HOE 077 Reduces Fibrotic Overgrowth Around the Barium Alginate Microcapsules W.J. Zhang, S.-K. Marx, Ch. Laue, A. Hyder, A. Juergensen, M. Bickel, and J. Schrezenmeir M ICROENCAPSULATION of the pancreatic islets of Langerhans in a biocompatible and permselective membrane is an attractive method to protect the trans- planted graft from immune rejection. It has been demon- strated that allogenic or xenogenic microencapsulated islets can restore normoglycemia with either chemically in- duced 1–3 or autoimmune diabetes. 4,5 The graft function, however, was still limited. The reported duration of normo- glycemia varies considerably from a few days 1,5 to almost 2 years. 3 One of the most important factors affecting long- term viability of encapsulated islets is the pericapsular fibrotic infiltration (PCI) that had already been observed within 3 to 17 days after implantation 1,2,4,5 and seems to deteriorate oxygen and nutrients supply. 6 Oxygen supply is already limited by encapsulation 7 and was shown to be crucial for the function of encapsulated islet cells. 6–9 HOE 077 [Hoechst AG, Frankfurt, Germany] was devel- oped as an antifibrotic agent to treat fibrosis of the liver in man. Under in vivo conditions HOE 77 inhibited the fibrogenetic process in a variety of disease models of the liver fibrosis in rodents, in a dose range of 10 to 100 mg/kg p.o./day. 10 –14 Numerous investigations on the mode of action of the antifibrotic effect of HOE 77 in the above mentioned models, clearly showed, that the inhibitory effect of HOE 77 on collagen formation, was due to the inhibition of stellatae cells. As stellatae cells are the major cellular source of collagen synthesis in the liver, this explains the antifibrotic effects of the drug in liver fibrosis of different origins. The inhibition of the compound on fibrogenesis in the liver suggested, that it might be useful to reduce collagen formation around implanted microcapsules of islet transplantation in the liver. In the present study, microencapsulated porcine islet cells were implanted in mice to investigate the influence of HOE 077 on the PCI around these capsules and on the viability of the encapsulated cells. MATERIALS AND METHODS Design of the Study In a first experiment empty microcapsules were implanted in the liver and peritoneal cavity of Balb/c mice. For each transplantation site, recipient mice were divided into two groups: HOE 077-treated and an untreated group (n = 25). Empty capsules were used so that the effect of HOE 077 on the fibrotic reaction interfered with that of an eventual immune response against the islets. Following implantation, HOE 077 was administered with the drinking water in a concentration of 1.5 mg/mL and supplied ad libitum; the control animals received only water. The volume of consumed water was noted to calculate the dosage of HOE 077. In order to study whether HOE 077 may improve the viability of encapsulated cells, the islet cell-containing microcapsules were implanted in the liver. Similarly, the mice were divided into two groups: treated and untreated group (n = 10). Four weeks after transplantation, the liver and the microcapsules in the peritoneal cavity of all recipients were retrieved for histologic examination. The thickness of the PCI and viability of the islet cells were assessed for statistical analysis. Islet Isolation Islets were isolated by a modification of the method previously described by our group. 16 Porcine pancreata of adult pigs were obtained from the local slaughterhouse. After slaughter, the organ were removed immediately, limiting the warm ischemia time to less than 15 minutes; only the caudal parts were used. The common pancreatic duct was canulated, and the pancreas was then perfused with 0.6% collagenase solution (Serva, Heidelberg, Germany; w/v in Hank’s solution) and digested in a specially designed continuous digestion-filtration device at 37°C for 18 to 20 minutes. During the digestive process the digested tissue particles passed through a 350 m screen. Following centrifugation, the supernatant was dis- carded and the sediment was centrifuged on a continuous Nyco- denz (Nycomed pharma, Oslo, Norway) density gradient ranging from 1.055 to 1.095 g/mL using a Cobe 2991 cell separator (Blood Component Technology, Lakewood, USA) to separate free islets from exocrine tissue. The fraction enriched with islets was passed through a sieve with 45 m mesh to eliminate single cells and islet fragments. After purification, the islets (95% purity) were disso- ciated into single cells or cell clusters by shaking for encapsulation. From the Institute of Physiology and Biochemistry, Federal Research Centre, Kiel (W.J.Z., S.-K.M., C.L., A.H., J.S.) Institute of Pathology, Christian Albrechts University of Kiel (A.J.), and Hoechst Marion Roussel Deutschland, Frankfurt, (M.B.), Germany. This work was supported by a grant of “Stiftung Inseltrans- plantation” to Dr. Ch. Laue. Address reprint requests to Prof Dr Ju ¨ rgen Schrezenmeir, Institute of Physiology and Biochemistry, Federal Research Centre, Hermann-Weigmann-str. 1, 24103 Kiel, Germany. E- mail: Schrezenmeir@bafm.de. 0041-1345/00/$–see front matter © 2000 by Elsevier Science Inc. PII S0041-1345(99)00938-0 655 Avenue of the Americas, New York, NY 10010 206 Transplantation Proceedings, 32, 206–209 (2000)