Biomedical subjects

Thomas Szuwart

Publications and source records attributed to Thomas Szuwart.

6 recordsLinked to original sources

PubMed2005

Increase in the expression of the transmembrane surface receptor CD44v6 on chondrocytes in animals with osteoarthritis.

OBJECTIVE: To evaluate the expression of CD44v6 on chondrocytes from hyaline cartilage over the course of osteoarthritis (OA). METHODS: In 12 NZW rabbits, the anterior cruciate ligament (ACL) was resected to create anterior instability of the knee. In 12 control rabbits, only a sham operation, without resection of the ACL, was performed. Four animals from each group were killed at 3, 6, and 12 weeks. After opening the knee joint, OA was macroscopically graded and hyaline cartilage of the load-bearing area was evaluated histologically according to the Mankin scale and by immunostaining for CD44v6. RESULTS: There was a positive linear correlation between the time after surgery and the macroscopic and histologic OA scores. The scores in the control group were constant over the time course. Immunostaining showed constant expression of CD44v6 in the control group. In the experimental group, a positive linear correlation between CD44v6 expression and macroscopic and histologic grades was found. CONCLUSION: The results show an in vivo increase in the expression of the hyaluronan receptor CD44 over the time course of OA. Further studies are needed to evaluate whether this pattern applies to humans and whether new treatment approaches could evolve from this knowledge.

Animals↗

PubMed2005

Cellularity and apoptosis after radiofrequency-induced shrinkage of collagenous tissue: assessment of postoperative immobilization using an in vivo rabbit model.

BACKGROUND: Electrothermally-assisted capsular shrinkage has been gaining increased acceptance in the treatment of shoulder instability. Its indication in ACL-deficient knees has been discussed recently. METHODS: We examined the influence of immobilization on cell homeostasis of healing collagenous tissue after radiofrequency energy was applied to the patellar tendon in 23 rabbits. The animals were killed immediately after surgery (n = 6) or 3 weeks after surgery (n = 17). 10 rabbits were allowed normal cage activity, whereas the treated hind limb of 7 animals was immobilized for 3 weeks in a cast. Feulgen staining was used to stain the DNA of cell nuclei. Cells undergoing apoptosis were identified by the TUNEL method. Quantitative histological assessment was performed using imaging analysis software. RESULTS: Severe cellular damage in RF-treated collagenous tissue was partly induced by the immediate onset of apoptosis. At 3 weeks after surgery, non-immobilized tendon showed increased cellularity and apoptosis, whereas immobilization prevented the increase in cellularity and apoptosis significantly. The calculated ratio of apoptosis was not influenced by any postoperative treatment. INTERPRETATION: Diminished cellularity and apoptosis during tissue remodeling, due to immobilization, may protect the shortened collagenous scaffold from stretching and further optimize the clinical outcome after radiofrequency shrinkage. To stabilize the shrunken tissue, proliferation during postoperative wound healing should be minimized by careful rehabilitation.

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PubMed2003

Histological studies of bone formation during pedicle restoration and early antler regeneration in roe deer and fallow deer.

The purpose of the present study was to examine the process of bone formation in the regenerating cranial appendages of roe deer (Capreolus capreolus) and fallow deer (Dama dama) during the early postcasting period. After the antlers are cast, osteoclastic and osteoblastic activities lead to a smoothing of the pedicle's separation surface, a strengthening of the pedicle bone, and a partial restoration of the distal pedicle portion that was lost along with the cast antler. Initially, bone formation occurs by intramembranous ossification, but early during the regeneration process cartilage is formed at the tips of the cranial appendages, and is subsequently replaced by bone in a process of endochodral ossification. Shortly after the antlers are cast, the cambium layer of the periosteum in the distal pedicle is markedly enlarged, which suggests that the periosteum serves as a cell source for the bone-forming tissue covering the exposed pedicle bone. The histological findings of our study are consistent with the view that the bony component of the regenerating cranial appendages of deer is largely derived from the pedicle periosteum. Based on findings in other bone systems, we speculate that stem cells that can undergo both osteogenic and chondrogenic differentiation are present in the pedicle periosteum. The early onset of chondrogenesis in the regeneration process is regarded as an adaptation to the necessity of producing a huge volume of bone within a short period. This parallels the situation in other cases of chondrogenesis in membrane bones.

Animals↗

PubMed2003

Bone tissue engineering by primary osteoblast-like cells in a monolayer system and 3-dimensional collagen gel.

PURPOSE: To engineer living bone tissue in vitro, bone cells must be multiplied and differentiated in cell culture. Osteoblasts are known to be the crucial cells responsible for the bone modeling process. Periosteal-derived osteoblasts were therefore cultured for up to 3 weeks in Petri dishes as well as in a 3-dimensional collagen gel. METHODS: Proliferation, migration, and differentiation of cells as well as the synthesis of extracellular matrix proteins were monitored during the culture period by histology, electron microscopy, and immunohistochemistry. Mineral formation was investigated by electron diffraction studies and element analysis. RESULTS: Osteoblasts proliferated and migrated in Petri dishes as well as in the collagen gel without loss of viability during the whole experimental period. They demonstrated a mature osteoblast phenotype as indicated by the synthesis of a bone-like extracellular matrix. They formed an extracellular matrix containing osteocalcin, osteonectin, and newly synthesized collagen type I in both environments. Mineral formation was seen in colocalization with the bone-like extracellular matrix proteins in Petri dishes. Microanalytical investigations revealed a matrix vesicle-mediated mineral formation at early stages of culture. CONCLUSIONS: Our cell culture confirmed the ability to multiplicate differentiated and viable osteoblast-like cells in 2- and 3-dimensional space. Additionally, bone-like mineralization can be induced by primary osteoblasts in monolayer culture. The data suggest that this approach can be used as a tool in bone tissue engineering.

Animals↗

PubMed2002

Histochemical and ultrastructural studies of cartilage resorption and acid phosphatase activity during antler growth in fallow deer (Dama dama).

Cartilage resorption in forming primary fallow deer antlers was studied by histochemistry and electron microscopy. A high activity of tartrate-resistant acid phosphatase (TRAP), a histochemical marker of skeletal resorbing cells, was first detected in cells located in the mesenchymal tissue separating the columns of hypertrophic cartilage. No cartilage resorption was observed in this region. Intense TRAP staining occurred in large multinucleated cells (identified as inactive osteoclasts) as well as in smaller cells (regarded as mononuclear osteoclast progenitors). On the basis of these findings it was concluded that this was the region where osteoclasts differentiated from progenitor cells. Further proximally, the mineralized cartilage was eroded by active osteoclasts that were located in Howship's lacunae and exhibited an intense TRAP staining. Electron microscopy showed that the cells identified as inactive osteoclasts lacked a polarized organization. In contrast, the active osteoclasts in the zone of cartilage resorption exhibited a typical polarized organization: the nuclei congregated near the basolateral cell surface, and there was a zone of deep membrane infoldings (ruffled border) surrounded by a clear zone at the apical cell pole adjacent to the resorption surface of the mineralized cartilage. The multinucleated cartilage-resorbing cells of the forming antler thus exhibited the typical histochemical and morphological features of active mammalian osteoclasts. Low levels of TRAP activity were also observed in hypertrophic chondrocytes; however, the specificity and potential significance of this staining remain to be elucidated.

Acid Phosphatase↗

PubMedDate not supplied

Image-based extracorporeal tissue engineering of individualized bone constructs.

PURPOSE: Computer-aided technologies have been recently employed for use in extracorporeal bone tissue engineering strategies. In this pilot animal experimental study, the intention was to test whether autologous osteoblast-like cells cultured in vitro on individualized scaffolds can be used to support bone regeneration in a clinical environment. MATERIALS AND METHODS: For this purpose, mandibular bone defects were surgically introduced into the mandibles of minipigs and the scaffold of the defect site was modeled by computer-aided design/computer-aided manufacturing technique. Autologous bone cells from porcine calvaria were harvested from minipigs and grown in culture. Cells were seeded on scaffolds generated by rapid prototyping of polylactic acid/polyglycolic acid copolymers. The defects were then reconstructed by implanting the tissue constructs. RESULTS: The intraoperative sites as well as the postoperative computerized tomographic scans demonstrated an accurate fit in the defect sites. The implanted scaffold constructs enriched with osteoblast-like cells were well tolerated and appeared to support bone formation, as revealed by histologic and immunohistochemical analyses. DISCUSSION: These results indicated that in vitro expanded osteoblast-like cells spread on a resorbable individualized scaffold can be capable of promoting the repair of bony defects in vivo. CONCLUSION: These results warrant further attempts to combine computer modeling and tissue engineering for use in bone reconstructive surgery.

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