Cell-free repair of small cartilage defects in the Goettinger minipig: the effects of BMP-7 continuously released by poly(lactic-co-glycolid acid) microspheres.

OBJECTIVE: Cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed after treatment with cell-free collagen type-I gel with or without additional BMP-7 loaded poly(lactic-co-glycolid acid) microspheres. METHODS: Two full-thickness chondral defects were created in the trochlear groove of one hind leg knee in six Goettinger minipigs. Six defects were treated with a cell-free collagen type-I gel plug of 10 mm, the corresponding six defects were treated with a cell-free collagen type-I plug with poly(lactic-co-glycolid acid) microspheres loaded with recombinant BMP-7 (100 ng/ml gel). After 1 year, the animals were sacrificed. Immediately after recovery, non-destructive biomechanical testing was performed. The repair tissue quality was evaluated by immunohistochemistry and the O'Driscoll score was calculated. RESULTS: After 1 year, a robust cellular migration into the cell-free collagen gel plugs occurred and a hyaline-like repair tissue was found. Collagen type-II production and cellular organisation were higher in the BMP-7 microsphere group. The determination of the E-modulus, creep and relaxation revealed that mechanical properties of the BMP-7 microsphere group in summary were closer to control hyaline cartilage. CONCLUSIONS: While all specimens revealed a homogeneous cellular distribution, ECM production, cellular organisation and mechanical properties were enhanced by continuous BMP-7 release.

Reoperation rate after internal fixation of intertrochanteric femur fractures with the percutaneous compression plate: what are the risk factors?

OBJECTIVE: The aim was this study was to analyze the risk factors for reoperation after internal fixation of intertrochanteric fractures of the femur using the percutaneous compression plate (PCCP). DESIGN: This was a retrospective cohort study. SETTING: The study was conducted at the University Hospital. PATIENTS AND METHODS: Patients with intertrochanteric femur fractures who underwent internal fixation with a PCCP were included in this study. We investigated potential risk factors such as age, gender, body mass index, comorbidities of the patients (American Society of Anesthetist classification), type of fracture (AO/OTA classification), experience of the surgeons (in terms of the number of surgical procedures with the PCCP device), tip-apex distance (TAD), and operation time. The procedures were performed by 10 surgeons. Logistic regression was used to assess potential predictors for the need of reoperation. RESULTS: Of the 96 patients with 96 intertrochanteric fractures, 8 underwent reoperation due to local complications (8.3%). The most frequent complication was complete or imminent cutting out of the upper cervical screw (N = 5; 5.2%). Five of the 8 risk factors that were associated with reoperation in the initial univariable analyses with a P value of <0.20 were retained in a multivariable logistic regression model, including, age, body mass index, TAD, experience of the surgeons, and operation time. Of these, only the factor TAD proved to be a significant predictor for reoperation (P = 0.027, odds ratio = 1.089, 95% confidence interval 1.01-1.175). CONCLUSIONS: Our data show that the surgeon-related risk factors (number of operations, operation time, TAD) seem to be more relevant for the reoperation rate after internal fixation with the PCCP device when compared with the patient-related risk factors. This finding indicates a substantial learning curve for this technically demanding procedure. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Outcome after thoracoscopic ventral stabilisation of thoracic and lumbar spine fractures.

BACKGROUND AND PURPOSE: Thoracoscopic-assisted ventral stabilisation for thoracolumbar fractures has been shown to be associated with decreased recovery time and less morbidity when compared with open procedures. However, there are a limited number of studies evaluating late clinical and radiological results after thoracoscopic spinal surgery. METHODS: We performed an analysis of the late outcomes of thoracolumbar fractures after minimally invasive thoracoscopic ventral instrumentation. Between August 2003 and December 2008, 70 patients with thoracolumbar fractures (T5-L2) underwent ventral thoracoscopic stabilisation. Tricortical bone grafts, anterior plating systems (MACS-System), and cage implants were used for stabilisation. Outcomes measured include radiologic images (superior inferior endplate angle), Visual Analogue Scale (VAS), VAS Spine Score, quality of life scores SF-36 and Oswestry Disability Index (ODI). RESULTS: Forty seven patients (67%, 47 out of 70) were recruited for the follow up evaluation (2.2 ± 1.5 years). Lower VAS Spine scores were calculated in patients with intra- or postoperative complications (44.7 (± 16.7) vs. 65.8 (± 24.5), p=0.0447). There was no difference in outcome between patients treated with bone graft vs. cage implants. Loss of correction was observed in both bone graft and titanium cage groups. INTERPRETATION: The present study demonstrates diminished long-term quality of life in patients treated with thoracoscopic ventral spine when compared with the outcome of german reference population. In contrast to the other patients, those patients without intra-operative or post-operative complications were associated with improved outcome. The stabilisation method (bone graft versus spinal cage) did not affect the long-term clinical or radiographic results in this series.

Effects of low concentration BMP-7 on human osteoarthritic chondrocytes: comparison of different applications.

While BMP-7 (OP-1) is one of the most potent growth factors in cartilage tissue engineering, the effects of exogenous low concentration BMP-7 on osteoarthritic chondrocytes are still unknown. Human osteoarthritic chondrocytes obtained from the femoral condyles of 10 patients were grown either in monolayer or in 3D collagen type-I gel culture in vitro. The growth factor was either given as a single dose of 50 ng/mL, a repeated dose, or continuously released from PGLA microspheres. Matrix formation was monitored by immunohistochemical staining and real-time PCR. In contrast to monolayer culture, the differentiated phenotype was prevailed in 3D culture. Collagen type-II protein production in the 3D group with a continuous BMP-7 release was enhanced in comparison to all other groups. Gene expression of collagen type-II and aggrecan was elevated in all treatment groups, with the highest extent in the BMP-7 microsphere group. In summary, treatment of articular chondrocytes with a low dose of BMP-7 leads to an elevated production of extracellular matrix components. This effect is further increased when BMP-7 is given repeatedly or continuously, which proved to be the most effective form of application.

Cell-free repair of small cartilage defects in the Goettinger minipig: which defect size is possible?

PURPOSE: Cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed by treatment with cell-free collagen type-I gel plugs of three different sizes. METHODS: In 6 adult Goettinger minipigs, three full-thickness chondral defects were created in the trochlear groove of one knee of the hind leg. These defects were treated with a cell-free collagen type-I gel plug of 8, 10, or 12 mm diameter. All animals were allowed unlimited weight bearing. After 1 year, the animals were killed. Immediately after recovery, a non-destructive biomechanical testing was performed. The repair tissue quality was evaluated immunohistologically, collagen type-II protein was quantified, and a semiquantitative score (O'Driscoll score) was calculated. RESULTS: After 1 year, a high number of cells migrated into the initially cell-free collagen gel plugs and a hyaline-like repair tissue had been created. The O'Driscoll scores were: 8 mm, 21.2 (SD, 2.8); 10 mm, 21.5 (SD, 1.6); and 12 mm, 22.3 (SD, 1.0). The determination of the e-modulus, creep and relaxation revealed that mechanical properties of the two smaller defects were closer to unaffected hyaline cartilage. CONCLUSIONS: As cell-free collagen type-I gel plugs of all three different sizes created hyaline-like repair tissue, this system seems suitable for the treatment of even larger defects.

Vascular injury accompanying displaced proximal humeral fractures: two cases and a review of the literature.

We present two cases in which displaced proximal humeral fractures are accompanied by vascular injury. These Injuries are very rare but severe and the accompanying vascular impairment can have great clinical consequences. Therefore, we try to emphasize on the importance of thorough and accurate diagnostics, because it is obligatory for early diagnosis and improving the eventual outcome of these injuries. The specific order in treatment (internal fixation first or vascular repair first) depends on the severity of the accompanying vascular injury. The increasing use of endovascular procedures to treat vascular lesions is a very interesting development with several advantages, especially in elderly and multimorbid patients.

A comparative study of 3 different cartilage repair techniques.

PURPOSE: The value of cell-free techniques in the treatment of cartilage defects remains under debate. In this study, cartilage repair of full-thickness chondral defects in the knees of Goettinger minipigs was assessed by treatment with a cell-free collagen type-I gel or a collagen type-I gel seeded with autologous chondrocytes. As a control, abrasion arthroplasty was included. METHODS: In 18 adult Goettinger minipigs, three full-thickness chondral defects were created in one knee of the hind leg. They were either treated with a cell-free collagen gel, a collagen gel seeded with 2 × 10(5)/ml chondrocytes, or left untreated. All animals were allowed unlimited weight bearing. At 6, 12, and 52 weeks, 6 animals were sacrificed. Immediately after recovery, a non-destructive biomechanical testing was performed. The repair tissue quality was evaluated histologically, and the O'Driscoll score was calculated. RESULTS: After 6 weeks, a high number of cells migrated into the initially cell-free collagen gel. After 1 year, a hyaline-like repair tissue in both groups has been created. As assessed by O'Driscoll scoring and col-II staining, repair tissue quality of the initially cell-free gel was equal to defects treated by cell-seeded collagen gel implantation after 1 year. All untreated control defects displayed a fibrous repair tissue. The mechanical properties represented by the e-modulus were inconsistent in the course of the study. CONCLUSIONS: The implantation of a cell-free collagen type-I gel can lead to a high-quality repair tissue in the Goettinger minipig that equals a cell-based procedure after 1 year postoperatively. This study demonstrates the high chondrogenic potential of the applied collagen gel, which might help to overcome the disadvantages inherent in conventional cartilage tissue engineering methods.

Scoring systems for outcome after knee injuries.

Outcome assessment after knee injuries and periarticular fractures are not well described in the literature. This review focuses on outcome assessment, specifically surveying various scoring systems after knee trauma. Additionally, we include a report on a series of 637 patients with multiple injuries that were re-examined at least 10 years after the inciting incident. The series includes 48 patients with lower extremity injuries isolated to the knees, and for comparison, 107 poly-traumatized patients with femoral diaphyseal fractures and no other lower extremity injuries. The outcomes were assessed utilizing the Lysholm score, the Tegner activity score, the Hannover Score for Polytrauma Outcome (HASPOC), and the 12-item short-form health survey (SF-12). We calculated correlation coefficients to compare the general health questionnaires with the more specific knee scores. For the comparison of knee injured patients with femoral shaft fracture patients, we applied the Wilcoxon test. With respect to the Tegner activity score, we observed deterioration from a mean preoperative score of 5.0, to 2.8 points at follow up. The mean Lysholm score was 81.97, ranging from 15 to 100 points. However, there was no correlation between results obtained from the Lysholm score with the results of the general health questionnaires. Although not statistically significant, the general health questionnaires (HASPOC and SF-12) trended towards a less favourable outcome for polytraumatized patients who sustained a knee injury in comparison to those with a femoral shaft fracture. In conclusion, the outcomes of knee injuries in poly-traumatized patients are rather heterogeneous, but generally are worse than in those with lower extremity injuries that spare the knee joint.

Effects of controlled released BMP-7 on markers of inflammation and degradation during the cultivation of human osteoarthritic chondrocytes.

The aim of the present study is to investigate the effects of BMP-7 released from polylactide microspheres on the appearance of various catabolic and inflammatory cytokines secreted by osteoarthritic chondrocytes cultivated in a collagen gel. Articular chondrocytes of 15 patients suffering from osteoarthritis are transferred to a collagen type-I gel. Additionally, BMP-7 encapsulated into polylactide microspheres (50 ng BMP-7/mL gel) is added. After 14 days, gene expression and protein appearance of various genes involved in matrix turnover and inflammation are investigated by immunohistochemical staining and RT-PCR and compared to untreated controls. TNF-α, MMP-13, IL-6, IL-1ß, and VEGF gene expressions are decreased in the treatment group. In contrast, BMP-7-induced matrix synthesis is not affected, leaving collagen type-II (Col-II) gene expression to be elevated, while collagen type-I (Col-I) is decreased. In summary, controlled release of low concentrated BMP-7 from polylactide microspheres leads to a decrease in gene expression of the investigated inflammation and matrix degradation markers whereas matrix synthesis is induced.

Millicurrent stimulation of human articular chondrocytes cultivated in a collagen type-I gel and of human osteochondral explants.

BACKGROUND: Here we investigate the effect of millicurrent treatment on human chondrocytes cultivated in a collagen gel matrix and on human osteochondral explants. METHODS: Human chondrocytes from osteoarthritic knee joints were enzymatically released and transferred into a collagen type-I gel. Osteochondral explants and cell-seeded gel samples were cultivated in-vitro for three weeks. Samples of the verum groups were stimulated every two days by millicurrent treatment (3 mA, sinusoidal signal of 312 Hz amplitude modulated by two super-imposed signals of 0.28 Hz), while control samples remained unaffected. After recovery, collagen type-I, type-II, aggrecan, interleukin-1beta, IL-6, TNFalpha and MMP13 were examined by immunohistochemistry and by real time PCR. RESULTS: With regard to the immunostainings 3 D gel samples and osteochondral explants did not show any differences between treatment and control group. The expression of all investigated genes of the 3 D gel samples was elevated following millicurrent treatment. While osteochondral explant gene expression of col-I, col-II and Il-1beta was nearly unaffected, aggrecan gene expression was elevated. Following millicurrent treatment, IL-6, TNFalpha, and MMP13 gene expression decreased. In general, the standard deviations of the gene expression data were high, resulting in rarely significant results. CONCLUSIONS: We conclude that millicurrent stimulation of human osteoarthritic chondrocytes cultivated in a 3 D collagen gel and of osteochondral explants directly influences cell metabolism.

Effects of low concentrated BMP-7 administered by co-cultivation or plasmid transfection on human osteoarthritic chondrocytes.

INTRODUCTION: While BMP-7 has proven to be one of the most potent growth factors in cartilage tissue engineering, protein concentration and route of administration remain a matter of debate. Here we investigated the effects of a low concentration of BMP-7 on human osteoarthritic chondrocytes administered by protein co-cultivation and plasmid transfection. METHODS: Freshly released (P0) or in vitro propagated chondrocytes (P2) were cultivated in a collagen type-I gel for 3 weeks in vitro or in nude mice. Seeded chondrocytes were treated with 50 ng/mL BMP-7 directly added to the medium or were subject to transient BMP-7 plasmid transfection prior to gel cultivation. Untreated specimens served as a control. After recovery, samples were investigated by histological and immunohistochemical staining and real-time PCR. RESULTS: In vitro, collagen type-II protein production was enhanced, and it was stored mainly pericellularly. Collagen type-II and aggrecan gene expression were enhanced in both treatment groups. After nude mouse cultivation, col-II protein production was further enhanced, but specimens of the BMP-7 transfection group revealed a clustering of col-II positive cells. Gene expression was strongly upregulated, chondrocyte number was increased and the differentiated phenotype prevailed. In general, freshly released chondrocytes (P0) proved to be superior to chondrocytes pre-amplified in vitro (P2). CONCLUSIONS: Both BMP-7 co-cultivation and plasmid transfection of human osteoarthritic chondrocytes led to improved cartilage repair tissue. Nevertheless, the col-II distribution following BMP-7 co-cultivation was homogeneous, while samples produced by transient transfection revealed a col-II clustering.

BMP-7-loaded PGLA microspheres as a new delivery system for the cultivation of human chondrocytes in a collagen type I gel: the common nude mouse model.

PURPOSE: Bone morphogenic protein 7 (BMP-7) released from polylactide (PLGA) microspheres has proven to be a potent system in cartilage tissue engineering in vitro. However, in vivo data are still lacking. The aim of this study was to investigate this BMP-7 release system utilizing the nude mouse as a small animal model. METHODS: Human osteoarthritic chondrocytes of 10 patients were enzymatically released and transferred into a collagen type-I gel. A concentration of 2x10(5) cells/mL was used. BMP-7 encapsulated in PGLA microspheres was added at an initial concentration of 500 ng BMP-7/mL gel. Untreated specimens and specimens with empty microspheres served as control. Samples were cultivated subcutaneously in nude mice for 6 weeks. RESULTS: After recovery, chondrocytes of all groups displayed a spheroid morphology without signs of dedifferentiation. The proteoglycan and collagen type II content of the control groups was restricted to the immediate pericellular region, whereas treatment group samples showed enhanced collagen type II production. Collagen type II and aggrecan gene expression was enhanced in treatment group samples with respect to the two control groups (mean +/- SD: 0.268 +/- 0.450 to 0.152 +/- 0.129 and 0.155 +/- 0.216 ng/ng beta-actin for collagen type II; 0.535 +/- 0.731 to 0.367 +/- 0.651 and 0.405 +/- 0.326 ng/ng beta-actin for aggrecan), whereas collagen type I gene expression decreased by a factor of 10. Relative protein quantification of collagen type II, collagen type I and proteoglycan was in accordance. CONCLUSIONS: Our data suggest that BMP-7 release from PGLA microspheres led to an improved tissue-engineered cartilage analogue in vivo with an increase in hyaline-cartilage-specific components.

A cell-free collagen type I device for the treatment of focal cartilage defects.

The purpose of this study was to evaluate the potential value of a cell-free collagen type I gel plug for the treatment of focal cartilage defects. Cellular migration and proliferation was addressed in vitro, and the formation of repair tissue in a nude mouse-based defect model. A cell-free plug made of collagen type I was placed in the center of an incubation plate. Surrounding space was filled with a collagen type I gel (Arthro Kinetics, Esslingen, Germany) seeded with 2 x 10(5) human articular chondrocytes/mL gel. After cultivation for up to 6 weeks in vitro, samples were subject to histological and immunohistochemical staining and gene expression analysis. Subsequently, chondral defects of human osteochondral blocks were treated with the plug, and specimens were cultivated subcutaneously in nude mice for 6 weeks. The repair tissue was evaluated macroscopically, and collagen type II production was investigated immunohistochemically. In vitro, morphology of immigrated cells did not show any differences, as did collagen type II gene expression. After 4 weeks, the plug was homogeneously inhabited. After 6 weeks of cultivation in nude mice, collagen gel plug treatment led to a macroscopically excellent repair tissue. Histological staining revealed a tight bonding, and the collagen gel plug started to be remodeled. We conclude that the novel collagen gel plug device offers an environment favorable for the migration of articular chondrocytes and leads to a good-quality repair tissue in the nude mouse model. The arthroscopic transplantation of a collagen gel plug may be one option in the treatment of focal cartilage defects.

Peer teaching: a randomised controlled trial using student-teachers to teach musculoskeletal ultrasound.

OBJECTIVES: This study (a post-intervention assessment) was designed to assess the effectiveness of peer-assisted learning (PAL) using student-teachers (STs) with limited training to teach complicated technical skills for interpreting ultrasound images of the shoulder. METHODS: Students in Years 3 and 4 of medical school were randomly assigned to two groups. In the PAL group (PG), teaching was delivered by a group of nine STs from Years 3 and 4, who undertook a 30-minute general training and 1 week of self-teaching. In the staff-led group (SG), students were taught by a group of three ultrasound-experienced doctors. Exposure took place in two separate lessons (each of 120 minutes) and introduced eight standard sectional planes (EULAR) using a 10-MHz Nemio XG system (Toshiba Medical Systems GmbH). The theoretical and practical learning outcomes were tested using a multiple-choice question (MCQ) test and an objective structured clinical examination (OSCE). Qualitative differences were evaluated using Likert scale-based items. RESULTS: Evaluation of differences between the PG (n = 75) and SG (n = 76) in the theoretical (MCQ score; P = 0.644) and practical (total OSCE score; P = 0.133) outcomes showed no difference between the two groups. However, the STs themselves showed significantly better results overall (P < 0.05). Staff members were rated more highly than STs, especially on items relating to competence (P < 0.05). CONCLUSIONS: Complicated technical skills can be adequately taught to students using the PAL system by STs with limited training. Self-teaching learning strategies are successful in contexts of limited teacher training. However, despite positive objective results, STs still face prejudice from students with regard to competency.

Ablation of articular cartilage with an erbium:YAG laser: an ex vivo study using porcine models under real conditions-ablation measurement and histological examination.

BACKGROUND AND OBJECTIVES: The use of an erbium:YAG laser in arthroscopic surgery has the advantage of a precise treatment of soft tissue. Due to the high absorption in water, the laser energy is perfectly matched to smoothing the hydrous, fibrillated articular cartilage surface. In minimal invasive surgery, the workspace is filled with aqueous liquids for enlargement. This appears contrary to the absorption characteristics of erbium:YAG laser radiation in water. The purpose of this study was to evaluate the ablated volume per pulse of cartilage lesions and the potential side effects including thermal damage and tissue necrosis. STUDY DESIGN/MATERIALS AND METHODS: Twenty-four osteochondral specimens of porcine knee joints were irradiated with an Er:YAG laser completely submerged in water, with distances to the cartilage surface of 1, 3 and 5 mm and pulse durations of 75 and 100 microseconds. To keep a constant peak power of approximately 6 kW, pulse energies of 450 and 580 mJ were used at a pulse repetition rate of 15 Hz. After a histological preparation, ablated volumes, depths, and widths of the cuts were investigated. Additionally, laser protocols were correlated with different markers of cartilage tissue damage and apoptosis. RESULTS: Ablation could be observed for every measurement. The influence of the distance showed a statistical significance (P < 0.001) for the volume, depth, and width of the cuts. For the pulse duration, statistical significance (P < 0.001) was found only for the volume and the depth. We observed no loss of proteoglycan or collagen type II. The total cell number, cell morphology, and number of apoptotic cells in an area close to the cutting edge and in a corresponding unaffected area of the same specimens revealed no differences regardless of the applied protocol. CONCLUSION: The use of an Er:YAG laser demonstrates the successful application in liquid environments for cartilage removal without any damage of the surrounding tissue.

Effects of pulsed and sinusoid electromagnetic fields on human chondrocytes cultivated in a collagen matrix.

Although several effects of electromagnetic fields (EMFs) on articular cartilage have been reported in recent studies, the use of EMFs to treat osteoarthritis remains a matter of debate. In an in vitro study, human chondrocytes harvested from osteoarthritic knee joints were released from their surrounding matrix and transferred in defined concentration into a 3D matrix (type-I collagen gel). The cultivation, performed under standard conditions, lasted up to 14 days. During this time, treatment groups were continuously exposed to either sinusoid or pulsed electromagnetic fields (PEMFs). The PEMFs revealed the following characteristics: maximum magnetic flux density of 2 mT, frequency of the bursts of 16.7 Hz with each burst consisting of 20 pulses. Similarly, the sinusoid EMFs also induced a maximum flux density of 2 mT with a frequency of 50 Hz. Control groups consisting of equal number of samples were not exposed to EMF. Immunohistological examinations of formalin-fixed, paraffin-embedded samples revealed positive staining for type-II collagen and proteoglycans in the immediate pericellular region with no differences between the two different treatment groups and the control groups. With increasing cultivation time, both type-II collagen and aggrecan gene expression declined, but no significant differences in gene expression were found between the treatment and control groups. In conclusion, using our in vitro setting, we were unable to detect any effects of pulsed and sinusoidal magnetic fields on human adult osteoarthritic chondrocytes.

Combined approach for a locked unilateral facet fracture-dislocation of the cervicothoracic junction.

The authors present the case of a 36-year-old patient who sustained a unilateral fracture-dislocation C7-T1 involving all three columns, given the lesion of the C7-T1 disc on MRI. In view of the fractured facet, closed reduction without anaesthesia was not attempted. First, open reduction and instrumentation were performed from posteriorly. In a second operation, anterior fusion C7-T1 was added, using a tricortical bone graft and instrumentation. The authors felt that this three-column lesion at the cervicothoracic junction necessitated combined posterior-anterior stabilisation.

Effects of cyclic hydrostatic pressure on the metabolism of human osteoarthritic chondrocytes cultivated in a collagen gel.

Among other parameters, the application of mechanical force may provide an important stimulus in modulating the structure and function of tissue-engineered articular cartilage. We developed a cultivation chamber in which six collagen type-I gel samples, seeded with human osteoarthritic chondrocytes, can be cultivated simultaneously. A cyclic hydrostatic pressure of up to 40 kPa with a frequency of 0.0125 Hz was applied, and cultivation was performed for 1, 4, 7, or 14 days. Histological examinations revealed a spheroidal cell morphology in the treatment group. In contrast, control samples of the same patients represented a more fibroblastic appearance. Collagen type-II (col-II) protein was found in the very pericellular region of all investigated samples; the col-II content did not obviously vary between the control and treatment groups. In the treatment group, col-II and aggrecan gene expression were elevated. A spectrophotometric quantification of proteoglycan concentrations in media supernatants revealed a statistically significant enhancement in the treatment group.

BMP-7 loaded microspheres as a new delivery system for the cultivation of human chondrocytes in a collagen type-I gel.

In recent years, interest in chondrocyte cultures for transplantation has gained increasing attention. We investigated the use of PGLA microspheres as a new delivery system for BMP-7 and the effects on human chondrocytes cultivated in a 3D collagen gel culture. In an in vitro study, human chondrocytes obtained from osteoarthritic knee joints were released, transferred into a collagen type-I gel, and cultivated up to 14 days. In the treatment group PGLA microspheres loaded with human recombinant BMP-7 protein were added to the matrix. After the cultivation period, histological and immunohistochemical investigations were performed. In addition, the aggrecan core protein and type-II collagen mRNA concentrations were measured by real-time PCR. Histological staining for proteoglycan and collagen type-II protein and quantification via digital image processing revealed a significantly higher content in the samples cultivated with BMP-7 loaded microspheres in comparison to the control samples. Moreover, the collagen gel scaffold was partially remodeled by the chondrocytes and replaced by newly synthesized extracellular matrix. Cellular proliferation as well as apoptosis were low. In conclusion, we consider the PGLA microsphere system to be a functional device for the delivery of growth factors during the cultivation of articular chondrocytes leading to an increased content of type-II collagen and proteoglycan in the extracellular matrix.

In vitro comparison of six different matrix systems for the cultivation of human chondrocytes.

In recent years, a great variety of different matrix systems for the cultivation of chondrocytes have been developed. Although some of these scaffolds show promising experimental results in vitro, the potential clinical value remains unclear. In this comparative study, we propagated human articular chondrocytes precultivated in monolayer culture on six different scaffolds (collagen gels, membranes and sponges) under standardized in vitro conditions. Mechanical properties of the matrix systems were not improved significantly by cultivation of human chondrocytes under the given in vitro conditions. The gel systems (CaReS, Ars Artho, Germany and Atelocollagen, Koken, Japan) showed a homogeneous cell distribution; chondrocytes propagated on Chondro-Gide (Geistlich Biomaterials, Switzerland) and Integra membranes (Integra, USA) were building multilayers. Only few cells penetrated the two Atelocollagen honeycomb sponges (Koken, Japan). During cultivation, chondrocytes propagated on all systems showed a partial morphological redifferentiation, which was best with regard to the gel systems. In general, only small amounts of collagen type-II protein could be detected in the pericellular region and chondrocytes failed to build a territorial matrix. During the first two weeks of cultivation, the two gel systems showed a significantly higher collagen type-II gene expression and a lower collagen type-I gene expression than the other investigated matrix systems. Although collagen gels seem to be superior when dealing with deep cartilage defects, membrane systems might rather be useful in improving conventional autologous chondrocyte transplantation or in combination with gel systems.