiency of prostaglandin E2 delivery while also promoting circulation in the damaged muscle area. Our experimental results showed that, compared with the classical moxibustion treatment, the system could more quickly restore muscle strength and the cross-sectional area of muscle bundle fibers in a mouse model of muscular injury. In addition, it could also successfully induce the proliferation and differentiation of muscle stem cells to effectively repair injured muscle tissues. Above all, this light-controlled photothermal MN (microneedle) drug-delivery system avoided the common problems of traditional moxibustion such as large levels of smoke, slow efficacy and risk of scalding. Collectively, we put forward a safe, accurate and efficient approach for skeletal muscle damage treatment using carbonized wormwood.

Age- and gender-related hemorheological alterations in intestinal ischemia-reperfusion in the rat

BACKGROUND

Intestinal ischemia-reperfusion (I/R) is a life-threatening clinical disorder. During I/R, the microrheological parameters of blood (red blood cell deformability and aggregation) worsen, which may contribute to microcirculatory deterioration. Age and gender also have a great influence on hemorheological parameters. We aimed to investigate the gender and age-related microrheological alterations during intestinal I/R.

MATERIALS AND METHODS

After the cannulation of the left femoral artery, median laparotomy was performed in Crl:WI rats under general anesthesia. In the young control animals there were no other interventions (female n = 7; male n = 7). In the young (female n = 7; male n = 7) and older I/R groups (female n = 6; male n = 6), the superior mesenteric artery was clipped for 30 min, and a 120-min reperfusion period was observed afterward. Blood samples were taken before and at the 30-min ischemia, in the 30th, 60th, and 120th min of the reperfusion. Hematological parameters, erythrocyte deformability, and aggregation were determined.

RESULTS

Hematocrit increased significantly in the younger female I/R group. Red blood cell count was higher in male and older animals. In case of white blood cell count, male animals had higher values compared with females. Platelet count elevated in the younger male and older female I/R animals. Red blood cell deformability worsened, mainly in the male and older I/R groups. Enhanced erythrocyte aggregation was seen in all groups, being more expressed in the female I/R groups.

CONCLUSIONS

Microrheological parameters show gender and age-related differences during intestinal I/R. These observations have importance in the planning and evaluation of experimental data.

[Hemorheological investigations in experimental surgery]

The hemorheological parameters, such as whole blood viscosity, plasma viscosity, hematocrit, fibrinogen concentration as well as the micro-rheological properties of red blood cells (red blood cell deformability and aggregation) play an important role in tissue perfusion. The alternating hemorheological parameters, which are also inter-related, have important effects in determining hemodynamical properties, as well. The altered hemorheological status has a direct effect on endothelial function by changing shear force profile on the endothelial wall, and impairment of red blood cell deformability and aggregation (presence of rigid red blood cell, and enhanced red blood cell aggregation) slows down microcirculation with disturbing capillary perfusion. In experimental surgery vascular clamping and release cause ischemia-reperfusion, which affect red blood cells in many ways: changes pH level, leads to free-radical release, changes osmolarity and lactate and NO concentrations as well as it causes mechanical trauma. Understanding of these pathophysiological processes and determining the extent of reversible-irreversible changes may help to delineate underlying causes in tissue perfusion and microcirculation better, and develop prophylactic and therapeutic possibilities. The challenges of experimental surgery also include the questions of comparability in different measurement methods, and understanding of interspecies-differences of experimental/laboratory animal models in order to increase the relevance of results in terms of applicability for the original, clinical question.

Allopurinol Prevents Erythrocyte Deformability Impairing but Not the Hematological Alterations After Limb Ischemia–Reperfusion in Rats

The measurement of red blood cell deformability provides a possible method for detecting the effect of ischemia-reperfusion on erythrocytes. In our study the effect of 1-h ischemia-reperfusion with or without allopurinol pretreatment on hematological parameters and red blood cell deformability was investigated in a follow-up experiment of 26 male CD outbred rats that were subjected to unilateral hind-limb ischemia by microvascular clips on femoral vessels for 1 h (IR, n = 6), some rats received allopurinol pretreatment under the same conditions (50 mg/kg, AP + IR, n = 8), others were subjected to sham operation (n = 6), and the rest of animals served as control (n = 6). Measurement of erythrocyte deformability using a bulk filtrometer with special setting of cell suspension hematocrit (1%), and determination of hematological parameters were performed daily for one week. In the IR group, relative cell transit time increased significantly on postoperative days 1 and 2, which was not observed in the other groups. Settings for the measurement of erythrocyte deformability by reducing the blood sample volume gave the possibility of monitoring the resulting changes in rats. Mean corpuscular volume and hemoglobin, platelet count, and platelet volume were higher in the IR and AP + IR groups than in the other groups. In summary, short-term ischemia and reperfusion induced lower red blood cell deformability in the early postoperative period, which could be prevented by allopurinol pretreatment.

Combined enzymatic and antioxidative treatment reduces ischemia-reperfusion injury in rabbit skeletal muscle

BACKGROUND

Ischemia/reperfusion (I/R) injury is characterized by the production of oxygen-free radicals leading to disturbances in vasomotility (microvascular constriction) and microvascular permeability (interstitial edema formation). The objective was to evaluate the effect of the combined antioxidative and enzymatic preparation Phlogenzym on I/R injury of skeletal muscle.

MATERIALS AND METHODS

A rabbit hindlimb model of I/R (2.5/2 h) was used (IR group). Phlogenzym, containing rutin, trypsin, and bromelain, was applied enterally (60 mg/kg body weight) as a bolus 30 min prior to ischemia (Ph group). Sham-operated animals served as controls (CO group). Plasma malondialdehyde, potassium, and microvascular perfusion (monitored by laser flowmetry) were assessed. Histomorphometry and electron microscopy were performed from major adductor muscles.

RESULTS

Two hours after reperfusion, potassium levels were significantly elevated in IR compared to Ph group (6.7 +/- 1.2 versus 4.9 +/- 0.9 mmol/l, P < 0.006). Enhanced lipid peroxidation, apparent by increased plasma malondialdehyde levels, was ameliorated in the Ph group (1.0 +/- 0.1 versus 0.7 +/- 0.1 nmol/ml, P < 0.0001). No-reflow (reduction of blood flow by 62% in IR group) was not observed in the Ph group (P < 0.004). Phlogenzym treatment prevented microvascular constriction (17.6 +/- 2.3 versus 12.6 +/- 1.1 microm(2), P < 0.0001) and mollified interstitial edema (21.5 +/- 2.0 versus 26.0 +/- 3.7%, P < 0.017), resulting in mild ultrastructural alterations in contrast to pronounced sarcolemmal and mitochondrial damage in untreated rabbits.

CONCLUSIONS

Phlogenzym had a protective effect on skeletal muscle during I/R injury expressed by prevention of no-reflow and preservation of muscle tissue.

Study of warm ischemia followed by reperfusion on a lower limb model in rats: effect of allopurinol and streptokinase

Prolonged tissue ischemia leads to changes in microcirculation and production of oxygen free radicals. The event eventually responsible for tissue death is the no-reflow phenomenon and its management is a challenge for the surgeon dealing with replantation or transplantation. We introduce a model of warm ischemia and reperfusion of the lower limb of rats with which we studied the effect of allopurinol and streptokinase.

METHOD

Section of the lower limb with preservation of vessels and nerves was performed in 110 rats. Femoral vessels clamped for periods of 0, 2, 4, 6, and 8 hours of ischemia were allowed to reperfuse (groups M0, M2, M4, M6, and M8 respectively). Other groups, E1, E2, and E3, received streptokinase, allopurinol, or a combination of the two drugs after 6 hours of ischemia.

RESULTS

Viability rates of the ischemic limbs after 7 days were 100% (M0), 80% (M2), 63.6% (M4), 50% (M6), and 20% (M8). In the experimental groups, E1, E2, and E3, viability rates were 67% (E1), 70% (E2), and 70% (E3). Groups M0, M2, M4, M6, and M8 differed among themselves except for groups M4 and M6. Group E1 had a higher rate of limb viability than M6 (control group) but not than M4. Groups E1, E2 and E3 had higher rates of limb viability than M6 but not than M2 or M4.

DISCUSSION

The results suggest that increased viability of limbs after 6 hours of ischemia occurs when allopurinol or streptokinase is used. The combination of the two drugs does not appear to produce any additional effect.

Combined L-arginine and antioxidative vitamin treatment mollifies ischemia-reperfusion injury of skeletal muscle

Enhanced production of superoxide in L-arginine-depleted environments and concomitant reduction of nitric oxide (NO) concentration are involved in ischemia-reperfusion (I/R) injury. Treatment with L-arginine or antioxidative vitamins alone and in combination was used to mollify I/R injury in skeletal muscle. Untreated rabbits were compared with those treated with L-arginine/antioxidative vitamin cocktail Omnibionta only, or a combination of L-arginine/ antioxidative vitamins during hind limb I/R (2.5 hours/2 hours). NO was continuously measured in vivo. Plasma malondialdehyde (MDA) served as the measure of oxygen free radical formation. Interstitial edema formation, microvessel diameter alterations, microvessel plugging, and blood flow changes were used as indicators of I/R injury. The MDA level in untreated animals 2 hours after reperfusion was significantly higher than in control animals (0.81 micromol/L +/- 0.14 micromol/L vs 0.57 micromol/L +/- 0.11 micromol/L; P<.05), indicating enhanced production of oxygen free radicals. This sequela paralleled the decreasing concentration of NO, which dropped below the detection limit (1 nmol/L) after reperfusion. Microvascular changes during I/R injury were expressed as a 40% decrease in microvessel diameter and adhesion of neutrophils in 20% of microvessels, which led to a consequent 60% reduction in blood flow, demonstrating "no reflow" (reperfusion failure after restoration of blood flow). The increase in the fraction of muscle interfiber area by 85% indicated prominent edema formation. Treatment with antioxidative vitamins alone had a minimally positive effect on edema formation and microvascular plugging, possibly by suppression of oxygen free radical production, as expressed by the reduction in plasma MDA levels. However, this therapy failed to preserve basal NO production and to protect from microvascular constriction and no reflow. Treatment with L-arginine alone had a stronger protective effect, maintaining basal NO production, further reduction of neutrophil plugging, abolition of microvascular constriction, and no reflow. The combination of antioxidative vitamins and L-arginine was the best treatment against I/R injury, expressed not only by the protection of microvessel constriction, but also by abolition of microvascular plugging, increase in NO production (68 nmol/L +/- 5 nmol/L) over the basal level (52 nmol/L +/- 7 nmol/L), and higher blood flow, as compared with treatment with L-arginine or antioxidative vitamins alone.

Changes in microcirculation after ischemic process in rat skeletal muscle

Laser Doppler flowmetry (LDF) is a good method to investigate tissue microcirculation, but it has many standardization and measuring problems. To exclude these effects, we performed a test using LDF on rat skeletal muscle. In 12 CD outbred anesthetized rats, bilateral femoral vessels and the quadriceps femoris muscle were exposed. The left femoral artery and vein were clamped for 1 h by microvascular clips (ischemic side). On the right side, no other intervention was made (control side). An LDF probe was applied on the medial vastus muscle. Short-term occlusions (2-3 s) were performed before and after the 1-h clamping and on the control side while LDF curves were registered. The halftimes of ascending curves on the ischemic side were significantly elongated vs. the condition before clamping (P = 0.0007) or the control side (P = 0.0017). Microcirculatory changes caused by 1-h ischemia were shown by this simple, quick, and well-reproducible test on rat skeletal muscle.

Ischemia/reperfusion injury of skeletal muscle: plasma taurine as a measure of tissue damage

BACKGROUND

Cell membrane rupture by oxygen-derived free radicals is a systematic feature of ischemia/reperfusion (I/R) injury. High taurine concentration gradients in skeletal muscle prompted us to evaluate whether plasma taurine levels (pTau) are a useful marker of I/R injury after different periods of ischemia.

METHODS

Rabbits were randomly assigned to either 1 or 2.5 hours of hind-limb ischemia followed by 2 hours of reperfusion (groups IR1 [n = 12] and IR2.5 [n = 13], respectively). Corresponding sham groups (SHAM1 [n = 8] and SHAM2.5 [n = 9]) were used as controls. Analyzed parameters included histomorphometry and electron microscopy of skeletal muscle biopsies, pTau, and plasma level of malondialdehyde. Skeletal muscle function was assessed 3 weeks after I/R injury.

RESULTS

No significant morphologic changes were detectable at the end of ischemia. After reperfusion, mild interstitial edema with intact muscle cell membranes developed in IR1 group; pTau was not increased. IR2.5 group, by contrast, showed severe interstitial edema formation (interfiber area increased by 112%, P <.005), microvascular constriction (microvessel area decreased by 33%, P <.0005), and damage to the muscle cell membranes that was confirmed by the increased plasma malondialdehyde. pTau was higher than in the SHAM2.5 group (P <.0005). Pronounced cell damage in IR2.5 group resulted in impaired muscle function (maximal tetanic tension was reduced 2 times, P <.005) but not in IR1 group.

CONCLUSION

Skeletal muscle tolerates 1 h/2 h but not 2.5 h/2 h of I/R, the latter resulting in interstitial edema formation, microvascular constriction, and a late muscle dysfunction. Cell membrane rupture through stimulated lipid peroxidation promotes leakage of intracellular taurine, leading to increased pTau after reperfusion and may be considered as prognostically unfavorable in terms of organ function reversibility. In the rabbit model, pTau seems to be a sensitive marker of I/R injury to skeletal muscle.