Designing of spider silk proteins for human induced pluripotent stem cell-based cardiac tissue engineering

Materials made of recombinant spider silk proteins are promising candidates for cardiac tissue engineering, and their suitability has so far been investigated utilizing primary rat cardiomyocytes. Herein, we expanded the tool box of available spider silk variants and demonstrated for the first time that human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes attach, contract, and respond to pharmacological treatment using phenylephrine and verapamil on explicit spider silk films. The hiPSC-cardiomyocytes contracted for at least 14 days on films made of positively charged engineered Araneus diadematus fibroin 4 (eADF4(κ16)) and three different arginyl-glycyl-aspartic acid (RGD)-tagged spider silk variants (positively or negatively charged and uncharged). Notably, hiPSC-cardiomyocytes exhibited different morphologies depending on the spider silk variant used, with less spreading and being smaller on films made of eADF4(κ16) than on RGD-tagged spider silk films. These results indicate that spider silk engineering is a powerful tool to provide new materials suitable for hiPSC-based cardiac tissue engineering.

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hiPSC-cardiomyocytes attach and contract on positively charged and/or RGD-tagged spider silk variants.

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hiPSC-cardiomyocytes exhibit spider silk variant-dependent morphology upon adhesion.

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Explicit spider silk variants promote long-term contractility of hiPSC-cardiomyocytes.

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hiPSC-cardiomyocytes grown on spider silk materials respond to pharmacological treatment.

Intracellular calcium release and protein kinase C activation stimulate sonic hedgehog gene expression during gastric acid secretion

BACKGROUND & AIMS

Hypochlorhydria during Helicobacter pylori infection inhibits gastric Sonic Hedgehog (Shh) expression. We investigated whether acid-secretory mechanisms regulate Shh gene expression through intracellular calcium (Ca2(+)(i))-dependent protein kinase C (PKC) or cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) activation.

METHODS

We blocked Hedgehog signaling by transgenically overexpressing a secreted form of the Hedgehog interacting protein-1, a natural inhibitor of hedgehog ligands, which induced hypochlorhydria. Gadolinium, ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) + 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), PKC-overexpressing adenoviruses, and PKC inhibitors were used to modulate Ca(2+)(i)-release, PKC activity, and Shh gene expression in primary gastric cell, organ, and AGS cell line cultures. PKA hyperactivity was induced in the H(+)/K(+)-β-cholera-toxin-overexpressing mice.

RESULTS

Mice that expressed secreted hedgehog-interacting protein-1 had lower levels of gastric acid (hypochlorhydria), reduced production of somatostatin, and increased gastrin gene expression. Hypochlorhydria in these mice repressed Shh gene expression, similar to the levels obtained with omeprazole treatment of wild-type mice. However, Shh expression also was repressed in the hyperchlorhydric H(+)/K(+)-β-cholera-toxin model with increased cAMP, suggesting that the regulation of Shh was not solely acid-dependent, but pertained to specific acid-stimulatory signaling pathways. Based on previous reports that Ca(2+)(i) release also stimulates acid secretion in parietal cells, we showed that gadolinium-, thapsigargin-, and carbachol-mediated release of Ca(2+)(i) induced Shh expression. Ca(2+)-chelation with BAPTA + EGTA reduced Shh expression. Overexpression of PKC-α, -β, and -δ (but not PKC-ϵ) induced an Shh gene expression. In addition, phorbol esters induced a Shh-regulated reporter gene.

CONCLUSIONS

Secretagogues that stimulate gastric acid secretion induce Shh gene expression through increased Ca(2+)(i)-release and PKC activation. Shh might be the ligand transducing changes in gastric acidity to the regulation of G-cell secretion of gastrin.

[Mutation in factor II and factor V gene in patients with peripheral arterial occlusive disease]

Mutations in factor-V- and factor-II-genes are correlated with an increased risk for venous thrombosis according to the literature. The significance of the mutations in factor- II- and factor-V-genes for the development of the peripheral arterial occlusive disease is not known. Therefore, we investigated the presence of these mutations in 152 patients with documented peripheral arterial occlusive disease and 318 controls without peripheral arterial occlusive disease with polymerase chain reaction (PCR). There was no association between factor-II-mutation and peripheral arterial occlusive disease. The factor-V-mutation, however, was increased in patients with peripheral arterial occlusive disease double fold (12 positive cases in 318 controls, 12 positive cases in 152 patients with peripheral arterial occlusive disease). The significance level was reached (p = 0.05) in statistical analysis but the result did not fall below the significance level as necessary to reach statistical significance (odds ratio 2.19). Nevertheless, from these data we have to discuss a biological relevance of factor-V-mutation in the pathogenesis of peripheral arterial occlusive disease.

Chronisch-arterielle Verschlusskrankheit der Beine im Stadium IIb-IV

Die Faktor-V- und Faktor-II-Mutationen sind nach der Literatur mit einem erhöhten Risiko für venöse Thrombosen verbunden. Die Bedeutung der Mutationen im Faktor-IIund -V-Gen für die Entstehung und das Fortschreiten der arteriellen Verschlusskrankheit ist bislang nicht geklärt. Wir untersuchten das Vorhandensein dieser Mutationen bei 152 Patienten mit dokumentierter pAVK und 318 Kontrollen (ohne pAVK) mittels Polymerase-Kettenreaktion (PCR) und RFLP-Analyse. Die Ergebnisse erbrachten keinen Hinweis auf eine Assoziation zwischen einer Faktor-II-Mutation und der Entstehung einer pAVK. Dagegen waren Faktor- V-Mutationen bei pAVK-Patienten doppelt so häufig zu beobachten wie bei Gesunden (in der Kontrollgruppe ergaben sich 12 positive Fälle bei 318 Probanden, in der Patientengruppe ergaben sich 12 positive Fälle bei 152 Patienten). In der statistischen Analyse wurde das Signifikanzniveau (p = 0,05) zwar erreicht, aber nicht unterschritten. Das Chancenverhältnis (Odds-Ratio) betrug 2,19 (Konfidenzintervall 0,96-4,99). Schlussfolgerung: Die biologische Relevanz der Faktor-V-Mutation in der Pathogenese der pAVK kann aufgrund unserer Daten diskutiert werden.

[Chromogenic substrate as antidote against the thrombin inhibitor Melagatran?]

It could be shown in vitro that a chromogenic substrate (Chromozym TH, Roche Mannheim) acts at least partially as antidote against the new thrombin inhibitor Melagatran (AstraZeneca, Mölndal, Sweden). It is discussed that this antidote effect of a chromogenic substrate might be due to a substrate competition of fibrinogen, thrombin inhibitor, and chromogenic substrate for thrombin. Further animal experiments will clarify whether this in vitro observation is of practical relevance in vivo, too.

Chromogenes Substrat als Antidot gegen den Thrombininhibitor Melagatran?

Mit In-vitro-Untersuchungen wird gezeigt, dass ein chromogenes Substrat (Chromozym TH von Roche, Mannheim) die gerinnungshemmende Wirkung des neuen Thrombininhibitors Melagatran (AstraZeneca, Mölndal, Schweden) zumindest partiell antagonisieren kann. Der hier beschriebene Antidoteffekt eines chromogenen Substrats gegenüber einem Thrombininhibitor könnte seine Erklärung darin finden, dass eine Substratkompetition zwischen Thrombins im Testsystem und Fibrinogen, Thrombininhibitor und chromogenem Substrat vorliegt. Tierversuche unter Einbeziehung weiterer Thrombininhibitoren könnten klären, ob die beschriebene Antidotwirkung die beobachteten Blutungskomplikationen tatsächlich reduzieren kann oder ob ein In-vitro-Phänomen vorliegt, das in vivo wenig Relevanz besitzt.

Effect of gamma-interferon on binding of gliadin and other food peptides to the human intestinal cell line HT-29

gamma-Interferon is one of the main cytokines released during activation of intestinal lymphocytes in coeliac patients. The question has never been addressed whether gamma-interferon influences binding of gliadin and other food peptides to human enterocytes. Therefore, the human intestinal epithelial cell line HT-29 was cultured with gliadin, casein, beta-lactoglobulin and ovalbumin, with or without gamma-interferon, and peptide binding to cells was determined by flow cytometry and fluorescence microscopy. gamma-Interferon stimulated gliadin binding by a factor of 4. Binding was saturable with half maximal binding at 0.15 mg/ml. For maximal binding, an incubation of at least 24 h was necessary. gamma-Interferon increased binding of beta-lactoglobulin and casein, too, but inhibited that of ovalbumin. Binding of gliadin was inhibited by the other peptides. Under the conditions of ongoing mucosal inflammatory reactions and release of gamma-interferon, enhanced binding may trigger intestinal lymphocytes, increase secretion of cytokines and thus induce a vicious circle.

Reconstruction of pelvic exenterative wounds with transpelvic rectus abdominis flaps: a case series

Exenterative pelvic surgery is commonly performed for advanced carcinoma of the cervix and selected cases of locally advanced colorectal cancers. Low-lying lesions that are locally invasive in contiguous organs require resection of the perineal body en bloc with the resected specimen. The resulting defect, both in the pelvis and the perineum, creates a difficult management problem. Dead space in the pelvis, especially with adjunctive irradiation, leads to delayed wound healing and prolapse of small bowel into the pelvis. Small bowel obstruction and/or fistula formation are the greatest sources of morbidity in the operative group. Fifteen patients underwent exenterative pelvic procedures (total exenteration, 1 patient; posterior exenteration, 8 patients; abdominoperineal resection, 6 patients). All patients were reconstructed by transpelvic placement of the rectus abdominis muscle (muscle only, 4 patients; muscle with skin grafting, 8 patients; musculocutaneous, 3 patients). Eighty-seven percent received radiation therapy. One patient had Crohn's disease and all others had carcinoma. Healing was complete in 12 of 15 patients at discharge. There were no complications related to pelvic dead space (i.e., bowel obstruction, perineal fistula), with a mean follow-up time of 24.3 months. Small bowel was effectively excluded from the pelvis to the level of the acetabular roof by computerized axial tomography scan. The transpelvic rectus abdominis muscle flap is effective in preventing major morbidity after exenterative pelvic surgery.

"Medicine on wheels": an opportunity for outreach and housestaff education

Ambulatory-care teaching programs have been traditionally based in hospital settings. As many patients, in particular the homeless and underinsured, have never reached these settings, we describe a nontraditional outreach health-care program for medical residents. This multidisciplinary program places medical residents on a mobile van to deliver care to a population in New Haven where 18.2% of its families are below the poverty level and have limited or no access to health care at the teaching hospital. On-site urgent care is given along with HIV, pregnancy testing, and blood pressure screening. Health-care follow-up, dental care, alcohol detoxification, and drug counseling are scheduled. A total of 764 adult patients were seen between November 1991 and June 1993 by PGY2 residents on ambulatory rotations. One hundred forty-one patients consented to respond to a questionnaire. Thirty-seven (26%) were homeless with a mean length of homelessness of 15 months. Forty-one percent had been victimized within one year and 33% currently used illicit drugs. The benefits of this unique ambulatory teaching program for medical residents are described.

Cyclosporin enhancement of cisplatin chemotherapy in patients with refractory gynecologic cancer. A Gynecologic Oncology Group Study

BACKGROUND

Cyclosporin has been demonstrated to reverse resistance to several antineoplastic agents including cisplatin in vitro. The purpose of this Phase I trial was to study the potential clinical application of cyclosporin modulation of cisplatin and to establish a tolerable dose of cyclosporin when combined with a standard dose of cisplatin of 75 mg/m2.

METHODS

A course of therapy consisted of two cyclosporin infusions over 2 hours each, 24 hours apart, with cisplatin given 6 hours after the first dose. Treatment was repeated every 21 days. Cyclosporin was studied in a Phase I fashion at five different levels, from 1-5 mg/kg per dose. Twenty patients with refractory gynecologic cancer received 81 courses of therapy. All patients had received extensive prior chemotherapy containing cisplatin.

RESULTS

Grade 4 nephrotoxicity was seen in 4 of 20 patients: 1 treated at 1 mg/kg, 1 at 2 mg/kg, and 2 at 5 mg/kg of cyclosporin. The patient treated at the 1 mg/kg level was a partial clinical responder and tolerated six courses. The patient at the 2 mg/kg level had received 14 prior courses of cisplatin and tolerated only two additional courses before a Grade 4 renal toxicity developed. Grade 4 nephrotoxicity developed in the two patients receiving 5 mg after two courses of chemotherapy. Two of the 20 patients achieved a complete response (CR) and 3 patients achieved a partial response (PR), for a total response rate of 25% (5 of 20). The two women who achieved CR started treatment with symptomatic ascites; one of whom also had multiple pulmonary lesions that were no longer evident after three courses of therapy.

CONCLUSIONS

Cyclosporin at a dose of 4 mg/kg per day given for 2 consecutive days in association with 75 mg/m2 of cisplatin can be given with reasonable assurance of safety.