الفهرس 
Embryology of Articular CartilageOnly 14 pages are availabe for public view
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Abstract
Cartilage is a highly specialized avascular tissue consisting of chondrocytes and intercellular protein matrix reinforced by a three-dimensional network of collagen type II and glycoaminoglycan (GAG)-chained aggrecan and hyaluronic acid (HA). The adult cartilage tissue has limited self-repair capability due to the presence of relatively few cells with low mitotic activity, low supply of progenitor cells, and lack of vascularization.
Articular cartilage degeneration starts by either acute traumatic injury or a degenerative joint disease, such as osteoarthritis, and results in the formation of unhealthy tissue with inferior structural and mechanical properties. Pure chondral lesions that do not penetrate the underlying subchondral bone are unable to self-repair spontaneously, while full-thickness defects can undergo only a partial healing response.
Focal lesions of the articular cartilage are very common and clinically important as they can be symptomatic and disabling, with pain and/ or locking of the joint, and can predispose to further cartilage loss and development of osteoarthritis (OA).
Importantly, the symptoms are often associated with significant functional impairment, as well as signs and symptoms of inflammation, including pain, stiffness and loss of mobility.
The challenge to restore the damaged articular surface is multidisciplinary and has provoked great interest among researchers, clinicians and patients. Reasonable progress has been made but further advances in the management of this problem can be expected over the next decades.
Numerous strategies have been employed to repair cartilage defects with an end goal of filling the defect with tissue having biochemical and biomechanical properties approximating surrounding native tissue. The goal of the treatment is to repair the defect by generating a healthy and durable hyaline cartilage and maintains its biomechanical characteristics.
This will provide clinical resolution of pain and recovery of articular functions, and also protects the joint against daily stresses and inhibits osteoarthritis and/or delays its onset. Another practical anticipation is the postponement of prosthetic replacement for a significantly longer time interval.
Although various methods have been developed for the treatment of cartilage defect, a long-term solution is not yet available. Optimal treatment for cartilage defect must be cost-effective and should inhibit the development of osteoarthritis in the long term.
Such clinical and experimental efforts include subchondral drilling (e.g., microfracture technique), osteochondral graft transplantation, periosteal transplantation, perichondrial arthroplasty, suspended chondrocyte implantation, undifferentiated bone marrow–derived mesenchymal stem cells (MSCs), and the tissue-engineered constructs.
These approaches exhibit technical complexities of varying degree that must be overcome before acceptance as the best clinical treatment option.
Previous review of the best available evidence reveals that perichondrial grafts and MSCs show superior clinical results for treatment of full-thickness articular cartilage defects compared to other procedures.
The qualities of perichondrial tissue make it an attractive option. It is living autologous tissue, which is readily available and is chondrogenic. In vivo experiments showed that the grafts can proliferate to fill the full-thickness defects in articular cartilage with a neocartilage that has biochemical characteristics similar to those of hyaline cartilage with a high content of Type-II collagen and glycosaminoglycans.
A mesenchymal stem cell (MSC) is a multilineage potential progenitor cell that keeps its capacity to divide and whose progeny differentiate to mesodermal tissue cells, such as cartilage, bone, muscle, fat, tendon, ligament, etc. These cells are easy to use clinically because they proliferate (grow) in culture without loss of the ability of differentiation. These cells, when transplanted into tissue defects, may provide a practical source of autologous cells with potential for differentiation.
Both perichondrial graft and bone marrow derived MSCs implantation have been used aiming at restoring cartilaginous articular surfaces with good clinical results were obtained in previous studies. However no comparison between these two techniques was done.
In this current study, these two techniques were compared experimentally to restore critical articular cartilage defect in the knee joint of 15 adult New-Zealand rabbits.
The comparison included: the gross morphology, the postoperative range of motion, and the histological evaluation regarding the quality of the neocartilage.
Although the gross morphology of the neocartilage produced by bone marrow derived MSCs was better than that produced by perichondrial grafts, with neocartilage confluent and reach the surface of the surrounding articular cartilage, a firm conclusion could not be taken with the superiority of this technique, because the difference was statistically insignificant.
However the level of the neocartilage was different because the neocartilage produced by BM derived MSCs was leveled with surrounding articular cartilage, while neocartilage produced by perichondrial graft didn’t reach the surface of the surrounding articular cartilage.
This study shows that both histological evaluation and postoperative passive ROM have statistically significant better results in group II which reconstructed with MSCs as the neocartilage showed more hyaline component with more chondrocytes and higher amount of cartilage matrix.
Group II showed also wider ROM, with shorter mean operative time compared to perichondrial graft (group I) which showed more fibrous component and less chondrocyes and few amount of cartilage matrix, with narrow ROM, and also needs longer time in harvesting the graft and in its fixation to the defect.
The results of this series are in favor of using bone marrow derived mesenchymal stem cells in the management of articular cartilage defects: it is readily available and easily obtained cells with less invasive procedure is required to obtain MSCs than perichondrial grafts, it have a limited donor site morbidity, and a greater proliferative capacity.
Another advantage in MSCs technique is that the reparative cells provide repair for both subchondral bone and cartilage. As the full-thickness articular cartilage defect encompasses the subchondral bone and the cartilage, the reparative cells must be so situated as to provide repair for both of these very different types of skeletal tissue. The MSCs cells, when implanted in such defects, appear capable both of differentiating into articular cartilage and of inducing the formation of subchondral bone.
This technique yields hyaline cartilage with superior morphological and histological configuration than perichondrial grafts but clinical cases and long term results are still needed to confirm this.
Better results can be obtained when using MSCs injection into the defect or when MSCs seeded on tissue engineered constructs with scaffold which includes growth factors inducing chondrogenesis instead of using proline mesh.