Stem cell-based regenerative opportunities for the liver: State of the art and beyond

The existing mismatch between the great demand for liver transplants and the number of available donor organs highlights the urgent need for alternative therapeutic strategies in patients with acute or chronic liver failure. The rapidly growing knowledge on stem cell biology and the intrinsic repair processes of the liver has opened new avenues for using stem cells as a cell therapy platform in regenerative medicine for hepatic diseases. An impressive number of cell types have been investigated as sources of liver regeneration: adult and fetal liver hepatocytes,intrahepatic stem cell populations,annex stem cells,adult bone marrow-derived hematopoietic stem cells,endothelial progenitor cells,mesenchymal stromal cells,embryonic stem cells,and induced pluripotent stem cells. All these highly different cell types,used either as cell suspensions or,in combination with biomaterials as implantable liver tissue constructs,have generated great promise for liver regeneration. However,fundamental questions still need to be addressed and critical hurdles to be overcome before liver cell therapy emerges. In this review,we summarize the state-of-the-art in the field of stem cell-based therapies for the liver along with existing challenges and future perspectives towards a successful liver cell therapy that will ultimately deliver its demanding goals.     

Suppression of dynamic Ca(2+) transient responses to pacing in ventricular myocytes from mice with genetic calmodulin kinase II inhibition

The multifunctional Ca(2+) and calmodulin-dependent protein kinase II (CaMKII) is important for regulating L-type Ca(2+) current (I(Ca)) and cytoplasmic Ca(2+) (Ca(2+)(i)) uptake and release from the sarcoplasmic reticulum (SR), key elements of the 'Ca(2+)-induced Ca(2+) release' (CICR) mechanism. However, the effects of chronic CaMKII inhibition on Ca(2+)(i) responses during CICR are unknown. We hypothesized that chronic CaMKII inhibition significantly affects CICR in ventricular myocytes. We studied CICR by simultaneously measuring Ca(2+)(i) transients and I(Ca) in voltage-clamped ventricular myocytes isolated from a recently developed genetic mouse model of cardiac CaMKII inhibition. These measurements were repeated in ventricular myocytes from novel mice with cardiac CaMKII inhibition lacking phospholamban (PLN), a known CaMKII substrate and a negative regulator of Ca(2+)(i) uptake into the SR Ca(2+) store. CaMKII inhibition eliminated a pattern of I(Ca) increases called facilitation and significantly reduced beat-to-beat and cell-to-cell variability of peak Ca(2+)(i) transients in ventricular myocytes with PLN. PLN ablation eliminated I(Ca) facilitation even in the absence of CaMKII inhibition and the effects of CaMKII inhibition to reduce SR Ca(2+) content and slow SR Ca(2+) uptake were lost in the absence of PLN. PLN ablation significantly reduced I(Ca) beat-to-beat variability in cells with CaMKII inhibition. These findings show that chronic CaMKII inhibition reduces variability of CICR responses in a manner that is partly dependent on the presence of PLN.     

Cardiac-specific overexpression of sarcolipin in phospholamban null mice impairs myocyte function that is restored by phosphorylation

Sarcolipin (SLN) inhibits the cardiac sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA2a) by direct binding and is superinhibitory if it binds as a binary complex with phospholamban (PLN). To demonstrate whether overexpression of SLN in the heart might impair cardiac function directly, transgenic (TG) mice with cardiac-specific overexpression of NF-SLN (SLN tagged at its N terminus with the FLAG epitope) were generated on a phospholamban (PLN) null (PLN KO) background. In NF-SLN TG/PLN KO cardiac microsomes, the apparent affinity of SERCA2a for Ca2+ was decreased compared with non-TG littermate PLN KO hearts. Analyses of isolated NF-SLN/PLN KO cardiomyocytes revealed impaired cardiac contractility, reduced calcium transient peak amplitude, and slower decay kinetics compared to PLN KO animals. In these cardiomyocytes, isoproterenol restored calcium dynamics to the levels seen in PLN KO. Invasive hemodynamic and echocardiographic analyses of NF-SLN/PLN KO mouse cardiac muscle in vivo showed no direct effects of NF-SLN overexpression when compared to PLN KO mice. A possible mechanism for the lack of effects in the whole heart may be a responsiveness to phosphorylation because we determined that NF-SLN can be phosphorylated in cardiomyocytes in response to isoproterenol, and we provide evidence that serine/threonine kinase 16 is a kinase that can phosphorylate NF-SLN. Site-directed mutagenesis showed that SLN Thr-5 is the target site for this kinase. These data show that overexpression of NF-SLN can inhibit SERCA2a in the absence of PLN and that the inhibition of SERCA2a is correlated with impairment of contractility and calcium cycling in cardiomyocytes.     

The effects of treatment with octreotide, diuretics, or both on portal hemodynamics in nonazotemic cirrhotic patients with ascites

GOALS: To evaluate the effects of diuretic treatment, octreotide, or both on portal hemodynamics in nonazotemic cirrhotic patients with ascites. BACKGROUND: Diuretics and octreotide have been associated with a decrease in portal pressure in cirrhotic patients, suggested to be mediated by plasma volume depletion and splanchnic vasoconstriction, respectively. However, liver cirrhosis is characterized by activation of the renin-angiotensin-aldosterone axis, which increases hepatic vascular resistance and is augmented or suppressed by diuretics or octreotide, respectively. STUDY: Twenty nonazotemic cirrhotic patients with ascites were treated with furosemide and spironolactone. Of them, 10 (group 1) discontinued diuretic treatment for 7 days. Thereafter for 5 days, each patient received subcutaneous octreotide, 300 microg twice per day; ten of them (group 2) received the octreotide in addition to their usual diuretic treatment. Portal and systemic hemodynamics with Doppler ultrasound and endogenous vasoactive systems were evaluated while the patients received diuretics (both groups), after discontinuation of diuretics (group 1), and after octreotide administration (both groups). RESULTS: The withdrawal of diuretics did not alter portal hemodynamics, but it impaired systemic hemodynamics and suppressed the renin-aldosterone axis. The addition of octreotide to diuretic treatment but not octreotide alone improved portal and systemic hemodynamics. In both groups the initiation of octreotide administration suppressed the renin-aldosterone axis and plasma glucagon levels. CONCLUSIONS: In nonazotemic cirrhotic patients with ascites, the combination of diuretics and octreotide improves systemic hemodynamics and inhibits the diuretic-related component of the activated renin-aldosterone axis, which in turn augments the portal hypotensive effect of diuretic-induced plasma volume depletion.     

Transtelephonic electrocardiographic monitoring of an outpatient cardiac rehabilitation programme

OBJECTIVE: To address whether transtelephonic electrocardiographic monitoring (TEM) of patients with chronic cardiac diseases, being exercised in public gyms, is safe and efficacious. DESIGN: Data were obtained from 91 patients (72 men and 19 women; with a mean (SD) age of 56 (6) years and over a total of 11 820 exercise hours) with coronary heart disease and/or chronic heart failure (< or = stage III NYHA (New York Heart Association)), who were referred for cardiac exercise rehabilitation (phase III). METHOD: Twelve-lead electrocardiograms of indicated patients were transmitted from the qualified trainers in real time by standard telephone lines and were evaluated by the medical staff at the base. The TEM kits contain a telemedicine 12-lead electrocardiographic unit, a telephone modem, a computer receiver with special operating software and a laser printer. As soon as the ECG was monitored and diagnosed, the cardiologist contacted the exercise trainer and provided all the necessary instructions for intervention. RESULTS: In total, 280 cases were monitored. Successful TEM was reported in 99.3% of the cases. The mean (SD) time from ECG recordings to final interventions was estimated at 294 (13) s. The patients were referred for TEM during or soon after exercise sessions, because of chest pain (36% of the TEM cases), palpitations (33%), dizziness (12%), unexpected fatigue (9%), hypertensive crises (7%) and other disorders (3%). Ischaemic ECG changes were recorded in 14 cases with thoracic pain and arrhythmias in nine patients with palpitations. In only one case was a medical emergency reported and an ambulance response required. CONCLUSION: These data demonstrate that TEM provides a workable facility in cardiac rehabilitation for monitoring patients who are exercising in gyms.     

Comparison of molecular markers expression in vacuum-assisted biopsies and surgical specimens of human breast carcinomas

In this study, we examined whether vacuum-assisted breast biopsy (VABB) specimens provide an accurate immunohistochemical assessment of estrogen receptors (ER), progesterone receptors (PR), c-erbB-2, and p53 proteins.