Engraftment of autologous retrovirally transduced hepatocytes after intraportal transplantation into nonhuman primates: implication for ex vivo gene therapy

The main impediment to effective ex vivo liver gene therapy of metabolic diseases is the lack of experimental work on large animals to resolve such important issues as effective gene delivery, cell-processing techniques, and the development of appropriate vectors. We have used a nonhuman primate, as a preclinical model, to analyze the limiting steps of this approach using recombinant retroviruses. Seven monkeys (Macaca fascicularis) underwent the complete protocol: their left liver lobe was resected, a catheter was placed in the inferior mesenteric vein and connected to an infusion chamber, and the hepatocytes were isolated, cultured, and transduced with a retroviral vector containing the beta-galactosidase gene. The hepatocytes were harvested and returned to the host via the infusion chamber. Biopsies were taken 4-40 days later. No animal was killed in the course of the experiments. They all tolerated the procedure well. We have developed and defined conditions that permit the proliferation and transduction of up to 90% of the plated hepatocytes. A significant proportion of genetically modified cells, representing up to 3% of the liver mass, were safely delivered to the liver via the chamber. Polymerase chain reaction analysis detected integrated viral DNA sequences and quantitative analysis of the in situ beta-Gal-expressing hepatocytes indicated that a significant amount of transduced hepatocytes, up to 2%, had become integrated into the liver and were functional. These results represent substantial advances in the development of the ex vivo approach and suggest that this approach is of clinical relevance for liver-directed gene therapy.

Transabdominal amnioinfusion to avoid fetal demise and intestinal damage in fetuses with gastroschisis and severe oligohydramnios

BACKGROUND/PURPOSE

Despite dramatic improvement in survival rate for neonates with gastroschisis, significant postoperative morbidity and a low mortality rate still occur. Furthermore, even in recent publications, some fetal death has been reported. Does this mean that antenatal diagnosis of gastroschisis is a missed opportunity? In fact, decreased amniotic fluid (AF) volume is observed in some fetuses with gastroschisis. However, oligohydramnios is associated with an increased risk of fetal suffering. When severe oligohydramnios is observed, intrapartum amnioinfusion, to restore AF volume, may help avoid fetal complications.

METHODS

Two fetuses with gastroschisis and severe oligohydramnios were treated antenatally with amnioinfusion of saline solution. In one case, fetal heart beat decelerations were observed at 27 weeks' gestation among with the oligohydroamnios and serial transabdominal amnioinfusions were performed. In the second case, severe oligohydramnios was observed at 31, weeks and an amnioinfusion was performed. The 2 babies were delivered at 31 and 34 weeks, respectively.

RESULTS

In both cases, exteriorized bowel was nearly normal at birth, and primary closure could be performed. Outcome was favorable, and they were discharged home on day 43 and day 54, respectively.

CONCLUSIONS

Because fetuses with gastroschisis and oligohydramnios are part of a particular high-risk group, serial ultrasound examination and computerized fetal heart beat monitoring are necessary during the third trimester. In selected cases of gastroschisis associated with severe oligohydramnios, serial amnioinfusion may be required.

In utero allotransplantation of retrovirally transduced fetal hepatocytes in primates: feasibility and short-term follow-up

In utero allotransplantation of fetal hepatocytes into a preimmune fetus could be used in early treatment of many inherited hepatic metabolic diseases. This study was designed to assess the tolerance to hepatocyte transplantation and to test the feasability and toxicity of such an injection in a primate model. Fetal hepatocytes were obtained from two 120-day-old Macaca mulatta fetuses and cryopreserved. They were thawed, cultured in vitro, and transduced with a recombinant retrovirus expressing beta-galactosidase. Transduction efficiency was 75-85%. Three unrelated fetuses (90, 100, and 104 days old) were each given 1-2 x 10(7) transduced cells via the umbilical vein. This caused vasospasm and severe bradycardia. Two fetuses died in the 48 hours after transplantation; the third survived and was killed at the end of gestation. No evidence of the infused cells was found. Three fetuses (90 days old) were, therefore, given 3-4 10(7) hepatocytes by direct intrahepatic injection. All the fetuses survived without side effect. Donor cells were not apparent from histochemical staining and PCR reactions. There was no evidence of inflammatory reaction. These findings indicate that the protocole could be improved by increasing the number of transplanted cells and using specific hepatic promoters in the retroviral vectors to achieve an effective postnatal chimerism.

Anatomic study of the umbilical vein and ductus venosus in human fetuses: ultrasound application in prenatal examination of left congenital diaphragmatic hernia

For clinicians it is very difficult to evaluate the prognosis of a left congenital diaphragmatic hernia (CDH) at prenatal ultrasound examination. Surgical studies show that the presence of a large part of the liver in the chest is a criterion of poor prognosis. However, ultra-sonography encounters some difficulties in determining the precise position of the liver in the thoracic cavity. The aim of this anatomic study was to define the relationship between the position of the liver and the path of the ductus venosus and of the umbilical v., which are easily recognizable at prenatal sonography. Twenty dead fetuses were used for the study (12 with a left CDH and 8 without). All fetuses underwent radiographic assessment, anatomic dissection and cross-sectional study. The angle between the umbilical v. and the ductus venosus in different planes was measured. The more the liver was in the thorax, the greater was the angle between the ductus venosus and the sagittal plane, and the less the angle between the ductus venosus and the umbilical v. These angles can be easily measured by prenatal ultrasound examination of the fetus. Our findings suggest that it is now possible to offer the clinician a new and reliable way to determine the prognosis of a left CDH before birth.

Preclinical studies for cell transplantation: isolation of primate fetal hepatocytes, their cryopreservation, and efficient retroviral transduction

Fetal hepatocytes are an attractive target for in utero cellular transplantation. Their use could provide a very efficient way for implanting normal or transduced cells into the livers of affected fetuses. Marking cells with recombinant retroviruses is a powerful tool for evaluating the chimerism of grafted animals. The technique relies on the ex vivo transduction efficiency of the engrafted cells. We have isolated fetal primary hepatocytes from nonhuman primates. The cells were cultured and transduced with a retroviral vector carrying the Escherichia coli beta-galactosidase gene. Optimal gene transfer efficiency was obtained 48-60 hr after plating and was as high as 90%. Cryopreservation had little effect on cell viability and infectivity: The viability of thawed hepatocytes remained high (75-85%) and the infection efficiency was identical to that of freshly isolated cells. Efficient ex vivo retroviral gene transfer into fetal hepatocytes provides an appropriate system for testing allogenic grafting and for modifying immunogenicity of engrafted cells. These results open up new perspectives for cell transplantation through cell banking.