Enhancing cartilage repair with optimized supramolecular hydrogel-based scaffold and pulsed electromagnetic field.

Functional tissue engineering strategies provide innovative approach for the repair and regeneration of damaged cartilage. Hydrogel is widely used because it could provide rapid defect filling and proper structure support, and is biocompatible for cell aggregation and matrix deposition. Efforts have been made to seek suitable scaffolds for cartilage tissue engineering. Here Alg-DA/Ac-ß-CD/gelatin hydrogel was designed with the features of physical and chemical multiple crosslinking and self-healing properties. Gelation time, swelling ratio, biodegradability and biocompatibility of the hydrogels were systematically characterized, and the injectable self-healing adhesive hydrogel were demonstrated to exhibit ideal properties for cartilage repair. Furthermore, the new hydrogel design introduces a pre-gel state before photo-crosslinking, where increased viscosity and decreased fluidity allow the gel to remain in a semi-solid condition. This granted multiple administration routes to the hydrogels, which brings hydrogels the ability to adapt to complex clinical situations. Pulsed electromagnetic fields (PEMF) have been recognized as a promising solution to various health problems owing to their noninvasive properties and therapeutic potentials. PEMF treatment offers a better clinical outcome with fewer, if any, side effects, and wildly used in musculoskeletal tissue repair. Thereby we propose PEMF as an effective biophysical stimulation to be 4th key element in cartilage tissue engineering. In this study, the as-prepared Alg-DA/Ac-ß-CD/gelatin hydrogels were utilized in the rat osteochondral defect model, and the potential application of PEMF in cartilage tissue engineering were investigated. PEMF treatment were proven to enhance the quality of engineered chondrogenic constructs in vitro, and facilitate chondrogenesis and cartilage repair in vivo. All of the results suggested that with the injectable self-healing adhesive hydrogel and PEMF treatment, this newly proposed tissue engineering strategy revealed superior clinical potential for cartilage defect treatment.

Pulsed Electromagnetic Field Enhances Healing of a Meniscal Tear and Mitigates Posttraumatic Osteoarthritis in a Rat Model.

BACKGROUND: Meniscal tears in the avascular region are thought to rarely heal and are a considerable challenge to treat. Although the therapeutic effects of a pulsed electromagnetic field (PEMF) have been extensively studied in a variety of orthopaedic disorders, the effect of a PEMF on meniscal healing has not been reported. HYPOTHESIS: PEMF treatment would promote meniscal healing and prevent osteoarthritis progression. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 72 twelve-week-old male Sprague-Dawley rats with full-thickness longitudinal medial meniscal tears in the avascular region were divided into 3 groups: control (Gcon), treatment with a classic signal PEMF (Gclassic), and treatment with a high-slew rate signal PEMF (GHSR). Macroscopic observation and histological analysis of the meniscus and articular cartilage were performed to evaluate the meniscal healing and progression of osteoarthritis. The synovium was harvested for histological and immunofluorescent analysis to evaluate the intra-articular inflammation. Meniscal healing, articular cartilage degeneration, and synovitis were quantitatively evaluated according to their scoring systems. RESULTS: Dramatic degenerative changes of the meniscus and articular cartilage were noticed during gross observation and histological evaluation in Gcon at 8 weeks. However, the menisci in the 2 treatment groups were restored to normal morphology, with a smooth surface and shiny white color. Particularly, the HSR signal remarkably enhanced the fibrochondrogenesis and accelerated the remodeling process of the regenerated tissue. The meniscal healing scores of the PEMF treatment groups were significantly higher than those in Gcon at 8 weeks. Specifically, the HSR signal showed a significantly higher meniscal repair score than did the classic signal at week 8 (P < .01). Additionally, the HSR signal significantly downregulated the secretion levels of interleukin 1 beta (IL-1ß) and tumor necrosis factor alpha (TNF-α) in the meniscus and synovium as compared with the control group. When compared with the 2 treatment groups, Gcon had significantly higher degeneration scores (Gcon vs Gclassic, P < .0001; Gcon vs GHSR, P < .0001). The HSR signal also exhibited significantly lower synovitis scores compared with the other two groups (Gcon vs Gclassic, P < .0001; Gclassic vs GHSR, P = .0002). CONCLUSION: A PEMF promoted the healing of meniscal tears in the avascular region and restored the injured meniscus to its structural integrity in a rat model. As compared with the classic signal, the HSR signal showed increased capability to promote fibrocartilaginous tissue formation and modulate the inflammatory environment, therefore protecting the knee joint from posttraumatic osteoarthritis development. CLINICAL RELEVANCE: Adjuvant PEMF therapy may offer a new approach for the treatment of meniscal tears attributed to the enhanced meniscal repair and ameliorated osteoarthritis progression.

Initial experiences with in vivo intravascular coronary vessel wall imaging.

PURPOSE: To evaluate potential use of a loopless internal receiver coil for in vivo coronary artery vessel wall imaging in five domestic swine. MATERIALS AND METHODS: Intravascular free-breathing black blood coronary vessel wall imaging was performed using a previously described double inversion fast spin echo technique after x-ray guided placement of an internal receiver coil in or in close proximity to the target vessel (LAD, LCX). RESULTS: Image quality using the phased array coil was reproducible, while image quality with the internal receiver coil was heavily dependent on coil position with respect to the examined artery, and likely also dependent on blood flow and/or cardiac-related coil motion. With internal coil placement in the left circumflex coronary artery, images of the left anterior descending vessel wall appeared similar or superior compared to commercially available phased array surface coil images. With coil placement in the target vessel itself, imaging was suboptimal because of the extremely high signal intensity (hotspot) in close proximity to the vessel wall, leading to low contrast between the vessel wall and the surrounding tissues and blood. CONCLUSION: In this study, we demonstrate the feasibility of in vivo intravascular coronary vessel wall imaging. Continued research is necessary to minimize coil motion and optimize coil sensitivity algorithms.

Use of internal coils for independent and direct MR imaging-guided endovascular device tracking.

PURPOSE: To test the hypotheses that a single internal guide wire coil (i) permits independent and direct depiction of guide wires and catheters and (ii) improves catheter-tracking accuracy and depiction compared to external receiver coils. MATERIALS AND METHODS: Standard 5-6-F angiographic catheters were filled with dilute 4% gadolinium chelate. A single 0.030-inch-diameter internal guide wire coil was placed inside the catheter. True fast imaging with steady-state precession was used to directly visualize the guide wire. Inversion recovery-prepared fast low-angle shot technique was used to track catheters over a thick slice. In phantom experiments, we compared catheter signal-to-noise ratios (SNRs) with the internal coil and a phased-array surface coil with use of the Wilcoxon signed-rank test. Tip-tracking accuracy was assessed with use of linear regression. In pigs (n = 7), catheters and guide wires were independently tracked in real time. RESULTS: In phantoms, catheter SNR with the internal coil (12.0) was significantly greater than that with the surface coil (4.0; P =.001). Tip-tracking accuracy was also improved with use of the internal coil (R(2) = 0.94 vs 0.50). In swine vasculature, catheters and guide wires could be directly and independently tracked at 1.7-2.0 frames per second. Catheters were clearly visualized with use of the internal coil, with a typical catheter background contrast-to-noise ratio of 6.6. Catheters were not visible with use of the external coil because of the small catheter size compared to the slice thickness. CONCLUSION: Internal guide wire coils permit independent and direct depiction of guide wires and catheters in vivo for MR imaging-guided endovascular interventions. They also improve catheter tracking accuracy and depiction compared to external coils.