Tissue engineering is a promising approach for the treatment of tissue defects. Mesenchymal stem cells are of potential use as a source of repair cells or of important growth factors for tissue engineering. The purpose of this study was to examine the role of mesenchymal stem cells in meniscal tissue repair. This was tested using several cell and biomaterial-based treatment options for repair of defects in the avascular zone of rabbit menisci. Circular meniscal punch defects (2 mm) were created in the avascular zone of rabbit menisci and left empty or filled with hyaluronan-collagen composite matrices without cells, loaded with platelet-rich plasma, autologous bone marrow, or autologous mesenchymal stem cells. In some experiments, matrices with stem cells were precultured in chondrogenic medium for 14 days before implantation. Rabbits were then allowed free cage movement after surgery for up to 12 weeks. Untreated defects and defects treated with cell-free implants had muted fibrous healing responses. Neither bone marrow nor platelet-rich plasma loaded in matrices produced improvement in healing compared with cell-free implants. The implantation of 14 days precultured chondrogenic stem cell-matrix constructs resulted in fibrocartilage-like repair tissue, which was only partially integrated with the native meniscus. Non-precultured mesenchymal stem cells in hyaluronan-collagen composite matrices stimulated the development of completely integrated meniscus-like repair tissue. The study shows the necessity of mesenchymal stem cells for the repair of meniscal defects in the avascular zone. Mesenchymal stem cells seem to fulfill additional repair qualities besides the delivery of growth factors.

Induction of chondrogenesis in mesenchymal stem cells (MSCs) with TGF-β leads to a hypertrophic phenotype. The hypertrophic maturation of the chondrocytes is dependent on the timed removal of TGF-β and sensitive to hypertrophy-promoting agents in vitro. In this study, we have investigated whether TGF-β3, which has been shown to be more prochondrogenic compared to TGF-β1, similarly enhances terminal differentiation in an in vitro hypertrophy model of chondrogenically differentiating MSCs. In addition, we tested the impact of the time of chondrogenic conditioning on the enhancement of hypertrophy. MSCs were chondrogenically differentiated in pellet culture in medium containing TGF-β1 or TGF-β3. After 2 or 4 weeks, chondrogenic medium was switched to hypertrophy-inducing medium for 2 weeks. Aggregates were analyzed histologically and biochemically on days 14, 28 and 42. The switch to hypertrophy medium after 14 days induced hypertrophic cell morphology and significant increase in alkaline phosphatase activity compared to the chondrogenesis only control using both TGF-β1 and TGF-β3. After 28 days predifferentiation, differences between hypertrophic and control groups diminished compared to 14 days predifferentiation. In conclusion, chondrogenic conditioning with both TGF-β isoforms similarly induced hypertrophy in our experiment and allowed the enhancement of the hypertrophic chondrocyte phenotype by hypertrophic medium. Enhancement of hypertrophy was seen more clearly after the shorter chondrogenic conditioning. Therefore, to utilize this experimental model as a tool to study hypertrophy in MSC chondrogenesis, a predifferentiation period of 14 days is recommended.

Meniscal tears in the avascular zone have a poor self-healing potential, however partial meniscectomy predisposes the knee for early osteoarthritis. Tissue engineering with mesenchymal stem cells and a hyaluronan collagen based scaffold is a promising approach to repair meniscal tears in the avascular zone. 4 mm longitudinal meniscal tears in the avascular zone of lateral menisci of New Zealand White Rabbits were performed. The defect was left empty, sutured with a 5-0 suture or filled with a hyaluronan/collagen composite matrix without cells, with platelet rich plasma or with autologous mesenchymal stem cells. Matrices with stem cells were in part precultured in chondrogenic medium for 14 days prior to the implantation. Menisci were harvested at 6 and 12 weeks. The developed repair tissue was analyzed macroscopically, histologically and biomechanically. Untreated defects, defects treated with suture alone, with cell-free or with platelet rich plasma seeded implants showed a muted fibrous healing response. The implantation of stem cell-matrix constructs initiated fibrocartilage-like repair tissue, with better integration and biomechanical properties in the precultured stem cell-matrix group. A hyaluronan-collagen based composite scaffold seeded with mesenchymal stem cells is more effective in the repair avascular meniscal tear with stable meniscus-like tissue and to restore the native meniscus.

Purpose Mesenchymal stem cells (MSCs) express markers of hypertrophic chondrocytes during chondrogenic differentiation. We tested the suitability of parathyroid hormonerelated protein (PTHrP), a regulator of chondrocyte hypertrophy in embryonic cartilage development, for the suppression of hypertrophy in an in vitro hypertrophy model of chondrifying MSCs. Methods Chondrogenesis was induced in human MSCs in pellet culture for two weeks and for an additional two weeks cultures were either maintained in standard chondrogenic medium or transferred to a hypertrophy-enhancing medium. PTHrP(1-40) was added to the medium throughout the culture period at concentrations from 1 to 1,000 pM. Pellets were harvested on days one, 14 and 28 for biochemical and histological analysis. Results Hypertrophic medium clearly enhanced the hypertrophic phenotype, with increased cell size, and strong alkaline phosphatase (ALP) and type X collagen staining. In chondrogenic medium, 1-100 pM PTHrP(1-40) did not inhibit chondrogenic differentiation, whereas 1,000 pM PTHrP(1-40) significantly reduced chondrogenesis. ALP activity was dose-dependently reduced by PTHrP(1-40) at 10-1,000 pM in chondrogenic conditions. Under hypertrophy-enhancing conditions, PTHrP(1-40) did not inhibit the induction of the hypertrophy. At the highest concentration (1,000 pM) in the hypertrophic group, aggregates were partially dedifferentiated and differentiated areas of these aggregates maintained their hypertrophic appearance. Conclusions PTHrP(1-40) treatment dose-dependently reduced ALP expression in MSC pellets cultured under standard chondrogenic conditions and is thus beneficial for the maintenance of the chondrogenic phenotype in this medium condition. When cultured under hypertrophy-enhancing conditions, PTHrP(1-40) could not diminish the induced enhancement of hypertrophy in the MSC pellets.

Objective. We undertook this study to examine the effects of estradiol on chondrogenesis of human bone marrow-derived mesenchymal stem cells (MSCs), with consideration of sex-dependent differences in cartilage repair.Methods. Bone marrow was obtained from the iliac crest of young men. Density-gradient centrifugation-separated human MSCs proliferated as a monolayer in serum-containing medium. After confluence was achieved, aggregates were created and cultured in a serum-free differentiation medium. We added different concentrations of 17␤-estradiol (E2)

Background Open reduction and stabilization of dorsal pelvic ring injuries is accompanied by a high rate of soft tissue complications. Minimally invasive techniques have the potential to decrease soft tissue trauma, but the risk of iatrogenic nerve and vessel damage through the reduced surgical exposure should be considered. We treated these injuries using a transiliac internal fixator (TIFI) in a minimally invasive technique characterized by implantation of a pedicle screw and rod system, bridging the sacroiliac joints and the sacral area. Questions/purposes We asked whether (1) we could achieve anatomic restoration with the device, (2) specific complications were associated with this minimally invasive approach (particularly enhanced intraoperative blood loss, soft tissue complications, and iatrogenic neurovascular damage), and (3) function 3 years after trauma was comparable to that of established methods. Methods We retrospectively reviewed 67 patients with dorsal pelvic injuries during a 7-year period. We evaluated the (1) reduction by grading the maximal displacement measured with three radiographic views, (2) the complications during the observation period, and (3) the function with a validated questionnaire (Pelvic Outcome Score) in all but five patients at least 3 years after trauma (mean, 37 months; range, 36-42 months). Results At last followup we observed a secondary fracture displacement greater than 5 mm in one patient. The intraoperative blood loss was less than 50 mL in all patients. No neurovascular lesions occurred owing to implantation. Four patients had wound infections, one had loosening of a single pedicle screw, and one had an iatrogenic screw malpositioning. Thirty-five of the 62 patients achieved Pelvic Outcome Scores of either a maximum score or 6 of 7 points. Conclusion Our observations suggest TIFI is a reasonable alternative to other established fixation devices for injuries of the dorsal pelvic ring with minor risks of major blood loss or iatrogenic neurovascular damage.

Objective: Bankart and Hill-Sachs lesions are often associated with anterior shoulder dislocation. The MRI technique is sensitive in diagnosing both injuries. The aim of this study was to investigate Bankart and Hill-Sachs lesions with MRI to determine the correlation in occurrence and defect sizes of these lesions. Methods: Between 2006 and 2013, 446 patients were diagnosed with an anterior shoulder dislocation and 105 of these patients were eligible for inclusion in the study. All patients were examined using MRI. Bankart lesions were classified as cartilaginous or bony lesions. Hill-Sachs lesions were graded I-III using a modified Calandra classification.

We report the functional and socioeconomic long-term outcome of patients with pelvic ring injuries. We identified 109 patients treated at a Level I trauma centre between 1973 and 1990 with multiple blunt orthopaedic injuries including an injury to the pelvic ring, with an Injury Severity Score (ISS) of ≥ 16. These patients were invited for clinical review at a minimum of ten years after the initial injury, at which point functional results, general health scores and socioeconomic factors were assessed. In all 33 isolated anterior (group A), 33 isolated posterior (group P) and 43 combined anterior/posterior pelvic ring injuries (group A/P) were included. The mean age of the patients at injury was 28.8 years (5 to 55) and the mean ISS was 22.7 (16 to 44). At review the mean Short-Form 12 physical component score for the A/P group was 38.71 (22.12 to 56.56) and the mean Hannover Score for Polytrauma Outcome subjective score was 67.27 (12.48 to 147.42), being significantly worse compared with the other two groups (p = 0.004 and p = 0.024, respectively). A total of 42 patients (39%) had a limp and 12 (11%) required crutches. Car or public transport usage was restricted in 16 patients (15%). Overall patients in groups P and A/P had a worse outcome. The long-term outcome of patients with posterior or combined anterior/posterior pelvic ring injuries is poorer than of those with an isolated anterior injury.