A Safety and Efficacy Study of Infusions of HepaStem in Urea Cycle Disorders Pediatric Patients

Inclusion Criteria: * The patient is a pediatric patient \<12 years * The patients presents with one of the following UCDs. (CPS1D, OTCD, ASSD, ASLD, ARGD) * The patient has severe disease with impaired protein tolerance defined as: chronic protein restricted diet AND chronic treatment with at lease one nitrogen scavenger. * The patient shows patency of the portal vein and its branches including mesenteric veins, with normal flow velocity as confirmed by Doppler US and accessibility of the portal vein and/or affluents. * The patient (if capable of signing) and parents or legal representative have signed a written informed consent form. Exclusion Criteria: * The patient presents acute liver failure. * The patient presents clinical or radiological evidence of liver cirrhosis. * The patient presents or has a history of hepatic or extrahepatic malignancy. * The patient has a known clinically significant cardiac malformation. * The patient has a personal history of venous thrombosis, or has a clinically significant abnormal value for protein S, protein C, anti-thrombin III, and/or activated Protein C Resistance (aPCR) at screening. In case of known family history, a complete coagulation work-up should be performed. in all above described cases, results need to be discussed with sponsor before enrolling the patient in the study. * Patient currently receiving other unapproved investigational drug or device. * The patient underwent previous mature liver cell or stem cell transplantation or received an organ liver transplant or received HepaStem infusion. * The patient has a contraindication to methylprednisolone, tacrolimus. * The patient has a known hypersensitivity or allergy to heparin. * The patient has a known hypersensitivity or allergy to the antibiotics preventing post-operative infections that are prescribed according to institutional guidelines, and no alternative prophylaxis can be found. * The patient had or has a renal insufficiency treated by dialysis. * The patient requires valproate therapy. * The patient has a known hypersensitivity or allergy to contrast agents (if applicable) that cannot be treated adequately. * The patient has a thrombosis of the portal vein or persisting impairment of anterograde portal blood flow. * The patient has a porto systemic shunt or fistula assessed by Doppler US or an Arantius channel or protal hypertension. * The site where the catheter is intended to be placed has previously suffered from venous thrombosis or vascular surgical procedures. * The patient has an ongoing infection or suffered from an infection in the last 2 weeks (including active EBV infection at screening). The patient may be enrolled after resolution of the infection. * There is any significant condition or disability that, in the investigator's opinion, may interfere with the patient's participation in the study.