Biomedical subjects

Guoping Chen

Publications and source records attributed to Guoping Chen.

17 recordsLinked to original sources

PubMed2007

Regeneration of the esophagus using gastric acellular matrix: an experimental study in a rat model.

Recently, tissue engineering of the autologous esophagus has been thought to provide a promising strategy for esophageal substitution. In this study, gastric acellular matrix (GAM) was used as a scaffold for regeneration of the esophagus in a rat model. Usage of GAM has an advantage that naturally derived extracellular matrix autograft can be prepared less invasively in a clinical setting. Twenty-seven F344 female rats were used as recipients. Patch defects created in the abdominal esophagus were replaced by GAM patch grafts. The rats were sacrificed 1 week to 18 months after implantation. The specimen was examined macroscopically as well as microscopically. 5'-Bromo-2'-deoxyuridine (BrdU) proliferation assay was performed in six rats that were sacrificed 1, 2, and 4 weeks after implantation. Twenty-four rats survived without complications. The graft site did not show esophageal stenosis or dilatation in any rat. Keratinized stratified squamous esophageal mucosa was regenerated in the entire graft 2 weeks after implantation. Regeneration of the muscle layer or lamina muscularis mucosae in the graft site was not observed even 18 months after implantation. Marked incorporation of BrdU was observed only in the mucosal layer but not in the muscle layer. GAM patch graft provided satisfactory mucosal regeneration of the esophagus without stenosis or dilatation, although muscle regeneration was still a future challenge.

Animals↗

PubMed2006

Heterotypic cell interactions on a dually patterned surface.

It is worth investigating heterotypic cell-cell interactions by mimicking their in vivo structures and environment. In the present study, physiological cellular response and behavior of hepatocytes and endothelial cells were investigated by controlling their contact periphery in a new co-culture system. Rat primary hepatocytes and bovine endothelial cells were co-cultured on a dually patterned surface. Hepatic physiological functions such as albumin secretion and ammonium metabolism were enhanced by increasing heterotypic cell-cell interactions in a patterned co-culture. Furthermore, enhanced hepatic functions through heterotypic interactions are effective within a limited area apart from endothelial cells as evidenced by immunofluorescence staining of hepatic intracellular albumin, indicating that heterotypic interactions act in a paracrine manner. Thus, heterotypic cell communications that play indispensable roles in increasing hepatic physiological functions should be obtained with an increasing periphery of two-cell domains. These findings are important for the reconstruction of complex tissues such as liver and pancreas.

Animals↗

PubMed2006

Culture of mouse embryonic stem cells on photoimmobilized polymers.

Mouse embryonic stem (ES) cells were cultured on four types of polymer with different surface properties. The polymers were poly(acrylic acid), polyallylamine, gelatin, and poly(2-methacryloyloxyethyl phosphorylcholine-co-methacrylic acid) (PMAc50), and were coupled with azidophenyl groups and photoimmobilized on conventional polystyrene cell-culture dishes. Mouse ES cells were cultured on the immobilized polymer surfaces, and cell morphology, cell growth, staining for alkaline phosphatase, activation of the transcription factor stat3, and expression of the octamer-binding protein 3/4 (Oct3/4) transcription factor and the zinc finger-containing transcription factor (GATA4) were observed. Morphology and growth rate were significantly affected by the polymer surface properties. The ES cells attached to gelatin or polyallylamine surfaces; however, colonies formed on the former but not the latter. In addition, significant enhancement of growth was observed on the gelatin surface. In contrast, ES cells aggregated to form an embryoid body on the photoimmobilized poly(acrylic acid) surface and the PMAc50 surface, although cell growth was reduced. Significant enhancement of aggregation of ES cells on the PMAc50 surface was observed in morphology and gene expression analyses.

Animals↗

PubMed2005

Culturing of skin fibroblasts in a thin PLGA-collagen hybrid mesh.

A thin biodegradable hybrid mesh of synthetic poly(DL-lactic-co-glycolic acid) (PLGA) and naturally derived collagen was used for three-dimensional culture of human skin fibroblasts. The hybrid mesh was constructed by forming web-like collagen microsponges in the openings of a PLGA knitted mesh. The behaviors of the fibroblasts on the hybrid mesh and PLGA knitted mesh were compared. The efficiency of cell seeding was much higher and the cells grew more quickly in the hybrid mesh than in the PLGA mesh. The fibroblasts in the PLGA mesh grew from the peripheral PLGA fibers toward the centers of the openings, while those in the hybrid mesh also grew from the collagen microsponges in the openings of the mesh resulting in a more homogenous growth. The proliferated cells and secreted extracellular matrices were more uniformly distributed in the hybrid mesh than in the PLGA mesh. Histological staining of in vitro cultured fibroblast/mesh implants indicated that the fibroblasts were distributed throughout the hybrid mesh and formed a uniform layer of dermal tissue having almost the same thickness as that of the hybrid mesh. However, the tissue formed in the PLGA mesh was thick adjacent to the PLGA fibers and thin in the center of the openings. Fibroblasts cultured in the hybrid mesh were implanted in the back of nude mouse. Dermal tissues were formed after 2 weeks and became epithelialized after 4 weeks. The results indicate that the web-like collagen microsponges formed in the openings of the PLGA knitted mesh increased the efficiency of cell seeding, improved cell distribution, and therefore facilitated rapid formation of dermal tissue having a uniform thickness. PLGA-collagen hybrid mesh may be useful for skin tissue engineering.

Absorbable Implants↗

PubMed2004

Chondrogenic differentiation of human mesenchymal stem cells cultured in a cobweb-like biodegradable scaffold.

Human mesenchymal stem cells (MSCs) were cultured in vitro in a cobweb-like biodegradable polymer scaffold: a poly(dl-lactic-co-glycolic acid)-collagen hybrid mesh in serum-free DMEM containing TGF-beta3 for 1-10 weeks. The cells adhered to the hybrid mesh, distributed evenly, and proliferated to fill the spaces in the scaffold. The ability of the cells to express gene encoding type I collagen decreased, whereas its ability to express type II collagen and aggrecan increased. Histological examination by HE staining indicated that the cells showed fibroblast morphology at the early stage and became round after culture for 4 weeks. The cartilaginous matrices were positively stained by safranin O and toluidine blue. Immunostaining with anti-type II collagen and anti-cartilage proteoglycan showed that type II collagen and cartilage proteoglycan were detected around the cells. In addition, a homogeneous distribution of cartilaginous extracellular matrices was detected around the cells. These results suggest the chondrogenic differentiation of the mesenchymal stem cells in the hybrid mesh. The PLGA-collagen hybrid mesh enabled the aggregation of mesenchymal stem cells and provided a promotive microenvironment for the chondrogenic differentiation of the MSCs.

Absorbable Implants↗

PubMed2004

Identification of a specific isoform of tomato lipoxygenase (TomloxC) involved in the generation of fatty acid-derived flavor compounds.

There are at least five lipoxygenases (TomloxA, TomloxB, TomloxC, TomloxD, and TomloxE) present in tomato (Lycopersicon esculentum Mill.) fruit, but their role in generation of fruit flavor volatiles has been unclear. To assess the physiological role of TomloxC in the generation of volatile C6 aldehyde and alcohol flavor compounds, we produced transgenic tomato plants with greatly reduced TomloxC using sense and antisense constructs under control of the cauliflower mosaic virus 35S promoter. The expression level of the TomloxC mRNA in some transgenic plants was selectively reduced by gene silencing or antisense inhibition to between 1% and 5% of the wild-type controls, but the expression levels of mRNAs for the four other isoforms were unaffected. The specific depletion of TomloxC in transgenic tomatoes led to a marked reduction in the levels of known flavor volatiles, including hexanal, hexenal, and hexenol, to as little as 1.5% of those of wild-type controls following maceration of ripening fruit. Addition of linoleic or linolenic acid to fruit homogenates significantly increased the levels of flavor volatiles, but the increase with the TomloxC-depleted transgenic fruit extracts was much lower than with the wild-type control. Confocal imaging of tobacco (Nicotiana tabacum) leaf cells expressing a TomloxC-GFP fusion confirmed a chloroplast localization of the protein. Together, these results suggest that TomloxC is a chloroplast-targeted lipoxygenase isoform that can use both linoleic and linolenic acids as substrates to generate volatile C6 flavor compounds. The roles of the other lipoxygenase isoforms are discussed.

Aldehydes↗

PubMed2004

Growth factor combination for chondrogenic induction from human mesenchymal stem cell.

During the last decade, many strategies for cartilage engineering have been emerging. Stem cell induction is one of the possible approaches for cartilage engineering. The mesenchymal stem cells (MSCs) with their pluripotency and availability have been demonstrated to be an attractive cell source. It needs the stimulation with cell growth factors to make the multipluripotent MSCs differentiate into chondrogenic lineage. We have shown particular patterns of in vitro chondrogenesis induction on human bone marrow MSCs (hBMSCs) by cycling the growth factors. The pellet cultures of hBMSCs were prepared for chondrogenic induction. Growth factors: TGF-beta3, BMP-6, and IGF-1 were used in combination for cell induction. Gene expression, histology, immunohistology, and real-time PCR methods were measured on days 21 after cell induction. As shown by histology and immunohistology, the induced cells have shown the feature of chondrocytes in their morphology and extracellular matrix in both inducing patterns of combination and cycling induction. Moreover, the real-time PCR assay has shown the expression of gene markers of chondrogenesis, collagen type II and aggrecan. This study has demonstrated that cartilage tissue can be created from bone marrow mesenchymal stem cells. Interestingly, the combined growth factors TGF-beta3 and BMP-6 or TGF-beta3 and IGF-1 were more effective for chondrogenesis induction as shown by the real-time PCR assay. The combination of these growth factors may be the important key for in vitro chondrogenesis induction.

Cartilage↗

PubMed2004

Constitutive expression of EIL-like transcription factor partially restores ripening in the ethylene-insensitive Nr tomato mutant.

Climacteric fruit ripening is regulated by the phytohormone ethylene. ETHYLENE-INSENSITIVE3 (EIN3) is a transcription factor that functions downstream from the ethylene receptors in the Arabidopsis ethylene signal transduction pathway. Three homologues of the Arabidopsis EIN3 gene have been identified in tomato, Lycopersicon esculentum, EIN3-like or LeEIL, LeEIL1, LeEIL2, and LeEIL3. These transcription factors have been proposed to be functionally redundant positive regulators of multiple ethylene responses. In order to test the role of such factors in the ethylene signal transduction pathway during ripening, EIL1 fused to green fluorescent protein (GFP) has been over-expressed in the ethylene-insensitive non-ripening Nr mutant of tomato. Increased levels of LeEIL1 compensated for the normally reduced levels of LeEIL1 in the Nr mutant, and transgenic Nr plants that exhibited high-level constitutive expression of LeEIL1GFP phenotypically resembled wild-type plants, the fruit ripened and the leaves exhibited epinasty, unlike Nr plants. The EIL1GFP fusion protein was located in the cell nuclei of ripe tomato fruit. The mRNA profile of these plants showed that the expression of certain ethylene-dependent ripening genes was up-regulated, including polygalacturonase and TOMLOX B. However, not all ripening genes and ethylene responses, such as seedling triple response, were restored. These results demonstrate that expressing candidate genes in the Nr ethylene-insensitive background is a valuable general approach for testing the role of putative downstream components in the ethylene-signalling pathway.

Arabidopsis Proteins↗

PubMed2004

Custom-shaping system for bone regeneration by seeding marrow stromal cells onto a web-like biodegradable hybrid sheet.

New bone for the repair or the restoration of the function of traumatized, damaged, or lost bone is a major clinical need, and bone tissue engineering has been heralded as an alternative strategy for regenerating bone. A novel web-like structured biodegradable hybrid sheet has been developed for bone tissue engineering by preparing knitted poly(DL-lactic-co-glycolic acid) sheets (PLGA sheets) with collagen microsponges in their openings. The PLGA skeleton facilitates the formation of the hybrid sheets into desired shapes, and the collagen microsponges in the pores of the PLGA sheet promote cell adhesion and uniform cell distribution throughout the sheet. A large number of osteoblasts established from marrow stroma adhere to the scaffolds and generate the desired-shaped bone in combination with these novel sheets. These results indicate that the web-like structured novel sheet shows promise for use as a tool for custom-shaped bone regeneration in basic research on osteogenesis and for the development of therapeutic applications.

Absorbable Implants↗

PubMed2004

Biodegradable polymer with collagen microsponge serves as a new bioengineered cardiovascular prosthesis.

OBJECTIVE: Biodegradable materials with autologous cell seeding have attracted much interest as potential cardiovascular grafts. However, pretreatment of these materials requires a complicated and invasive procedure that carries the risk of infection. To avoid these problems, we sought to develop a biodegradable graft material containing collagen microsponge that would permit the regeneration of autologous vessel tissue. The ability of this material to accelerate in situ cellularization with autologous endothelial and smooth muscle cells was tested with and without precellularization. METHODS: Poly(lactic-co-glycolic acid) as a biodegradable scaffold was compounded with collagen microsponge to form a vascular patch material. These poly(lactic-co-glycolic acid)-collagen patches with (n = 10) or without (n = 10) autologous vessel cellularization were used to patch the canine pulmonary artery trunk. Histologic and biochemical assessments were performed 2 and 6 months after the implantation. RESULTS: There was no thrombus formation in either group, and the poly(lactic-co-glycolic acid) scaffold was almost completely absorbed in both groups. Histologic results showed the formation of an endothelial cell monolayer, a parallel alignment of smooth muscle cells, and reconstructed vessel wall with elastin and collagen fibers. The cellular and extracellular components in the patch had increased to levels similar to those in native tissue at 6 months. CONCLUSIONS: The poly(lactic-co-glycolic acid)-collagen microsponge patch with and without precellularization showed good histologic findings and durability. This patch shows promise as a bioengineered material for promoting in situ cellularization and the regeneration of autologous tissue in cardiovascular surgery.

Animals↗

PubMed2003

The use of a novel PLGA fiber/collagen composite web as a scaffold for engineering of articular cartilage tissue with adjustable thickness.

It has been a great challenge to make the thickness of engineered cartilage adjustable to cover the range of both partial-thickness and full-thickness articular cartilage defects. We developed a novel kind of composite web scaffold that could be used for tissue enginnering of articular cartilage with the thickness adjustable between 200 microm and 8 mm. The composite web showed a unique structure having web-like collagen microsponges formed in the openings of a mechanically strong knitted mesh of poly(lactic-co-glycolic acid). The knitted mesh served as a skeleton reinforcing the composite web, while the web-like collagen microsponges facilitated cell seeding, cell distribution, and tissue formation. Bovine chondrocytes cultured in the composite web showed a spatially even distribution, maintained their natural morphology, and produced cartilaginous extracellular matrices such as type II collagen and aggrecan. The thickness of the implant can be simply adjusted by laminating or rolling the web sheets. Not only did the histological structure of the engineered cartilage patches match the bovine native articular cartilage, but also their dynamic complex modulus, structural stiffness, and phase lag reached 37.8, 57.0, and 86.3% of those of native bovine articular cartilage, respectively. The composite web could be an important scaffold for tissue engineering.

Aggrecans↗

PubMed2003

Redifferentiation of dedifferentiated bovine chondrocytes when cultured in vitro in a PLGA-collagen hybrid mesh.

Bovine articular chondrocytes dedifferentiated and lost their ability to express articular cartilage-specific extracellular matrices such as type II collagen and aggrecan when cultured in a culture flask during in vitro multiplication. A poly(DL-lactic-co-glycolic acid) (PLGA)-collagen hybrid mesh was prepared and used to redifferentiate the dedifferentiated cells. The two passaged dedifferentiated chondrocytes were seeded in a PLGA-collagen hybrid mesh and cultured in vitro in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum. The cells adhered to the hybrid mesh, distributed evenly, and proliferated to fill the spaces in the scaffold. The gene expression of type I collagen, type II collagen, and aggrecan was analyzed after the cells were cultured in the hybrid mesh for 2-12 weeks. The expression of the gene encoding type I collagen was downregulated, whereas those of type II collagen and aggrecan were upregulated. Histological examination by hematoxylin-eosin and safranin O/fast green staining indicates that the cells regained their original round morphology. In addition, a homogeneous distribution of articular cartilage extracellular matrices was detected around the cells. These results suggest redifferentiation of the differentiated chondrocytes in the hybrid mesh. The hybrid mesh, which facilitated the redifferentiation of the dedifferentiated multiplied chondrocytes, would be an effective scaffold for the assembly of cells to regenerate three-dimensional cartilaginous tissue.

Aggrecans↗

PubMed2003

Tissue-engineered urinary bladder wall using PLGA mesh-collagen hybrid scaffolds: a comparison study of collagen sponge and gel as a scaffold.

PURPOSE: Tissue engineering of the urinary bladder using autologous cells and biodegradable scaffold is a promising method for augmentation. The authors developed 2 hybrid scaffolds by combining poly (DL-lactic-co-glycolic acid; PLGA) mesh for mechanical strength with collagen sponge or gel suitable for cell seeding. The aim of this study was to compare collagen as a scaffold between collagen sponge and gel and to construct a tissue-engineered urinary bladder wall utilizing these hybrid scaffolds. METHODS: The PLGA mesh-collagen hybrid scaffolds were prepared by introducing collagen sponge or gel into the PLGA knitted mesh. Urothelial and smooth muscle cells were obtained from porcine urinary bladder wall and were cultured in their respective media. The cells were seeded on these hybrid scaffolds. These constructs were analyzed morphologically and immunohistochemically. RESULTS: The urothelial layer was generated 3 dimensionally by culturing urothelial cells with PLGA mesh and collagen sponge. The smooth muscle layer was constructed by culturing smooth muscle cells with PLGA mesh and collagen gel. And a novel tissue-engineered urinary bladder wall was constructed laminating the urothelial and smooth muscle layers. CONCLUSIONS: Ex vivo construction of urinary bladder wall using hybrid scaffolds prepared by combining PLGA mesh with collagen sponge or gel was successful. This tissue-engineered urinary bladder wall allows easy handling and may become a promising tool for bladder augmentation.

Absorbable Implants↗

PubMed2002

[Effects of the mechanical stress on the proliferation and function of osteoblast-like cells in vitro].

OBJECTIVE: The aim of this study was to investigate the effects of the mechanical stress on the proliferation and function of osteoblast-like cells (UMR106) of rats, and further to explore the mechanism of remodeling of periodontium from an angle of mechanics. METHODS: The flow cytometry and MTT method was used to examine the number of osteoblasts-like cells and their proliferation and metabolic enzymic activity 6 h, 12 h, 18 h, 24 h, 30 h, and 36 h after the top-bottom axial stress (225 x g) was exerted on the UMR106 in vitro. RESULTS: The difference of cell phase fraction and function between the experimental group and the control group were of great significance (P < 0.01). The maximum SPF increasing and functional decreasing appeared 12 h after the appliance of the stress, and all indexes were no significantly different between the two groups 24 h after the stress was supplied. Forward light scatter had no remarkable alteration. CONCLUSION: The top-bottom axial stress (225 x g) could inevitably influence the proliferation and function of osteoblast-like cells without pathological damage occurred.

Animals↗

PubMed2002

[The effects of the mechanical stress on the cytoskeleton filament F-actin of osteoblast-like cells in vitro].

OBJECTIVE: Mechanical stimulation alters cell's metabolism, but little is known about the effects of mechanical strain on the cytoskeleton of osteoblasts. This study was to investigate the changes of F-actin, a cytoskeleton protein of rat-derived osteoblast-like cell line UMR-106, and to provide theoretical basis for further investigation of mechanism of bone-remodeling. METHODS: Centrifugation was used to inflict UMR-106 the top-bottom axial stress (225 x g) expected and, confocal laser scanning microscope (LSCM) was used to examine the morphological changes 15, 30 min, and 1, 4, 6, 12, and 24 hr after undergoing physical strain. Unstrained cells were used as the controls respectively. The distribution of F-actin was observed after immunofluorescent staining and electronic photo was scanned for further analysis of osteoblasts' average fluorescence by spectrofluorimetric quantification. RESULTS: Except the 24 hr group, the actin filaments of the strained osteoblasts were much shorter, more flimsy and tenuous than that of untreated osteoblasts and unlike the normal distribution of bundles or membrane-like of the control group, and they were arranged without direction. Its quantified fluorescence was significantly less than that of the controls. But the 24 hr group showed a normal distribution and a stronger fluorescence. CONCLUSION: It is concluded that the cytoskeleton of the strained osteoblasts has a reduced number of F-actin fibers and a unique abnormal morphology and could recover in 24 hr.

Actins↗

PubMedDate not supplied

L-Phe end-capped poly(L-lactide) as macroinitiator for the synthesis of poly(L-lactide)-B-poly(L-lysine) block copolymer.

A poly(L-lactide)-b-poly(Nepsilon-(Z)-L-lysine) (PLLA-b-PZLys) block copolymer was synthesized through the ring-opening polymerization of Nepsilon-(Z)-lysine-N-carboxyanhydride using L-Phe-terminated PLLA as a macroinitiator. The L-Phe-terminated PLLA was prepared through a novel three-step process. First, the hydroxyl-terminated PLLA was synthesized through the ring-opening polymerization of L-lactide initiated by n-butanol under the existence of tin(II) ethylhexanoate. Subsequently, the complete capping of the hydroxyl end group of PLLA with BOC-L-Phe was achieved by using a mixed anhydride of BOC-L-Phe under the catalysis of 4-(1-pyrrolidinyl) pyridine. Finally, the free amino end group was obtained by removal of the t-butoxycarbonyl group through trifluoroacetic acid treatment under anhydrous condition. All these treatments were conducted under mild conditions, thus avoiding the breakdown of the PLLA backbone. Poly(L-lactide)-b-poly(L-lysine) block copolymer was produced after deprotection treatment of PLLA-b-PZLys. The structure of the block copolymer was confirmed by 1H NMR, IR, and GPC. Adjustment of the ratio of the NCA monomer to the macroinitiator could control the chain length of the PLys block.

Biocompatible Materials↗

PubMedDate not supplied

Tissue engineering of cartilage using a hybrid scaffold of synthetic polymer and collagen.

A biodegradable hybrid scaffold of synthetic polymer, poly (DL-lactic-co-glycolic acid) (PLGA), and naturally derived polymer, collagen, was prepared by forming collagen microsponges in the pores of PLGA sponge. This was then used as the three-dimensional scaffold for tissue engineering of bovine articular cartilage, both in vitro and in vivo. In vitro studies show that hybridization with collagen facilitated cell seeding in the sponge and raised seeding efficiency. Chondrocytes adhered to the collagen microsponges, where they proliferated and secreted extracellular matrices with time, filling the space within the sponge. Hematoxylin and eosin staining revealed that most of the chondrocytes after 4 weeks of culture, and almost all cell types after 6 weeks of culture, maintained their phenotypically rounded morphology. While new tissue formed, the scaffold degraded and lost almost 36.9% of its original weight after 10 weeks. Subcutaneous implantation studies in nude mice demonstrated more homogeneous tissue formation in hybrid sponge than in PLGA sponge. The new tissue formed maintained the original shape of the hybrid sponge. The synthetic PLGA sponge, serving as a skeleton, facilitated easy formation into desired shapes and provided appropriate mechanical strength to define the ultimate shape of engineered tissue. Incorporation of collagen microsponges facilitated cell seeding and homogeneous cell distribution and created a favorable environment for cellular differentiation. The hybrid sponge could therefore represent a promising candidate as a three-dimensional scaffold for articular cartilage tissue engineering.

Animals↗