Clean-Up Human Embryonic Stem Cell Lines Using Humanized Culture Condition

Human embryonic stem cell (hESC) culture system has been changing culture conditions from conventional to xeno-free for therapeutic cell applications, and N-glycolylneuraminic acid (Neu5Gc) could be a useful indicator of xenogeneic contaminations in hESCs because human cells can no longer produce it genetically. We set up the humanized culture condition using commercially available humanized materials and two different adaptation methods: sequential or direct. SNUhES4 and H1 hESC lines, previously established in conventional culture conditions, were maintained using the humanized culture condition and were examined for the presence of Neu5Gc. The hESCs showed the same morphology and character as those of the conventional culture condition. Moreover, they were negative for Neu5Gc within two passages without loss of pluripotency. This study suggested that this method can effectively cleanse previously established hESC lines, bringing them one step closer to being clinical-grade hESCs.

The utility of sperm DNA damage assay using toluidine blue and aniline blue staining in routine semen analysis / 대한생식의학회지

OBJECTIVE: The aim of the present study was to examine the relationship among male age, strict morphology, and sperm chromatin structure and condensation. METHODS: Sperm samples from a total of 100 men underwent semen analysis, and sperm chromatin structure and condensation were assessed with toluidine blue (TB) and aniline blue (AB) tests. RESULTS: Prevalence of strict morphology of less than 4%, and abnormal sperm chromatin structure and condensation did not show any statistically significant differences according to male age (p=0.605, p=0.235, and p=0.080). No significant correlation was demonstrated among age of male partners, strict morphology, and abnormal sperm chromatin structure using TB and AB tests. However, abnormal sperm chromatin condensation was positively associated with sperm chromatin structure (r=0.594, p=0.000) and showed negative correlation with strict morphology (r=-0.219, p=0.029). CONCLUSION: The tests for sperm chromatin condensation showed a significant association with strict morphology. Further study is needed to elucidate the relationship between clinical outcome and sperm chromatin tests.

Successful birth with preimplantation genetic diagnosis using single-cell allele-specific PCR and sequencing in a woman with hypochondroplasia due to FGFR3 mutation (c.1620C>A, p.N540K) / 대한생식의학회지

Hypochondroplasia (HCH) is an autosomal dominant inherited skeletal dysplasia, usually caused by a heterozygous mutation in the fibroblast growth factor receptor 3 gene (FGFR3). A 27-year-old HCH woman with a history of two consecutive abortions of HCH-affected fetuses visited our clinic for preimplantation genetic diagnosis (PGD). We confirmed the mutation in the proband (FGFR3:c.1620C>A, p.N540K), and established a nested allele-specific PCR and sequence analysis for PGD using single lymphocyte cells. We performed this molecular genetic analysis to detect the presence of mutation among 20 blastomeres from 18 different embryos, and selected 9 embryos with the wild-type sequence (FGFR3:c.1620C). A successful pregnancy was achieved through a frozen-thawed cycle and resulted in the full-term birth of a normal neonate. To the best of our knowledge, this is the first report of a successful pregnancy and birth using single-cell allele-specific PCR and sequencing for PGD in an HCH patient.

A case of isodicentric chromosome 15 presented with epilepsy and developmental delay / 소아과

We report a case of isodicentric chromosome 15 (idic(15) chromosome), the presence of which resulted in uncontrolled seizures, including epileptic spasms, tonic seizures, and global developmental delay. A 10-month-old female infant was referred to our pediatric neurology clinic because of uncontrolled seizures and global developmental delay. She had generalized tonic-clonic seizures since 7 months of age. At referral, she could not control her head and presented with generalized hypotonia. Her brain magnetic resonance imaging scans and metabolic evaluation results were normal. Routine karyotyping indicated the presence of a supernumerary marker chromosome of unknown origin (47, XX +mar). An array-comparative genomic hybridization (CGH) analysis revealed amplification from 15q11.1 to 15q13.1. Subsequent fluorescence in situ hybridization analysis confirmed a idic(15) chromosome. Array-CGH analysis has the advantage in determining the unknown origin of a supernumerary marker chromosome, and could be a useful method for the genetic diagnosis of epilepsy syndromes associated with various chromosomal aberrations.

Application of Hot Start PCR Method in PCR-based Preimplantation Genetic Diagnosis

PURPOSE: To determine a method to improve the efficacy and accuracy of preimplantation genetic diagnosis (PGD) - polymerase chain reaction (PCR), we compared hot start PCR and conventional multiplex nested PCR. MATERIALS AND METHODS: This study was performed with single lymphocyte isolated from whole blood samples that were obtained from two couples with osteogenesis imperfecta (OI). We proceeded with conventional multiplex nested PCR and hot start PCR in which essential reaction components were physically removed, and we compared the amplification rate, allele dropout rate and nonspecific products. Afterward, we used selective method for PGD. RESULTS: In the two couples, the respective amplification rate were 93.5% and 80.0% using conventional multiplex nested PCR and 95.5% and 92.0% using hot start PCR. The respective mean allele dropout rates for the two couples were 42.0% and 14.0% with conventional multiplex nested PCR and 36.0% and 6.0% with hot start PCR. CONCLUSION: The results demonstrate that the hot start PCR procedure provides higher amplification rates and lower allele dropout rate than the conventional method and that it decreased the nonspecific band in multiplex nested PCR. The hot start method is more efficient for analyzing a single blastomere in clinical PGD.

Reactive oxygen species enhance differentiation of human embryonic stem cells into mesendodermal lineage

Recently, reactive oxygen species (ROS) have been studied as a regulator of differentiation into specific cell types in embryonic stem cells (ESCs). However, ROS role in human ESCs (hESCs) is unknown because mouse ESCs have been used mainly for most studies. Herein we suggest that ROS generation may play a critical role in differentiation of hESCs; ROS enhances differentiation of hESCs into bi-potent mesendodermal cell lineage via ROS-involved signaling pathways. In ROS-inducing conditions, expression of pluripotency markers (Oct4, Tra 1-60, Nanog, and Sox2) of hESCs was decreased, while expression of mesodermal and endodermal markers was increased. Moreover, these differentiation events of hESCs in ROS-inducing conditions were decreased by free radical scavenger treatment. hESC-derived embryoid bodies (EBs) also showed similar differentiation patterns by ROS induction. In ROS-related signaling pathway, some of the MAPKs family members in hESCs were also affected by ROS induction. p38 MAPK and AKT (protein kinases B, PKB) were inactivated significantly by buthionine sulfoximine (BSO) treatment. JNK and ERK phosphorylation levels were increased at early time of BSO treatment but not at late time point. Moreover, MAPKs family-specific inhibitors could prevent the mesendodermal differentiation of hESCs by ROS induction. Our results demonstrate that stemness and differentiation of hESCs can be regulated by environmental factors such as ROS.

Discrepancy in cytogenetic results between amniotic fluid cells and other fetal tissues: A case report / 대한산부인과학회지

We present two fetuses who were prenatally diagnosed by amniocentesis as having chromosomal mosaicism but who had a normal karyotype in the fetal blood by cordocentesis. One of the both fetuses had Turner and the other had trisomy 20 mosaicism. The prognosis for Turner mosaicism and trisomy 20 mosaicism diagnosed prenatally has yet to be established. The pregnancy with 45,X/46,XX mosaicism was terminated at 23+3 weeks' gestation. Autopsy findings showed no features of Turner's syndrome. Postnatal cytogenetic analysis revealed 45,X[4]/46,XX[52] mosaicism in skin and 46,XX in the lung tissue. The other fetus had amniocytes with trisomy 20 mosaicism and fetal cord blood cells with a normal karyotype. The baby was delivered at 38+2 weeks' gestation. At birth and 3 months after birth, no apparent abnormal findings were found. These cases with chromosomal discrepancy among various fetal tissues are rare. Two cases were discussed with the review of literature.

A Cytogenetic Analysis of Abortus with Spontaneous Abortion

PURPOSE: Chromosomal abnormalities of abortuses have been used to investigate common etiologies of spontaneous abortion, but the frequencies and types of spontaneous abortions have demonstrated considerable variation among different countries and races. MATERIALS AND METHODS: A cytogenetic analysis of 75 abortuses was performed at GenDix, Inc. from January 2006 to December 2007. RESULTS: The frequency of chromosome abnormalities in abortuses was 32.0% (24/75 cases). Among the chromosomal abnormalities, trisomy was present in 62.5% (15/24 cases) of cases and the most frequent trisomy was trisomy 21 with an occurrence rate of 26.6% (4/15 cases). The following was trisomy 22 (3/15 cases) and trisomy 20 (2/15 cases). The average maternal age for abnormal karyotypes was 34.3+/-3.3. CONCLUSION: Cytogenetic analysis of abortus is important for diagnosis and genetic counseling of patients with spontaneous abortion.

Midtrimester Amniocentesis for Prenatal Diagnosis

PROPOSE: To analyze the indications and cytogenetic results of midtrimester amniocentesis. MATERIAL AND METHODS: This study reviewed 2,523 cases of midtrimester prenatal genetic amniocentesis performed at MizMedi Hospital between January 2000 and December 2007. RESULTS: The most frequent indication for midtrimester amniocentesis was advanced maternal age (45.9%), followed by positive serum markers (29.9%). Chromosomal aberrations were diagnosed in 110 cases (4.4%), for which numerical aberration accounted for 38 cases (34.5%), structural aberration accounted for 65 cases (59.1%), and mosaicism accounted for 7 cases (6.4%). Among the autosomal aberrations, there were 20 cases of trisomy 21 and 8 cases of trisomy 18. With respect to structural aberrations, there were 14 cases of reciprocal translocation and 8 cases of robertsonian translocation. The frequencies of chromosomal aberrations according to the indication were highest in individuals with a family history of chromosome abnormality 14.0% (8/57) followed by previous congenital anomaly 5.9% (2/34). CONCLUSION: Midtrimester amniocentesis is an effective tool for prenatal diagnosis. Indications such as advanced maternal age, maternal serum markers, and ultrasound are important for predicting abnormal fetal karyotypes.

Use of Long-term Cultured Embryoid Bodies May Enhance Cardiomyocyte Differentiation by BMP2

PURPOSE: Human embryonic stem cells (hESCs) can proliferate for a prolonged period and differentiate into cardiomyocytes in vitro. Recent studies used bone morphogenetic protein 2 (BMP2) to generate cardiomyocytes from hESCs, however, all those studies used early embryoid bodies (EBs) and did not retrieve cardiomyocytes with a high yield. In this study, we treated long-term cultured EBs with BMP2 in order to promote differentiation into cardiomyocytes from hESCs. MATERIALS AND METHODS: hESC lines, including SNUhES3 and SNUhES4, were used in this study. Undifferentiated hESC colonies were detached to form EBs and cultured for up to 30 days. These long-term cultured EBs were differentiated into cardiomyocytes in serum-containing media. In our protocol, BMP2 was applied for 5 days after attachment of EBs. Cardiac specific markers, beating of differentiated cells and electron microscopic (EM) ultrastructures were evaluated and analyzed. RESULTS: Compared to 10-day or 20-day EBs, 30-day EBs showed a higher expression level of cardiac specific markers, Nkx2.5 and a-myosin heavy chain (alphaMHC). Treatment of BMP2 increased expression of cardiac troponin (cTn) I and a-actinin when evaluated at 20 days after attachment of 30-day EBs. Beating of differentiated cells was observed from 7 to 20 days after attachment. Moreover, EM findings demonstrated fine structures such as Z bands in these differentiated cardiomyocytes. These long-term cultured EBs yielded cardiomyocytes with an efficiency of as high as 73.6% when assessed by FACS. CONCLUSION: We demonstrated that the use of long-term cultured EBs may enhance differentiation into cardiomyocytes from hESCs when treated with BMP2.

Alterations of proliferative and differentiation potentials of human embryonic stem cells during long-term culture

Human embryonic stem cells (hESCs) are considered to be able to stably maintain their characteristics in vitro for prolonged periods, but we had previously encountered changes in proliferative ability and differentiation potential during extended culture of hESCs. Therefore, we investigated the proliferative ability and differentiation potential of hESCs during long-term culture. The hESCs, SNUhES3, were used to analyze population-doubling time, proliferation rate and differentiation potential. We classified hESCs into three groups according to culture period. Ten colonies of hESCs for each group were daily measured colony area and population-doubling time was assessed by the changes of colony area. Proliferation rate of hESCs was measured by 5-bromo-2'-deoxyuridine (BrdU) assay and telomerase activity. To evaluate differentiation potentials for hESCs, expression levels of undifferentiated and/or differentiated hESCs markers were examined by FACS, RT-PCR and immunostaining. Population-doubling time of early passage hESCs was longer than those of middle or late passage. Proliferative ability of hESCs was accelerated depending on culture periods. Cellular morphologies and the expression level of each three germ layer markers were obviously different from each passage of reattached embryoid bodies (EBs) after spontaneous differentiation. Differentiated cells of late passage expressed higher levels of undifferentiated markers such as Oct4 and SSEA4 than those of early and middle passage. But differentiated cells of early and middle passage expressed higher level of differentiated state markers, Nestin (ectoderm), Brachyury (mesoderm), HNF3beta (endoderm). From these results, it can be inferred that hESCs show higher proliferative abilities and reduced differentiation potentials as the passage number increased. Therefore, we conclude that early passage hESCs could be more suitable than middle and late passage hESCs in differentiation studies.

Simplified EM Grid Vitrification Is a Convenient and Efficient Method for Mouse Mature Oocyte Cryopreservation

This study was performed to evaluate the efficiency of simplified EM grid vitrification, skipping the step of removing the cryoprotectant (5.5M EG + 1.0M sucrose) droplet on the grid after loading oocytes, compared to conventional cryopreservation protocols for mouse mature oocytes. Firstly, the recovery, survival, fertilization and hatching rates of simplified EM grid vitrification were compared with those of the slow freezing method using 1.5M DMSO. Then, conventional EM grid vitrification was compared with simplified EM grid vitrification. Simplified EM grid vitrification showed higher survival, fertilization and hatching rates than those of the slow freezing method (85.6% vs. 63.2%; 51.0% vs. 22.3%; 38.7% vs. 12.5%, p < 0.01, respectively). Moreover, simplified EM grid vitrification showed higher recovery, survival and fertilization rates than those of conventional EM grid vitrification (100% vs. 95.0%, p=0.024; 90.0% vs. 78.9%, p=0.033; 56.7% vs. 38.7%, p=0.021, respectively). Hatching rate tended to be higher for simplified EM grid vitrification compared to conventional EM grid vitrification (41.1% vs. 24.1%). In conclusion, simplified EM grid vitrification is a convenient and efficient method for cryopreservation of mouse mature oocytes, compared to conventional EM grid vitrification and slow freezing methods.

Erratum: Efficient gene delivery in differentiated human embryonic stem cells. Exp Mol Med 2005;37:36-44

The authors would like to amend a reference (Lee et al., 2003) that was cited in "Cell culture" section of "Materials and Methods". Instead of "(Lee et al., 2003)", we would like to change the reference to "(Kim et al., 2003)". In "References", it also needs to include the following reference. Kim YY, Seol HW, Ahn HJ. Temporal expression of differentiation markers in embryoid bodies from various human embryonic stem cell line. International Society for Stem Cell Research 1st Annual Meeting, Washington, DC. U.S.A. June 8-11, 2003, Abstract No. 35. The authors apologize for any inconvenience.

Efficient gene delivery in differentiated human embryonic stem cells

Human embryonic stem (hES) cells are capable of differentiating into pluralistic cell types, however, spontaneous differentiation generally gives rise to a limited number of specific differentiated cell types and a large degree of cell heterogeneity. In an effort to increase the efficiency of specified hES cell differentiation, we performed a series of transient transfection of hES cells with EGFP expression vectors driven by different promoter systems, including human cellular polypeptide chain elongation factor 1 alpha (hEF1alpha), human cytomegalo-virus, and chicken beta-actin. All these promoters were found to lead reporter gene expression in undifferentiated hES cells, but very few drug-selectable transfectants were obtained and failed to maintain stable expression of the transgene with either chemical or electroporation methods. In an attempt to increase transfection efficiency and obtain stable transgene expression, differentiated hES cells expressing both mesodermal and ectodermal markers were derived using a defined medium. Differentiated hES cells were electroporated with a hEF1alpha promoter-driven EGFP or human noggin expression vector. Using RT-PCR, immunocytochemistry and fluorescence microscopy, the differentiated hES cells transfected with foreign genes were confirmed to retain stable gene and protein expression during prolonged culture. These results may provide a new tool for introducing exogenous genes readily into hES cells, thereby facilitating more directed differentiation into specific and homogenous cell populations.

Human Amniotic Fluid Cells Support Expansion Culture of Human Embryonic Stem Cells / 대한불임학회지

OBJECTIVE: This study was performed to evaluate the possibility of prolonged culture of human embryonic stem cells (hESC; SNUhES2) on human amniotic fluid cells (hAFC), which had been storaged after karyotyping. METHOD: The hAFC was prepared for feeder layer in the presence of Chang's medium and STO medium (90% DMEM, 10% FBS) at 37degrees C in a 5% CO2 in air atmosphere. Prior to use as a feeder layer, hAFC was mitotically inactivated by mitomycin C. The hESCs on hAFC were passaged mechanically every seven days with ES culture medium (80% DMEM/F12, 20% SR, bFGF). RESULTS: The hAFC feeder layer support the growth of undifferentiated state of SNUhES2 for at least 59 passages thus far. SNUhES2 colonies on hAFC feeder appeared slightly angular and flatter shape as compared with circular and thicker colonies observed with STO feeder layer and showed higher level with complete undifferentiation in seven days. Like hESC cultured on STO feeders, SNUhES2 grown on hAFC expressed normal karyotype, positive for alkaline phosphatase activity, high telomerase activity, Oct-4, SSEA-3, SSEA-4, Tra-1-60 and Tra-1-81 and formed embryoid bodies (EBs). CONCLUSION: The hAFC supports undifferentiated growth of hESC. Therefore, these results may help to provide a clinically practicable method for expansion of hESC for cell therapies.

Prenatal Aneuploidy Detection in Uncultured Amniotic Fluid Interphase Cells by Fluorescence in situ Hybridization (FISH) / 대한불임학회지

OBJECTIVE: The aim of the present study was to evaluate the clinical efficiency of fluorescent in situ hybridization (FISH) in the prenatal diagnosis of chromosomal aneuploidy. METHODS: We reviewed data of 268 cases to identify women undergoing genetic amniocentesis at cytogenetic laboratory, from January 2000 to December 2002. Amniotic fluid was submitted for both rapid FISH on uncultured interphase amniocytes using a commercially available DNA probe for chromosome 13, 18, 21, X, Y and standard karyotyping on cultured metaphase amniocytes. Results from FISH and full karyotype were compared. RESULTS: There were 251 cases (84%) normal and 17 cases (16%) abnormal in FISH results. All 17 cases of trisomy 13, 18, 21 including two cases of mosaicism and sex chromosome aneuploidies which are detected by FISH were confirmed with conventional cytogenetics and there was no false positive result. Twenty two cases had karyotypically proven abnormalities that could not have been detected by the targeted FISH. CONCLUSION: Interphase FISH analysis of uncultured amniotic fluid cells has been shown to be an effective and reliable technique for rapid fetal aneuploidy screening during pregnancy as an adjunctive test to conventional cytogenetics.

The Study on Comparison of Clinical Outcomes of Intracytoplasmic Sperm Injection in Patients with Epididymal Sperm and Testicular Sperm / 대한불임학회지

OBJECTIVE: This study was carried out to compare the clinical outcomes of intracytoplasmic sperm injection (ICSI) in patients with obstructive azoospermia according to sperm retrieval site and technique; microsurgical epididymal sperm aspiration (MESA), percutaneous epididymal sperm aspiration (PESA), testicular sperm extraction by open biopsy (TESE). METHODS: The outcomes of ICSI and IVF-ET were evaluated and compared among 3 groups. Seventy three men suffering from infertility due to obstructive azoospermia had 107 ICSI cycles using MESA (21 cycles in 15 patients), PESA (26 cycles in 17 patients) and TESE (60 cycles in 41 patients). RESULTS: In the clinical outcomes in patients undergoing ICSI with epididymal or testicular sperm, there were no significant differences in fertilization rate (66.1% vs. 60.5%), cleavage rate (94.9% vs. 97.6%), cumulative embryo score (CES) (51.3 vs. 58.8), implantation rate (7.9% vs. 6.1), and clinical pregnancy rate per ET (30.4% (14/46) vs. 25.4% (15/59)) between both groups. Also, in the clinical outcomes in ICSI patients using MESA, PESA, TESE, there were no significant differences in fertilization rate (61.8%, 69.4%, 60.5%), cleavage rate (92.1%, 97.3%, 97.6%), CES (38.1, 52.0, 58.8), implantation rate (9.5%, 6.6%, 6.1%), and clinical pregnancy rate per ET (35% (7/20), 26.9% (7/26), 25.4% (15/59)) among 3 groups. CONCLUSION: When compared with MESA or TESE, PESA, the clinical outcomes were similar in ICSI patients with obstructive azoospermia whatever the origin or the technique of sperm retrieval. However, we considered PESA is more time-saving and cost effective for ICSI in patients with obstructive azoospermia.

The Study on Comparison of Clinical Outcomes of Intracytoplasmic Sperm Injection in Patients with Epididymal Sperm and Testicular Sperm / 대한불임학회지

OBJECTIVE: This study was carried out to compare the clinical outcomes of intracytoplasmic sperm injection (ICSI) in patients with obstructive azoospermia according to sperm retrieval site and technique; microsurgical epididymal sperm aspiration (MESA), percutaneous epididymal sperm aspiration (PESA), testicular sperm extraction by open biopsy (TESE). METHODS: The outcomes of ICSI and IVF-ET were evaluated and compared among 3 groups. Seventy three men suffering from infertility due to obstructive azoospermia had 107 ICSI cycles using MESA (21 cycles in 15 patients), PESA (26 cycles in 17 patients) and TESE (60 cycles in 41 patients). RESULTS: In the clinical outcomes in patients undergoing ICSI with epididymal or testicular sperm, there were no significant differences in fertilization rate (66.1% vs. 60.5%), cleavage rate (94.9% vs. 97.6%), cumulative embryo score (CES) (51.3 vs. 58.8), implantation rate (7.9% vs. 6.1), and clinical pregnancy rate per ET (30.4% (14/46) vs. 25.4% (15/59)) between both groups. Also, in the clinical outcomes in ICSI patients using MESA, PESA, TESE, there were no significant differences in fertilization rate (61.8%, 69.4%, 60.5%), cleavage rate (92.1%, 97.3%, 97.6%), CES (38.1, 52.0, 58.8), implantation rate (9.5%, 6.6%, 6.1%), and clinical pregnancy rate per ET (35% (7/20), 26.9% (7/26), 25.4% (15/59)) among 3 groups. CONCLUSION: When compared with MESA or TESE, PESA, the clinical outcomes were similar in ICSI patients with obstructive azoospermia whatever the origin or the technique of sperm retrieval. However, we considered PESA is more time-saving and cost effective for ICSI in patients with obstructive azoospermia.

Fragile X Premutation in Patients with Idiopathic Premature Ovarian Failure / 대한산부인과학회잡지

OBJECTIVE: To explore the incidence of fragile X premutation in patients with idiopathic premature ovarian failure, particularly in the Korean population. DESIGN: A prospective study. MATERIALS AND METHODS: Eighty-three women affected by idiopathic premature ovarian failure were recruited for this study. Patient with known causes of premature ovarian failure were excluded: cytogenetic abnormalities, prior chemotherapy, prior bilateral oophorectomy. DNA was extracted from peripheral blood. Fragile X (FRAXA) premutation was evaluated by PCR amplification of and Southern blot analysis for FMR1 gene. RESULTS: The FRAXA premutation was detected in three (3.6%) out of 83 patients with idiopathic premature ovarian failure. CONCLUSION: This result suggests that fragile X premutation screening is indicated in patients with idiopathic premature ovarian failure, particularly in the Korean population.

MHC Expression in Human Embryonic Stem Cells and Embryoid Bodies / 대한이식학회지

PURPOSE: Human embryonic stem (ES) cell is pluripotent cell derived from a group of cells called the inner cell mass and has the ability to reproduce itself for long periods and give rise to types of cells that develop from the three germ layers. Due to its pluripotency, ES cell holds the promise of being able to replace cells that are damaged or destroyed by many devastating diseases. However, the potential for the recipient of an ES cell transplant to reject this cell as foreign is very high. Thus, it is essential to determine whether human ES cells express MHC antigens. The purpose of this study is to characterize the stem cell properties of our cell line (SNUhES1) and the expression profile of MHC antigens on the surface of these cells and their differentiated derivatives, embryoid bodies (EBs). METHODS: The ES cells were grown on STO fibroblast in DMEM-F12. The EBs were grown in the same medium with exception that it lacked LIF and bFGF. The expression of self-renewal-associated genes and three germ layer cell-specific genes in ES cells and EBs were measured by RT-PCR at varying time point of incubation (1, 7, 14 and 28 day). The expression of MHC molecules were measured by RT-PCR and FACS analysis. RESULTS: The SNUhES1 cells expressed all self-renewal- associated genes (Fgf4, FoxD3, Oct4, Sox2 and TERT) we tested. During the differentiation three germ layer cell-specific genes in EBs were expressed as following order: ecto-, meso- and endodermal cell-specific genes. MHC class I proteins (HLA-ABC and beta2m) on the surfaces of ES cells and EBs were expressed in very low levels. MHC class II proteins (HLA-DP, -DQ and -DR) and HLA-G were not expressed on the surface of these cells. However, the expression of MHC class II proteins were detected in 1% more or less cells of 28-day-old EBs which were hardly detected in the population of 1-day-old EBs. CONCLUSION: These data imply that SNUhES1 cells and EBs have stem cell properties. Although they express very low MHC antigens, further investigation determining whether the MHC expression in the ES cells and EBs may alter under inflammatory condition which can be occurred in damaged tissue or through surgical process.