Cell-material systems for anterior cruciate ligament regeneration

Advanced Gene Therapy Strategies for the Repair of ACL Injuries

The anterior cruciate ligament (ACL), the principal ligament for stabilization of the knee, is highly predisposed to injury in the human population. As a result of its poor intrinsic healing capacities, surgical intervention is generally necessary to repair ACL lesions, yet the outcomes are never fully satisfactory in terms of long-lasting, complete, and safe repair. Gene therapy, based on the transfer of therapeutic genetic sequences via a gene vector, is a potent tool to durably and adeptly enhance the processes of ACL repair and has been reported for its workability in various experimental models relevant to ACL injuries in vitro, in situ, and in vivo. As critical hurdles to the effective and safe translation of gene therapy for clinical applications still remain, including physiological barriers and host immune responses, biomaterial-guided gene therapy inspired by drug delivery systems has been further developed to protect and improve the classical procedures of gene transfer in the future treatment of ACL injuries in patients, as critically presented here.

Adhesion strength of human tenocytes to extracellular matrix component-modified poly(DL-lactide-co-glycolide) substrates

We report a direct measurement of the adhesion strength of human embryonic tenocytes (HETCs) and transformed human embryonic tenocytes (THETCs) to fibronectin (FN)- and type I collagen (CNI)- modified poly(DL-lactide-co-glycolide) (PLGA) substrates with a micropipette aspiration technique. PLGA substrates were first coated with poly-D-lysine (PDL), and then with various concentrations (1 microg/ml, 2 microg/ml, 5 microg/ml, and 10 microg/ml) of FN and CNI in serum-free F12 media. Anti-FN and Anti-CNI antibodies were used to inhibit attachment of tenocytes to FN- and CNI- modified substrates in a dilution range of 1:5000-1:500 and 1:1500-1:250, respectively. The substrates were employed for incubation of HETCs and THETCs for 30 min at 37 degrees C before the adhesion strength measurements. We found that the adhesion strengths showed a strong dependence on the seeding time and FN or CNI concentrations. Anti-FN and Anti-CNI antibodies significantly compromised adhesion of HETCs and THETCs to the corresponding modified substrates (P < 0.05). These findings show that FN- or CNI-modified polymer substrates offer significant advantages for tissue engineering tendon scaffolds concerning tenocyte adhesion. In addition, HETCs and THETCs bear similar biological behaviors in terms of adhesion, indicating the possibility of using THETCs in place of HETCs in tissue engineering construction of human tendons.

Fiber-based tissue-engineered scaffold for ligament replacement: design considerations and in vitro evaluation

The anterior cruciate ligament (ACL) is the major intraarticular ligamentous structure of the knee, which functions as a joint stabilizer. It is the most commonly injured ligament of the knee, with over 150,000 ACL surgeries performed annually in the United States. Due to limitations associated with current grafts for ACL reconstruction, there is a significant demand for alternative graft systems. We report here the development of a biodegradable, tissue-engineered ACL graft. Several design parameters including construct architecture, porosity, degradability, and cell source were examined. This graft system is based on polymeric fibers of polylactide-co-glycolide 10:90, and it was fabricated using a novel, three-dimensional braiding technology. The resultant micro-porous scaffold exhibited optimal pore diameters (175-233 microm) for ligament tissue ingrowth, and initial mechanical properties of the construct approximate those of the native ligament.

Tissue engineering: orthopedic applications

Because of an aging population and increased occurrence of sports-related injuries, musculoskeletal disorders have become one of the major health concerns in the United States. Current treatments, although fairly successful, do not provide the optimum therapy. These treatments typically rely on donor tissues obtained either from the patient or from another source. The former raises the issue of supply, whereas the latter poses the risk of rejection and disease transfer. This has prompted orthopedic surgeons and scientists to look for viable alternatives. In recent years, tissue engineering has gained increasing support as a method to treat orthopedic disorders. Because it uses principles of engineering, biology, and chemistry, tissue engineering may provide a more effective approach to the treatment of musculoskeletal disorders than traditional methods. This chapter presents a review of current methods and new tissue-engineering techniques for the treatment of disorders affecting bone, ligament, and cartilage.