Biomedical subjects

Wolf Petersen

Publications and source records attributed to Wolf Petersen.

At least 55 records · Page 3Linked to original sources

PubMed2003

The angiogenic peptide pleiotrophin (PTN/HB-GAM) is expressed in fracture healing: an immunohistochemical study in rats.

INTRODUCTION: Formation of new blood vessels is essential for the process of fracture healing. MATERIALS AND METHODS: We investigated the expression of the angiogenic factor pleiotrophin/HB-GAM in a closed fracture model in rats by immunohistochemical methods. RESULTS: Histologically, 5 days after fracture the callus was predominantly composed of fibrous tissue. On day 10 a prominent chondral callus connected both ends of the fractured tibia. There was a continuous transition from the chondral callus to the newly formed bone adjacent to the corticalis of the tibia. On day 15 the amount of woven bone had increased, and in 3 of 5 animals the proximal and distal tibiae were connected by a bridge of woven bone. Pleiotrophin could be immunostained in fibroblasts and endothelial cells of the fibrous tissue between the fractured tibia ends. The chondral callus remained largely pleiotrophin-negative. Only single chondrocytes adjacent to the newly formed bone were pleiotrophin-positive. On days 10 and 15 strong immunoreactivity for pleiotrophin in the well vascularized, newly formed, woven bone was detectable. Osteoblasts, endothelial cells and fibroblasts were strongly pleiotrophin-positive. CONCLUSIONS: These results show the presence of the angiogenic peptide pleiotrophin during fracture healing.

Angiogenesis Inducing Agents↗

PubMed2003

Structure and vascularization of the acetabular labrum with regard to the pathogenesis and healing of labral lesions.

INTRODUCTION: The aim of this study is to examine the structure and vascularization of the acetabular labrum with regard to the pathogenesis and healing of labral tears. MATERIALS AND METHODS: The labral tissue was characterized immunohistochemically and under light microscopy; the collagen fibril texture was demonstrated by scanning electron microscopy after temporary staggered maceration of the tissue; and the vascularization of the acetabular labrum was studied immunohistochemically using antibodies against laminin. RESULTS: The peripheral aspect of the acetabular labrum consists of dense connective tissue. The internal layer consists of type II collagen-positive fibrocartilage. Scanning electron microscopy revealed three distinct layers in the acetabular labrum: (1) the articular surface was covered by a meshwork of thin fibrils; (2) beneath the superficial network, there is a layer of lamella-like collagen fibrils; (3) the majority of the collagen fibrils are oriented in a circular manner. Blood vessels enter the labrum from the adjacent joint capsule. The distribution of vessels within the labrum is not homogenous. Blood vessels can be detected only in the peripheral one-third of the labrum. The internal part is avascular. CONCLUSION: The result of this study demonstrates that the structure of the acetabular labrum is highly significant for the direction of traumatic and dysplastic labral lesions. The biomechanical analysis of the structure suggests that the labrum is stressed by compressive load. Therefore, excision or removal of the labrum may alter physiological functions such as enhancing joint stability and load distribution. The vascular pattern identified should encourage surgeons to develop repair strategies of peripheral labral tears to maintain its functions in the hip.

Acetabulum↗

PubMed2003

The splice variants 120 and 164 of the angiogenic peptide vascular endothelial cell growth factor (VEGF) are expressed during Achilles tendon healing.

BACKGROUND: The Achilles tendon is one of the most common sites of tendon injury and rupture. One of the early events of wound healing is angiogenesis, in which neovascularization prompts delivery of inflammatory cells and fibroblasts to the wound site. Angiogenesis is controlled by a variety of mitogenic, chemotactic, or inhibitory peptides and lipid factors that act on invading endothelial and smooth muscle cells. One of the most important angiogenic factors is the vascular endothelial cell growth factor (VEGF), a glycosylated protein of 46-48 kDa composed of two disulfide-linked subunits. METHODS: We therefore investigated the expression of VEGF during healing of artificial lesions of the Achilles tendon in a sheep model by immunohistochemical, biochemical, molecular, and cell biology methods. Two groups were created, the Achilles tendon was tenotomized, and the animals were killed at 3 and 24 weeks. Each group consisted of 6 specimens. Six animals which did not undergo surgery served as controls. RESULTS: VEGF could be immunostained in tenocytes of ruptured but not in normal adult tendons. At microvessels, the receptors VEGFR-1 (flt-1) and VEGFR-2 (KDR) could also be visualized. High VEGF levels in ruptured and negligible levels in normal Achilles tendons could be confirmed and quantified by enzyme-linked immunoassay (ELISA). The highest VEGF concentrations were found in ruptured tendons, whereas the VEGF content in healthy adult tendons was negligible. Interestingly, the VEGF concentration of the original tendon stump was higher after 3 weeks than that of the newly regenerated tendon tissue. However, this difference was not significant (p>0.05). Reverse transcription-polymerase chain reaction (RT-PCR) showed that the splice variants VEGF(120 )and VEGF(164) are expressed at 3 weeks and 24 weeks, respectively. CONCLUSION: These results prove the presence of the splice variants VEGF(120 )and VEGF(164) in ruptured tendons during the healing process. The demonstrated up-regulation of VEGF in intrinsic tenocytes suggests a role for VEGF in mechanisms of angiogenesis and Achilles tendon repair. Further research is needed to evaluate if VEGF might be a possible tool to enhance the process of tendon healing.

Animals↗

PubMed2003

Quantitative assessment of blood vessels of the human Achilles tendon: an immunohistochemical cadaver study.

BACKGROUND: The pathogenesis of Achilles tendon rupture remains unclear, but vascular patterns may play an important role. Hypoxia is considered to be an important factor in the aetiology of tendon degeneration. METHODS: Statements from the literature regarding the vascularization of the Achilles tendon are controversial. We determined the vascular density of the Achilles tendon using a new method involving antibodies against laminin, a component of the basement membrane. RESULTS: The blood supply of the Achilles tendon mainly arose from the anterior paratenon of the tendon from which vessels run into the tendon. The proximal part of the tendon was supplied by a recurrent branch of the posterior tibial artery, while the distal part of the tendon was vascularized by the rete arteriosum calcaneare, supplied by the fibular and posterior tibial arteries. An avascular area could be seen close to the insertion of the tendon to the calcaneus. Three regions with different vascular density could be determined in the Achilles tendon. The distal part of the Achilles tendon had a vascular density of 56.6 vessels/cm(2). In the middle part of the tendon, the vascular density was much lower: 28.2 vessels/cm(2). The proximal part of the tendon had a vascular density of 73.4 vessels/cm(2). CONCLUSION: The reduced vascularization in the tendon waist may be a predisposing factor for degeneration and spontaneous rupture of the human Achilles tendon.

Achilles Tendon↗

PubMed2003

Hypoxia and PDGF have a synergistic effect that increases the expression of the angiogenetic peptide vascular endothelial growth factor in Achilles tendon fibroblasts.

BACKGROUND: Angiogenesis, the formation of new blood vessels from pre-existing vessels, is an essential step in the process of tendon healing and tendon graft remodelling, e.g. after anterior cruciate ligament reconstruction. To address the question of whether platelet-derived growth factor (PDGF) could influence vascular endothelial growth factor (VEGF) expression in tenocytes, we challenged primary cultures of rat tenocytes with different stimulators (hypoxia, PDGF) and measured their VEGF secretion. METHODS: To measure the VEGF secretion and the effect of PDGF, we used cell culture and stimulation of rat tenocytes (2-5 days old), immunohistochemistry as well as enzyme-linked immunosorbent assay (ELISA). RESULTS: Tenocytes cultivated under normal oxygen pressure released measurable amounts of VEGF into their culture supernatants. Stimulation with PDGF, a cytokine that activates mitogen-activated protein kinases, raised VEGF secretion 2-fold. Hypoxic conditions alone (5% O(2)) raised VEGF secretion only 2-fold. However, the combination of cytokines and hypoxia increased VEGF production 5-fold, apparently a synergistic effect. CONCLUSION: These data are useful to further our understanding of angiogenesis in tendon healing and tendon graft remodelling after ACL reconstruction.

Achilles Tendon↗

PubMed2003

Structure of the human tibialis posterior tendon.

BACKGROUND: The most common site of rupture of the posterior tibial tendon is the retromalleolar region where the tendon changes its direction of pull. The aim of this study was to characterize the tissue of the gliding zone of the tibialis posterior tendon to gain further knowledge about possible structural causes for spontaneous tendon rupture. METHODS: Light microscopy, transmission electron microscopy and immunohistochemical methods were used to describe the structure of the human tibialis posterior tendon. RESULTS: In the region where the tendon wraps around the medial malleolus, the structure of the tissue changes from the typical structure of a traction tendon. The superficial zone which was directed towards the pulley tissue had the structure of fibrocartilage with a specific three-dimensional collagen fibril texture. Transmission electron microscopy showed chondrocytes with a felt-like pericellular matrix that increased in size towards the gliding surface. The extracellular matrix of the fibrocartilage was rich in acid glycosaminoglycans and stained intensively with alcian blue at pH 1. Immunohistochemical staining of cartilage-specific extracellular matrix components such as type II collagen, chondroitin-4-sulphate, chondroitin-6-sulphate, keratan sulphate and aggrecan was positive. CONCLUSION: The location of the fibrocartilage corresponds to the region where the tibialis posterior tendon wraps around the medial malleolus, which serves as a pulley. According to the theory of 'causal histogenesis', the stimulus for the development of fibrocartilage within dense connective tissue is intermittent compressive and shear stress. The fibrocartilaginous region is the region where most spontaneous ruptures of the tibialis posterior tendon occur. Due to its structure, the fibrocartilaginous region may be more vulnerable to repetitive tensile microtrauma; degeneration may occur due to the poor repair response of the avascular fibrocartilaginous tissue.

Adult↗

PubMed2003

Intra-articular ganglion cysts of the cruciate ligaments: case report and review of the literature.

BACKGROUND: A ganglion can arise as a cystic lesion from a tendon sheath or a joint capsule and contain a glassy, clear, and jelly-like fluid. They can occur within muscles, menisci, and tendons. Intra-articular ganglion cysts of the knee joint are rare. We report on three ganglion cysts of the cruciate ligaments: Two were intercruciate, and one was located around the posterior cruciate ligament. METHODS: The clinical diagnosis was established using magnetic resonance imaging. All patients were treated successfully using arthroscopic debridement by basket punch and shaver. Subsequent histological examination confirmed the diagnosis. RESULTS: All three patients were asymptomatic at the postoperative follow-up of 16-36 months. CONCLUSION: A review of the literature reveals a controversial discussion about the clinical significance as well as the etiology of ganglion cysts arising from the cruciate ligaments. These case reports show that an intra-articular ganglion cyst of the cruciate ligaments is difficult to diagnose. A cyst does not necessarily have to be associated with specific clinical symptoms or a previous trauma. Preoperatively, MRI is essential when diagnosing ganglion cysts of the knee joint. An intra-articular ganglion cyst of the knee joint can be successfully treated by arthroscopy.

Adult↗

PubMed2003

The angiogenic peptide vascular endothelial growth factor (VEGF) is expressed during the remodeling of free tendon grafts in sheep.

BACKGROUND: Angiogenesis is important for the remodeling of autologous tendon grafts. A sheep model was used to examine the expression of the angiogenic peptide vascular endothelial growth factor (VEGF) in autologous tendon grafts after anterior cruciate ligament (ACL) reconstruction. METHODS: Merino sheep underwent ACL reconstruction with an autologous Achilles tendon split graft. VEGF and its receptors, the Fms-like tyrosine kinase receptor (FLT-1, VEGFR-1) and the kinase insert domain-containing receptor KDR (VEGFR-2/FLK-1) were detected immunohistochemically. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to detect which of the different VEGF splice forms are expressed during ACL remodeling. RESULTS: At 6 weeks, light microscopy showed zones with hypocellular necrotic graft tissue in the central part surrounded by hypercellular and hypervascularized reparative tissue invading the former graft tissue from the periphery. In contrast to the necrotic tissue, all cell types of the reparative tissue labeled strongly positive for VEGF. The VEGF receptors FLT-1 and KDR could be detected on endothelial cells of blood vessels. At 12 weeks, the complete graft diameter showed an increased vascular density (anti-factor VIII immunoreactivity), but zones of non-remodeled former graft tissue could not be found. Fusiform fibroblasts labeled strongly for VEGF. At 24 weeks, VEGF immunostaining decreased, and at 52 and 104 weeks, the grafts were largely VEGF-negative. RT-PCR supported the immunohistochemical results regarding VEGF expression and showed further that the splice variants VEGF(120 )and VEGF(164) are expressed during angiogenesis during the remodeling of tendons. CONCLUSION: We conclude that the angiogenic peptide VEGF plays a role in tendon graft remodeling.

Achilles Tendon↗

PubMed2003

Expression of pleiotrophin, an embryonic growth and differentiation factor, in rheumatoid arthritis.

OBJECTIVE: Pleiotrophin (PTN), a 15.3-kd heparin-binding peptide, is expressed in mesodermal and neuroectodermal cells during development, but rarely in adult tissues. Since developmentally regulated factors often reappear during disease, we sought to determine whether there was PTN expression in the synovial membranes of patients with rheumatoid arthritis (RA). METHODS: PTN messenger RNA expression was assayed by quantitative reverse transcriptase-polymerase chain reaction. The protein was localized by immunohistochemistry and quantified by enzyme-linked immunosorbent assay (ELISA). Effects of PTN on cell proliferation in vitro were determined by DNA measurements. RESULTS: PTN expression in normal adult synovial membranes and cartilage was barely detectable. However, PTN was strongly up-regulated in synovial tissues from patients with RA. In contrast, samples from patients with pyogenic arthritis had moderate PTN levels, and those from patients with osteoarthritis had only a slight increase in PTN, as measured by ELISA. In RA patients, PTN was localized primarily in synoviocytes but was also found in endothelial cells of blood vessels. In cultured mouse fibroblasts used as a model, PTN expression was up-regulated by tumor necrosis factor alpha and was more weakly up-regulated by epidermal growth factor. Recombinant PTN stimulated the proliferation of cultured human synoviocytes and the monocyte cell line THP-1, but not human dermal fibroblasts, in which PTN increased the synthesis of vascular endothelial growth factor. CONCLUSION: In addition to certain types of cancer, the embryonic growth and differentiation factor PTN is expressed in adults with inflammatory diseases, in particular, RA. Proinflammatory cytokines enhance the expression of PTN. Thus, we propose that PTN is a further paracrine angiogenesis and growth factor for synovial cells in RA.

Animals↗

PubMed2003

The angiogenic peptide vascular endothelial growth factor (VEGF) is expressed in chronic sacral pressure ulcers.

Chronic decubital lesions have a limited potential to heal. Evidence suggests that a lack of local revascularization is involved in this aetiology. The present study investigated the expression of one of the most important angiogenic factors, the vascular endothelial growth factor (VEGF), in different regions of sacral chronic decubital lesions and in normal skin by immunohistochemical, biochemical, molecular, and cell biology methods. To elucidate some of the factors responsible for the induction of VEGF in chronic skin ulcers, cultured fibroblasts were exposed to hypoxia and/or growth factors. In the central part (zone I) of chronic ulcers and in normal skin, immunostaining for VEGF remained largely negative. However, VEGF could be immunostained in cells in the granulation tissue adjacent to central necrosis (zone II). VEGF receptor 2 (VEGFR-2; KDR) could also be identified in microvessels. High VEGF levels were present in homogenates from granulation tissue by enzyme-linked immunosorbent assay (ELISA) and western blot experiments: low concentrations were found in areas of central necrosis and negligible amounts were present in normal skin. Reverse transcriptase-polymerase chain reaction (RT-PCR) showed that only the splice variants VEGF(121) and VEGF(165) were expressed. In cultured fibroblasts, hypoxia or platelet-derived growth factor (PDGF) raised VEGF production. The angiogenic peptide VEGF is present in all zones of chronic decubital ulcers. Its strong expression within the adjacent granulation tissue supports the view that there is no deficiency of VEGF. VEGF may be involved in the healing process of chronic skin lesions, but it seems that loss of another factor may be responsible for the poor healing response.

Aged↗

PubMed2003

Thromboembolic complication after arthroscopic shoulder surgery.

Thromboembolic complications after arthroscopic shoulder surgery are very unusual and need thorough investigation of the possible origin. In this case of venous pulmonary thromboembolism after arthroscopy of the shoulder, neither a hint of coagulopathy nor an anatomic abnormality could be found that explains this complication. Therefore, irritation of the subclavian vein caused by compression by the motor-driven shaver is probably one cause for our thromboembolic complication. Careful attention to positioning, fluid management, and use of traction, as well as an appreciation of shoulder anatomy to select portal placement will help decrease the common complications associated with shoulder arthroscopy. A further option to prevent thrombembolic complications in shoulder arthroscopy patients might be prophylaxis with a low-weight heparin in patients with risk factors. In conclusion, awareness of uncommon complications such as deep venous thrombosis and pulmonary embolism will help the orthpaedic surgeon promptly diagnose and treat these problems.

Anticoagulants↗

PubMed2003

Primary stability of bone-patellar tendon-bone graft fixation with biodegradable pins.

PURPOSE: We evaluated the initial bone-patellar tendon-bone (BPTB) graft fixation strength of biodegradable pins compared with interference screws in anterior cruciate ligament reconstruction using bovine knees. TYPE OF STUDY: Biomechanical in vitro study. METHODS: Ten BPTB grafts from human donors fixed with 2 biodegradable 2.7-mm pins (Rigid Fix; Ethicon, Mitek Division, Norderstedt, Germany) crossing the bone block perpendicular and 10 BPTB grafts fixed with conventional biodegradable interference screws (Absolute Absorbable Interference Screw; Innovasive Devices, Marlborough, MA) underwent ultimate single-cycle failure loading at a rate of 200 mm/min. The grafts were fixed to bovine tibia to simulate young human femoral bone density. Failure mode, displacement before failure, and ultimate failure load were tested with a testing machine. The pullout force was in line with the bone tunnel to simulate a worst case scenario. RESULTS: The failure mode for cross pins was either fracture of the bone block (5 specimens) or fracture of the articular pin (5 specimens). The failure mode for interference screws was slippage past the screw in all specimens. In the single cycle loading test, the mean yield load for the biodegradable pins was 400.2 (+/- 122.4) N, maximum load, 524.6 (+/- 136.6) N, with a mean stiffness of 155.2 (+/- 32.4) N/mm. The yield load at failure for the interference screw was 402.7 (+/- 143.9) N, maximum load 515.7 (+/- 168.5) N with a mean stiffness of 168 (+/- 42) N/mm. CONCLUSIONS: Fixation of a BPTB graft with 2 biodegradable 2.7-mm pins (Rigid Fix) leads to primary stability that is comparable to fixation with biodegradable interference screws.

Absorbable Implants↗

PubMed2003

The role of vascular endothelial growth factor in glucocorticoid-induced bone loss: evaluation in a minipig model.

Vascular endothelial growth factor (VEGF) has been recently shown to play an important role during endochondral bone formation in hypertrophic cartilage remodeling, ossification, and angiogenesis. To our knowledge there are no previous studies investigating the role of VEGF in osteoporosis. We hypothesized that VEGF expression in bone would be reduced under glucocorticoid (GC) treatment and tested this in a minipig model. As part of a larger study, 17 primiparous sows (Göttingen minipig) were allocated to two experimental groups when they were 15 months old: a control group (n = 9) and a group receiving GC treatment for 15 months (n = 8). All animals were fed a semisynthetic diet until they were sacrificed. The GC group received prednisolone orally at a daily dose of 1 mg/kg body wt for 8 weeks and thereafter 0.5 mg/kg body wt. VEGF levels in lumbar vertebrae were measured by enzyme-linked immunosorbent assay (ELISA) and verified by Western blot analysis. VEGF and its receptors (VEGFR) were localized by immunohistochemistry. Expression of VEGF-mRNA was analyzed by reverse transcription-polymerase chain reaction. VEGF protein was quantified in supernatants of cultivated osteoblasts by ELISA. Spinal bone mineral density was assessed in vivo by quantitative computed tomography. Expression of cyclooxygenase-2 (COX-2) protein was investigated by immunohistochemistry. High VEGF concentrations were measured in normal lumbar vertebrae whereas VEGF concentrations were 60% lower (P < 0.0001) in GC-treated minipigs. VEGF levels were associated (r = 0.7) with rates of spinal trabecular bone loss, which differed significantly (P < 0.0013) between controls (-0.47 +/- 2.2% SEM) and GC-treated minipigs (-12.8 +/- 2.3% SEM). Osteoblasts were immunopositive for VEGF. VEGF receptors VEGFR-2 (KDR, flk-1) and VEGFR-1 (flt-1) could be immunostained on osteoclasts and osteoblasts. VEGF-mRNA and protein were detectable in the lumbar vertebrae of all animals. The expression of COX-2 protein was decreased in GC-treated animals. VEGF is produced in osteoblasts and its concentration is decreased in GC-treated animals as well as in osteoblasts exposed to GC. Since reductions in VEGF concentrations correlate with parallel measurement of bone mineral density in GC-treated minipigs we hypothesize that VEGF may be an important modulating factor for bone remodeling, specifically in GC-induced osteoporosis. GC inhibit COX-2 and hence prostaglandin E2 (PGE2) production. Since PGE2 is able to increase VEGF synthesis, this may be the link between GC and VEGF decrease.

Adipocytes↗

PubMed2003

Mechanical factors influence the expression of endostatin--an inhibitor of angiogenesis--in tendons.

Avascular zones of tendons are predisposed for degenerative changes and spontaneous rupture. Therefore, we analyzed the expression of the endogenous angiogenesis inhibiting factor endostatin in human fetal and adult tendons by immunohistochemical and biochemical methods. Moreover, to elucidate factors involved in the regulation of vascularity, we exposed primary cultures of rat tendon cells to intermittent hydrostatic pressure (0.2 MPa, 0.1 Hz for 24 h), and measured the endostatin content by ELISA and the effect of the conditioned medium to the proliferation of human umbilical vein endothelial cells (HUVEC). In fetal tendons high endostatin levels could be quantified by ELISA whereas low levels were found in adult tissue. In fetal tendons endostatin could also be immunostained in endothelial cells but mainly in fibroblasts. In adult Achilles tendons endostatin immunostaining was restricted to endothelial cells. In the tibialis posterior tendon--as an example for "wrap around"--endostatin immunostaining remained positive in the fibrocartilage adjacent to the medial malleolus. Fibrochondrocytes of the type II collagen positive fibrocartilage were intensively stained with the endostatin antibody. Factor VIII immunostaining showed that this region was largely avascular. Monolayer cultures of tendon cells released measurable amounts of endostatin into their culture supernatants. Application of intermittent hydrostatic pressure increased endostatin expression significantly. The conditioned media of tendon fibroblasts cultivated under intermittent hydrostatic pressure inhibited the proliferation of HUVEC in a dose dependent way. The spatial expression of endostatin in adult gliding tendons suggests that mechanical factors are involved in the regulation of this anti-angiogenic factor. In accordance, tendon cells exposed to intermittent hydrostatic pressure inhibit endothelial cell proliferation via humoral factors and produce endostatin. These findings support the view that the development and maintenance of avascular zones in tendons might be caused by a mechanically induced upregulation of anti-angiogenic factors.

Achilles Tendon↗

PubMed2003

Reduced vascular endothelial growth factor correlates with alveolar epithelial damage after experimental ischemia and reperfusion.

BACKGROUND: After clinical lung transplantation, the amount of vascular endothelial growth factor (VEGF) was found to be decreased in the bronchoalveolar lavage from lungs with acute lung injury. Since Type II pneumocytes are a major site of VEGF synthesis, VEGF depression may be an indicator of pulmonary epithelial damage after ischemia and reperfusion. METHODS: Using an established rat lung model, we investigated the relationship between VEGF protein expression, oxygenation capacity and structural integrity after extracorporeal ischemia and reperfusion (ischemia 6 hours at 10 degrees C, reperfusion 50 minutes) and preservation with either low-potassium dextran solution (Perfadex 40 kD, n = 8) or Celsior (n = 6). Untreated, non-ischemic lungs served as controls (n = 5 per group). Perfusate oxygenation was recorded during reperfusion. An enzyme-linked immunoassay (ELISA) for VEGF protein and reverse transcription-polymerase chain reaction (RT-PCR) for mRNA splice variants were determined on tissue collected from the left lungs, whereas the right lungs were fixed by vascular perfusion for VEGF immunohistochemistry as well as structural analysis by light and electron microscopy. Tissue collection by systematic uniform random sampling was representative for the whole organ and allowed for quantification of structures by stereological means. RESULTS: After ischemia and reperfusion, the 3 major VEGF isoforms, VEGF(120), VEGF(164) and VEGF(188), were present. VEGF protein expression was reduced, which correlated significantly with perfusate oxygenation (r = 0.736; p = 0.002) at the end of reperfusion. It was inversely related to Type II cell volume (r = 0.600; p = 0.047). VEGF protein was localized by immunohistochemistry in Type II pneumocytes, alveolar macrophages as well as bronchial epithelium, and staining intensity of Type II cells was reduced after ischemia and reperfusion. Alveolar edema did not occur but significant interstitial edema accumulated around vessels and in the blood-gas barrier, which showed a higher degree of epithelial damage after preservation with Celsior compared with the other groups. CONCLUSIONS: Depression in VEGF protein expression can be considered an indicator for increased alveolar epithelial damage. Preservation with low-potassium dextran solution resulted in improved oxygenation and tissue integrity compared with Celsior.

Animals↗

PubMed2003

Blood supply of the flexor hallucis longus tendon with regard to dancer's tendinitis: injection and immunohistochemical studies of cadaver tendons.

The flexor hallucis longus is the most common site of lower extremity tendon disorders in ballet dancers. Reduced vascularity is an important factor contributing to tendon degeneration and rupture under strain. A study was conducted on the vascular pattern of the human flexor hallucis longus tendon with injection techniques and immunohistochemically by using antibodies against laminin. Blood supply arose from the posterior tibial and the medial plantar artery. Peritendinous blood vessels penetrated the tendon and anastomosed with a longitudinally oriented intratendinous network. Injection specimens and immunohistochemistry revealed one avascular zone in which the tendon passed behind the talus and a second in which the tendon wrapped around the first metatarsal head. These are the most typical areas for tendon degeneration and rupture.

Adult↗

PubMed2002

Quantitative measurement of the splice variants 120 and 164 of the angiogenic peptide vascular endothelial growth factor in the time flow of fracture healing: a study in the rat.

Formation of new blood vessels is essential for the process of wound and fracture healing. Little is known about the time-dependent expression and the involved splice variants of the vascular endothelial growth factor (VEGF). We therefore quantified and differentiated the angiogenic factor VEGF and its receptors (VEGFR) in a rat fracture model by immunohistochemical, biochemical and molecular biological methods. VEGF could be immunostained in chondrocytes and osteoblasts of the callus, but not in fibrous callus. In the capillaries, VEGFR-1 (flt-1) and VEGFR-2 (flk-1/KDR) were also visualized. Both receptors were also detectable in some chondrocytes and in osteoclasts. Enzyme-linked immunosorbent assay (ELISA) measurements showed high levels of VEGF in fractured tibiae and negligible ones in non-injured bone. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed expression of the rat splice variants VEGF(120) and VEGF(164) during the course of fracture healing, which corresponds to human VEGF121 and VEGF165 splice variants. VEGF plays the most important role during the early phase of fracture healing, but VEGF concentrations decrease further after day 5.

Alternative Splicing↗

PubMed2002

Angiogenesis in fetal tendon development: spatial and temporal expression of the angiogenic peptide vascular endothelial cell growth factor.

In traction tendons, whose line of action corresponds to that of the muscle, few blood vessels are uniformly distributed within the tendon tissue. In gliding tendons, which change their direction of pull, an avascular zone is normally found in the region where the tendon wraps around the pulley. This avascular fibrocartilaginous gliding zone is predisposed for degenerative changes and spontaneous rupture. Since factors regulating angiogenesis in tendons are largely unknown, we analyzed the expression of the vascular endothelial growth factor (VEGF) and its receptors VEGFR-1 (flt-1) and VEGFR-2 (KDR) in human fetal and adult tendon tissue by immunohistochemical, biochemical, and molecular biology methods. In order to elucidate whether mechanical stress might influence VEGF expression in tendon tissue we loaded primary cultures of rat tenocytes with intermittent hydrostatic pressure in a special cell culture chamber (amplitude: 0.2 Mpa, frequency: 0.1 Hz, time period: 5 h/day) and measured VEGF expression using ELISA. In fetal tendons high VEGF levels could be quantified by ELISA, whereas negligible ones were found in adult tissue. VEGF could be immunostained in tenocytes and endothelial cells. In the tibialis posterior tendon - as an example for a gliding tendon - VEGF immunostaining decreased in the gliding zone adjacent to the bony hypomochlion between week 20 and week 24 after gestation. This region remained largely avascular during the fetal period. In the peritendineum and in regions proximally and distally of the gliding zone immunostaining for VEGF was positive and factor VIII-positive microvessels could be detected. In these vessels, the VEGFR-1 (flt-1) and the VGEFR-2 could also be visualized. Reverse transcription-polymerase chain reaction (RT-PCR) confirmed the results regarding VEGF expression and showed further that the splice variants VEGF(121) and VEGF(165) are expressed exclusively during angiogenesis in fetal tendons. Monolayer cultures of tendon cells released measurable amounts of VEGF. Application of intermittent hydrostatic pressure decreased VEGF expression significantly. Thus, the angiogenic peptide VEGF is present in human fetal tendons, which are exposed to traction, but not in the avascular zone of gliding tendons, which are predominantly exposed to compressive and shearing forces. These findings support the view that the development of avascular zones in tendons might be caused by a mechanically induced downreglation of VEGF expression.

Achilles Tendon↗