Shih-Chieh Hung

Mesenchymal stem cells in the Wharton's jelly of the human umbilical cord.

The Whartons jelly of the umbilical cord contains mucoid connective tissue and fibroblast‐like cells. Using flow cytometric analysis, we found that mesenchymal cells isolated from the umbilical cord express matrix receptors (CD44, CD105) and integrin markers (CD29, CD51) but not hematopoietic lineage markers (CD34, CD45). Interestingly, these cells also express significant amounts of mesenchymal stem cell markers (SH2, SH3). We therefore investigated the potential of these cells to differentiate into cardiomyocytes by treating them with 5‐azacytidine or by culturing them in cardiomyocyte‐conditioned medium and found that both sets of conditions resulted in the expression of cardiomyocyte markers, namely N‐cadherin and cardiac troponin I. We also showed that these cells have multilineage potential and that, under suitable culture conditions, are able to differentiate into cells of the adipogenic and osteogenic lineages. These findings may have a significant impact on studies of early human cardiac differentiation, functional genomics, pharmacological testing, cell therapy, and tissue engineering by helping to eliminate worrying ethical and technical issues.

Oct-4 Expression Maintained Cancer Stem-Like Properties in Lung Cancer-Derived CD133-Positive Cells

CD133 (prominin-1), a 5-transmembrane glycoprotein, has recently been considered to be an important marker that represents the subset population of cancer stem-like cells. Herein we report the isolation of CD133-positive cells (LC-CD133+) and CD133-negative cells (LC-CD133−) from tissue samples of ten patients with non-small cell lung cancer (LC) and five LC cell lines. LC-CD133+ displayed higher Oct-4 expressions with the ability to self-renew and may represent a reservoir with proliferative potential for generating lung cancer cells. Furthermore, LC-CD133+, unlike LC-CD133−, highly co-expressed the multiple drug-resistant marker ABCG2 and showed significant resistance to chemotherapy agents (i.e., cisplatin, etoposide, doxorubicin, and paclitaxel) and radiotherapy. The treatment of Oct-4 siRNA with lentiviral vector can specifically block the capability of LC-CD133+ to form spheres and can further facilitate LC-CD133+ to differentiate into LC-CD133−. In addition, knock-down of Oct-4 expression in LC-CD133+ can significantly inhibit the abilities of tumor invasion and colony formation, and increase apoptotic activities of caspase 3 and poly (ADP-ribose) polymerase (PARP). Finally, in vitro and in vivo studies further confirm that the treatment effect of chemoradiotherapy for LC-CD133+ can be improved by the treatment of Oct-4 siRNA. In conclusion, we demonstrated that Oct-4 expression plays a crucial role in maintaining the self-renewing, cancer stem-like, and chemoradioresistant properties of LC-CD133+. Future research is warranted regarding the up-regulated expression of Oct-4 in LC-CD133+ and malignant lung cancer.

Isolation and Characterization of Size‐Sieved Stem Cells from Human Bone Marrow

Bone marrow mesenchymal stem cells (MSCs) have the capacity for renewal and the potential to differentiate into multiple lineages of mesenchymal tissues. In the laboratory, MSCs have the tendency to adhere to culture dish plastic and are characterized by fibroblastic morphology, but possess no specific markers to select them. To isolate and purify MSCs from bone marrow, we use a culture device—a plastic culture dish comprising a plate with 3‐μm pores—to sieve out a homogeneous population of cells (termed size‐sieved [SS] cells) from bone marrow aspirates. SS cells that adhered to the upper porous plate surface were a relatively homogeneous population as indicated by morphology and other criteria, such as surface markers. They had the capacity for self‐renewal and the multilineage potential to form bone, fat, and cartilage, and satisfy the characteristics of MSCs. In addition, if all the cells from each passage had been plated and cultured in our defined conditions, over 1014 SS cells would have been obtained from each 10‐ml aspirate in 15 additional weeks of culture. This technically simple method leads to an efficient isolation and purification of cells with the characteristics of MSCs.

Mesenchymal Stem Cell Targeting of Microscopic Tumors and Tumor Stroma Development Monitored by Noninvasive In vivo Positron Emission Tomography Imaging

The aim of this study was to assess the efficacy human mesenchymal stem cells (hMSC) for targeting microscopic tumors and suicide gene or cytokine gene therapy. Immunodeficient mice were transplanted s.c. with human colon cancer cells of HT-29 Inv2 or CCS line, and 3 to 4 days later, i.v. with “tracer” hMSCs expressing herpes simplex virus type 1 thymidine kinase (HSV1-TK) and enhanced green fluorescent protein (EGFP) reporter genes. Subsequently, these tumors were examined for specificity and magnitude of HSV1-TK+, EGFP+ stem cell engraftment and proliferation in tumor stroma by in vivo positron emission tomography (PET) with 18F-labeled 9-(4-fluoro-3-hydroxymethylbutyl)-guanine ([18F]-FHBG). In vivo PET images of tumors growing for 4 weeks showed the presence of HSV1-TK+ tumor stroma with an average of 0.36 ± 0.24% ID/g [18F]-FHBG accumulation. In vivo imaging results were validated by in situ correlative histochemical, immunofluorescent, and cytometric analyses, which revealed EGFP expression in vWF+ and CD31+ endothelial cells of capillaries and larger blood vessels, in germinal layer of dermis and hair follicles proximal to the s.c. tumor site. These differentiated HSV1-TK+, GFP+ endothelial cells had limited proliferative capacity and a short life span of <2 weeks in tumor fragments transplanted into secondary hosts. We conclude that hMSCs can target microscopic tumors, subsequently proliferate and differentiate, and contribute to formation of a significant portion of tumor stroma. PET imaging should facilitate clinical translation of stem cell–based anticancer gene therapeutic approaches by providing the means for in vivo noninvasive whole-body monitoring of trafficking, tumor targeting, and proliferation of HSV1-tk-expressing “tracer” hMSCs in tumor stroma.

In vitro differentiation of size-sieved stem cells into electrically active neural cells.

Size‐sieved stem (SS) cells isolated from human bone marrow and propagated in vitro are a population of cells with consistent marker typing, and can form bone, fat, and cartilage. In this experiment, we demonstrated that SS cells could be induced to differentiate into neural cells under experimental cell culture conditions. Five hours after exposure to antioxidant agents (β‐mercaptoethanol ± retinoic acid) in serum‐free conditions, SS cells expressed the protein for nestin, neuron‐specific enolase (NSE), neuron‐specific nuclear protein (NeuN), and neuron‐specific tubulin‐1 (TuJ‐1), and the mRNA for NSE and Tau. Immunofluorescence showed that almost all the cells (>98%) expressed NeuN and TuJ‐1. After 5 days of β‐mercaptoethanol treatment, the SS cells expressed neurofilament high protein but not mitogen‐activated protein‐2, glial filament acidic protein, and galactocerebroside. For such long‐term‐treated cells, voltage‐sensitive ionic current could be detected by electrophysiological recording, and the intracellular calcium ion, Ca2+, concentration can be elevated by high potassium (K+) buffer and glutamate. These findings suggest that SS cells may be an alternative source of undifferentiated cells for cell therapy and gene therapy in neural dysfunction.

The Therapeutic Potential of Human Umbilical Mesenchymal Stem Cells from Wharton's Jelly in the Treatment of Rat Liver Fibrosis

We investigated the effect of human umbilical mesenchymal stem cells (HUMSCs) from Whartons jelly on carbon tetrachloride (CCl4)–induced liver fibrosis in rats. Rats were treated with CCl4 for 4 weeks, and this was followed by a direct injection of HUMSCs into their livers. After 4 more weeks of CCl4 treatment (8 weeks in all), rats with HUMSC transplants [CCl4 (8W)+HUMSC liver] exhibited a significant reduction in liver fibrosis, as evidenced by Sirius red staining and a collagen content assay, in comparison with rats treated with CCl4 for 8 weeks without HUMSC transplants [CCl4 (8W)]. Moreover, rats in the CCl4 (8W)+HUMSC (liver) group had significantly lower levels of serum glutamic oxaloacetic transaminase, glutamic pyruvate transaminase, α‐smooth muscle actin, and transforming growth factor‐β1 in the liver, whereas the expression of hepatic mesenchymal epithelial transition factor–phosphorylated type (Met‐P) and hepatocyte growth factor was up‐regulated, in comparison with the CCl4 (8W) group. Notably, engrafted HUMSCs scattered mostly in the hepatic connective tissue but did not differentiate into hepatocytes expressing human albumin or α‐fetoprotein. Instead, these engrafted, undifferentiated HUMSCs secreted a variety of bioactive cytokines that may restore liver function and promote regeneration. Human cytokine assay revealed that the amounts of human cutaneous T cell–attracting chemokine, leukemia inhibitory factor, and prolactin were substantially greater in the livers of the CCl4 (8W)+HUMSC (liver) group, with considerably reduced hepatic inflammation manifested by a micro positron emission tomography scan. Our findings suggest that xenogeneic transplantation of HUMSCs is a novel approach for treating liver fibrosis and may be a promising therapeutic intervention in the future. Liver Transpl 15:484–495, 2009.

Identification of CD133-Positive Radioresistant Cells in Atypical Teratoid/ Rhabdoid Tumor

Atypical teratoid/rhabdoid tumor (AT/RT) is an extremely malignant neoplasm in the central nervous system (CNS) which occurs in infancy and childhood. Recent studies suggested that CD133 could be considered a marker for brain cancer stem-like cells (CSCs). However, the role of CD133 in AT/RT has never been investigated. Herein we report the isolation of CD133-positive cells (CD133+), found to have the potential to differentiate into three germ layer tissues, from tissues of nine AT/RT patients. The migration/invasion/malignancy and radioresistant capabilities of CD133+ were significantly augmented when compared to CD133−. The clinical data showed that the amount of CD133+ in AT/RTs correlated positively with the degree of resistance to radiation therapy. Using cDNA microarray analysis, the genotoxic–response profiles of CD133+ and CD133− irradiated with 10 Gy ionizing radiation (IR) were analyzed 0.5, 2, 6, 12 and 24 h post-IR. We then validated these microarray data and showed increased phosphorylation after IR of p-ATM, p-RAD17, and p-CHX2 as well as increased expression of BCL-2 protein in CD133+ compared to CD133−. Furthermore, we found that CD133+ can effectively resist IR with cisplatin- and/or TRAIL-induced apoptosis. Immunohistochemical analysis confirmed the up-regulated expression of p-ATM and BCL-2 proteins in IR-treated CD133+ xenotransgrafts in SCID mice but not in IR-treated CD133−. Importantly, the effect of IR in CD133+ transplanted mice can be significantly improved by a combination of BCL-2 siRNA with debromohymenialdisine, an inhibitor of checkpoint kinases. In sum, this is the first report indicating that CD133+ AT/RT cells demonstrate the characteristics of CSCs. The IR-resistant and anti-apoptotic properties in CD133+ may reflect the clinical refractory malignancy of AT/RTs and thus the activated p-ATM pathway and BCL-2 expression in CD133+ could be possible targets to improve future treatment of deadly diseases like AT/RT.

In vitro stage-specific chondrogenesis of mesenchymal stem cells committed to chondrocytes

OBJECTIVEnOsteoarthritis is characterized by an imbalance in cartilage homeostasis, which could potentially be corrected by mesenchymal stem cell (MSC)-based therapies. However, in vivo implantation of undifferentiated MSCs has led to unexpected results. This study was undertaken to establish a model for preconditioning of MSCs toward chondrogenesis as a more effective clinical tool for cartilage regeneration.nnnMETHODSnA coculture preconditioning system was used to improve the chondrogenic potential of human MSCs and to study the detailed stages of chondrogenesis of MSCs, using a human MSC line, Kp-hMSC, in commitment cocultures with a human chondrocyte line, hPi (labeled with green fluorescent protein [GFP]). In addition, committed MSCs were seeded into a collagen scaffold and analyzed for their neocartilage-forming ability.nnnRESULTSnCoculture of hPi-GFP chondrocytes with Kp-hMSCs induced chondrogenesis, as indicated by the increased expression of chondrogenic genes and accumulation of chondrogenic matrix, but with no effect on osteogenic markers. The chondrogenic process of committed MSCs was initiated with highly activated chondrogenic adhesion molecules and stimulated cartilage developmental growth factors, including members of the transforming growth factor beta superfamily and their downstream regulators, the Smads, as well as endothelial growth factor, fibroblast growth factor, insulin-like growth factor, and vascular endothelial growth factor. Furthermore, committed Kp-hMSCs acquired neocartilage-forming potential within the collagen scaffold.nnnCONCLUSIONnThese findings help define the molecular markers of chondrogenesis and more accurately delineate the stages of chondrogenesis during chondrocytic differentiation of human MSCs. The results indicate that human MSCs committed to the chondroprogenitor stage of chondrocytic differentiation undergo detailed chondrogenic changes. This model of in vitro chondrogenesis of human MSCs represents an advance in cell-based transplantation for future clinical use.

cAMP/PKA Regulates Osteogenesis, Adipogenesis and Ratio of RANKL/OPG mRNA Expression in Mesenchymal Stem Cells by Suppressing Leptin

Background Mesenchymal stem cells (MSCs) are a pluripotent cell type that can differentiate into adipocytes, osteoblasts and other cells. The reciprocal relationship between adipogenesis and osteogenesis was previously demonstrated; however, the mechanisms remain largely unknown. Methods and Findings We report that activation of PKA by 3-isobutyl-1 methyl xanthine (IBMX) and forskolin enhances adipogenesis, the gene expression of PPARγ2 and LPL, and downregulates the gene expression of Runx2 and osteopontin, markers of osteogenesis. PKA activation also decreases the ratio of Receptor Activator of the NF-κB Ligand to Osteoprotegerin (RANKL/OPG) gene expression – the key factors of osteoclastogenesis. All these effects are mediated by the cAMP/PKA/CREB pathway by suppressing leptin, and may contribute to PKA stimulators-induced in vivo bone loss in developing zebrafish. Conclusions Using MSCs, the center of a newly proposed bone metabolic unit, we identified cAMP/PKA signaling, one of the many signaling pathways that regulate bone homeostasis via controlling cyto-differentiation of MSCs and altering RANKL/OPG gene expression.

Bmi-1 Regulates Snail Expression and Promotes Metastasis Ability in Head and Neck Squamous Cancer-Derived ALDH1 Positive Cells

Recent studies suggest that ALDH1 is a putative marker for HNSCC-derived cancer stem cells. However, the regulation mechanisms that maintain the stemness and metastatic capability of HNSCC-ALDH1+ cells remain unclear. Initially, HNSCC-ALDH1+ cells from HNSCC patient showed cancer stemness properties, and high expression of Bmi1 and Snail. Functionally, tumorigenic properties of HNSCC-ALDH1+ cells could be downregulated by knockdown of Bmi-1. Overexpression of Bmi-1 altered in expression property ALDH1− cells to that of ALDH1+ cells. Furthermore, knockdown of Bmi-1 enhanced the radiosensitivity of radiation-treated HNSCC-ALDH1+ cells. Moreover, overexpression of Bmi-1 in HNSCC-ALDH1− cells increased tumor volume and number of pulmonary metastatic lesions by xenotransplant assay. Importantly, knock-down of Bmi1 in HNSCC-ALDH1+ cells significantly decreased distant metastases in the lungs. Clinically, coexpression of Bmi-1/Snail/ALDH1 predicted the worst prognosis in HNSCC patients. Collectively, our data suggested that Bmi-1 plays a key role in regulating Snail expression and cancer stemness properties of HNSCC-ALDH1+ cells.