Biomedical subjects

Christian Kaps

Publications and source records attributed to Christian Kaps.

12 recordsLinked to original sources

PubMed2006

Gene expression profiling of human articular cartilage grafts generated by tissue engineering.

Cartilage tissue engineering is applied clinically to cover and regenerate articular cartilage defects. In this study autologous human cartilage tissue engineering grafts based on bioresorbable polyglactin/polydioxanone scaffolds were analyzed on the broad molecular level. RNA from freshly isolated, primary and expanded adult articular chondrocytes and from three-dimensional cartilage grafts were used for gene expression profiling using oligonucleotide microarrays. The capacity of cartilage grafts to form cartilage matrix was evaluated after subcutaneous transplantation into nude mice. Gene expression profiling showed reproducibly the regulation of 905 genes and documented that chondrocytes undergo fundamental changes during cartilage tissue engineering regarding chondrocyte metabolism, growth, and differentiation. Three-dimensional assembly of expanded, dedifferentiated chondrocytes initiated the re-differentiation of cells that was accompanied by the reversal of the expression profile of multiple players of the transforming growth factor (TGF) signaling pathway including growth and differentiation factor-5 and inhibitor of differentiation-1 as well as by the induction of typical cartilage-related matrix genes such as type II collagen and cartilage oligomeric matrix protein. Cartilage grafts formed a cartilaginous matrix after transplantation into nude mice. Three-dimensional tissue culture of expanded articular chondrocytes initiates chondrocyte re-differentiation in vitro and leads to the maturation of cartilage grafts towards hyaline cartilage in vivo.

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PubMed2006

Decrease in expression of bone morphogenetic proteins 4 and 5 in synovial tissue of patients with osteoarthritis and rheumatoid arthritis.

Bone morphogenetic proteins (BMPs) have been identified as important morphogens with pleiotropic functions in regulating the development, homeostasis and repair of various tissues. The aim of this study was to characterize the expression of BMPs in synovial tissues under normal and arthritic conditions. Synovial tissue from normal donors (ND) and from patients with osteoarthritis (OA) and rheumatoid arthritis (RA) were analyzed for BMP expression by using microarray hybridization. Differential expression of BMP-4 and BMP-5 was validated by semiquantitative RT-PCR, in situ hybridization and immunohistochemistry. Activity of arthritis was determined by routine parameters for systemic inflammation, by histological scoring of synovitis and by semiquantitative RT-PCR of IL-1beta, TNF-alpha, stromelysin and collagenase I in synovial tissue. Expression of BMP-4 and BMP-5 mRNA was found to be significantly decreased in synovial tissue of patients with RA in comparison with ND by microarray analysis (p < 0.0083 and p < 0.0091). Validation by PCR confirmed these data in RA (p < 0.002) and also revealed a significant decrease in BMP-4 and BMP-5 expression in OA compared with ND (p < 0.015). Furthermore, histomorphological distribution of both morphogens as determined by in situ hybridization and immunohistochemistry showed a dominance in the lining layer of normal tissues, whereas chronically inflamed tissue from patients with RA revealed BMP expression mainly scattered across deeper layers. In OA, these changes were less pronounced with variable distribution of BMPs in the lining and sublining layer. BMP-4 and BMP-5 are expressed in normal synovial tissue and were found decreased in OA and RA. This may suggest a role of distinct BMPs in joint homeostasis that is disturbed in inflammatory and degenerative joint diseases. In comparison with previous reports, these data underline the complex impact of these factors on homeostasis and remodeling in joint physiology and pathology.

Adult↗

PubMed2006

Treatment of articular cartilage defects in horses with polymer-based cartilage tissue engineering grafts.

The objective of our study was to evaluate the integration of autologous cartilage tissue engineering transplants based on resorbable polyglactin/polydioxanone scaffolds into full-thickness cartilage defects of horses. Cartilage biopsies were taken from the non-load-bearing area of the lateral talus of the left tibiotarsal joint of eight healthy Haflinger horses. Tissue engineering cartilage transplants were generated by three-dimensional arrangement of autologous chondrocytes in biocompatible and resorbable polymer scaffolds. Full-thickness cartilage defects of 8 mm in diameter were created in the tubular bone condyle of the fetlock joint and cartilage grafts were fixed using an anchor system, while defects without grafting served as controls. After 6 and 12 months the repair tissue was evaluated histologically and showed formation of a cartilaginous tissue and good integration into the surrounding host tissue with firm bonding of the graft to the adjacent cartilage and the underlying subchondral bone. Biochemical analysis demonstrated that the content of glycosaminoglycans and hydroxyproline is comparable in repair tissue derived from treated and control defects. The use of three-dimensional autologous cartilage transplants based on resorbable polymer scaffolds ensures secure fixation, good integration of the graft into cartilage lesions, and is therefore suggested as a promising therapeutic option for the treatment of cartilage defects.

Animals↗

PubMed2004

Changes in the gene expression pattern of cytokeratins in human respiratory epithelial cells during culture.

The replacement of extensive tracheal defects resulting from intensive care medicine, trauma or large resections is still challenged by the re-epithelialization of an autologous or alloplastic trachea replacement. Therefore, this study was performed to investigate the potential of culture-expanded human respiratory epithelial cells (hREC) to regenerate a functional epithelium for tracheal tissue engineering. hREC from seven male nasal turbinates were freshly isolated, expanded on a collagenous matrix and subsequently cultured in high-density multi-layers to allow epithelial differentiation. The composition of epithelial cells in native respiratory epithelial tissue and culture-expanded hREC was analyzed by histological staining with Alcian blue and by immunohistochemical staining of cytokeratin pairs CK1/10 and CK5/14 with the antibodies 34betaE12 and CD44v6. Differentiation of culture-expanded hREC was further characterized by gene expression analysis of cytokeratins CK5, CK13, CK14 and CK18 using semi-quantitative real-time RT-PCR technique. Histological and immunohistochemical staining of culture-expanded hREC demonstrated basal cells covering the collagenous matrix. These cells formed a cellular multi-layer, which was composed of a basal layer of undifferentiated basal cells and an upper layer of cells differentiating along the squamous metaplasia and ciliated cell lineage. Lineage development of culture-expanded hREC was further documented by the induction of cytokeratins CK13 and CK18. Our results suggest that culture-expanded hREC have the potential to colonize collagen-coated biomaterials and to regenerate epithelial cell types for tracheal tissue engineering.

Adult↗

PubMed2004

Distinct roles of BMP receptors Type IA and IB in osteo-/chondrogenic differentiation in mesenchymal progenitors (C3H10T1/2).

The functional roles of BMP type IA and IB receptors mediating differentiation into the osteogenic and chondrogenic lineage were investigated in the mesenchymal progenitor line C3H10T1/2 in vitro. The capacity of type IA and IB BMP receptors was assessed by the forced expression of the wild-type (wtBMPR-IA or IB) and of the kinase-deficient, dominant-negative form (dnBMPR-IA or -IB) in parental C3H10T1/2 progenitors as well as in C3H10T1/2 progenitors which recombinantly express BMP2 (C3H10T1/2-BMP2) or GDF5 (C3H10T1/2-GDF5). Consistent with the higher endogenous expression rate of BMPR-IA in comparison with BMPR-IB, BMPR-IA plays the dominant role in BMP2-mediated osteo-/chondrogenic development. BMPR-IB moderately influences osteogenic and hardly chondrogenic development. BMPR-IB seems to be unable to efficiently activate downstream signaling pathways upon forced expression. However, a mutation conferring constitutive activity to the BMPR-IB receptor indicates that this receptor possesses the capacity to activate downstream signaling cascades. These results suggest that in mesenchymal progenitors C3H10T1/2 BMPR-IA is responsible for the initiation of the osteogenic as well as chondrogenic development and that BMPR-IA and -IB receptor pathways are well separated in this mesenchymal progenitor line and may not substitute each other. In addition this indicates that type IB and IA BMP receptors may transmit different signals during the specification and differentiation of mesenchymal lineages.

Animals↗

PubMed2003

Elastic cartilage engineering using novel scaffold architectures in combination with a biomimetic cell carrier.

Tissue engineering of an elastic cartilage graft that meets the criterion for both structural and functional integration into host tissue, as well as allowing for a clinically tolerable immune response, is a challenging endeavour. Conventional scaffold technologies have limitations in their ability to design and fabricate complex-shaped matrix architectures of structural and mechanical equivalence to elastic cartilage found in the body. We attempted to investigate the potential of conventionally isolated and passaged chondrocytes (2D environment) when seeded and cultured in combination with a biomimetic hydrogel in a mechanically stable and biomimetic composite matrix to form elastic cartilage within ectopic implantation sites. In vitro cultured scaffold/hydrogel/chondrocytes constructs showed islets of cartilage and mineralized tissue formation within the cell-seeded specimens in both pig and rabbit models. Specimens with no cells seeded showed only vascularized fibrous tissue ingrowth. These studies demonstrated the potential of such scaffold/hydrogel/cell constructs to support chondrogenesis in vivo. However, it also showed that even mechanically stable scaffolds do not allow regeneration of a large mass of structural and functional cartilage within a matrix architecture seeded with 2D passaged chondrocytes in combination with a cell biomimetic carrier. Hence, future experiments will be designed to evaluate an initial 3D culture of chondrocytes, effect on cell phenotype and their subsequent culture within biomimetic 3D scaffold/cell constructs.

Adult↗

PubMed2003

Tissue engineering of bone for mandibular augmentation in immunocompetent minipigs: preliminary study.

Large mandibular defects caused by trauma, infection or resection of a tumour are still a major problem for plastic and maxillofacial surgeons. The modern concept of tissue engineering combines the osteoinductive effects of osteogenic cells with a suitable scaffold structure to promote differentiation of osteoblasts and optimal matrix production. Critical size mandibular bone defects were therefore made to investigate the osteogenic potential of periosteal cells and a bioabsorbable polymer fleece (Ethisorb 510) in minipigs. Periosteal cells were isolated from four minipigs, expanded in vitro and seeded with fibrin glue into Ethisorb 510 fleeces. Tissue constructs were used to repair critical size mandibular defects and compared with two minipigs with untreated bone defects. Bone healing was evaluated after 90 and 180 days by radiographs and a histological scoring system. The radiographs showed increased radiodensity of defects filled with the cell-fibrin-fleece-constructs compared with the untreated control group after 90 and 180 days in vivo. The defects repaired by the cell-fibrin-scaffolds (180 days in vivo) obtained the highest histological mean score 2.9 (range 2-3), while defects filled by cell-fibrin-scaffolds (90 days in vivo) achieved a mean score of 2.1 (range 2-3). In contrast, the control group (n = 2) scored 1 and 2. The results show that a combination of periosteal cells and polymer fleeces may be a promising approach for clinical mandibular augmentation.

Absorbable Implants↗

PubMed2003

BMP2 initiates chondrogenic lineage development of adult human mesenchymal stem cells in high-density culture.

Human bone marrow-derived mesenchymal stem cells (MSCs) have been shown to differentiate into distinct mesenchymal tissues including bone and cartilage. The capacity of MSCs to replicate undifferentiated and to mature into cartilaginous tissues suggests these cells as an attractive cell source for cartilage tissue engineering. Here we show that the stimulation of human bone marrow-derived MSCs with recombinant bone morphogenetic protein-2 (BMP2) results in chondrogenic lineage development under serum-free conditions. Histological staining of proteoglycan with Alcian blue and immunohistochemical staining of cartilage-specific type II collagen revealed the deposition of typical cartilage extracellular matrix components. Semi-quantitative real-time gene expression analysis of characteristic chondrocytic matrix genes, such as cartilage link protein, cartilage oligomeric matrix protein, aggrecan, and types I, II, and IX collagen, confirmed the induction of the chondrocytic phenotype in high-density culture upon stimulation with BMP2 and transforming growth factor-beta3 (TGFbeta3). Histologic staining of mineralized extracellular matrix with von Kossa, immunostaining of type X collagen (typical for hypertrophic chondrocytes), and gene expression analysis of osteocalcin and adipocyte-specific fatty acid binding protein (aP2) further documented that BMP2 induced chondrogenic lineage development and not osteogenesis and/or adipogenesis in human MSCs. These results suggest BMP2 as a promising candidate for tissue engineering approaches regenerating articular cartilage on the basis of mesenchymal progenitors from bone marrow.

Adult↗

PubMed2002

Stem cells for regenerative medicine: advances in the engineering of tissues and organs.

The adult bone marrow stroma contains a subset of nonhematopoietic cells referred to as mesenchymal stem or mesenchymal progenitor cells (MSC). These cells have the capacity to undergo extensive replication in an undifferentiated state ex vivo. In addition, MSC have the potential to develop either in vitro or in vivo into distinct mesenchymal tissues, including bone, cartilage, fat, tendon, muscle, and marrow stroma, which suggest these cells as an attractive cell source for tissue engineering approaches. The interest in modern biological technologies such as tissue engineering has dramatically increased since it is feasible to isolate living, healthy cells from the body, expand them under cell culture conditions, combine them with biocompatible carrier materials and retransplant them into patients. Therefore, tissue engineering gives the opportunity to generate living substitutes for tissues and organs, which may overcome the drawbacks of classical tissue reconstruction: lacking quality and quantity of autologous grafts, immunogenicity of allogenic grafts and loosening of alloplastic implants. Due to the prerequisite for tissue engineering to ensure a sufficient number of tissue specific cells without donor site morbidity, much attention has been drawn to multipotential progenitor cells such as embryonic stem cells, periosteal cells and mesenchymal stem cells. In this report we review the state of the art in tissue engineering with mesenchymal stem and mesenchymal progenitor cells with emphasis on bone and cartilage reconstruction. Furthermore, several issues of importance, especially with regard to the clinical application of mesenchymal stem cells, are discussed.

Adult↗

PubMed2002

Porcine mesenchymal stem cells. Induction of distinct mesenchymal cell lineages.

The potential of mesenchymal stem and progenitor cells (MSC) to replicate undifferentiated and to mature into distinct mesenchymal tissues suggests these cells as an attractive source for tissue engineering. The objective was to establish a protocol for the isolation of porcine MSC from bone marrow and to demonstrate their ex vivo differentiation into various mesenchymal tissue cells. MSC from passage 2 were selected for differentiation analysis. Differentiation along the osteogenic lineage was documented by deposition of calcium, visualization of alkaline phosphatase activity, and by analysis of osteogenic marker genes. Adipocytes were identified morphologically and by gene-expression analysis. Deposition of type II collagen and histological staining of proteoglycan indicated chondrogenic differentiation. Therefore, porcine MSC may be introduced as a valuable model system with which to study the mesenchymal lineages for basic research and tissue engineering.

Adipocytes↗

PubMed2002

The T-box transcription factor Brachyury mediates cartilage development in mesenchymal stem cell line C3H10T1/2.

The BMP2-dependent onset of osteo/chondrogenic differentiation in the acknowledged pluripotent murine mesenchymal stem cell line (C3H10T1/2) is accompanied by the immediate upregulation of Fibroblast Growth Factor Receptor 3 (FGFR3) and a delayed response by FGFR2. Forced expression of FGFR3 in C3H10T1/2 is sufficient for chondrogenic differentiation, indicating an important role for FGF-signaling during the manifestation of the chondrogenic lineage in this cell line. Screening for transcription factors exhibiting a chondrogenic capacity in C3H10T1/2 identified that the T-box containing transcription factor Brachyury is upregulated by FGFR3-mediated signaling. Forced expression of Brachyury in C3H10T1/2 was sufficient for differentiation into the chondrogenic lineage in vitro and in vivo after transplantation into muscle. A dominant-negative variant of Brachyury, consisting of its DNA-binding domain (T-box), interferes with BMP2-mediated cartilage formation. These studies indicate that BMP-initiated FGF-signaling induces a novel type of transcription factor for the onset of chondrogenesis in a mesenchymal stem cell line. A potential role for this T-box factor in skeletogenesis is further delineated from its expression profile in various skeletal elements such as intervertebral disks and the limb bud at late stages (18.5 d.p.c.) of murine embryonic development.

Animals↗

PubMed2002

Bone morphogenetic proteins promote cartilage differentiation and protect engineered artificial cartilage from fibroblast invasion and destruction.

OBJECTIVE: An important role in joint and cartilage homeostasis in adults has been demonstrated recently for morphogenetic factors of the transforming growth factor beta family. Therefore, this study was undertaken to investigate the potential of bone morphogenetic proteins (BMPs) in chondrocyte differentiation using current technologies of tissue engineering. METHODS: Complementary DNAs of recombinant human BMPs 2, 4, 5, 6, and 7 were transfected into primary bovine articular chondrocytes. Transgenic chondrocytes were assembled 3-dimensionally in alginate or in bioresorbable co-polymer fleeces of vicryl and polydioxanon embedded in low-melting-point agarose. Redifferentiation and formation of cartilage tissue in vitro or after subcutaneous transplantation into nude mice were assayed by semiquantitative reverse transcriptase-polymerase chain reaction, histology, and in situ hybridization, and findings were compared with those in unmodified or control-transfected primary chondrocytes. RESULTS: Compared with other BMPs and control vector, BMP-7 induced a decrease in type I collagen expression in artificial cartilage, while transcription of the cartilage-specific type II collagen remained stable. In transplantation experiments, BMP-7 transgenic cartilage revealed the greatest amount of matrix synthesis, and BMP-7 was the only morphogen to suppress the infiltrative response of mouse fibroblastic cells into engineered cartilage, thereby preventing transplant destruction. CONCLUSION: Cartilage differentiation and matrix maturation are promoted by BMPs in cartilage engineering. The inhibitory effect of BMP-7 on a nonspecific infiltrative response in immunocompromised nude mice further suggests that individual morphogens not only may contribute to cartilage maturation, but also may protect it from nonspecific inflammation and invasive destruction. These properties advance BMPs as promising tools for engineering of cartilaginous joint bioprostheses and as candidate biologic agents or genes for cartilage stabilization in arthritis.

Animals↗