Cell sheet technology enables novel approaches to tissue engineering without the use of biodegradable scaffolds. Cell sheet technology consists of a temperature‐responsive culture dish, which enables reversible cell adhesion to and detachment from the dish surface by controllable hydrophobicity of the surface. This allows for a non‐invasive harvest of cultured cells as an intact monolayer cell sheet including deposited extra cellular matrices. The monolayer cell sheet can be transplanted to host tissues without using biodegradable scaffolds and sutures. Thick tissue constructs and patterned cell sheets using two or more kinds of cell source are also developed by means of layered cell sheets in vitro. This Progress Report summarizes temperature‐controlled cell adhesion‐detachment behavior and applications of the cell sheet technology to regeneration of cornea, periodontal ligament, bladder epithelia, oesophageal epithelia, myocardium, and liver.

RADA16 is a synthetic peptide that exists as a viscous solution in an acidic formulation. In an acidic aqueous environment, the peptides spontaneously self-assemble into β-sheet nanofibers. Upon exposure and buffering of RADA16 solution to the physiological pH of biological fluids such as blood, interstitial fluid and lymph, the nanofibers begin physically crosslinking within seconds into a stable interwoven transparent hydrogel 3-D matrix. The RADA16 nanofiber hydrogel structure closely resembles the 3-dimensional architecture of native extracellular matrices. These properties make RADA16 formulations ideal topical hemostatic agents for controlling bleeding during surgery and to prevent post-operative rebleeding. A commercial RADA16 formulation is currently used for hemostasis in cardiovascular, gastrointestinal, and otorhinolaryngological surgical procedures, and studies are underway to investigate its use in wound healing and adhesion reduction. Straightforward application of viscous RADA16 into areas that are not easily accessible circumvents technical challenges in difficult-to-reach bleeding sites. The transparent hydrogel allows clear visualization of the surgical field and facilitates suture line assessment and revision. The shear-thinning and thixotropic properties of RADA16 allow its easy application through a narrow nozzle such as an endoscopic catheter. RADA16 hydrogels can fill tissue voids and do not swell so can be safely used in close proximity to pressure-sensitive tissues and in enclosed non-expandable regions. By definition, the synthetic peptide avoids potential microbiological contamination and immune responses that may occur with animal-, plant-, or mineral-derived topical hemostats. In vitro experiments, animal studies, and recent clinical experiences suggest that RADA16 nanofibrous hydrogels can act as surrogate extracellular matrices that support cellular behavior and interactions essential for wound healing and for tissue regenerative applications. In the future, the unique nature of RADA16 may also allow us to use it as a depot for precisely regulated drug and biopharmaceutical delivery.

The role of protein kinase C (PKC) isoforms in myogenic tone of the ferret coronary microcirculation was investigated by measuring fura 2 Ca(2+) signals, PKC immunoblots, contractile responses, and confocal microscopy of PKC translocation. Phorbol ester-evoked contractions were completely abolished in the absence of extracellular Ca(2+) but involved a Ca(2+) sensitization relative to KCl contractions. Immunoblotting using isoform-specific antibodies showed the presence of PKC-alpha and -iota and traces of PKC-epsilon and -mu in the ferret coronary microcirculation. PKC-beta was not detectable. When intraluminal pressure (40 to 60 and 80 mmHg) was increased, ferret coronary arterioles showed a transient increase in fura 2 Ca(2+) signals, whereas the myogenic tone remained sustained. The increase in Ca(2+) and tone was sustained at 100 mmHg. Isolated ferret coronary arterioles were fixed and immunostained for PKC-alpha at 40 and 100 mmHg intraluminal pressure. PKC translocation was determined by confocal microscopy. Increased PKC translocation was observed when vessels were exposed to 100 mmHg relative to that at resting pressure (40 mmHg). These results suggest a link between the Ca(2+) sensitization that occurs during the myogenic contraction and activation of the alpha-isoform of PKC.

The plasma concentrations of brain natriuretic peptide (BNP), a cardiac hormone, were measured in 30 consecutive adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) during the perioperative period. BNP concentrations remained unchanged until 6 h after the cessation of bypass, and were elevated 12, 24, and 48 h post-bypass (P < 0.0001 versus baseline). They had returned to the baseline values when measured 3 weeks postoperatively. The preoperative plasma BNP concentration correlated significantly with the left ventricular ejection fraction (r = -0.895). The peak plasma BNP concentration 24 h after bypass correlated with the cardiac index (r = -0.64), stroke volume index (r = -0.62), injection rate of dopamine hydrochloride (r = 0.65), and aortic crossclamp time (r = 0.57). There was also a significant correlation between the preoperative BNP concentration and the plasma BNP concentration 24 h post-CPB. These findings led us to conclude that the plasma concentrations of BNP become markedly and acutely elevated after cardiac surgery with CPB, and reflect the state of left ventricular function. Moreover, the severity of acute heart failure after cardiac surgery can be predicted by the preoperative plasma BNP concentration.

No abstract

The plasma concentrations of brain natriuretic peptide (BNP), a cardiac hormone, were measured in 30 consecutive adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) during the perioperative period. BNP concentrations remained unchanged until 6 h after the cessation of bypass, and were elevated 12, 24, and 48 h post-bypass (P < 0.0001 versus baseline). They had returned to the baseline values when measured 3 weeks postoperatively. The preoperative plasma BNP concentration correlated significantly with the left ventricular ejection fraction (r = -0.895). The peak plasma BNP concentration 24 h after bypass correlated with the cardiac index (r = -0.64), stroke volume index (r = -0.62), injection rate of dopamine hydrochloride (r = 0.65), and aortic crossclamp time (r = 0.57). There was also a significant correlation between the preoperative BNP concentration and the plasma BNP concentration 24 h post-CPB. These findings led us to conclude that the plasma concentrations of BNP become markedly and acutely elevated after cardiac surgery with CPB, and reflect the state of left ventricular function. Moreover, the severity of acute heart failure after cardiac surgery can be predicted by the preoperative plasma BNP concentration.

The use of Mg2+-supplemented hyperkalemic cardioplegia preserves microvascular function. However, the mechanism of this beneficial action remains to be elucidated. We investigated the effects of Mg2+ supplementation on the regulation of intracellular calcium concentration ([Ca2+]i) and vascular function using an in vitro microvascular model. Ferret coronary arterioles (80–150 μm in diameter) were studied in a pressurized (40 mmHg) no-flow, normothermic (37°C) state. Simultaneous monitoring of internal luminal diameter and [Ca2+]iusing fura 2 were made with microscopic image analysis. The microvessels ( n = 6 each group) were divided into four groups according to the content of MgCl2 (nominally 0, 1.2, 5.0, and 25.0 mM) in a hyperkalemic cardioplegic solution ([K+] 25.0 mM). After baseline measurements, vessels were subjected to 60 min of hypoxia with hyperkalemic cardioplegia (equilibrated with 95% N2-5% CO2) containing each concentration of Mg2+([Mg2+]) and were then reoxygenated. During hyperkalemic cardioplegia, [Ca2+]iincreased in a time-dependent manner in all groups. In the lower [Mg2+] cardioplegia groups, [Ca2+]iwas significantly increased at the end of the 60-min cardioplegic period (247 ± 44 nM and 236 ± 49 nM in [Mg2+] 0 and 1.2 mM groups, respectively; both P < 0.05 vs. baseline) with 19.6–17.2% vascular contraction. Conversely, there was no significant [Ca2+]iincrease in the higher [Mg2+] cardioplegia groups and less vascular contraction (5.4–4.1%, both P < 0.05 vs. [Mg2+] 1.2 mM group). After reperfusion, agonist (U-46619, thromboxane A2 analog)-induced vascular contraction was significantly enhanced in the lower [Mg2+] cardioplegia groups (both P < 0.05 vs. control) but was normalized in the higher [Mg2+] cardioplegia groups. Intrinsic myogenic contraction was significantly decreased in the lower [Mg2+] cardioplegia groups (both P < 0.05 vs. control) but was preserved in the higher [Mg2+] cardioplegia groups. These results suggest that supplementation of the solution with >5.0 mM [Mg2+] may prevent hyperkalemic cardioplegia-related intracellular Ca2+ overloading and preserve vascular contractile function in coronary microvessels.

No abstract