The Viability and Function of Cryopreserved Hepatocyte Spheroids with Different Cryopreservation Solutions

PURPOSE: The bioartificial liver via extracorporeal circulation and the hepatocyte transplantation have been studied due to donor organ shortage. Hepatocyte spheroids, which are tightly packed multicellular aggregates, showed enhanced liver specific activities. The authors have studied the bioartificial liver system using hepatocyte spheroids. For the effective application of this system, the effective cryopreservation technique is necessary. In this study, the aim was to evaluate the viability and function of cryopreserved hepatocyte spheroids with different cryopreservation solutions and to elucidate the efficiency of cryopreservation. METHODS: Hepatocytes were isolated Sprague-Dawley rat. The hepatocyte spheroids were formed with 24 hours by rotational culturing. The hepatocyte spheroids were frozen in different cryopreservation solutions (UW solution, William E media, FBS and mixture) by programmed linear freezer, preserved in liquid nitrogen tank for 24 hours and cultured for 4 days after thawing. For the viabilities of each hepatocyte spheroids, the MTT assay was made and for their hepatocyte specific functions, ammonia clearance, urea nitrogen synthesis and albumin secretion of the spheroids were evaluated. RESULTS: The viabilities of the cyropreserved hepatocyte spheroids after culturing for 4 hours following thawing were 64.8+/-10.2, 33.2+/-9.7, 69.3+/-8.7 and 48.4+/-15.5% in the UW, WE, FBS and MIX media, respectively. The ammonia clearance of the spheroids cyropreserved in the UW solution was 0.93+/-0.13 mM/well/day, which was not significantly different from that of the freshly cultured spheroids. With regard to the urea nitrogen synthesis, the cryopreserved spheroids in the UW, FBS and MIX solutions were not significantly different from the freshly cultured spheroids. The amount of albumin secretion of the cryopreserved spheroids in the UW solution was significantly higher than those of cryopreserved spheroids in the other solutions. CONCLUSION: With regard to the viability and function, the hepatocyte spheroids cryopreserved in the UW solution were not significantly different from the freshly cultured spheroids, which were superior to the other cryopreserved spheroids. Further studies relating to the optimal culture and cryopreservation environments, such as freezing rate or cryoprotectant from damage during freezing, are needed.

Evaluation of the Embolic Effect of Polyvinyl Alcohol Foam particles According to Particle Size on the Cerebral Artery of a Cat, Focusing on T2 Weighted MR Images and Pathologic Study After 24 Hours

PURPOSE: This study was designed to determine the embolic effect of PVA particles of various sizes on the cerebral artery of a cat and to determine the appropriate particle size for embolization. MATERIALS AND METHODS: A total of 21 cats were divided into three groups according to the PVA particle size injected: group I(n=7), embolized with 45-150 micrometer PVA; group II(n=7), with 150-250 micrometer PVA; and group III(n=7), with 350-500 micrometer PVA. PVA particles were slowly injected into the left common carotid artery of each cat, and T2-weighted coronal MR images were obtained 24 hours after injection. During histologic examination of brain sections we analyzed the size, number of occluded vessels, and the ischemic changes caused by the particles. RESULTS: On T2 weighted images, areas of high signal intensity (infarction) were observed in four of the seven cats (57%) in group Iand in two of the seven (29%) in group II. High signal intensity was not found in group III. The mean percentage of areas of high signal intensity was 11.86 +/-1 . 37 % in group Iand 5.18 +/-1 . 77% in group II( P <0.05). During histologic examination, occlusion of the distal branches of the anterior cerebral (ACA) and/or the middle cerebral arteries(MCA) by PVA particles was observed in all seven cats (100%) in group I, and in four of the seven cats (57%) in group II. No group IIIcat showed occlusion of the distal branches of the ACA and/or MCA. The mean caliber of occluded vessels was 175 micrometer in Group Iand 258 micrometer in Group II. The mean number of occluded vessels seen on all slide sections was 14 in Group I and 5 in Group II. CONCLUSION: Small PVA particles had a greater cerebral embolic effect than did those which were medium or large. For the induction of embolic infarction in cat brain, PVA particles 45-150 micrometer in size are appropriate.

Evaluation of the Embolic Effect of Polyvinyl Alcohol Foam particles According to Particle Size on the Cerebral Artery of a Cat, Focusing on T2 Weighted MR Images and Pathologic Study After 24 Hours

PURPOSE: This study was designed to determine the embolic effect of PVA particles of various sizes on the cerebral artery of a cat and to determine the appropriate particle size for embolization. MATERIALS AND METHODS: A total of 21 cats were divided into three groups according to the PVA particle size injected: group I(n=7), embolized with 45-150 micrometer PVA; group II(n=7), with 150-250 micrometer PVA; and group III(n=7), with 350-500 micrometer PVA. PVA particles were slowly injected into the left common carotid artery of each cat, and T2-weighted coronal MR images were obtained 24 hours after injection. During histologic examination of brain sections we analyzed the size, number of occluded vessels, and the ischemic changes caused by the particles. RESULTS: On T2 weighted images, areas of high signal intensity (infarction) were observed in four of the seven cats (57%) in group Iand in two of the seven (29%) in group II. High signal intensity was not found in group III. The mean percentage of areas of high signal intensity was 11.86 +/-1 . 37 % in group Iand 5.18 +/-1 . 77% in group II( P <0.05). During histologic examination, occlusion of the distal branches of the anterior cerebral (ACA) and/or the middle cerebral arteries(MCA) by PVA particles was observed in all seven cats (100%) in group I, and in four of the seven cats (57%) in group II. No group IIIcat showed occlusion of the distal branches of the ACA and/or MCA. The mean caliber of occluded vessels was 175 micrometer in Group Iand 258 micrometer in Group II. The mean number of occluded vessels seen on all slide sections was 14 in Group I and 5 in Group II. CONCLUSION: Small PVA particles had a greater cerebral embolic effect than did those which were medium or large. For the induction of embolic infarction in cat brain, PVA particles 45-150 micrometer in size are appropriate.

Sonographic Findings of Lipoma in the Neck

PURPOSE: The purpose of this study is to analyze the sonographic features of lipoma of the neck. MATERIALS AND METHODS: The cases of 13 patients (35 to 70 years old, nine males and four females) with lipoma of the neck were retrospectively reviewed. Lipomas were confirmed pathologically in six patients, and by CT and MR in seven. RESULT: Lipomas were well-defined in 11 cases (85%), and elliptical shaped masses in 12 (92%) with the longest diameter parallel to the skin surface. As compared with adjacent muscles, 54% of all lipomas (n=7) were hyperechoic, 15% (n=2) were isoechoic and 31% (n=4) were hypoechoic. In 11 cases (85%), lipomas were insinuated into intermuscular space or were found between muscle and adjacent organs. CONCLUSION: The sonographic feature of lipoma of the neck are a well-defined elliptical shaped mass parallel to the skin surface, with linear echogenic lines and either insinuated into intermuscular space or lying between muscle and adjacent organs. The echogenicity of the mass varied.