No abstract

This study was undertaken to determine whether the cells of the fibrocartilaginous meniscal substance are capable of proliferation and matrix synthesis. Cells were isolated from the fibrocartilaginous menisci of young New Zealand white rabbits, and grown in two alternative culture regimens differing only in the basal nutrient medium used to initiate primary monolayer growth. Under each culture regimen, the cells attached and proliferated both initially and after passage into secondary (2 degrees) culture. Differences were noted in cell morphology and time to reach confluence in primary (1 degrees) culture. Upon passage into 2 degrees culture, the fibrochondrocytes assumed two distinct morphologies depending upon the type of medium used for 1 degree culture. These morphological changes were accompanied by differences in the population doubling time and incorporation of 35SO4 into sulfated proteoglycans. The proliferation of both fibrochondrocyte subtypes was stimulated by the addition of either pituitary fibroblast growth factor (FGF) or human platelet lysate in a dose-dependent manner. Both FGF (10 ng/ml) and ascorbate (40 micrograms/ml) decreased 35-sulfate incorporation, whereas only ascorbate was found to alter the amount of sulfated glycosaminoglycan in the pericellular coat. We conclude that the fibrochondrocytes of the meniscal substance are capable of replication and synthesis of matrix macromolecules if given the proper stimuli. Additionally, there may be two subpopulations of fibrochondrocytes that can be distinguished by their in vitro behavior.

We sought to create a regeneration template for the meniscal cartilage of the knee to induce complete meniscal regeneration, and to develop the technique for implanting the prosthetic appliance in vivo. We designed a resorbable collagen-based scaffold and con-* Presented in part at the 16th annual meeting of the AOSSM, Sun Valley,

No abstract

We describe an in vitro organ culture system that can be used to test the effect of various substances and compounds on the wound healing process in the fibrocartilaginous substance of the knee joint meniscus. Using culture medium containing either 10% fetal bovine serum (FBS) or our recently developed serum-free, defined culture medium (DM), we have demonstrated the ability of meniscal fibrochondrocytes from intact rabbit menisci to extricate themselves from their surrounding matrix and migrate into an exogenous, purified fibrin clot in vitro. After 4 weeks of culture in FBS-containing medium, the cells which had invaded the clot had initiated the early aspects of a typical reparative response; the same response did not occur in DM alone. Morphologically, the cells on the surface of the clot resembled the original superficial fibrochondrocytes, whereas those cells within the substance of the clot more closely resembled the original deep fibrochondrocytes. After 10 weeks, the reparative response had progressed only to a certain point and then failed to progress further under these culture conditions. However, use of this culture system should now make it possible to rapidly identify and quantitate those factors which would most likely be useful in continuing the reparative response and in affecting meniscal wound repair. Elucidation of the mechanisms and requirements for meniscal healing will eventually allow the practicing orthopaedic surgeon to effect in situ meniscal repair and obviate the need for meniscectomy and its morbid sequelae.

No abstract

We have formulated a serum-free medium capable of supporting DNA synthesis in rabbit meniscal fibrochondrocytes at a level equivalent to 10% fetal bovine serum (FBS). The medium consists of a 1:1 mixture of Dulbecco's Modified Eagle's Medium and Ham's F-12 medium supplemented with transferrin (1 microgram/ml), selenium (1 pg/ml), trace metal mix (1:100), dexamethasone (100 ng/ml), insulin-like growth factors I and II (50 ng/ml each), pituitary fibroblast growth factor (100 ng/ml), and lactalbumin hydrolysate (2 micrograms/ml). Endothelial cell growth supplement could be substituted for lactalbumin hydrolysate to obtain similar results. Ventrex PC-1, a commercially available, low-protein, serum-free medium, was found to support proliferation of fibrochondrocytes but not as well as 10% FBS or our medium formulation. Lipid supplements, which are known to support the serum-free growth of hyaline chondrocytes, were found to be either of no value or antagonistic for the culture of fibrochondrocytes. Likewise, vitamin E alone, progesterone, putrescine, and hydrocortisone were also without benefit in our culture system. The cells had a more chondrocytic morphology when grown in defined medium as opposed to 10% FBS. The results of this study should now make it possible to identify and quantitate those factors necessary to affect meniscal repair by utilizing further techniques in vitro.

Meniscal fibrochondrocytes from male and female New Zealand white rabbits, ages 6, 12, and 24 months, were grown in primary and secondary monolayer cell culture. Neither age nor sex affected the majority of their cell culture characteristics. Cells from young males (6 months old) synthesized greater amounts of sulfated proteoglycans than did those from young females, but by 2 years of age, this result was reversed. All age groups synthesized 2 classes of proteoglycans, based on hydrodynamic size, but the ratio of the 2 classes changed as a function of age. Overall, the meniscal fibrochondrocytes from both skeletally immature and skeletally mature rabbits of both sexes were capable of proliferation and matrix synthesis in vitro.One of the most frequently performed orthopedic operations is knee joint arthrotomy with meniscectomy. The frequent and widespread use of this procedure was encouraged by early reports of successful postoperative results (1-4). However, longer-term studies indicate that, very often, there are complications after meniscectomy (5-12). The most frequent and debilitating of such complications is precocious osteo,arthritis in the joint (10,12,13). In an attempt to