Synergistic Promoting Effects of X-Linked Inhibitor of Apoptosis Protein and Matrix on the In Vitro Follicular Maturation of Marmoset Follicles

BACKGROUND@#In Vitro follicular maturation (IVFM) of ovarian follicles is an emerging option for fertility preservation. Many paracrine factors and two-dimensional or three-dimensional (3D) environments have been used for optimization. However, since most studies were conducted using the murine model, the physiological differences between mice and humans limit the interpretation and adaptation of the results. Marmoset monkey is a non-human primate (NHPs) with more similar reproductive physiology to humans. In this study, we attempted to establish a 3D matrix (Matrtigel)-based IVFM condition for marmoset ovarian follicles in combination with anti-apoptotic factor, X-linked inhibitor of apoptosis protein (XIAP). @*METHODS@#Marmoset follicles were isolated as individual follicles and cultured in a single drop with the addition of 0, 10, and 100 lg/mL of XIAP molecules. Matured oocytes and granulosa cells from mature follicles were collected and analyzed. The average number of isolated follicles was less than 100, and primordial and antral follicles were abundant in the ovaries. @*RESULTS@#IVFM of marmoset follicles in 3D matrix conditions with XIAP increased the rates of survival and In Vitro follicle development. Furthermore, oocytes from the 3D cultures were successfully fertilized and developed In Vitro. The addition of XIAP increased the secretion of estradiol and aromatase. Furthermore, expression of granulosa-specific genes, such as bone morphogenetic protein 15, Oct4, and follicle-stimulating hormone receptor were upregulated in the In Vitro-matured follicles than in normal, well-grown, and atretic follicles. Apoptosis-related B-cell lymphoma-2 was highly expressed in the atretic follicles than in the XIAP-treated follicles, and higher caspase-3 was localized in the XIAP-treated follicles. @*CONCLUSION@#In this study, we attempted to establish a 3D-matrix-based marmoset IVFM condition and demonstrated the synergistic effects of XIAP. The use of a 3D matrix may be applied as an optimal culture condition for marmoset ovarian follicles.

Autologous Retinal Flap Transplantation of a Refractory Giant Macular Hole with Retinal Detachment

Purpose@#A giant macular hole with retinal detachment occurred in a patient who had undergone several surgical treatments for retinal detachment, macular hole, and complicated cataracts. Here we report a case of successful retinal attachment and macular hole closure for this patient after autologous retinal flap transplantation.Case summary: Recently, an 18-year-old female presented with a newly developed visual field disturbance in her left eye. She had been on medication for severe atopic dermatitis in the past and seven years ago underwent scleral buckling, pars plana vitrectomy, and complicated cataract surgery due to rhegmatogenous retinal detachment of the left eye. Five years ago, extensive internal limiting membrane peeling, intravitreal gas tamponade, and aftercataract removal were performed due to the development of a macular hole with retinal detachment of the left eye. Thereafter, although the retina was reattached, closure of the macular hole was not successful. Recently, a giant macular hole with a retinal detachment was detected in this patient accompanied by symptoms of visual disturbance. Autologous retinal flap transplantation and intravitreal silicone oil tamponade were performed. Two months after the operation, she underwent silicone oil removal. Successful closure of the macular hole and retinal reattachment were confirmed. @*Conclusions@#In a patient with a refractory giant macular hole with retinal detachment, the closure of the hole and retinal reattachment were successfully achieved after retinal flap transplantation, without viscoelastics or perfluorocarbon liquid.

Effect of Hydrogen Sulfide on the Oxidative Stress and Senescence inTrabecular Meshwork Cells

Purpose@#To investigate the effects of hydrogen sulfide (H2S) on the senescence and oxidative stress of cultured human trabecularmeshwork cells (HTMCs). @*Methods@#After inducing oxidative stress with 200 μM hydrogen peroxide (H2O2), primary cultured HTMCs were exposed to 0, 50,and 100 μM sodium hydrogen sulfide (NaHS) for 24 hours. Cell survival and senescence were measured using an MTT assayand SA-β-galactosidase staining, respectively. Generation of reactive oxygen species (ROS) and superoxide were measuredusing the dichlorofluorescein assay and modified cytochrome c assay. Production of nitric oxide (NO) and expression of eNOSmRNA were assessed using the Griess assay and reverse polymerase chain reaction. @*Results@#Cell survival was not affected by 200 μM H2O2. Exposure to 50 and 100 μM NaHS significantly decreased cellular senescence,compared with the H2O2-exposed control. Exposure to 50 and 100 μM NaHS decreased the generation of ROS, andexposure to 100 μM NaHS decreased the generation of superoxide. Treatment with 100 μM NaHS increased the production ofNO and expression of eNOS mRNA, respectively. @*Conclusions@#NaHS decreased the cellular senescence associated with the decreased generation of free radicals. Thus, H2Scould inhibit the senescence of HTMCs by reducing oxidative stress.

Modulatory Effects of Single and Complex Vitamins on the In Vitro Growth of Murine Ovarian Follicles

BACKGROUND: Vitamin is a well-known co-factor for many metabolic processes and its roles in fertility and follicular growth have been studied. Vitamin supplementation is frequently achieved by daily ingestion in the form of a complex capsule. However, the role of single and complex vitamins in in vitro maturation of murine follicles is not fully elucidated. METHODS: In this study, we evaluated the effects of two forms of vitamins. Pure L-ascorbic acid, and multi-vitamin (vitamin C+vitamin B complex) was treated at two different concentrations (50 and 100 µg/ml), to pre-puberty murine follicles during in vitro maturation. To determine the specific stage of growth that is affected by treatment with vitamins, the vitamins were treated from day 0, 4, 9, and 13. Growth of each follicle was assessed by measuring diameters of whole expanded area and of the granulosa cells. Expression of follicular and oocyte growth-related genes and the effect of vitamin on the viability of follicles was assessed using senescence associated β-galactosidase staining. RESULTS: Treatment with vitamins promoted the in vitro growth of murine follicles and the upregulated the expression of granulosa cell- and oocyte-specific genes such as BMP15, Fsh receptor, and GDF9. The proliferation of the granulosa cells was enhanced by the treatment of vitamin. Fifty µg/ml concentration vitamin showed greater effects compared to higher concentration. The viability of in vitro grown follicles was also significantly improved in vitamin-treated follicles. The effects of single L-ascorbic acid and complex vitamin were not significantly different to those of day 4 and day 9 follicles. Vitamins promoted murine follicle development in vitro with different effects on specific growth stage. CONCLUSION: Supplementation of vitamins during in vitro maturation of murine follicles is an efficient strategy for in vitro expansion of follicular cells. These results could be customized to the sophisticated culture of follicles retrieved from aged or cancer-survived female that contain smaller number of follicles with reduced potential to develop into mature follicles.

Efficient Production of Murine Uterine Damage Model

BACKGROUND: Thin or damaged endometrium causes uterine factor-derived infertility resulting in a failure of embryonic implantation. Regeneration of endometrium is a major issue in gynecology and reproductive medicine. Various types of cells and scaffolds were studied to establish an effective therapeutic strategy. For this type of investigations, production of optimal animal models is indispensable. In this study, we tried to establish various murine uterine damage models and compared their features. METHODS: Three to ten-week-old C57BL/6 female mice were anesthetized using isoflurane. Chemical and mechanical methods using ethanol (EtOH) at 70 or 100% and copper scraper were compared to determine the most efficient condition. Damage of uterine tissue was induced either by vaginal or dorsal surgical approach. After 7-10 days, gross and microscopic morphology, safety and efficiency were compared among the groups. RESULTS: Both chemical and mechanical methods resulted in thinner endometrium and reduced number of glands. Gross morphology assessment revealed that the damaged regions of uteri showed various shapes including shrinkage or cystic dilatation of uterine horns. The duration of anesthesia significantly affected recovery after procedure. Uterine damage was most effectively induced by dorsal approach using 100% EtOH treatment compared to mechanical methods. CONCLUSION: Taken together, murine uterine damage models were most successfully established by chemical treatment. This production protocols could be applied further to larger animals such as non-human primate.

Proliferation Profile of Uterine Endometrial Stromal Cells during In Vitro Culture with Gonadotropins: Recombinant versus Urinary Follicle Stimulating Hormone

BACKGROUND: Provision of optimal endometrial stromal cells is essential in uterine tissue engineering. Culture of these cells is significantly influenced by gonadotropin hormones. This investigation attempted to define the proliferation profiles of murine uterine endometrial stromal cells during in vitro culture with recombinant follicle stimulating hormone (rFSH), urinary follicle stimulating hormone (uFSH), and human chorionic gonadotropin (hCG). METHODS: Murine uterine endometrial stromal cells were collected from 8-week-old mice and cultured in vitro up to 72 h, with rFSH, uFSH, or hCG. Cell cycles were analyzed by BrdU assay, and cyclin D1 expression was evaluated according to dose and duration of gonadotropin treatment. RESULTS: BrdU assay showed a further inhibitory effect on murine uterine endometrial stromal cell proliferation when cultured with rFSH compared to uFSH, and a similar inhibitory proliferation profile when cultured with hCG at a specific range of concentrations. The expression of cyclin D1 of murine uterine endometrial stromal cells was down-regulated when cultured with rFSH, uFSH, or hCG, compared to control. CONCLUSIONS: FSH may inhibit the proliferation of murine uterine endometrial stromal cells during in vitro culture. rFSH may have more significant inhibitory effects on the proliferation of endometrial stromal cells than uFSH. Establishing an optimal endocrine milieu is necessary using more advanced combination of female hormones for in vitro culture of this type of cells.

The Use of Normal Stem Cells and Cancer Stem Cells for Potential Anti-Cancer Therapeutic Strategy

BACKGROUND: Despite recent advance in conventional cancer therapies including surgery, radiotherapy, chemotherapy, and immunotherapy to reduce tumor size, unfortunately cancer mortality and metastatic cancer incidence remain high. Along with a deeper understanding of stem cell biology, cancer stem cell (CSC) is important in targeted cancer therapy. Herein, we review representative patents using not only normal stem cells as therapeutics themselves or delivery vehicles, but also CSCs as targets for anti-cancer strategy. METHODS: Relevant patent literatures published between 2005 and 2017 are discussed to present developmental status and experimental results on using normal stem cells and CSCs for cancer therapy and explore potential future directions in this field. RESULTS: Stem cells have been considered as important element of regenerative therapy by promoting tissue regeneration. Particularly, there is a growing trend to use stem cells as a target drug-delivery system to reduce undesirable side effects in non-target tissues. Noteworthy, studies on CSC-specific markers for distinguishing CSCs from normal stem cells and mature cancer cells have been conducted as a selective anti-cancer therapy with few side effects. Many researchers have also reported the development of various substances with anticancer effects by targeting CSCs from cancer tissues. CONCLUSION: There has been a continuing increase in the number of studies on therapeutic stem cells and CSC-specific markers for selective diagnosis and therapy of cancer. This review focuses on the current status in the use of normal stem cells and CSCs for targeted cancer therapy. Future direction is also proposed.

Profile of MicroRNA Expression in Endometrial Cell during In Vitro Culture According to Progesterone Concentration

Artificial uterus using endometrium implant can be a novel treatment strategy for infertile women with refractory endometrial dysfunction. At early pregnancy, the function of uterine endometrial cells for the communication between the conceptus of pre-implantation period and maternal reproductive system is essential. MicroRNA (miR) expression profile of endometrial cells according to progesterone, a crucial pregnancy-maintaining hormone, provides important data for in vitro endometrial cell culture strategy that is useful for engineering artificial uteri using endometrial implants. The present study aimed to evaluate the miR expression profile of in vitro cultured endometrial cells under hormonal milieu mimicking early pregnancy period in terms of progesterone concentration. We cultured murine uterine endometrial cells, human uterine endometrial carcinoma cells, and immortalized human uterine endometrial cells using different progesterone concentrations, and analyzed the expression of miRs critical for early pregnancy. The expression of miR-20a, -21, -196a, -199a, and -200a was differently regulated according to progesterone concentration in different endometrial cell lines. The analysis of candidate target genes showed that the expression of phosphatase and tensin homolog, mucin 1 (MUC1), progesterone receptor, transforming growth factor β receptor II, matrix metallopeptidase-9 was up-regulated by progesterone treatment in mouse and human endometrial cell lines. These results indicate that physiological concentration range (10⁻⁷ and 10⁻⁹ M) of progesterone affect the survival and target gene expression via modulating miR expression. Taken together, progesterone can be a crucial factor in regulating miR expression on in vitro cultured endometrial cells.

Differential MicroRNA Expression Profile of Human Embryonic Stem Cell-Derived Cardiac Lineage Cells

MicroRNAs (miRNAs) are small non-coding RNA molecules that participate in transcriptional and post-transcriptional regulation of gene expression. miRNAs have numerous roles in cellular function including embryonic development. Human embryonic stem cells (hESCs) are capable of self-renewal and can differentiate into most of cell types including cardiomyocytes (CMs). These characteristics of hESCs make them considered as an important model for studying human embryonic development and tissue specific differentiation. In this study, we tried to demonstrate the profile of miRNA expression in cardiac differentiation from hESCs. To induce differentiation, we differentiated hESCs into CMs by direct differentiation method and characterized differentiated cells. To analyze the expression of miRNAs, we distinguished (days 4, 8, 12, 16, 20, 24, 28) and isolated RNAs from each differentiation stage. miRNA specific RT-qPCR was performed and the expression profile of miR-1, -30d, -133a, -143, -145, -378a, -499a was evaluated. The expression of all miRs was up-regulated at day 8. miR-143 and -145 expression was also up-regulated at the later stage of differentiation. Only miR-378a expression returned to undifferentiated hESC levels at the other stages of differentiation. In conclusion, we elucidated the expression profile of miRNAs during differentiation into cardiomyocytes from hESCs. Our findings demonstrate the expression of miRNAs was stage-dependent during differentiation and suggest that the differentiation into CMs can be regulated by miRNAs through direct or indirect pathway.

Effects of Estradiol on the Paracrine Regulator Expression of In Vitro Maturated Murine Ovarian Follicles

The preservation of female germ cells is important in the individuals with ovarian dysfunction and failure. For this purpose, ovarian follicle in vitro maturation (OFIVM) is an important technology for the retrieval of mature oocytes. In the in vivo follicular development, paracrine factors such as angiotensin (AT) and anti-Müllerian hormone (AMH) play important roles. We attempted to add estrogen during the OFIVM and to assess their expression on the follicular cells. The ovaries and pre-antral follicles were collected from 13-day C57BL/6 mice and cultured in vitro with estradiol (E₂) treatment for up to two weeks. In the whole ovaries, the expression of AT II was decreased and the expression of AMH was similar between control and E₂-treated ovaries after in vitro culture. Although there was no difference in the survival, ovulation, maturation and fertilization rates between control and E₂-treated groups, the expression of AT II in the follicular cells was down-regulated after E₂ treatment at mRNA level, and AMH showed similar expression. In conclusion, adding E₂ in OFIVM may regulate paracrine factors and their receptors that are related to follicular development. Further investigations are necessary to elucidate the roles of various sex hormones in the regulation of AT and AMH expression during the OFIVM.

Effects of Estrogen on Intracellular Calcium-Related T-Lymphocyte Function

Regulation of immune cell function is an important in the field of hormone-related tissue engineering and regenerative medicine. In this sense, hormonal regulation of immune cell function is a critical issue to be solved. It has been known that ovarian sex hormone play an important roles in immune function, however, little has been known whether estrogen affects T-lymphocyte function. Human Jurkat T cells were treated with estradiol (E₂) at concentrations of 0, 10, 100, 1000 ng/mL, and calcium response was evaluated. Intracellular calcium concentrations after Fura-2 acetoxymethyl ester treatment show an increasing trend at higher E₂ concentrations although these alterations did not reach a statistical significance. The expression of calcium channel-related gene CACNA1C did not show any significant changes according to the concentration of E₂. Taken together, estrogen has an implication as a possible hormonal regulator of intracellular calcium release in human Jurkat T cells via non-genomic pathway. Further studies are necessary to investigate the combined effects of sex hormones and cytokines in both T- and B-lymphocytes.

Use of Nonhuman Primates for the Development of Bioengineered Female Reproductive Organs

Nonhuman primates (NHPs) have been widely used in reproductive biology, neuroscience, and drug development since a number of primate species are phylogenetically close to humans. In this review, we summarize the use of NHPs for nonclinical application in the reproductive system disorders including the loss or failure of an organ or tissue. Causes of infertility include congenital aplasia and acquired disorders of the reproductive organs. In addition, anti-cancer treatments can deplete ovarian follicles, leading to premature ovarian failure, infertility and long-term health risks. Along with a limited supply of human reproductive organs, anatomic/physiologic similarities to humans support the need for NHP models (New-World monkeys such as the common marmoset and Old-World monkeys such as cynomolgus and rhesus monkeys) to promote the advances in female infertility studies. For maintaining and executing animal studies using NHP, special protocols including animal care, anesthetic protocol, surgical technique, and immunosuppressive protocol are necessary. With a growing interest in the potential therapies such as endometrial tissue engineering, and ovary/follicle cryopreservation and grafting in Korea, this review can be useful in selecting appropriate animal models and can bridge between nonclinical studies and clinical applications by providing detailed information on the use of NHPs in the field of reproductive organ disorders.

Efficient Biomaterials for Tissue Engineering of Female Reproductive Organs

Current investigations on the bioengineering of female reproductive tissues have created new hopes for the women suffering from reproductive organ failure including congenital anomaly of the female reproductive tract or serious injuries. There are many surgically restore forms that constitute congenital anomaly, however, to date, there is no treatment except surgical treatment of transplantation for patients who are suffering from anomaly or dysfunction organs like vagina and uterus. Restoring and maintaining the normal function of ovary and uterus require the establishment of biological substitutes that can cover the roles of structural support for cells and passage of secreting molecules. As in the case of constructing other functional organs, reproductive organ manufacturing also needs biological matrices which can provide an appropriate condition for attachment, growth, proliferation and signaling of various kinds of grafted cells. Among the organs, uterus needs special features such as plasticity due to their amazing changes in volume when they are in the state of pregnancy. Although numerous natural and synthetic biomaterials are still at the experimental stage, some biomaterials have already been evaluated their efficacy for the reconstruction of female reproductive tissues. In this review, all the biomaterials cited in recent literature that have ever been used and that have a potential for the tissue engineering of female reproductive organs were reviewed, especially focused on bioengineered ovary and uterus.

The Expression Profile of Angiotensin System on Thawed Murine Ovaries

Freezing and thawing is one of the most widely used tissue engineering techniques for the preservation of ovaries. Many cells and tissues demonstrate changes in functional gene expression after thawing. Several studies have reported the important roles of angiotensin (AT) system during the ovarian follicular growth. AT system consists of ATII, and ATII receptors type I (ATII-RI) and type II (ATII-RII). However, little is known whether frozen-thawed ovaries show any alteration of AT system member gene expression when treated with survival-enhancing factors. We aimed to investigate whether mass freezing and thawing with or without the use of Rho-associated kinase (ROCK) inhibitors up- or down-regulate the expression of ATII, ATII-RI, and ATII-RII genes on frozen-thawed ovarian tissues. Significant changes in the expression of ATII, ATII-RI, and ATII-RII genes were observed on thawed ovaries when compared to fresh control. The treatment with ROCK inhibitors did not significantly alter their expression. In conclusion, freezing and thawing of ovarian tissue may affect the mRNA expression levels of intra-ovarian AT system genes, and modulation of ROCK inhibitor activity may not regulate AT system on the frozenthawed ovarian tissue.

Implant esthetic restoration with bone graft in the extended maxillary anterior area: A case report / 대한치과보철학회지

The maxillary anteriors play an important role in esthetics. Therefore after extraction, it is crucial to preserve the hard tissue and soft tissue in order to promote esthetics of restoration. There are several challenges when restoring the maxillary anteriors via implant. Some of the challenges are be maintaining consistency with neighboring teeth in terms of shade, form, and texture : as well as having harmonious emergency with the gingival margin. In this case, a traumatized patient with crown-root fracture of the maxillary central and lateral incisors is presented. The cracked teeth were extracted, and implants were inserted with bone grafts to compensate the volume of damaged area of the maxillary anterior. Cantilever implant prosthetics were planned while precise adjustments to the gingival area were made using customized impression coping to perform the esthetic restorations. The final outcome of the treatment was satisfying in both esthetic and utilitarian perspective.

Implant esthetic restoration with bone graft in the extended maxillary anterior area: A case report / 대한치과보철학회지

The maxillary anteriors play an important role in esthetics. Therefore after extraction, it is crucial to preserve the hard tissue and soft tissue in order to promote esthetics of restoration. There are several challenges when restoring the maxillary anteriors via implant. Some of the challenges are be maintaining consistency with neighboring teeth in terms of shade, form, and texture : as well as having harmonious emergency with the gingival margin. In this case, a traumatized patient with crown-root fracture of the maxillary central and lateral incisors is presented. The cracked teeth were extracted, and implants were inserted with bone grafts to compensate the volume of damaged area of the maxillary anterior. Cantilever implant prosthetics were planned while precise adjustments to the gingival area were made using customized impression coping to perform the esthetic restorations. The final outcome of the treatment was satisfying in both esthetic and utilitarian perspective.

Secondary Choroidal Lymphoma Associated with Systemic Choroidal Lymphoma

PURPOSE: To report a case of secondary choroidal lymphoma. CASE SUMMARY: A 57-year-old female presented at our clinic with decreased vision in her right eye 1 month in duration. Slit-lamp examination showed vitreous cells in the right eye. Fundus examination of the right eye revealed an elevated yellowish mass-like lesion at the temporal area and multifocal yellowish patches at the choroidal level. The clinical impression was intraocular lymphoma. We performed diagnostic vitrectomy, but the result was negative. A systemic evaluation revealed enlarged cervical lymph nodes and lymph node biopsy showed diffuse large B-cell lymphoma. The patient was diagnosed as secondary choroidal lymphoma associated with systemic lymphoma and was treated with systemic chemotherapy and 4 injections of intravitreal methotrexate. The patient is scheduled for regular follow-ups. CONCLUSIONS: Choroidal mass may be the initial presenting sign of systemic lymphoma, and an extensive systemic evaluation should be performed.

Full mouth rehabilitation of fully edentulous patient using implant hybrid prosthesis / 대한치과보철학회지

Loss of teeth may not only imply impaired oral function and loss of alveolar bone but is also often accompanied by reduced self-confidence. This results in a larger problem with the fully edentulous patient. The patient introduced in this study showed multiple missing teeth and mobility of remaining teeth and wanted to have fixed dental prosthesis using implants. Remaining teeth were extracted because of periodontally bad prognosis. This article reports a satisfactory clinical and esthetic outcome of full mouth rehabilitation using implant hybrid prosthesis in fully edentulous patient.

The Effect of Gas Tamponade with Vitrectomy in Lamellar Macular Hole

PURPOSE: To investigate the effect of gas tamponade with vitrectomy for lamellar macular hole. METHODS: This study included 18 eyes of 18 patients with lamellar macular hole who reported visual acuity loss or distorted vision. All patients underwent vitrectomy, epiretinal membrane removal and internal limiting membrane peeling. Intravitreal gas tamponade was performed only in 8 eyes of 8 patients. The patients were divided into 2 groups: 8 eyes in the gas tamponade with vitrectomy group and 10 eyes that did not receive gas tamponade in the control group. The best-corrected visual acuity (BCVA) and appearance based on optical coherence tomography (OCT) were obtained retrospectively. RESULTS: Epiretinal membranes were observed in all cases. Average visual acuity of the gas tamponade group improved from log MAR 0.50 +/- 0.24 to log MAR 0.25 +/- 0.14 (p = 0.041). In the control group, average visual acuity improved from log MAR 0.53 +/- 0.36 to log MAR 0.32 +/- 0.28 (p = 0.041), however, no significant difference was observed in visual acuity between the 2 groups (p = 0.584). Anatomical closure or normalized foveal contour after surgery was confirmed in 6 of 8 eyes in the gas tamponade group and in 7 of 10 eyes in the control group. No significant difference between the 2 groups was observed (p = 1.00). CONCLUSIONS: Gas tamponade combined with vitrectomy for lamellar macular hole did not affect postoperative anatomical and functional recovery.

Comparative study of fracture strength depending on the occlusal thickness of full zirconia crown / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the fracture strength of traditional metal-ceramic crowns and full zirconia crowns according to the occlusal thickness. MATERIALS AND METHODS: A mandibular first molar resin tooth was prepared with 1.5 mm occlusal reduction, 1.0 mm rounded shoulder margin and 6degrees taperness in the axial wall. Duplicating the resin tooth, 64 metal dies were fabricated. 48 full zirconia crowns were fabricated using Prettau zirconia blanks by ZIRKONZAHN CAD/CAM and classified into six groups according to the occlusal thickness (0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm). 16 metal-ceramic crowns were fabricated and classified into two groups according to the occlusal porcelain thickness (1.0 mm, 1.5 mm). All crowns were cemented on each metal die and mounted in a universal testing machine. The load was directed at the functional cusp of each specimen until catastrophic failure occurred. One-way ANOVA, Tukey multiple comparison test (alpha=.05) and t-test (alpha=.05) were used. RESULTS: The results were as follows. 1. The test 1 group (646.48 N) showed the lowest fracture strength (P.05). The value of test 6 group (1781.24 N) was significantly higher than those of the other groups (P<.05). 2. There were no significant differences of the fracture strength of metal ceramic crowns according to occlusal porcelain thickness 1.0 mm (2515.71 N) and 1.5 mm (3473.31 N) (P<.05). CONCLUSION: Full zirconia crown needs to be 1.0 mm or over in occlusal thickness for the posterior area to have higher fracture strength than maximum bite force.