Differentiated chondrocytes for cartilage tissue engineering.

Trauma to the articular cartilage surface of the joint represents a challenging clinical problem due to the very limited ability of this tissue to self-repair. Moreover, repair techniques such as microfracture, which introduce cells into the joint, have unpredictable clinical outcomes as they produce a fibrocartilage tissue that degenerates with time. Alternative treatments include tissue reconstruction with autograft and allograft tissue. However, these procedures are restricted by the availability of suitable donor tissue. These limitations have been the driving force behind the emerging field of articular cartilage tissue engineering. This paper will highlight and contrast the key challenges associated with the tissue engineering of this neo-tissue using differentiated adult cells. The various components of the tissue engineering process will be described including the choice of donor cell/tissue type and the selection of scaffolds that guide the formation of tissue. The ability of the tissue engineered implants to stimulate the repair of defects in vivo will also be discussed. Tissue engineering approaches may, in the future, provide an ideal alternative to the current surgical treatments for cartilage repair.

Repair of osteochondral defects with allogeneic tissue engineered cartilage implants.

The objective of this study was to evaluate the effect of allogeneic tissue engineered cartilage implants on healing of osteochondral defects. Rabbit chondrocytes were cultured in monolayer, then seeded onto biodegradable, three-dimensional polyglycolic acid meshes. Cartilage constructs were cultured hydrodynamically to yield tissue with relatively more (mature) or less (immature) hyalinelike cartilage, as compared with adult rabbit articular cartilage. Osteochondral defects in the patellar grooves of both stifle joints either were left untreated or implanted with allogeneic tissue engineered cartilage. Histologic samples from in and around the defect sites were examined 3, 6, 9, and 12, and 24 months after surgery. By 9 months after surgery, defects sites treated with cartilage implants contained significantly greater amounts of hyalinelike cartilage with high levels of proteoglycan, and had a smooth, nonfibrillated articular surface as compared to untreated defects. In contrast, the repair tissue formed in untreated defects had fibrillated articular surfaces, significant amounts of fibrocartilage, and negligible proteoglycan. These differences between treated and untreated defects persisted through 24 months after surgery. The results of this study suggest that the treatment of osteochondral lesions with allogenic tissue engineered cartilage implants may lead to superior repair tissue than that found in untreated osteochondral lesions.

A method for tissue engineering of cartilage by cell seeding on bioresorbable scaffolds.

This chapter describes a method for the in vitro generation of a 3-dimensional cartilage matrix from articular chondrocytes seeded onto a bioresorbable polymeric scaffold. This particular growth system was chosen for the subject of this chapter owing to the relative simplicity of the methods required and the ease with which the necessary materials can be obtained. The tissue produced using this protocol is a cellular, metabolically active hyaline-like matrix, containing the major cartilage constituents: sulfated proteoglycan, collagen type II, and water. It serves as a useful in vitro tool for studying the influence of various mechanical and chemical factors on cartilage metabolism, as well as providing an implantable material for in vivo cartilage repair studies.

Bioreactor development for tissue-engineered cartilage.

The development of tissue engineered cartilage is emerging as a potential treatment for the repair of cartilage defects. By seeding chondrocytes onto poly-glycolic acid (PGA) biodegradable scaffolds within a convective-flow bioreactor, the synthesis of tissue-engineered articular cartilage has been recently demonstrated. The ability to cultivate and manipulate this cell-polymer construct to possess specific dimensions, as well as biochemical and biomechanical properties is critical for potential application as an in vivo therapy of damaged articular surfaces. Bioreactor design requirements for stages from research to development to commercialization are discussed. Advantages and limitations to various bioreactor designs are critiqued. These studies illustrate the ability to synthesize tissue-engineered cartilage under convective-flow conditions for potential human tissue repair.

Cartilage production by rabbit articular chondrocytes on polyglycolic acid scaffolds in a closed bioreactor system.

Rabbit articular chondrocytes were seeded onto three-dimensional polyglycolic acid (PGA) scaffolds and placed into a closed bioreactor system. After 4 weeks of growth, meshes were examined for cartilage formation. Gross examination revealed solid, glistening material that had the appearance of cartilaginous tissue. Histologic examination revealed cell growth and deposition of extracellular matrix throughout the mesh with a less dense central core. Alcian blue and Safranin 0 staining showed deposition of glycosaminoglycans (GAGs). Immunostaining showed positive reactivity for type II collagen and chondroitin sulfate and no reactivity for type I collagen. Biochemical analysis showed collagen and GAG values to be 15% and 25% dry weight, respectively. Our results indicate that this type of system compares well with those previously described and should be useful for producing cartilage for evaluation in a clinical setting. (c) 1995 John Wiley & Sons, Inc.

Tgf-Beta promotes the growth of bovine chondrocytes in monolayer culture and the formation of cartilage tissue on three-dimensional scaffolds.

We have investigated the ability of transforming growth factor beta (TGF-beta) to promote the growth and differentiation of chondrocytes in monolayer and on three-dimensional scaffolds. Treatment of chondrocytes with TGF-beta and ascorbate individually stimulated the proliferation of bovine articular chondrocytes about 2-fold when cells were grown in monolayer culture: the combination of TGF-beta and ascorbate resulted in a 3-fold increase in cell number over a 72-h period. Peak stimulation with TGF-beta occurred at about 1.0 ng/ml: bFGF was slightly inhibitory in these assays. TGF-beta led to an increase in glycosaminoglycan synthesis as detected by Western blotting using anti-chondroitin sulfate antibodies. No significant change in collagen type II mRNA or protein was observed. When cells were grown on grown on three-dimensional scaffolds composed of polyglyocolic acid, TGF-beta treatment led to an increase in the size of the cartilage-like constructs produced. This was accompanied by increases in collagen and glycosaminoglycan deposition; immunohistochemical staining showed that the predominant collagen was type II. These results indicate that TGF-beta is capable of increasing the proliferation rate of chondrocytes in monolayer as well as increasing cartilage production on three-dimensional scaffolds and may find utility in the in vitro engineering of cartilage tissue.

Pectoralis major muscle rupture in windsurfing.

Board sailing (windsurfing) has become a popular water recreational activity. However, there is little in the medical literature concerning musculoskeletal complications resulting from participation in this sport. We present the first reported case of pectoralis major rupture sustained during board sailing. The patient was initially misdiagnosed, which happens commonly when this muscle ruptures. Only after conservative management failed was the correct diagnosis made and appropriate surgical intervention provided. Proper technique in board sailing requires sustained isometric contraction of the pectoralis major, deltoid and scapular stabilizers to maintain appropriate pull of the sail against wind resistance. Sharp increases in wind speed underly the mechanism of injury. Ruptures of the pectoralis major are usually complete, occur at or near the humeral insertion, and can be associated with misleading physical signs. Therefore, anatomy, clinical findings, surgical technique, and the postoperative rehabilitation program are stressed as to expedite diagnosis and maximize functional outcome.