Long-term expansion, genomic stability and in vivo safety of adult human pancreas organoids

BACKGROUND

Pancreatic organoid systems have recently been described for the in vitro culture of pancreatic ductal cells from mouse and human. Mouse pancreatic organoids exhibit unlimited expansion potential, while previously reported human pancreas organoid (hPO) cultures do not expand efficiently long-term in a chemically defined, serum-free medium. We sought to generate a 3D culture system for long-term expansion of human pancreas ductal cells as hPOs to serve as the basis for studies of human pancreas ductal epithelium, exocrine pancreatic diseases and the development of a genomically stable replacement cell therapy for diabetes mellitus.

RESULTS

Our chemically defined, serum-free, human pancreas organoid culture medium supports the generation and expansion of hPOs with high efficiency from both fresh and cryopreserved primary tissue. hPOs can be expanded from a single cell, enabling their genetic manipulation and generation of clonal cultures. hPOs expanded for months in vitro maintain their ductal morphology, biomarker expression and chromosomal integrity. Xenografts of hPOs survive long-term in vivo when transplanted into the pancreas of immunodeficient mice. Notably, mouse orthotopic transplants show no signs of tumorigenicity. Crucially, our medium also supports the establishment and expansion of hPOs in a chemically defined, modifiable and scalable, biomimetic hydrogel.

CONCLUSIONS

hPOs can be expanded long-term, from both fresh and cryopreserved human pancreas tissue in a chemically defined, serum-free medium with no detectable tumorigenicity. hPOs can be clonally expanded, genetically manipulated and are amenable to culture in a chemically defined hydrogel. hPOs therefore represent an abundant source of pancreas ductal cells that retain the characteristics of the tissue-of-origin, which opens up avenues for modelling diseases of the ductal epithelium and increasing understanding of human pancreas exocrine biology as well as for potentially producing insulin-secreting cells for the treatment of diabetes.

Human primary liver cancer-derived organoid cultures for disease modeling and drug screening

Human liver cancer research currently lacks in vitro models that can faithfully recapitulate the pathophysiology of the original tumor. We recently described a novel, near-physiological organoid culture system, wherein primary human healthy liver cells form long-term expanding organoids that retain liver tissue function and genetic stability. Here we extend this culture system to the propagation of primary liver cancer (PLC) organoids from three of the most common PLC subtypes: hepatocellular carcinoma (HCC), cholangiocarcinoma (CC) and combined HCC/CC (CHC) tumors. PLC-derived organoid cultures preserve the histological architecture, gene expression and genomic landscape of the original tumor, allowing for discrimination between different tumor tissues and subtypes, even after long-term expansion in culture in the same medium conditions. Xenograft studies demonstrate that the tumorogenic potential, histological features and metastatic properties of PLC-derived organoids are preserved in vivo. PLC-derived organoids are amenable for biomarker identification and drug-screening testing and led to the identification of the ERK inhibitor SCH772984 as a potential therapeutic agent for primary liver cancer. We thus demonstrate the wide-ranging biomedical utilities of PLC-derived organoid models in furthering the understanding of liver cancer biology and in developing personalized-medicine approaches for the disease.

SRC family kinase (SFK) inhibition reduces rhabdomyosarcoma cell growth in vitro and in vivo and triggers p38 MAP kinase-mediated differentiation

Recent data suggest that SRC family kinases (SFKs) could represent potential therapeutic targets for rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children. Here, we assessed the effect of a recently developed selective SFK inhibitor (a pyrazolo[3,4-d]pyrimidine derivative, called SI221) on RMS cell lines. SI221, which showed to be mainly effective against the SFK member YES, significantly reduced cell viability and induced apoptosis, without affecting non-tumor cells, such as primary human skin fibroblasts and differentiated C2C12 cells. Moreover, SI221 decreased in vitro cell migration and invasion and reduced tumor growth in a RMS xenograft model. SFK inhibition also induced muscle differentiation in RMS cells by affecting the NOTCH3 receptor-p38 mitogen-activated protein kinase (MAPK) axis, which regulates the balance between proliferation and differentiation. Overall, our findings suggest that SFK inhibition, besides reducing RMS cell growth and invasive potential, could also represent a differentiation therapeutic strategy for RMS.

The plastic liver: differentiated cells, stem cells, every cell?

The liver is capable of full regeneration following several types and rounds of injury, ranging from hepatectomy to toxin-mediated damage. The source of this regenerative capacity has long been a hotly debated topic. The damage response that occurs when hepatocyte proliferation is impaired is thought to be mediated by oval/dedifferentiated progenitor cells, which replenish the hepatocyte and ductal compartments of the liver. Recently, reports have questioned whether these oval/progenitor cells truly serve as the facultative stem cell of the liver following toxin-mediated damage. In this issue of the JCI, Kordes and colleagues use lineage tracing to follow transplanted rat hepatic stellate cells, a resident liver mesenchymal cell population, in hosts that have suffered liver damage. Transplanted stellate cells repopulated the damaged rat liver by contributing to the oval cell response. These data establish yet another cell type of mesenchymal origin as the progenitor for the oval/ductular response in the rat. The lack of uniformity between different damage models, the extent of the injury to the liver parenchyma, and potential species-specific differences might be at the core of the discrepancy between different studies. Taken together, these data imply a considerable degree of plasticity in the liver, whereby several cell types can contribute to regeneration.

Bovine valved venous xenograft in pulmonary position: medium term evaluation of risk factors for dysfunction and failure after 156 implants

AIM

This study evaluated risk factors for dysfunction and failure of the bovine Contegra valved conduit for right ventricle outflow tract reconstruction.

METHODS

A total of 156 bovine jugular vein conduits were reviewed. Early and late mortality were evaluated. Seriate echocardiography was performed through the follow-up (mean 58±43.2 months, range 12 to 108 months), and risk factors and adverse events evaluation were analyzed by multivariate logistic regression.

RESULTS

Hospital mortality was 7% (11/156). The only independent predictor of early mortality were cardiopulmonary bypass time >120 minutes and age <1 year. Postoperative mean RV to PA gradient was 10.4±9.1 mm Hg, increased to 18.7±14.5 mm Hg during the follow-up. A late gradient >30 mm Hg was assessed in 22 patients (15.1%),while 12 patients developed conduit valve regurgitation greater than 2+ without evidence of aneurismal formation. All patients with right ventricular (RV) to left ventricular (LV) pressure ratio >0.6 had conduit valve regurgitation. Acquired distal conduit stenosis was observed only in 1 patient. Thirteen patient underwent conduit replacement, diameter ≤14 mm was the only independent risk factor for reoperation. All explanted conduits were free from calcification and valve leaflets were intact and pliable. The Contegra graft itself was never cause of adverse event.

CONCLUSION

The Contegra conduit provided excellent results and freedom from calcification in a medium-term follow-up. Younger age at operation was associated with higher need of replacements for conduit patient mismatch due to patient growth.

Transesophageal echocardiographic diagnosis of a dehisced Carpentier mitral ring

We describe an unusual case of gross dehiscence of a Carpentier mitral ring, not due to bacterial endocarditis, causing severe mitral valve insufficiency and cardiac failure. Diagnosis was made by transesophageal echocardiography (TEE). Mitral valve replacement was then performed.

Emergency surgical management of acute aortic dissection: role of transesophageal echocardiography

The accuracy of transesophageal echocardiography in the diagnosis and surgical management of acute aortic dissection was determined in 54 patients who underwent surgery for acute aortic dissection. Results of the investigations were compared to the surgical assessment. From April 1993 to November 1997, we operated 54 patients (44 male and 10 female) for acute aortic dissection. Mean age was 60 +/- 9 years. At surgery, a De Bakey type I aortic dissection was diagnosed in 30 patients, type II in 23 and type III retrograde in 1. Operating procedures were: replacement of ascending aorta (24 cases), replacement of ascending aorta and aortic arch (17 cases), replacement of ascending aorta and aortic valve replacement (2 cases), Bentall procedure (6 cases) and end-to-end anastomosis of the ascending aorta (4 cases). Initial diagnosis, performed in emergency wards, was done on a clinical basis in 6 patients, on CT scan in 19, on transthoracic echocardiography in 14, and on TEE basis in 12. Three patients underwent angiography before our evaluation. As per our protocol, all patients underwent confirmation of the diagnosis by TEE. Seven patients needed additional instrumental investigations, 2 with CT scan and 5 with angiography. TEE confirmed the diagnosis of aortic dissection in all cases but one. Moreover, it described the site of the intimal tear, the extension of the dissecting process and accessory findings, such as pericardial effusion, aortic incompetence and left ventricular function. The interval between patient presentation and skin incision was a maximum of 70 minutes. At surgery, diagnosis of De Bakey classification was confirmed in 98% of cases; in 90.7% of cases exact location of the entry site was confirmed. In one case, an entry site in the arch diagnosed by TEE but not recognized at surgery, was observed at necropsy. Intraoperatively, we routinely used TEE to monitor retrograde systemic perfusion and correct implant of the vascular prosthesis. One case of malperfusion of the thoracic aorta through the false lumen was observed and managed. In one case we diagnosed acute obstruction of the prosthesis by bleeding in the wrapped aorta, which required reoperation. Assessment of ventricular function was obtained in all patients: in two cases, observation of low right ventricular function led us to perform aortocoronary by-pass to the right coronary artery. In conclusion, the high level of correspondence between TEE diagnosis and surgical anatomy prompted us to perform transesophageal echocardiography as the primary and often sole diagnostic procedure in acute aortic dissection. TEE, in experienced hands, has proven to be a highly reliable, safe and low-cost diagnostic tool. It can be performed at the patient's bedside within just a few minutes of the suspected diagnosis, thereby lowering the mortality rate of the natural history. Again, it can also be used in the operating theatre as an "on-line examination" as well as for assessment of correct surgical repair. Other diagnostic procedures do not yield more information and can cause dangerous delays in intervention.

Early massive thrombosis of a mechanical mitral valve

We report the case of a 74-year-old woman who underwent an elective procedure to replace her mitral valve with a 27-mm CarboMedics bileaflet valve (CarboMedics, Inc.; Austin, Tex) to correct mitral incompetence. Massive thrombosis of the prosthesis was clinically evident on the 6th postoperative day, despite administration of warfarin therapy according to our usual protocol. After an unsuccessful attempt at thrombolysis with recombinant tissue plasminogen activator, the mechanical prosthesis was replaced with a bioprosthesis. The cause of the thrombosis is unknown, but transient suboptimal anticoagulation is assumed to be responsible. Although very early massive valve thrombosis is a rare occurrence, it is a known risk of prosthetic valve implantation. Antiplatelet therapy, in addition to the usual warfarin anticoagulation, can help to prevent it. If thrombosis is diagnosed, it can be managed by thrombolysis or, when thrombolysis is unsuccessful, by reoperation. Transesophageal echocardiography is fundamental in the diagnosis and management of this sequela.

Type B aortic dissection involving an isolated right-sided aortic arch

We report a case of a 48-year-old man in whom type B aortic dissection in the right aortic arch and right descending aorta was diagnosed by transesophageal echocardiography and computed tomographic scan. Angiography was necessary to define the anatomy of the branching vessels. The patient was successfully treated by interposition of a Vascutek 24-mm Dacron woven tube with a right posterolateral thoracotomy approach. Circulatory arrest in profound hypothermia and cerebral retroperfusion were used.

One leaflet immobilization after mitral valve replacement with a bileaflet prosthesis

We report four cases of one leaflet immobilization which occurred early after mitral valve replacement with a Carbomedics bileaflet valve. The first case was diagnosed incidentally six days after surgery and did not require reoperation because of the spontaneous normalization of the valve movements the day before the scheduled reoperation. Since then, we have been using intraoperative transesophageal echocardiography in mitral procedures routinely (both valve repair or replacement). We were able to detect malfunctions which required reorientation in three other prostheses. We emphasize the importance of performing intraoperative transesophageal echocardiography routinely in these procedures; its high sensitivity and low risk can help to avoid a late reoperation.

Massive pulmonary embolism 3 hours after cardiopulmonary bypass. An exceeding rare case

A 70-year-old woman underwent an aortocoronary bypass. Three hours later, she experienced severe pulmonary embolism, diagnosed by transesophageal echocardiography and followed by cardiac arrest. Resuscitation maneuvers were unsuccessful. Autopsy confirmed the diagnosis. When pulmonary embolism occurs after cardiopulmonary bypass for cardiac surgery, it usually occurs in the 2nd postoperative week; and to the best of our knowledge, the literature contains no other reports of cases that occurred during a shorter postoperative interval. Prevention of pulmonary embolism in high-risk patients is mandatory. When embolism occurs, transesophageal echocardiography is an essential tool in making the diagnosis and in guiding the surgeon during intervention.

Coumarin anticoagulation during pregnancy in patients with mechanical valve prostheses

Between January 1987 and December 1989, 20 female patients with one mechanical valve prosthesis (MVP) for at least 1 year postoperatively were studied while on coumarin therapy for the full length of pregnancy. In each case, caesarean section was scheduled for the 38th week. Patients were selected according to the following criteria: (1) prothrombin ratios remaining within the therapeutic range for more than 85% of their total estimations in the previous 12 months with mean daily doses of warfarin less than 5 mg; (2) stable cardiac status; (3) no previous obstetric diseases and (4) full acceptance of the risks involved in the protocol. The patients were in NYHA functional class I or II. Their ages ranged from 23 to 31 years (mean 26 +/- 3). Ten patients had a mitral prosthesis and 10 an aortic prosthesis. Among the 20 mechanical valve prostheses, 10 were Sorin, 6 Starr-Edwards, 2 Bjørk-Shiley, and 2 Lillehei-Kaster. Eighteen patients were in sinus rythm, 1 in chronic atrial fibrillation, and 1 had a permanent endocardial pacemaker. Nineteen were delivered by caesarean section: warfarin was withdrawn 48 h before surgery and resumed 24 h thereafter. One patient had premature spontaneous delivery at 36 weeks. The mean prothrombin ratio measured weekly in the 20 patients was 2.06 +/- 0.45 INR, using a mean daily warfarin dose of 4.1 mg +/- 1.63. The mean value of the prothrombin ratio during caesarean section for the 19 patients was 1.23 +/- 0.38 INR. In the 20 live births, the mean birth weight was 2.9 kg +/- 0.40.(ABSTRACT TRUNCATED AT 250 WORDS)