[Fractures of the lateral process of the talus-snowboarder's ankle]. / Frakturen des Processus lateralis tali ­ "snowboarder's ankle".

Fractures of the lateral tubercle of the talus (PLT) are rare. With the increasing popularity of the trend sport snowboarding, the incidence of PLT fractures has increased. The most common classification of PLT fractures is the Hawkins classification. The aim of this review was to raise awareness for the injury and discuss the current evidence. A literature search revealed eight studies, each including at least seven patients. Six out of the eight studies were descriptive, retrospective case series without predefined treatment concepts. These resulted in only moderate treatment outcomes. Due to the low number of patients, the lack of computed tomography (CT) or magnetic resonance imaging (MRI) and inconsistent treatment approaches, these studies do not allow to draw conclusions on a treatment concept for PLT fractures. The other two studies validated existing treatment regimens. Overall, surgical treatment of dislocated fractures and conservative treatment of non-dislocated fractures was carried out with satisfactory results. The outcome of conservative treatment of dislocated factures remains unclear. A reason for the inconsistent treatment results could be the observed concomitant injuries, including dislocation of the tendons of the peroneus muscles (46%), calcaneal chondral injuries (48%) and subluxation of the subtalar joint (7%). Based on the limited evidence available, the authors recommend the application of CT and MRI for PLT fractures to assess concomitant injuries, which are the primary indication for surgery. Dislocated type I and II fractures (>2 mm) should be treated operatively, type III and non-dislocated type I and II fractures can be treated conservatively by immobilization and partial weight-bearing for 6 weeks.

Embryonic disruption of the candidate dyslexia susceptibility gene homolog Kiaa0319-like results in neuronal migration disorders.

Developmental dyslexia, the most common childhood learning disorder, is highly heritable, and recent studies have identified KIAA0319-Like (KIAA0319L) as a candidate dyslexia susceptibility gene at the 1p36-34 (DYX8) locus. In this experiment, we investigated the anatomical effects of knocking down this gene during rat corticogenesis. Cortical progenitor cells were transfected using in utero electroporation on embryonic day (E) 15.5 with plasmids encoding either: (1) Kiaa0319l small hairpin RNA (shRNA), (2) an expression construct for human KIAA0319L, (3) Kiaa0319l shRNA+KIAA0319L expression construct (rescue), or (4) controls (scrambled Kiaa0319l shRNA or empty expression vector). Mothers were injected with 5-bromo-2-deoxyuridine (BrdU) at either E13.5, E15.5, or E17.5. Disruption of Kiaa0319l function (by knockdown, overexpression, or rescue) resulted in the formation of large nodular periventricular heterotopia in approximately 25% of the rats, which can be seen as early as postnatal day 1. Only a small subset of heterotopic neurons had been transfected, indicating non-cell autonomous effects of the transfection. Most heterotopic neurons were generated in mid- to late-gestation, and laminar markers suggest that they were destined for upper cortical laminae. Finally, we found that transfected neurons in the cerebral cortex were located in their expected laminae. These results indicate that KIAA0319L is the fourth of four candidate dyslexia susceptibility genes that is involved in neuronal migration, which supports the association of abnormal neuronal migration with developmental dyslexia.

Salvage procedures for trochanteric femoral fractures after internal fixation failure: biomechanical comparison of a plate fixator and the dynamic condylar screw.

The aim of this study was the biomechanical evaluation of the reversed less invasive stabilization system (LISS) internal fixation as a joint-preserving salvage procedure for trochanteric fractures. Five LISS plates and five dynamic condylar screws (DCS) were tested using synthetic femora (Sawbones) with an osteotomy model similar to a type-A2.3 pertrochanteric fracture. The constructs were subjected to axial loading up to 1000 N for five cycles. Then, the force was continuously increased until fixation failure. For the evaluation of the biomechanical behaviour, the stiffness levels were recorded and the osteotomy gap displacement was mapped three-dimensionally. The average stiffness for the constructs with LISS plates was 412 N/mm (with a standard deviation (SD) of 103N/mm) and 572N/mm (SD of 116 N/mm) for the DCS constructs (p=0.051). Local displacement at the osteotomy gap did not yield any significant differences. The LISS constructs failed at a mean axial compression of 2103N (SD of 519N) and the DCS constructs at a mean of 2572N (SD of 372N) (p=0.14). It is concluded that the LISS plate offers a reliable fixation alternative for salvage procedures.

Injury patterns in polytraumatized children and consequences for the emergency room management.

INTRODUCTION: The effective initial treatment in the emergency room of polytraumatized children requires a sound knowledge of com- mon injury patterns, incidence, mortality, and consequences. The needed initial radiological imaging remains controversial and should be adapted to the expected injury pattern. PATIENTS AND METHODS: In this retrospective study, the injury patterns of 56 polytraumatized paediatric patients (age ≤ 16 years) in the period from December 2001 to May 2009 were evaluated. All children were initially diagnosed with a whole body CT scan. The cause of accident, the localization including the detailed diagnose, the lethality and the severity of the injuries were analyzed. The AIS (Abbreviated Injury Scale) and ISS (Injury Severity Score) were used to classify the severity of injuries in different body regions. Moreover the number and the kind of operation as a consequence of the initial made diagnoses were investigated. RESULTS: The mean ISS was 30 ± 13 in 38 boys and 18 girls with a mean age of 10 years. The lethality was 13% and 4% in the first 24 hours. The most severe and most frequent injury was craniocerebral trauma in 89% with an AIS ≥ 3 in 80%. Surgical intervention of the head was done in 41%. Thorax injuries were found in 63% with 57% with an AIS ≥ 3 and in 11% a thoracic drainage was needed. Abdominal trauma was found in 34% (surgery 4%) with an AIS ≥ 3 in 32%. Fractures of the spine occurred in 14% (surgery 5%) with an AIS ≥ 3 in 4% and pelvic injuries were diagnosed in 16% (surgery 4%) with an AIS ≥ 3 in 14%. Injuries of the upper extremity were found in 23% (surgery 11%) with an AIS ? 3 in 5% and of the lower extremity in 32% (surge- ry 16%) with an AIS ≥ 3 in 13%. CONCLUSION: The authors recommend a whole body CT scan in children who are potentially polytraumatized because of the detected high percentage of head and thorax injuries in polytraumatized children and the needed head surgery. The quickest imaging with a high sensitivity is the whole body CT scan which provides the clinicians with relevant information to initiate life-saving therapy.

Percutaneous iliosacral screw insertion: malpositioning and revision rate of screws with regards to application technique (navigated vs. Conventional).

BACKGROUND: Conventional percutaneous iliosacral screw placement in pelvic surgery is considered to be a highly demanding operative technique with a high rate of screw malpositions, which may be associated with the risk of neurologic damage or inefficient stability. In the conventional technique, the correct entry point for the screw and the small target corridor for the iliosacral screw may be difficult to visualize using an image intensifier. We tried to find out in this study whether the positioning of percutaneous screw implantations could be optimized by evaluating the rate and grade of malpositions and whether the needed revisions could be reduced by using computer navigation and three-dimensional (3D) image intensifier. METHODS: A group of 54 patients with 63 screws implanted using computer navigation was compared with 87 patients with 131 screws implanted using the conventional fluoroscopic technique. The exact screw position was controlled in a postoperative computed tomography scan, and the grade of malposition of every screw was investigated and compared. RESULTS: A complete intraosseous screw position was found in 42% of cases using the conventional technique and was significantly less compared with 81% using a 3D image intensifier in combination with a navigation system. Moreover, the revision rate of 1.6% was significantly less in the navigated group compared with 19% in the conventional group. CONCLUSIONS: The results indicate that 3D-computer navigation of the percutaneous iliosacral screw insertion can facilitate surgical performance in respect to reducing screw malposition and revision rates.

[The reversed locked internal plate fixator as an alternative internal fixation of problematic proximal femur fractures]. / Der umgedrehte Plattenfixateur zur osteosynthetischen Stabilisierung bei erschwerter Frakturheilung am proximalen Femur.

AIM: The aim of the study was to evaluate the application of a locked internal fixator in complex fractures of the proximal femur, in which the internal fixation with standard implants was not possible due to poor quality of bone or already failed internal fixation in the past. METHOD: Ten patients suffering from a pertrochanteric (n = 5), periprosthetic (n = 1) or subtrochanteric (n = 4) femural fracture between 2003 and 2008 were prospectively registered, underwent open reduction and internal fixation with an "upside-down" femur LISS (less invasive stabilisation system) and were followed up. In all these patients a primary internal fixation had failed or the local bone situation and circulation were poor. The mean follow-up was 14 +/- 25 months. X-ray images and a clinical examination were performed at each appointment. RESULTS: All fractures reached a primarily stable fixation with the locked internal plate fixator. Seven patients showed a complete bone healing after 3 months of follow-up and could bear full body weight afterwards. Three patients with preoperatively existing vascular disease or chronic osteomyelitis showed a deep wound infection postoperatively, which led to the explantation of the implant. CONCLUSIONS: The "reversed" locked internal fixator could be a successful alternative implant for stabilisation of proximal femur fractures which could not be fixated by standard implants due to poor bone quality and circulation. It can also be used as a salvage procedure after internal failed fixation in proximal femur fractures.

Survival of human mesenchymal stromal cells from bone marrow and adipose tissue after xenogenic transplantation in immunocompetent mice.

INTRODUCTION: Mesenchymal stromal cells (MSC) represent an attractive cell population for tissue engineering purposes. As MSC are described as immunoprivileged, non-autologous applications seem possible. A basic requirement is the survival of MSC after transplantation in the host. The purpose of the current paper was to evaluate the survival of undifferentiated and osteogenically induced human MSC from different origins after transplantation in immunocompetent mice. METHODS: Human MSC were isolated from bone marrow (BMSC) and adipose tissue (ASC). After cultivation on mineralized collagen, MSC were transplanted subcutaneously into immunocompetent mice (n=12). Undifferentiated MSC (group A) were compared with osteogenic-induced MSC (group B). Human-specific in situ hybridization and anti-vimentin staining was used to follow MSC after transplantation. Quantitative evaluation of lymphocytes and macrophages was performed as a measure of immunologic rejection. Unloaded scaffolds served as controls (group C). Specimens were harvested at 4 and 8 weeks. RESULTS: Undifferentiated BMSC and ASC were detected in the majority of cases after xenogenic transplantation (group A, a total of 22 out of 24 cases), while osteogenic-induced MSC (group B) could be detected in only three of 24 cases. Quantification of lymphocytes and macrophages revealed significantly higher cell numbers in group B compared with group A (P<0.05). DISCUSSION: Our results suggest that undifferentiated MSC are candidates for non-autologous cell transplantation, while osteogenic-induced MSC seem to be eliminated by the host's immune system. This observation seems independent of the origin of MSC and applies to BMSC and ASC.

[Management of ipsilateral femoral neck and shaft fractures]. / Management von Kombinationsfrakturen des Femurschafts und des proximalen Femurs.

PURPOSE: The combination of ipsilateral femoral neck and shaft fractures remains a treatment challenge in orthopedic surgery because both fracture types constitute separate entities and require specific treatment concepts. MATERIAL AND METHODS: In a case control study, incidence, treatment strategies, and outcomes of this injury were analyzed. All patients with femoral fractures treated between 1 January 2001 and 31 July 2007 at a level I trauma center were included in the study. RESULTS: Twenty-one out of 1,935 patients (1.1%) sustained 22 combined fractures of the femoral neck and shaft. Also considering the combination of femoral shaft fractures with fractures of the acetabulum and the distal femur (knee), the proportion of chain injuries of the femur was 3.1%. The rate of multiply injured patients in the group of patients with ipsilateral femoral neck and shaft fractures was 64%. The majority of the patients could be treated with a single implant for both fracture components. The leading fracture component was the femoral neck fracture in eight cases. All fractures consolidated after 4.7 months on average; one pseudarthrosis of the femoral neck was observed. All fractures were discovered in the course of primary diagnostic measures; in 73% of the patients, a computed tomography (CT) body scan was done. Fifty-nine percent of the patients with ipsilateral femoral neck and shaft fractures received primary definitive operative care. Complications included two torsional failures that needed correction and one case of postoperative infection that was easily treated. CONCLUSION: Treatment of ipsilateral femoral neck and shaft fractures is still demanding, but diagnosis has improved with regular use of CT body scans in the management of multiply injured patients. Furthermore, possibilities for operative treatment have been advanced by the introduction of the long proximal femoral nail and the antegrade femoral nail, two implants supporting stabilization of these fracture entities.

[In vitro study on the influence of fibrin in cartilage constructs based on PGA fleece materials]. / In-vitro-Studie zum Einfluss von Fibrin in Knorpelkonstrukten auf der Basis von PGA-Vliesstoffen.

BACKGROUND: The matrix component in autologous chondrocyte implantation plays an important role. In this study the influence of an additional fibrin component in cartilage constructs based on polyglycolide polymers (PGA) was investigated. METHODS: Human chondrocytes of femoral heads were isolated and cultured using a serum-free technique. The cells were seeded on PGA-91 scaffolds with and without an additional fibrin component; the constructs were cultured for 2 weeks in vitro. Besides cell viability, DNA content, pH, aggrecan production, mRNA expression of aggrecan, and collagen types I and II were determined by real-time PCR. Furthermore, cartilage grafts were histologically analyzed. RESULTS: All constructs contained viable, metabolically active cells in the investigated time period. There was no cell proliferation within the graft, and the DNA content was decreased over time. The pH level constantly remained within a physiologic range. The Alcian blue staining of the constructs showed the homogeneous cell distribution and a cell-associated proteoglycan production. Aggrecan concentration in the supernatants of fibrin-containing constructs was significantly lower compared to fibrin-free grafts (-24%), a result that correlated with diminished aggrecan mRNA expression (-80%). mRNA expression of collagen type II increased in the fibrin-free constructs over time and was 57% higher than in the fibrin-containing grafts. The immunohistochemical detection of collagen type II was possible in all constructs. CONCLUSION: Cartilage constructs based on carbohydrate matrices are suitable for matrix-associated chondrocyte implantation. The results of this study suggest a partially inhibitory effect of an additional fibrin component in PGA constructs for chondrogenic differentiation.

Proximal humerus fractures - current treatment options.

Proximal humerus fractures represent an increasing challenge for the health system due to epidemiological changes. As estimated by a Finnish study group the number of fractures may triple by the year 2030. The majority of patients with these fractures are older than 60 years and in this population most of the proximal humerus fractures have been related to osteoporosis. Nondisplaced fractures and fractures with minimal displacement and adequate stability are usually successfully treated non-operatively. The main challenge in the operative treatment of displaced and unstable proximal humerus fractures is to achieve effective stabilization of an adequately reduced fracture to maximize the functional patient outcome. Especially in osteoporotic bone and comminuted fractures operative stabilization is challenging and the management of displaced and unstable fractures remains controversial. The most important factor for favourable results in the treatment of complex three-part or four-part humerus fractures is anatomic reduction. Minimal exposure, high primary stability, and load transfer through the implant are important for avoiding complications such as secondary dislocation, osteonecrosis, and stiffness. Recently invented implants with angular stability provide better biomechanical properties and enhanced anchorage especially in the osteoporotic bone. These implants therefore have a potential for achieving better results in the treatment of these complex injuries.

Differential effects of BMP-2 and TGF-beta1 on chondrogenic differentiation of adipose derived stem cells.

OBJECTIVES: This article addresses the interaction of transforming growth factor beta1 (TGF-beta1) and bone morphogenic protein 2 (BMP-2) during osteo-chondrogenic differentiation of adipose-derived adult stem cells (ASC). TGF-beta1 was expected to modulate the BMP-2-induced effects through transcriptional regulation of Dlx-5, Msx-2 and Runx-2. MATERIALS AND METHODS: Encapsulated ASC were cultured for 14 days in medium containing TGF-beta1 and/or BMP-2. mRNA expression of the extracellular matrix molecules col2a1, cartilage oligomeric matrix protein, col10a1, alkaline phosphatase (AP) and transcription factors Msx-2, Dlx-5 and Runx-2 was analysed. Release of glycosaminoglycans, collagen types II and X into the extracellular matrix was demonstrated. RESULTS: BMP-2 and TGF-beta1 induced a chondrogenic phenotype in ASC. Combined growth factor treatment had a synergistic effect on col10a1 and an additive effect on col2a1 mRNA expression. Synthesis of glycosaminoglycans was enhanced by combined growth factor treatment. Addition of TGF-beta1 inhibited BMP-2 induced AP expression and activity and both proteins promoted chondrogenic maturation. CONCLUSIONS: Prevention of BMP-2-induced osteogenic transdifferentiation by TGF-beta1 seemed not to be mediated by transcriptional regulation of Dlx-5. Due to these findings, simultaneous stimulation of ASC with BMP-2 and TGF-beta1 seemed to be beneficial for complete differentiation of ASC into chondrocytes.

BM cells giving rise to MSC in culture have a heterogeneous CD34 and CD45 phenotype.

BACKGROUND: Mesenchymal stromal cells (MSC) isolated from adult human BM are characterized by their fibroblast-like morphology, adherent growth and capacity to differentiate into adipocytes, osteocytes, chondrocytes, cardiomyocytes and neuroprogenitors. After culturing these cells in vitro, they express the cell-surface molecules CD44, CD90, SH2 and SH3, and are negative for CD34 and the hematopoietic marker CD45. The aim of this study was to characterize the in vivo phenotype of MSC relative to the expression of CD34 and CD45. METHODS: BM mononuclear cells were stained with Ab against both molecules and separated into the CD34(+), CD34(-), CD45(+) CD34(+), CD45(high+) CD34(-), CD45(med,low+) CD34(-) and CD45(-) CD34(-) subpopulations, which were then cultured under the same conditions and analyzed for growth of MSC. RESULTS: A small population of MSC arose from the CD45(+) CD34(+) fraction, although the majority was obtained from the CD45(-) CD34(-) subpopulation. MSC from all fractions could be differentiated into adipocytes and osteocytes. In addition, MSC from the CD34(+) and CD34(-) fractions were shown to differentiate into chondrocytes. After in vitro culture, MSC from both fractions possessed the same phenotype, which was negative for CD34 and CD45. DISCUSSION: MSC from the CD45(+) CD34(+) fraction change their phenotype under in vitro conditions.

Seizure-induced muscle force can caused lumbar spine fracture.

Patients suffering form epilepsy have an increased risk for fractures. Beside fractures caused by fall or accident muscles forces alone generated during tonic-clonic seizure can result in severe musculoskeletal injury. Contractions of strong paraspinal muscles can lead to compression fracture of the mid-thoracic spine. We report a patient who had suffered from a tonic-clonic seizure during early morning hours. After a cracking sound the patient woke up in a state of post-ictal disorientation, loss of urine and tongue bite. He was admitted to our facilities with the suspected vertebral fracture albeit he just reported of mild lower back pain. Native X-rays and computer-tomography scans showed instable burst fractures of L2 and L4. The fractures were stabilised with a dorsally instrumented internal fixator from L1 to L5 followed by hemi-laminectomy and ventral spondylodesis. Muscle force alone can result in severe skeletal trauma including vertebral fractures. This example emphasizes the importance of critical examination of patients after grand mal seizures. Seizures-induced injuries can appear clinically asymptomatic and can easily be overseen due to absence of trauma and post-ictal impairment of consciousness.

bFGF influences human articular chondrocyte differentiation.

BACKGROUND: The possible functional role of basic fibroblast growth factor (bFGF) in regulating the mitotic and metabolic activity of primary human articular chondrocytes was investigated. METHODS: [EF1]Chondrocytes were enzymatically isolated from femoral head cartilage, and were cultured in vitro in monolayer. bFGF-dependent cell proliferation, production of collagen type II and aggrecan were monitored 10 days after isolation. Furthermore, effect of bFGF on cell cycle, cell morphology, and mRNA expression of integrins and chondrogenic markers determined by real time PCR were analyzed. RESULTS: bFGF concentrations in supernatants of primary human articular chondrocytes peaked immediately after isolation and then declined. In a dose-dependent manner, bFGF enhanced cell amplification and viability. BFGF induced a decrease in the apoptotic cell population, while the number of proliferating cells remained unchanged. Supplementation of cell culture with bFGF reduced collagen type II mRNA by 49%, but increased expression of the integrin alpha(2) by 70%. bFGF did not significantly regulate the integrins alpha(1), alpha(5), alpha(10), alpha(v) and type I collagen. bFGF reduced the amount of collagen type II by 53%, which was correlated with diminished mRNA production. Monolayer cultured chondrocytes secreted significant amounts of aggrecan that decreased over time. Secretion of this cartilage-specific marker was further reduced by the addition of bFGF. DISCUSSION: These findings highlight the potential role of bFGF as an endogenous chondrocyte mediator that can enhance cell amplification and regulate cell differentiation.

Comparison of cellular functionality of human mesenchymal stromal cells and PBMC.

BACKGROUND: Human mesenchymal stromal cells (MSC) and PBMC play significant roles in repair processes following inflammation. Mechanisms of recruitment are still under investigation. METHODS AND RESULTS: MIP-1alpha induced the chemotactic migration of MSC but not of PBMC. Correlating with this, 7.7% of MSC expressed the chemokine receptor CCR-1, as shown by FACS analysis. In contrast, PBMC did not express CCR-1 or CCR-2 but did express CXCR-4 (81.9%) and CCR-7 (42.2%). Setum induced the chemotaxis of both cell types, and zymosan activation increased the migration of PBMC but not of MSC. Corresponding with this, C5a induced the migration of PBMC but not of MSC. Dose-dependent and -specific adhesion to fibronectin, fibrinogen, collagen type I and collagen type II could be demonstrated for MSC; in contrast, PBMC did not adhere to any of the investigated proteins. Real-time PCR of receptor expression revealed a 12.2-fold higher expression of alphav in MSC compared with PBMC. Incubation of MSC with tumor necrosis factor-alpha (TNFalpha) induced NFkappaB activation and increased the chemotactic response to serum and adhesion to fibronedtin. DISCUSSION: Chemotaxis and adhesion are crucial and differing cell fundtons of MSC and PBMC.

[Injuries of the midfoot in children]. / Mittelfussverletzungen im Kindesalter.

Midfoot injuries of children are rare entities and often caused by high energy trauma mechanisms. Foot fractures in children may pose a diagnostic challenge but they usually have a good prognosis. In special cases computed tomography is necessary to find the right diagnosis in addition to plain X-rays. Based on two cases of midfoot injuries, a type II open Lisfranc fracture dislocation and a dislocation of a Chopart's joint, we describe the causes, diagnosis, and possibilities for treatment of juvenile midfoot injuries.

Transplantation of mesenchymal stromal cells on mineralized collagen leads to ectopic matrix synthesis in vivo independently from prior in vitro differentiation.

BACKGROUND: Tissue engineering using mesenchymal stromal cells (MSC) represents a promising approach for bone regeneration. Nevertheless, the optimal constructs have yet to be determined. It still remains unclear if there is a benefit of in vitro differentiation of MSC prior to transplantation or if undifferentiated MSC hold the optimal potential concerning new tissue formation. METHODS: After isolation and in vitro expansion, MSC were seeded on mineralized collagen sponges and transplanted in a heterotopic SCID mice model (n=12). While group A contained undifferentiated MSC, in group B cells were cultivated for 14 days in vitro under osteogenic conditions prior to implantation. Results were compared with non-loaded scaffolds (group C). Animals were killed for investigation at 4 and at 8 weeks. RESULTS: In situ hybridization demonstrated integration of MSC for up to 8 weeks in groups A and B. Histology revealed significantly more extracellular matrix synthesis in MSC-seeded scaffolds containing calcium phosphate and collagen type I at 4 and 8 weeks after transplantation compared with unloaded controls. At a biochemical level, higher levels of specific alkaline phosphatase expression were detected in MSC-loaded scaffolds (P<0.05). Scaffolds containing undifferentiated and differentiated MSC did not appear to differ in terms of matrix synthesis and protein expression, while the number of avital cells was significant higher in those probes loaded with differentiated MSC (P<0.01). DISCUSSION: The integration of transplanted cells and MSC-associated matrix synthesis encourages the use of MSC-loaded mineralized collagen for tissue engineering of bone. Furthermore, our data suggest that in vitro differentiation of MSC does not have a positive influence in terms of improved matrix synthesis.

Mesenchymal stem cells maintain TGF-beta-mediated chondrogenic phenotype in alginate bead culture.

This article addresses the stability of chondrogenic phenotype and the transdifferentiation potential of bone marrow-derived mesenchymal stem cells (MSCs) at distinct stages of differentiation. Differentiated MSCs were expected to maintain cartilage-like gene expression pattern in the absence of any chondrogenic growth factor or in the presence of osteogenic signals. MSCs encapsulated in alginate beads were treated with transforming growth factor (TGF)-beta 3 for 3, 6, or 14 days and then cultured in absence of TGF-beta for the remainder of the 2-week culture period. Additionally, cells were cultured in osteogenic medium after TGF-beta-mediated chondroinduction. Gene expression of col2a1, aggrecan, COMP, alkaline phosphatase (AP), and correlating protein synthesis was analyzed. After short-term stimulation with TGF-beta, MSCs maintained a chondrogenic phenotype. Chondrogenic gene expression and protein synthesis directly correlated with the extent of stimulation time and the concentration of TGF-beta. Pretreatment with TGF-beta could prevent AP mRNA expression of encapsulated MSCs. TGF- beta stimulation within the first 3 days of culture seems to be crucial for the expression of a chondrogenic phenotype. Fully differentiated and encapsulated MSCs are not able to transdifferentiate into osteoblasts. These findings give rise to a better understanding of the behavior of cartilage grafts affected by local factors of osteochondral transplantation sites in vivo.

Differential expression pattern of extracellular matrix molecules during chondrogenesis of mesenchymal stem cells from bone marrow and adipose tissue.

Adipose-derived adult stem cells (ADASCs) or bone marrow-derived mesenchymal stem cells (BMSCs) are considered as alternative cell sources for cell-based cartilage repair due to their ability to produce cartilage-specific matrix. This article addresses the differential expression pattern of extracellular matrix (ECM) molecules in BMSCs or ADASCs following chondrogenic differentiation. Human BMSCs or ADASCs were encapsulated in alginate and cultured in TGF-beta1-containing medium for 2 or 3 weeks. Chondrospecific mRNA expression was analyzed and alternative splicing of alpha(1)-procollagen type II mRNA was monitored via reverse transcriptase-polymerase chain reaction (RT-PCR). Corresponding ECM synthesis was demonstrated using immunohistochemistry. After chondroinduction, expression of collagen type II, type X, COMP and aggrecan mRNA was 3-15-fold higher than in ADASCs. The type IIA splicing form of alpha(1)-procollagen type II was expressed in both populations, and the type IIB splicing form was exclusively detected in BMSCs. In response to TGF-beta, collagen type II and X were secreted more strongly by BMSCs than by ADASCs. BMSCs express a more mature phenotype than ADASCs after chondroinduction. TGF-beta1 induces alternative splicing of the alpha(1)-procollagen type II transcript in BMSCs, but not in ADASCs. These findings may direct the development of a cell-specific culture environment either to prevent hypertrophy in BMSCs or to promote chondrogenic maturation in ADASCs.