Bernd Kinner

Smooth muscle actin expression by human articular chondrocytes and their contraction of a collagen—glycosaminoglycan matrix in vitro

Recent studies have demonstrated that human articular chondrocytes can express the gene for a contractile muscle actin, α‐smooth muscle actin (SMA), in situ. One objective of this work was to evaluate the SMA‐content of isolated human articular chondrocytes using Western blot analysis and to correlate the amount of SMA in the cells with passage number and the number of days in culture. A second objective was to determine if articular cartilage‐derived cells expressing the gene for SMA in vitro also continue to express type II collagen. A final aim of the current study was to determine if SMA‐containing cartilage‐derived cells were capable of contracting a collagen–glycosaminoglycan analog of extracellular matrix in vitro. Articular chondrocytes were isolated from 13 patients undergoing total joint arthroplasty. Cells were serially passaged through passage 7. Samples were allocated for Western blot analysis of SMA. Cells in monolayer culture were also stained immunohistochemically for SMA and type II collagen. Cells from passage 3 and 7 were seeded into a porous type I collagen–glycosaminoglycan matrix and the diameter of the scaffolds measured every other day for 21 days. Immunohistochemistry of the articular cartilage samples revealed SMA in the articular chondrocytes in situ with a greater percentage of cells staining positive in the superficial half (60 ± 1.2%; mean ± SEM) of the cartilage than in the basal half (28 ± 1.3%). There was an increasing amount of SMA in the cells in monolayer culture with passage number and a meaningful correlation of the SMA content with the days in culture (linear regression analysis; R2 = 0.72). Double staining for SMA and type II collagen showed that type II collagen‐expressing cells in monolayer could also express SMA. SMA‐containing cells were found to contract the collagen–glycosaminoglycan matrix, with the cells containing more SMA (passage 7 cells) displaying more matrix contraction than those with a lesser amount of SMA (passage 3 cells). The results indicate that control of the expression of SMA may be important when employing articular chondrocytes, expanded in monolayer culture, for implantation alone or in a cell‐seeded matrix for cartilage repair procedures.

Influence of the growth factors PDGF‐BB, TGF‐β1 and bFGF on the replicative aging of human articular chondrocytes during in vitro expansion

Decreasing replicative potential and dedifferentiation of articular chondrocytes during expansion in cell culture are essential limitations for tissue engineering and cell therapy approaches. Telomeres and telomerase play a key role in cell development, aging, and tumorigenesis. There is evidence that growth factors are involved in regulating telomerase activity. Therefore, the objective was to evaluate the effect of selected growth factors on telomere biology of serially passaged chondrocytes. Human articular chondrocytes were isolated from cartilage of three patients undergoing total knee arthroplasty. The chondrocytes were cultured in monolayer with the growth factors PDGF‐BB, TGF‐β1, and bFGF. Telomere length was measured by telomere restriction fragment length assay, and telomerase activity was determined by quantifying the gene expression of its catalytic subunit hTERT by rtPCR. Chondrocytes cultured with PDGF‐BB and TGF‐β1 showed a significantly higher proliferation rate than control cells. None of the growth factor cultures revealed an accelerated rate of telomere shortening. Telomerase was not expressed in significant amounts in any of the chondrocyte cultures. Growth factor treatment of chondrocyte cell cultures for cell therapy purposes can be regarded as safe in terms of telomere biology.

Expression of smooth muscle actin in connective tissue cells participating in fracture healing in a murine model

The role of alpha-smooth muscle actin (SMA)-expressing fibroblasts in the contraction of skin wounds has been known for three decades. Recent studies have demonstrated that osteoblasts can also express the gene for this contractile muscle actin isoform and can contract a collagen-glycosaminoglycan analog of extracellular matrix in vitro. These findings provided rationale for the hypothesis that SMA-expressing cells contribute to fracture healing by drawing the bone ends together. To begin to test this hypothesis, immunohistochemistry was employed to evaluate the distribution of connective tissue cells expressing SMA in a mouse model of successful fracture healing. The results demonstrated that the majority of the cells comprising the mesenchymal tissue interposed between the fracture ends contained SMA after 7 and 21 days, supporting the working hypothesis. Most of the osteoblasts lining the surfaces of newly forming bone and the chondrocytes comprising the cartilaginous callus also expressed this contractile actin isoform. The maximal SMA expression extended from 7 to 21 days postfracture. The finding of high levels of SMA expression in connective tissue cells participating in fracture healing suggests that SMA-enabled contraction may be playing a role in the healing process. These results warrant further study of the specific SMA-dependent cell behavior.

Expression of smooth muscle actin in osteoblasts in human bone

It is well known that certain connective tissue cells (viz., dermal fibroblasts) can express the gene for a muscle actin – α‐smooth muscle actin – and can contract. This process contributes to skin wound closure and is responsible for Dupuytrens contracture. The objective of this study was to determine if human osteoblasts can also express the gene for α‐smooth muscle actin. Immunohistochemistry using a monoclonal antibody for α‐smooth muscle actin was performed on human cancellous bone samples obtained from 20 individuals at the time of total joint arthroplasty. The percentages of resting and active osteoblasts on the bone surfaces containing this muscle actin isoform were evaluated. Explants of human bone were also studied for the expression of α‐smooth muscle actin in the tissue and in the outgrowing cells with time in culture. Western blot analysis was performed to quantify the α‐smooth muscle actin content of the outgrowing cells relative to smooth muscle cell controls.

Calcaneocuboid joint involvement in calcaneal fractures.

BACKGROUND The reported incidence of calcaneocuboid joint (CCJ) involvement in calcaneal fractures varies considerably. It is largely unknown to what extent CCJ involvement accounts for outcome in these fractures. Therefore, the goal of this study was to analyze the incidence and effects of CCJ involvement in calcaneal fractures. METHODS The clinical records of 106 patients, treated between 2000 and 2004, were reviewed for fracture classification, injury mechanism, surgical treatment, and complications. In a prospective cross-sectional study, 44 patients were assessed clinically (SF-36 American Orthopaedic Foot and Ankle Society score) and radiographically. Gait analysis was performed using dynamic pedography. RESULTS Sixty-eight percent of all fractures had involvement of the CCJ. Fractures with CCJ involvement were caused by a more severe injury than fractures without CCJ involvement (Mann-Whitney U test, p = 0.03); this is reflected by a strong association between CCJ involvement and fracture classification (Spearman, p < 0.006). Patients with involvement of the CCJ-especially those with a postoperative step in the CCJ-achieved a lower SF-36 score as well as a lower American Orthopaedic Foot and Ankle Society score than patients without CCJ involvement. CCJ involvement was associated with more difficulties in walking on rough surface (Spearman, p = 0.020). Limitations during gait were confirmed by dynamic pedography. Grading of posttraumatic osteoarthritis was associated with fracture classification (chi test p < 0.02) and quality of reduction (chi test p < 0.01). CONCLUSIONS These results indicate that calcaneal fractures with involvement of the CCJ are associated with more severe trauma and worse outcome. Thus, the CCJ should be given more credit during surgery and in our research efforts.

Functional donor-site morbidity following (osteo-) fasciocutaneous parascapular flap transfer.

Problem:The parascapular flap is extremely versatile in the armamentarium of the plastic surgeon. However, little is known about the donor-site morbidity. Our purpose was to investigate limitations and problems arising at the donor site of parascapular flaps. Methods:Twenty patients with free parascapular flaps were followed up over a period of 3 years. Donor-site morbidity was evaluated using standardized evaluation forms. Constant score was calculated to judge shoulder function, SF-36 score was used to evaluate patient satisfaction. Results:All flaps survived in our series. In 2 patients, delayed wound healing was recorded at the donor site. In 3 patients, shoulder function was limited. In 1 patient, the brachial plexus was affected, and another had preexisting rotator cuff disease. Scar dimensions varied considerably; however, cosmetic aspects of the donor site were not a complaint. Discussion:This is the first report evaluating donor-site morbidity of parascapular flaps. Limitations in shoulder function are low if correct operative technique with refixation of the musculature is maintained. In general, patients did not have any complaints about the cosmetic appearance of the donor site.

Expression of smooth muscle actin in cells involved in distraction osteogenesis in a rat model

Distraction osteogenesis has proven to be of great value for the treatment of a variety of musculoskeletal problems. Little is still known, however, about the phenotypic changes in the cells participating in the bone formation process, induced by the procedure. Recent findings of the expression of a contractile muscle actin isoform, α‐smooth muscle actin (SMA), in musculoskeletal connective tissue cells prompted this immunohistochemical study of the expression of SMA in cells participating in distraction osteogenesis in a rat model. The tissues within and adjacent to the distraction site could be distinguished histologically on the basis of cell morphology, density, and extracellular matrix make‐up. The percentage of SMA‐containing cells within each tissue zone was graded from 0 to 4. The majority of the cells in each of the zones stained positive for SMA within five days of the distraction period. The SMA‐containing cells included those with elongated morphology in the center of the distraction site and the active osteoblasts on the surfaces of the newly forming bone.

The use of ‘fasciocutaneous’ and ‘osteofasciocutaneous’ parascapular flaps for lower limb reconstruction: a retrospective study of 20 patients

BACKGROUND The parascapular flap is a widely accepted and suitable option for covering defects in almost all anatomical areas. Here, we report our experience with the microvascular transfer of parascapular flaps for the coverage of large lower leg defects with reference to our retrospective study. PATIENTS AND METHODS Twenty patients with free parascapular flaps (17 male, three female, age: 43+/-17 years, BMI 26.1+/-3.5) were examined 3 months to 3 years after free tissue transfer. All procedures and examinations were performed by the same experienced surgeon (2002-2005). Flap dimensions ranged from 8 x 4 cm to 30 x 13 cm, with an average of 20.4+/-6.6 cm x 8.9+/-2.6 cm. The parameters studied included perioperative morbidity, donor site morbidity, flap vitality, complications, functional shoulder tests, patient satisfaction (visual analog scale, VAS), the duration of the hospital stay and the long-term outcome. RESULTS All of the 20 flaps remained vital. Adequate coverage and complete healing were obtained in all patients during the follow-up period and all patients were physically mobile. General patient satisfaction with the intervention was high (VAS: median 7.5; x(25)=6.0; x(75)=9.5); donor site morbidity was low, that is, only one patient presented with reduced range of motion and shoulder function compared to the preoperative status. The hospital stay after flap transfer was 20.8+/-9.8 days and the overall hospital stay was 32.1+/-15.0 days. CONCLUSIONS Our study confirms that the parascapular flap is a very versatile and safe flap for lower limb reconstruction with low donor morbidity.

Post-traumatic fulminant paradoxical fat embolism syndrome in conjunction with asymptomatic atrial septal defect: a case report and review of the literature

IntroductionFat embolism syndrome with respiratory failure after intramedullary nailing of a femur fracture is a rare but serious complication in trauma patients.Case presentationWe present the case of a 20-year-old Caucasian man who experienced paradoxical cerebral fat embolism syndrome with fulminant progression after intramedullary nailing of a femur fracture, in conjunction with a clinically asymptomatic atrial septal defect in a high position resulting in a right-to-left shunt.ConclusionFat embolism syndrome may occur as a fulminant complication following femoral fracture repair in the presence of a concomitant atrial septal defect with right-to-left shunt. Thus, in patients with cardiac right-to-left shunts, femurs should not be nailed intramedullary, not even in cases of isolated injuries.

Peripheral Talus Fractures-A Clinical Observational Study of 16 Cases

Background: Peripheral talar fractures are rare injuries. They comprise fractures of the lateral process, the lateral and medial tubercle of the posterior process, the medio-caudal ridge, and traumatic osteochondral fractures of the lateral talar dome. The objective of this observational case series was to report the clinical and radiological outcome after surgical treatment.Methods: 16 peripheral talar fractures could be included in this retrospective case series. All patients were treated operatively and followed for a minimum of 12 months. Clinical and radiological outcome were recorded.Results: Mean follow-up was 16 months. 13 subjects presented with concomitant injuries. 2 patients suffered an additional spine fractures, and 4 patients were polytraumatized. No non-union or mal-union were observed. One patient needed subtalar and calcaneo-cuboidal fusion during follow up due to a concomitant calcaneal fracture. Other secondary procedures like implant removal were necessary in 5/16 subjects. During the last follow-up the recorded AOFAS score (mean ± SD) was 87.3 ± 6.6 and the EQ5-D (mean ± SD) 0.91 ± 0.06.Conclusion: With early diagnosis and timely surgical treatment good results can be expected after peripheral fractures of the talus. Less favourable outcomes are usually associated with concomitant injuries.