Wonjin Lee

Engineered extracellular microenvironment with a tunable mechanical property for controlling cell behavior and cardiomyogenic fate of cardiac stem cells.

Endogenous cardiac stem cells (CSCs) are known to play a certain role in the myocardial homeostasis of the adult heart. The extracellular matrix (ECM) surrounding CSCs provides mechanical signals to regulate a variety of cell behaviors, yet the impact in the adult heart of these mechanical properties of ECM on CSC renewal and fate decisions is mostly unknown. To elucidate CSC mechanoresponses at the individual cell and myocardial level, we used the sol-to-gel transitional gelatin-poly(ethylene glycol)-tyramine (GPT) hydrogel with a tunable mechanical property to construct a three-dimensional (3D) matrix for culturing native myocardium and CSCs. The elastic modulus of the GPT hydrogel was controlled by adjusting cross-linking density using hydrogen peroxide. The GPT hydrogel showed an ability to transduce integrin-mediated signals into the myocardium and to permit myocardial homeostatic processes in vitro, including CSC migration and proliferation into the hydrogel from the myocardium. Decreasing the elastic modulus of the hydrogel resulted in upregulation of phosphorylated integrin-mediated signaling molecules in CSCs, which were associated with significant increases in cell spreading, migration, and proliferation of CSCs in a modulus-dependent manner. However, increasing the elastic modulus of hydrogel induced the arrest of cell growth but led to upregulation of cardiomyocyte-associated mRNAs in CSCs. This work demonstrates that tunable 3D-engineered microenvironments created by GPT hydrogel are able to control CSC behavior and to direct cardiomyogenic fate. Our system may also be appropriate for studying the mechanoresponse of CSCs in a 3D context as well as for developing therapeutic strategies for in situ myocardial regeneration. STATEMENT OF SIGNIFICANCE The extracellular matrix (ECM) provides a physical framework of myocardial niches in which endogenous cardiac stem cells (CSCs) reside, renew, differentiate, and replace cardiac cells. Interactions between ECM and CSCs might be critical for the maintenance of myocardial homeostasis in the adult heart. Yet most studies done so far have used irrelevant cell types and have been performed at the individual cell level, none able to reflect the in vivo situation. By the use of a chemically defined hydrogel to create a tunable 3D microenvironment, we succeeded in controlling CSC behavior at the myocardial and individual cell level and directing the cardiomyogenic fate. Our work may provide insight into the design of biomaterials for in situ myocardial regeneration as well as for tissue engineering.

Effect of pretreatment with palonosetron on withdrawal movement associated with rocuronium injection

Background The main disadvantage of rocuronium is the pain associated with vascular injection. We evaluated the efficacy of palonosetron for reducing pain after rocuronium injection. Methods Eighty patients scheduled for elective surgery were randomly divided into two groups: Group C (normal saline 1.5 ml, n = 40) and Group P (palonosetron 0.075 mg, n = 40). Anesthesia was induced with thiopental 5 mg/kg and the test drug was injected over 10 seconds. Thirty seconds after the injection of the test drug, rocuronium 0.6 mg/kg was injected over 30 seconds and the response was recorded. Injection pain was graded using a 4-point scale. The grade was 0 points for no movement, 1 point for wrist movement, 2 points for elbow or shoulder movement, and 3 points for whole body movement. Mean arterial pressure and heart rate were recorded on arrival in the operating room and before and 30 seconds after rocuronim injection. Results There was no significant difference in the grade 1 response between the two groups; however, the grade 2 and 3 responses in Group P were 5 (12.5%) and 4 (10%), respectively, which were significantly lower than in Group C, with 13 (32.5%) responses for each grade. There were no significant differences in hemodynamic changes within each group. However, the difference in mean arterial pressure before and after the injection of rocuronium was significantly larger in Group C compared to Group P. Conclusions Pretreatment with palonosetron 0.075 mg reduced the incidence and severity of withdrawal movement after rocuronium administration.

The combination of sugammadex and neostigmine can reduce the dosage of sugammadex during recovery from the moderate neuromuscular blockade

Background Sugammadex is a novel neuromuscular reversal agent, but its associated hypersensitivity reaction and high cost have been obstacles to its widespread use. In the interest of reducing the necessary dosage of sugammadex, the reversal time of the combined use of sugammadex and neostigmine from moderate neuromuscular blockade were investigated. Methods The patients enrolled ranged in age from 18 to 65 years old with American Society of Anesthesiologists class 1 or 2. The subjects were randomly assigned into one of the four groups (Group S2, S1, SN, and N; n = 30 per group). The reversal agents of each groups were as follows: S2 - sugammadex 2 mg/kg, S1 - sugammadex 1 mg/kg, SN - sugammadex 1 mg/kg + neostigmine 50 µg/kg + glycopyrrolate 10 µg/kg, N - neostigmine 50 µg/kg + glycopyrrolate 10 µg/kg. The time to recovery of the train-of-four (TOF) ratio was checked in each group. Results The time to 90% recovery of TOF ratio was 182.6 ± 88.9, 371.1 ± 210.4, 204.3 ± 103.2, 953.2 ± 379.7 sec in group S2, S1, SN and N, respectively. Group SN showed a significantly shorter recovery time than did group S1 and N (P < 0.001). However, statistically significant differences between the S2 and SN groups were not be observed (P = 0.291). No hypersensitivity reactions occurred in all groups. Conclusions For the reversal from rocuronium-induced moderate neuromuscular blockade, the combined use of sugammadex and neostigmine may be helpful to decrease the recovery time and can also reduce the required dosage of sugammadex. However, the increased incidence of systemic muscarinic side effects must be considered.

Intracellular transduction of TAT-Hsp27 fusion protein enhancing cell survival and regeneration capacity of cardiac stem cells in acute myocardial infarction.

Myocardial infarction (MI) results in the substantial loss of functional cardiomyocytes, which frequently leads to intractable heart disorders. Cardiac stem cells (CSCs) that retain the capacity to replace all cardiac cells might be a promising strategy for providing a source of new functional cardiomyocytes; however, the poor survival and engraftment of transplanted CSCs in the hostile environment of MI critically mitigate their therapeutic benefits. To capitalize their therapeutic potential, an ex vivo strategy in which CSCs were introduced to the recombinant heat shock protein 27 (Hsp27) through a TAT protein transduction domain for increasing the viability and engraftment in the infarcted myocardium was designed. A recombinant TAT fused Hsp27 (TAT-Hsp27) was able to enter CSCs in a dose-dependent manner. CSCs transduced with TAT-Hsp27 expressed not only endogenous Hsp27 but externally introduced Hsp27, resulting in substantial increase of their anti-oxidative and anti-apoptotic properties via suppressing reactive oxygen species production, the MAPKs signaling pathway, and caspase activation. TAT-Hsp27 enabled CSCs to be protected from apoptotic- and hypoxic-induced cell death during in vitro cardiomyogenic differentiation. In vivo studies demonstrated that CSCs transduced TAT-Hsp27 significantly increased the survival and engraftment in the acutely infarcted myocardium, which is closely related to caspase activity suppression. Finally, CSCs transduced TAT-Hsp27 improved cardiac function and attenuated cardiac remodeling in comparison with non-transduced CSCs. Overall, our approach, which is based on the ex vivo intracellular transduction of TAT-Hsp27 into CSCs before myocardial delivery, might be effective in treating MI.

Gallium nitrate ameliorates type II collagen-induced arthritis in mice

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease. Gallium nitrate has been reported to reserve immunosuppressive activities. Therefore, we assessed the therapeutic effects of gallium nitrate in the mouse model of developed type II collagen-induced arthritis (CIA). CIA was induced by bovine type II collagen with Complete Freunds adjuvant. CIA mice were intraperitoneally treated from day 36 to day 49 after immunization with 3.5mg/kg/day, 7mg/kg/day gallium nitrate or vehicle. Gallium nitrate ameliorated the progression of mice with CIA. The clinical symptoms of collagen-induced arthritis did not progress after treatment with gallium nitrate. Gallium nitrate inhibited the increase of CD4(+) T cell populations (p<0.05) and also inhibited the type II collagen-specific IgG2a-isotype autoantibodies (p<0.05). Gallium nitrate reduced the serum levels of TNF-α, IL-6 and IFN-γ (p<0.05) and the mRNA expression levels of these cytokine and MMPs (MMP2 and MMP9) in joint tissues. Western blotting of members of the NF-κB signaling pathway revealed that gallium nitrate inhibits the activation of NF-κB by blocking IκB degradation. These data suggest that gallium nitrate is a potential therapeutic agent for autoimmune inflammatory arthritis through its inhibition of the NF-κB pathway, and these results may help to elucidate gallium nitrate-mediated mechanisms of immunosuppression in patients with RA.

A fibrin-supported myocardial organ culture for isolation of cardiac stem cells via the recapitulation of cardiac homeostasis

There is great interest in the development of cardiac stem cells (CSCs) cell-based therapeutics; thus, clinical translation requires an efficient method for attaining therapeutic quantities of these cells. Furthermore, an in vitro model to investigate the mechanisms regulating the cardiac homeostasis is crucial. We sought to develop a simple myocardial culture method for enabling both the recapitulation of myocardial homeostasis and the simultaneous isolation of CSCs. The intact myocardial fragments were encapsulated 3-dimensionally into the fibrin and cultured under dynamic conditions. The fibrin provided secure physical support and substratum to the myocardium, which mediated integrin-mediated cell signaling that allowed in situ renewal, outgrowth and cardiomyogenic differentiation of CSCs, mimicking myocardial homeostasis. Since our culture maintained the myocardial CSCs niches, it was possible to define the identity of in vitro renewed CSCs that situated in the interstitium between cardiomyocytes and microvessels. Lastly, the use of matrix-restricted fibrinolysis enabled the selective isolation of outgrown CSCs that retained the clonogenicity, long-term growth competency and cardiovascular commitment potential. Collectively, this myocardial culture might be used as an alternative tool for studying cardiac biology and developing cell-based therapeutics.

Effects of topical dexamethasone in postoperative sore throat

Background Postoperative sore throat (POST) is a complication that undermines patient satisfaction and increases discomfort in the postoperative period. The present study examined the effects of dexamethasone gargle and endotracheal tube cuff soaking on the incidence and severity of POST. Methods Ninety patients undergoing laparoscopic cholecystectomy were randomly allocated into three groups: 0.9% normal saline gargling and tube soaking (group C), 0.05% dexamethasone solution gargling and 0.9% normal saline tube soaking (group G), 0.9% normal saline gargling and 0.05% dexamethasone tube soaking (group S). The incidence and severity of POST were then assessed and recorded at 24 hours after surgery. Results The total incidence of POST was significantly different among the groups (P < 0.05), and group S exhibited a significantly lower incidence of POST than group C (P < 0.0167). In addition, the POST intensity of group G and group S was less severe than those of group C (Both P < 0.0167). Conclusions Among patients undergoing laparoscopic cholecystectomy, those who gargled with 0.05% dexamethasone solution exhibited lower severity of POST than the control group, and those whose endotracheal tube cuff was soaked in the dexamethasone solution before intubation exhibited significantly lower incidence and severity of POST than the control group.

Preoperative interscalene brachial plexus block aids in perioperative temperature management during arthroscopic shoulder surgery

Background Hypothermia is common during arthroscopic shoulder surgery under general anesthesia, and anesthetic-impaired thermoregulation is thought to be the major cause of hypothermia. This prospective, randomized, double-blind study was designed to compare perioperative temperature during arthroscopic shoulder surgery with interscalene brachial plexus block (IBPB) followed by general anesthesia vs. general anesthesia alone. Methods Patients scheduled for arthroscopic shoulder surgery were randomly allocated to receive IBPB followed by general anesthesia (group GB, n = 20) or general anesthesia alone (group GO, n = 20), and intraoperative and postoperative body temperatures were measured. Results The initial body temperatures were 36.5 ± 0.3℃ vs. 36.4 ± 0.4℃ in group GB vs. GO, respectively (P = 0.215). The body temperature at 120 minutes after induction of anesthesia was significantly higher in group GB than in group GO (35.8 ± 0.3℃ vs. 34.9 ± 0.3℃; P < 0.001). The body temperatures at 60 minutes after admission to the post-anesthesia care unit were 35.8 ± 0.3℃ vs. 35.2 ± 0.2℃ in group GB vs. GO, respectively (P < 0.001). The concentrations of desflurane at 0, 15, and 120 minutes after induction of anesthesia were 6.0 vs. 6.0% (P = 0.330), 5.0 ± 0.8% vs. 5.8 ± 0.4% (P = 0.001), and 3.4 ± 0.4% vs. 7.1 ± 0.9% (P < 0.001) in group GB vs. GO, respectively. Conclusions The present study demonstrated that preoperative IBPB could reduce both the intraoperative concentration of desflurane and the reduction in body temperature during and after arthroscopic shoulder surgery.

Comparison of dexmedetomidine and ketamine for the analgesic effect using intravenous patient-controlled analgesia after gynecological abdominal surgery.

Intravenous patient-controlled analgesia (IV-PCA) using opioids allows the patient to control the amount of analgesic according to the degree of pain. For effective pain reduction and avoidance of opioid-related complications, studies have investigated methods of combining opioid use with drugs such as NSAIDs, ketamine, clonidine, and dexmedetomidine [1]. The highly selective α2-agonist dexmedetomidine is effective in sedating and reducing anxiety. In addition, because it retains a simultaneous analgesic effect, it is expected to be helpful in postoperative pain management [2]. The authors compared ketamine and dexmedetomidine, each in combination with fentanyl, in postoperative IV-PCA for patients scheduled for gynecological abdominal surgery. For each method, we examined the reduction in pain score and opioid consumption as well as whether it was effective in reducing opioid-related complications. After obtaining approval from the Institutional Review Board, and informed consent was obtained. Ninety patients (20 to 60 years, American Society of Anesthesiologists [ASA] physical status I-II) scheduled for gynecological abdominal surgery were divided into three groups: a control group (Group C: n = 30), a ketamine group (Group K: n = 30), and a dexmedetomidine group (Group D: n = 30). Near the end of surgery, all three groups were injected with fentanyl 0.5 µg/kg, ketorolac 30 mg, and ramosetron 0.3 mg for postoperative pain management. PCA was performed using IV-PCA equipment (AutoMed 3000®, Ace Medical, Seoul, Korea). The pharmacological combinations for the three groups were as follows: fentanyl 20 µg/kg, ketorolac 180 mg, and ramosetron 0.6 mg for all three groups; normal saline for Group C; normal saline plus ketamine 40 mg for Group K; and normal saline plus dexmedetomidine (Precedex®, Hospira, Rocky Mount, NC, USA) 500 µg for Group D. Each mixture was made in 100 ml solutions. The basal infusion rate was set at 2 ml/hr, the bolus at 2 ml, and the lockout time at 10 minutes. After the completion of surgery, patients were transferred to the ward. The IV-PCA consumption volume, pain score (VAS; visual analogue scale) and side effects were assessed at postoperative hours 1, 6, 12, 24, 36, and 48. When the patients required pain control, ketorolac 30 mg or tramadol 50 mg was administered. To treat nausea and vomiting, an IV injection of macperan 10 mg or ondansetron 4 mg was administered. If nausea and vomiting continued despite the administration of antiemetics or if the sedation score was more than 2, the IV-PCA background infusion rate and bolus were reduced by 0.4 ml, respectively. If respiration was inhibited (fewer than 8 breaths/min), naloxone 0.1-0.4 mg was administered, and IV-PCA was discontinued until the respiration rate reached 9 breaths/min or higher. Data were analyzed using SAS 9.2 (SAS Institute Inc, Cary, NC, USA). One-way ANOVA was performed for the demographic data, and repeated measures ANOVA was performed for the between-group comparison of VAS pain scores, accumulated consumption of IV-PCA, accumulated consumption using bolus, and patient information. A P value of 0.05 or lower was considered statistically significant. There were no significant differences between the three groups in age, body mass index, ASA class, type of surgery, or surgery time. In Group K, the pain score was lower (in a resting state: 24 and 36 hours after surgery; during movement: 6, 12, 24, 36, and 48 hours after surgery) and there was no significant difference in IV-PCA consumption volume compared with Group C. In Group D, the pain score was significantly lower (in a resting state: 24 and 36 hours after surgery; during movement: 6, 12, 24, 36, and 48 hours after surgery) (Figs. 1A and 1B) and the total IV-PCA consumption volume was lower (26% at 24 hours, 10% at 48 hours) compared with Group C. When Group K and Group D were compared, there were no significant differences in the VAS score in a resting state or during movement. In addition, there were no significant differences in accumulated total consumption and bolus consumption between Group C and Group K. The number of patients that used the entire IV-PCA volume of 100 ml at 24, 36, and 48 hours after surgery was highest in Group C, followed by Group K and Group D, respectively (Fig. 1C). In order of descending frequency, complications (in groups C, K, D) that occurred were nausea (16, 14, 14) vomiting (4, 1, 0), sedation (12, 13, 15), dizziness (2, 8, 2), pruritus (0, 0, 2), and respiratory depression (0, 1, 0). Dizziness was significantly higher in Group K than in the other groups. Fig. 1 (A) Visual analogue scale (VAS) pain score at rest during the 48-hour study, (B) Visual analogue scale (VAS) pain score on movement during the 48-hour study. Values are mean ± SD. *P < 0.05 (group K versus group C), †P < ... The mechanism of the analgesic effect of dexmedetomidine as an α2-agonist is not yet completely understood, but it is thought that the spinal cord is the most important area. The α2-adrenergic receptors of the substantia gelatinosa are activated in the dorsal horn of the spinal cord; this represses the neurotransmission of peripheral Aδ and C fiber, represses wide dynamic range neurons, stimulates the secretion of acetylcholine, stimulates the serotonergic system, and represses the secretion of substance P, resulting in an analgesic effect [3-5]. Lin et al. [1], who conducted a study with patients receiving total abdominal hysterectomy, reported that combined morphine and dexmedetomidine significantly reduced the pain score over 24 hours of observation compared with a group that received only morphine. Furthermore, there was a reduction in morphine consumption of approximately 29%. These findings are similar to ours; in our study, the pain score was significantly reduced and there was an approximately 26% reduction in PCA consumption in IV-PCA up to 24 hours after surgery compared with Group C. Our study also showed a higher frequency of dizziness in Group K compared with Group C and Group D. There were no significant differences in sedation, hypoventilation, and itching between each group. In conclusion, low-dose ketamine added to IV-PCA in gynecological abdominal surgery did not decrease total IV-PCA consumption but reduced the pain score relative to Group C, while dexmedetomidine reduced both total IV-PCA consumption and the pain score relative to Group C.

The comparison of the effects of intravenous ketamine or dexmedetomidine infusion on spinal block with bupivacaine.

Background Ketamine and dexmedetomidine are commonly used for sedation and analgesia in patients. We tried to compare the effects of intravenous ketamine and dexmedetomidine infusion on spinal block with bupivacaine. Methods Ninety American Society of Anesthesiologists physical status class I or II patients, who were scheduled to spinal anesthesia were randomly assigned to one of three groups (n = 30). Normal saline 10 ml, 5 ml/hr (loading dose for 10 minutes, infusion) (Group NS), dexmedetomidine 1 µg/kg, 0.5 µg/kg/hr (Group DEX), or ketamine 0.2 mg/kg, 0.5 mg/kg/hr (Group KET) was infused intravenously before spinal anesthesia. We recorded the time to highest sensory block level, sensory and motor regression, and hemodynamic changes. Results Patients in Groups KET had a significantly faster onset time of sensory block than patients in Group NS. The highest sensory block levels were not significantly different between groups. Average time of sensory regression and knee flexion, was significantly longer in the Group KET and Group DEX than the Group NS. Conclusions Intravenous dexmedetomidine and ketamine were found to have a similar synergistic effect with intrathecal bupivacaine. Hemodynamic stability showed better results in Group KET.