Culture of Mouse Thymic Epithelial Cells in Serum-Free Medium.

Primary cell culture systems are widely used as a valuable method for analyzing the biological functions of specific cells in vitro. Recently, various serum-free primary cell culture methods have been developed that do not involve the use of animal serums. Since the thymus is comprised of many cell types, such as thymocytes, thymic epithelial cells, macrophages, and fibroblasts, thymic epithelial cells must be isolated for their functional analysis in vitro. This chapter describes the detailed protocol for the selective primary culture of thymic epithelial cells using defined serum-free medium.

Concurrent Overexpression of Two Hyaluronidases, KIAA1199 and TMEM2, Strongly Predicts Shorter Survival After Resection in Pancreatic Ductal Adenocarcinoma.

OBJECTIVES: Pancreatic ductal adenocarcinoma (PDAC) is characterized by accelerated hyaluronan metabolism. Our previous studies have shown increased expression of 2 newly identified hyaluronidases, KIAA1199 and transmembrane protein 2 (TMEM2), in PDAC. However, the relationship between these 2 hyaluronidases is unknown. In the present study, we investigated the correlation between KIAA1199 and TMEM2 expression in PDAC. METHODS: Using quantitative real-time reverse transcription polymerase chain reaction, we analyzed KIAA1199 and TMEM2 mRNA expression in 11 PDAC cell lines and frozen tissues from 12 patients with PDAC. We used immunohistochemistry to investigate expression patterns of KIAA1199 and TMEM2 in archival tissues obtained from 92 patients with PDAC who underwent surgical resection. We compared survival between 4 groups according to expression patterns of KIAA1199 and TMEM2. RESULTS: We found a significantly positive correlation between KIAA1199 and TMEM2 mRNA in PDAC cell lines and tissues. Immunohistochemical analysis found that median overall survival was 30.2 months in patients with low expression of KIAA1199 and TMEM2 and 12.5 months in those with high expression of both. Patients with high expression of KIAA1199 and TMEM2 had significantly shorter survival than other patient groups. CONCLUSIONS: Concurrent overexpression of these 2 hyaluronidases could be a strong prognostic marker in PDAC.

An advanced bipolar device helps reduce the rate of postoperative pancreatic fistula in laparoscopic gastrectomy for gastric cancer patients: a propensity score-matched analysis.

BACKGROUND: Advanced bipolar devices (ABD; e.g., LigaSure™) have a lower blade temperature than ultrasonically activated devices (USAD; e.g., Harmonic® and Sonicision™) during activation, potentially enabling accurate lymph node dissection with less risk of postoperative pancreatic fistula (POPF) due to pancreatic thermal injury in laparoscopic gastrectomy. Therefore, we compared the efficacy and safety of ABD and USAD in laparoscopic gastrectomy for gastric cancer patients. METHODS: A retrospective cohort study was conducted on patients who underwent laparoscopic distal gastrectomy (LDG) between August 2008 and September 2020. A total of 371 patients were enrolled, and short-term surgical outcomes, including the incidence of ISGPF grades B and C POPF, were compared between ABD and USAD. The risk factors for POPF in LDG were investigated by univariate and multivariate analyses. RESULTS: A propensity score-matching algorithm was used to select 120 patients for each group. The POPF rate was significantly lower (0.8 vs. 9.2%, p < 0.001), the morbidity rate was lower (13.3 vs. 28.3%, p < 0.001), the length of postoperative hospitalization was shorter (14 vs. 19 days, p < 0.001), and the lymph node retrieval rate was higher (34 vs. 26, p < 0.001) with an ABD than with a USAD. There were no mortalities in either group. A multivariate analysis showed that a USAD was the only independent risk factor with a considerably high odds ratio for the occurrence of POPF (USAD/ABD, odds ratio 8.38, p = 0.0466). CONCLUSION: An ABD may improve the safety of laparoscopic gastrectomy for gastric cancer patients.

Effects of Fatty Acids on Proliferation of Cultured Wild-type and FABP5-KO Thymic Epithelial Cells.

Lipids including fatty acids (FAs), which are water-insoluble molecules, are not only a cellular energy source but also signaling molecules that induce and modulate the expression of various cellular functions. Fatty acid-binding proteins (FABP) bind FAs in the cytoplasm, and are thought to determine the cellular localization of FAs. In a previous observation, FABP5 was expressed in thymic epithelial cells (TEC) in the thymus and was influenced by FAs. Fatty acids have mostly inhibitory effects on various cell types, including cancer cells, but their effects on TEC have not been well investigated. In this study, we investigated the effects of long-chain FAs (LCFAs) and the involvement of FABP5 in cell proliferation using a serum-free primary culture system. The results showed that saturated fatty acids did not affect proliferation, but n-3 long-chain polyunsaturated FA (LCPUFA) reduced, n-6 LCPUFA increased, and retinoic acid strongly reduced the percentage of proliferating wild-type TEC. The proliferation of FABP5-KO TEC was more significantly affected by LCPUFA, suggesting that FABP5 is an important modulator of FA-mediated TEC proliferation. These observations may provide a basis for exploring the properties of TEC.

Prognostic and functional role of hyaluronan-binding protein 1 in pancreatic ductal adenocarcinoma.

Hyaluronan-binding protein 1 (HABP1) is among the molecules known to bind to hyaluronan and is involved in a variety of cellular processes, including cell proliferation and migration. HABP1 has been implicated in the progression of various cancers; however, there have been (to the best of our knowledge) few studies on the expression and function of HABP1 in pancreatic ductal adenocarcinoma (PDAC), a topic that is examined in the present study. Immunohistochemical analysis of HABP1 protein was conducted in archival tissues from 105 patients with PDAC. Furthermore, the functional effect of HABP1 on proliferation, colony formation, and migration in PDAC cells was examined by knockdown of HABP1. It was revealed that HABP1 was overexpressed in 49 (46.2%) out of 105 patients with PDAC. Overall survival was significantly shorter in patients with high HABP1 expression than in those with low HABP1 expression (median survival time of 12.8 months vs. 28.5 months; log-rank test, P=0.004). Knockdown of HABP1 expression in PDAC cells resulted in decreased cell proliferation, colony formation, and cell migration activity. Thus, HABP1 may serve as a prognostic factor in PDAC and may be of use as a novel therapeutic target.

Invasive cribriform carcinoma of the breast detected incidentally on computed tomography: A case report.

Invasive cribriform carcinoma is a rare type of invasive breast carcinoma, and a few cases have been reported. Its features are a cribriform pattern resembling the histological structures of cribriform ductal carcinoma in situ and an excellent prognosis. However, the extent of progress for intraductal extension must be carefully evaluated.

Hypoxia increases KIAA1199/CEMIP expression and enhances cell migration in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is characterised by dense desmoplasia and hypoxic microenvironment. Our previous reports demonstrated that hyaluronan (HA), especially low-molecular-weight HA, provides a favourable microenvironment for PDAC progression. However, the effect of hypoxia on HA metabolism remains unknown. Using quantitative real-time RT-PCR and western blot analysis, we analysed the changes in the expression of HA-synthesizing enzymes (HAS2 and HAS3) and HA-degrading enzymes (HYAL1, KIAA1199/CEMIP) in PDAC cell lines under hypoxic conditions. Hypoxia increased the mRNA and protein expression of KIAA1199, whereas it decreased HYAL1 expression. The expression of HAS3 was increased and HAS2 remained unchanged in response to hypoxia. The effect of KIAA1199 on hypoxia-induced cell migration was determined using a transwell migration assay and small-interfering RNA (siRNA). Hypoxia enhanced the migratory ability of PDAC cells, which was inhibited by KIAA1199 knockdown. We also used immunohistochemistry to analyse the protein expression of hypoxia inducible factor (HIF) 1α and KIAA1199 in PDAC tissues. There was a significant immunohistochemically positive correlation between KIAA1199 and HIF1α. These findings suggest that hypoxia-induced KIAA1199 expression may contribute to enhanced motility in PDAC.

[A Case Report of Lateral Paracecal Hernia Treated with Single Port Surgery].

An 86-year-old female hospitalized for right femoral fracture complained of a sudden abdominal pain and vomited. Contrast-enhanced computed tomography (CECT) of the abdomen showed an ileal closed loop with dilatation of the oral side intestine. She was diagnosed with a bowel obstruction due to a paracecal hernia with incarceration and underwent an emergency operation. Under laparoscopy, the responsible ileum was incarcerated into the paracolic sulcus and strangulated. After releasing the strangulation by cutting the hernia hilum, the incarcerated ileum did not show any necrotic change. In this case, the CECT suggested paracecal hernia, showing the characteristic position between the cecum and the intestinal loop, which we successfully treated with a single incisional laparoscopic surgery.

Repeated partial tissue bite with inadequate cooling time for an energy device may cause thermal injury.

BACKGROUND: Over the past three decades, the use of ultrasonically activated device (USAD) and advanced bipolar device (ABD) has grown in minimally invasive surgeries. However, the thermal profile differences during repeated dissection with different grasping ranges of energy devices, which provide valuable information for preventing thermal injury by energy devices, remain unclear. METHODS: We developed an ex vivo benchtop model to examine the temperature profile of the blade and jaws of two USADs (HARMONIC® ACE + and Sonicision™) and a ABD (Ligasure™ Maryland) with different grasping ranges (partial tissue and full tissue bite) in repeated dissection with minimum cooling time. The maximum temperature, time required for completion to dissection of 10 cm of porcine muscle, thermal spread, and cooling time to reach 60 °C were continuously measured using video thermography. In addition, to evaluate one more grasping range "no tissue", we performed a stress test that activated the USAD without tissue intervention to assess the effects of excessive load on the blade and jaw. RESULTS: Repeated dissection of energy devices with minimal cooling time results in high blade and jaw temperatures proportional to the incision distance. In particular, the USADs with partial tissue bite showed a significantly higher temperatures at the blade and jaw, longer cooling times, and higher lateral thermal spread than those with a full tissue bite and the ABD. The stress test with a USAD showed an extremely high blade temperature exceeding 400 °C, with the tissue pad melting only 13.2 s after activation. CONCLUSION: Although USAD with partial tissue bite help ensure precise dissection, repeated long activation with inadequate cooling time may increase the risk of thermal injury during surgery. These results suggest that surgeons should use energy devices properly while understanding the risks of adjacent organ damage that could result from abuse of the device.

A case of gallbladder adenocarcinoma arising in association with intracystic papillary neoplasm (ICPN) with abundant mucin production.

Intracystic papillary neoplasm (ICPN) of the gallbladder is a rare clinicopathological entity with a wide range of malignant potentials. Here, we report a case of mucin-producing gallbladder carcinoma possibly derived from ICPN. A 78-year-old female patient was referred to our hospital for examination of jaundice. Abdominal CT showed dilated biliary trees and a contrast-enhanced large polypoid mass in the gallbladder. Duodenoscopy showed a large amount of mucin extravasating from the ampulla of Vater. Bile cytology showed no evidence of malignancy. Under the diagnosis of mucin-producing gallbladder tumor, we performed laparoscopic cholecystectomy. Macroscopically, there was a large papillary tumor throughout the entire gallbladder mucosa. Pathological examinations showed a gallbladder adenocarcinoma localized to the mucosa in association with ICPN. Immunohistochemical analysis of the tumor revealed positive staining for MUC2 and MUC5AC but negative for MUC1 and MUC6, suggestive of the intestinal type.

Overexpression of transmembrane protein 2 (TMEM2), a novel hyaluronidase, predicts poor prognosis in pancreatic ductal adenocarcinoma.

BACKGROUND: Abnormal metabolism of hyaluronan (HA), a major component of extracellular matrix, is a hallmark of cancer. Our previous studies have shown the importance of enzymes responsible for HA degradation in the aggressive phenotype of pancreatic ductal adenocarcinoma (PDAC). In the present study, we investigated the expression and function of transmembrane protein 2 (TMEM2), a recently identified HA-degrading enzyme, in PDAC. MATERIALS & METHODS: We used immunohistochemistry to investigate expression patterns of TMEM2 in archival tissues obtained from 100 patients with PDAC who underwent surgical resection from 1982 to 2012. The correlations between TMEM2 expression and clinicopathological variables, including survival, were determined using univariate and multivariate analyses. The effect of TMEM2 on proliferation and migratory ability (measured using transwell cell migration assay) of PDAC cells was determined by TMEM2 knockdown with small-interfering RNA (siRNA). RESULTS: Immunohistochemical analysis revealed high expression of TMEM2 in 22 (22%) of 100 patients. The overall survival was significantly shorter in patients with high TMEM2 expression than in those with low expression (P = 0.013). Multivariate analysis identified high TMEM2 expression as an independent factor predicting poor prognosis (P = 0.011). Unexpectedly, knockdown of TMEM2 resulted in increased migratory ability of PDAC cells, which was associated with increased expression of KIAA1199, a potent HA-degrading enzyme shown to enhance cell migration. CONCLUSION: TMEM2 overexpression is associated with poor prognosis in PDAC patients. Targeted disruption of this molecule, however, could enhance the aggressiveness of PDAC cells through a possible interaction with KIAA1199.

[A Case Report of Multiple Intussusceptions by Intestinal Metastases of Pleomorphic Carcinoma of the Lung].

A 68-year-old male with abdominal pain and vomiting was brought to our hospital by ambulance. Computed tomography showed multiple intussusceptions with pseudokidney signs in the jejunum and ileocecum, and a tumor of 5 cm in diameter in the left lower lobe of the lung. We performed an emergent operation, as a release of multiple intussusceptions was difficult by conservative treatment. There were two intussusceptions, in the jejunum and the ileocecum. We performed a partial resection of the jejunum and a resection of the ileocecum. Histopathological examination of the resected specimens and a biopsy specimen collected by bronchoscopy allowed us to diagnose multiple intussusceptions due to small intestine metastases from a pleomorphic carcinoma of the lung. This case is presented here, with a review of the literature.

Chronic Psychological Stress as a Risk Factor of Osteoporosis.

Osteoporosis, the most common metabolic skeletal disease, is characterized by decreased bone mass and deteriorated bone quality, leading to increased fracture risk. With the aging of the population, osteoporotic fracture is an important public health issue. Organisms are constantly exposed to various stressful stimuli that affect physiological processes. Recent studies showed that chronic psychological stress is a risk factor for osteoporosis by various signaling pathways. The purpose of this article is to review the recent progress of the association between chronic psychological stress and osteoporosis. Increasing evidence confirms the physiological importance of the central nervous system, especially the hypothalamus, in the regulation of bone metabolism. Both animal and human studies indicate that chronic psychological stress induces a decrease of bone mass and deterioration of bone quality by influencing the hypothalamic-pituitary-adrenocortical (HPA) axis, sympathetic nervous system, and other endocrine, immune factors. Active mastication, proven to be an effective stress-coping behavior, can attenuate stress-induced neuroendocrine responses and ameliorate stress-induced bone loss. Therefore, active mastication may represent a useful approach in preventing and/or treating chronic stress-associated osteoporosis. We also discuss several potential mechanisms involved in the interaction between chronic stress, mastication and osteoporosis. Chronic stress activates the HPA axis and sympathetic nervous system, suppresses the secretion of gonadal hormone and growth hormone, and increases inflammatory cytokines, eventually leading to bone loss by inhibiting bone formation and stimulating bone resorption.

Fatty acid-binding protein 5 regulates diet-induced obesity via GIP secretion from enteroendocrine K cells in response to fat ingestion.

Gastric inhibitory polypeptide (GIP) is an incretin released from enteroendocrine K cells in response to nutrient intake, especially fat. GIP is one of the contributing factors inducing fat accumulation that results in obesity. A recent study shows that fatty acid-binding protein 5 (FABP5) is expressed in murine K cells and is involved in fat-induced GIP secretion. We investigated the mechanism of fat-induced GIP secretion and the impact of FABP5-related GIP response on diet-induced obesity (DIO). Single oral administration of glucose and fat resulted in a 40% reduction of GIP response to fat but not to glucose in whole body FABP5-knockout (FABP5(-/-)) mice, with no change in K cell count or GIP content in K cells. In an ex vivo experiment using isolated upper small intestine, oleic acid induced only a slight increase in GIP release, which was markedly enhanced by coadministration of bile and oleic acid together with attenuated GIP response in the FABP5(-/-) sample. FABP5(-/-) mice exhibited a 24% reduction in body weight gain and body fat mass under a high-fat diet compared with wild-type (FABP5(+/+)) mice; the difference was not observed between GIP-GFP homozygous knock-in (GIP(gfp/gfp))-FABP5(+/+) mice and GIP(gfp/gfp)-FABP5(-/-) mice, in which GIP is genetically deleted. These results demonstrate that bile efficiently amplifies fat-induced GIP secretion and that FABP5 contributes to the development of DIO in a GIP-dependent manner.

Fatty acid binding protein 7 regulates phagocytosis and cytokine production in Kupffer cells during liver injury.

Kupffer cells (KCs) are involved in the progression of liver diseases such as hepatitis and liver cancer. Several members of the fatty acid binding proteins (FABPs) are expressed by tissue macrophages, and FABP7 is localized only in KCs. To clarify the role of FABP7 in the regulation of KC function, we evaluated pathological changes of Fabp7 knockout mice during carbon tetrachloride-induced liver injury. During liver injury in Fabp7 knockout mice, serum liver enzymes were increased, cytokine expression (tumor necrosis factor-α, monocyte chemoattractant protein-1, and transforming growth factor-ß) was decreased in the liver, and the number of KCs in the liver necrotic area was significantly decreased. Interestingly, in the FABP7-deficient KCs, phagocytosis of apoptotic cells was impaired, and expression of the scavenger receptor CD36 was markedly decreased. In chronic liver injury, Fabp7 knockout mice showed less fibrogenic response to carbon tetrachloride compared with wild-type mice. Taken together, FABP7 is involved in the liver injury process through its regulation of KC phagocytic activity and cytokine production. Such modulation of KC function by FABP7 may provide a novel therapeutic approach to the treatment of liver diseases.

Locally existing endothelial cells and pericytes in ovarian stroma, but not bone marrow-derived vascular progenitor cells, play a central role in neovascularization during follicular development in mice.

BACKGROUND: Neovascularization is necessary for follicular growth. Vascularization is first observed in preantral follicles, and thereafter the vasculature markedly increases in follicles undergoing development. Neovascularization includes angiogenesis and vasculogenesis. Vasculogenesis is the formation of new blood vessels by bone marrow-derived endothelial progenitor cells. It is unclear whether vasculogenesis occurs during follicular growth. Blood vessels must be mature to be functional blood vessels. Mature blood vessels are characterized by the recruitment of pericytes. However, it is unclear where pericytes come from and whether they contribute to neovascularization in the follicle during follicular growth. In this study, we investigated whether bone marrow-derived progenitor cells that differentiate into vascular endothelial cells or pericytes contribute to neovascularization during follicular growth. METHODS: A parabiosis model was used in this study. Six-week-old wild-type and transgenic female mice expressing green fluorescent protein (GFP) were conjoined between the lateral abdominal regions to create a shared circulatory system. After 6 weeks, the ovaries were obtained and immunostained for CD31/CD34 (a vascular endothelial cell marker), platelet-derived growth factor receptor-ß (PDGFR-ß) (a pericyte marker), and GFP (a bone marrow-derived cell marker). RESULTS: Cells that were positive for CD34 and PDGFR-ß were observed in the stroma adjacent to the primary or early preantral follicles and in the theca cell layer of the follicles from the late preantral stage to the preovulatory stage. CD31/CD34 and GFP double-positive cells were observed in the theca cell layer of the follicle from the antral stage to the preovulatory stage while the number of double-positive cells in the preovulatory follicles did not increase. PDGFR-ß and GFP double-positive cells were observed in the theca cell layer of the preovulatory follicle but not in the smaller follicle. CONCLUSIONS: Locally existing endothelial cells and pericytes in the stroma play a central role in the neovascularization during follicular growth, while bone marrow-derived endothelial cells and pericytes partially contribute to this process.

Cooling treatment transiently increases the permeability of brain capillary endothelial cells through translocation of claudin-5.

The blood-brain-barrier (BBB) is formed by different cell types, of which brain microvascular endothelial cells are major structural constituents. The goal of this study was to examine the effects of cooling on the permeability of the BBB with reference to tight junction formation of brain microendothelial cells. The sensorimotor cortex above the dura mater in adult male Wistar rats was focally cooled to a temperature of 5 °C for 1 h, then immunostaining for immunoglobulin G (IgG) was performed to evaluate the permeability of the BBB. Permeability produced by cooling was also evaluated in cultured murine brain endothelial cells (bEnd3) based on measurement of trans-epithelial electric resistance (TEER). Immunocytochemistry and Western blotting of proteins associated with tight junctions in bEnd3 were performed to determine protein distribution before and after cooling. After focal cooling of the rat brain cortex, diffuse immunostaining for IgG was observed primarily around the small vasculature and in the extracellular spaces of parenchyma of the cortex. In cultured bEnd3, TEER significantly decreased during cooling (15 °C) and recovered to normal levels after rewarming to 37 °C. Immunocytochemistry and Western blotting showed that claudin-5, a critical regulatory protein for tight junctions, was translocated from the membrane to the cytoplasm after cooling in cultured bEnd3 cells. These results suggest that focal brain cooling may open the BBB transiently through an effect on tight junctions of brain microendothelial cells, and that therapeutically this approach may allow control of BBB function and drug delivery through the BBB.

Involvement of bone marrow-derived vascular progenitor cells in neovascularization during formation of the corpus luteum in mice.

Neovascularization is necessary for formation of the corpus luteum (CL) and includes angiogenesis and vasculogenesis. Vasculogenesis is the formation of new blood vessels by bone marrow-derived endothelial progenitor cells. Here we investigated whether vasculogenesis occurs in neovascularization during CL formation. Mice transplanted with bone marrow from transgenic mice expressing green fluorescent protein (GFP) were injected with equine chorionic gonadotropin and human chorionic gonadotropin (hCG) to induce ovulation and subsequent CL formation. Immunohistochemistry was performed on the ovaries obtained before hCG injection and at 6, 12, and 24 h after hCG injection using antibodies for CD34 or CD31 (an endothelial cell marker), platelet-derived growth factor receptor beta (PDGFR-beta, a pericyte marker), F4/80 (a macrophage marker), and GFP (a bone marrow-derived cell marker). Cells immunostained for CD34, PDGFR-beta, F4/80, and GFP were present in the theca cell layer of the preovulatory follicle before hCG injection. Each of these cell types invaded the granulosa cell layer after hCG injection, and a number of them were observed in the CL 24 h after hCG injection. Fluorescence-based immunohistochemistry or double immunohistochemical staining revealed that a few CD34/CD31-positive cells and PDGFR-beta-positive cells were also positive for GFP in the preovulatory follicle and CL, and that many of the GFP-positive cells recruited to the CL during CL formation were F4/80-positive macrophages. In conclusion, bone marrow-derived vascular progenitor cells and macrophages contribute to neovascularization during CL formation.

Reduced size of sebaceous gland and altered sebum lipid composition in mice lacking fatty acid binding protein 5 gene.

Fatty acid binding proteins (FABPs) are capable of binding long-chain FA and are involved in intracellular FA transport and signal transduction. In sebaceous glands, FABP5 is highly expressed in differentiated sebocytes; though, its function remains unclear. In this study, we examined the role of FABP5 in sebocytes using FABP5-deficient mice. The size of sebaceous glands was significantly reduced, while the sebum volume was increased with altered lipid composition in FABP5-deficient mice. However, no significant differences were discerned in the expression of proliferation or differentiation markers including Blimp1, c-myc, Ki67 and peroxisome proliferator-activated receptors (PPAR)γ between wild-type and FABP5-deficient sebaceous glands. The expression of cellular retinoic acid binding protein-2 (CRABP2) that is a competitor of FABP5 for RA signalling was increased in FABP5-deficient mice. These results suggest that FABP5 is involved in the regulation of sebaceous gland activity through modulation of cellular lipid signalling and/or metabolism in the sebocytes.

Fatty acid-binding protein 4 (FABP4) and FABP5 modulate cytokine production in the mouse thymic epithelial cells.

Thymic stromal cells, including cortical thymic epithelial cells (cTEC) produce many humoral factors, such as cytokines and eicosanoids to modulate thymocyte homeostasis, thereby regulating the peripheral immune responses. In this study, we identified fatty acid-binding protein (FABP4), an intracellular fatty acid chaperone, in the mouse thymus, and examined its role in the control of cytokine production in comparison with FABP5. By immunofluorescent staining, FABP4(+) cells enclosing the thymocytes were scattered throughout the thymic cortex with a spatial difference from the FABP5(+) cell that were distributed widely throughout the cTEC. The FABP4(+) cells were immunopositive for MHC class II, NLDC145 and cytokeratin 8, and were identified as part of cTEC. The FABP4(+) cells were identified as thymic nurse cells (TNC), a subpopulation of cTEC, by their active phagocytosis of apoptotic thymocytes. Furthermore, FABP4 expression was confirmed in the isolated TNC at the gene and protein levels. To explore the function of FABP in TNC, TSt-4/DLL1 cells stably expressing either FABP4 or FABP5 were established and the gene expressions of various cytokines were examined. The gene expression of interleukin (IL)-7 and IL-18 was increased both in FABP4 and FABP5 over-expressing cells compared with controls, and moreover, the increase in their expressions by adding of stearic acids was significantly enhanced in the FABP4 over-expressing cells. These data suggest that both FABPs are involved in the maintenance of T lymphocyte homeostasis through the modulation of cytokine production, which is possibly regulated by cellular fatty acid-mediated signaling in TEC, including TNC.