Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2000-09-13
2003-06-24
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023510
Reexamination Certificate
active
06582471
ABSTRACT:
BACKGROUND OF THE INVENTION
Articular cartilage, an avascular tissue found at the ends of articulating bones, has no natural capacity to heal. During normal cartilage ontogeny, mesenchymal stem cells condense to form areas of high density and proceed through a series of developmental stages that ends in the mature chondrocyte. The final hyaline cartilage tissue contains only chondrocytes that are surrounded by a matrix composed of type II collagen, sulfated proteoglycans, and additional proteins. The matrix is heterogenous in structure and consists of three morphologically distinct zones: superficial, intermediate, and deep. Zones differ among collagen and proteoglycan distribution, calcification, orientation of collagen fibrils, and the positioning and alignment of chondrocytes (Archer et al.,
J. Anat.
189(1): 23-35, 1996; Morrison et al.,
J. Anat.
189(1): 9-22 1996, Mow et al.,
Biomaterials
13(2): 67-97, 1992). These properties provide the unique mechanical and physical parameters to hyaline cartilage tissue.
In 1965, a demineralized extraction from bovine long bones was found to induce endochondral bone formation in the rat subcutaneous assay (Urist
Science
150: 893-899, 1965). Seven individual factors, termed Bone Morphogenetic Proteins (BMPs), were isolated to homogeneity and, because of significant sequence homology, classified as members of the TGF&bgr; super-family of proteins (Wozney, et al.,
Science
242: 1528-34, 1988; Wang et al.,
Proc. Nat. Acad. Sci.
87: 2220-2224, 1990). These individual, recombinantly-produced factors also induce ectopic bone formation in the rat model (Luyten et al.,
J. Biol. Chem.
264: 13377-80, 1989; Celeste et al.,
Proc. Nat. Acad. Sci.
87: 9843-50, 1990). In addition, in vitro tests have demonstrated that both BMP-2 and TGF&bgr;-1 induce mesenchymal stem cells to form cartilage (Denker, et al.,
Differentiation
59(1): 25-34, 1995; Denker et al., 41
st Ann. Orthop. Res. Society
465: 1995). Both BMP-7 and BMP-2 have been shown to enhance matrix production of chondrocytes in vitro (Flechtenmacher
J. Arthritis Rheum.
39(11): 1896-904, 1996: Sailor et al.,
J. Orthop. Res.
14: 937-945, 1996). From these data we can conclude that not only are the BMPs important regulators of osteogenesis, but that they also play crucial roles during chondrogenic development in vitro.
A partially-purified protein mixture from bovine long bones, termed BP (Bone Protein), also induces cartilage and bone formation in the rat subcutaneous assay (Poser and Benedict, WO95/13767). BP in combination with calcium carbonate promotes bone formation in the body. In vitro, BP induces mesenchymal stem cells to differentiate specifically to the cartilage lineage, in high yields, and to late stages of maturation (Atkinson et al.,
J. Cellular Biochem.
65: 325-339, 1997).
The molecular mechanism for cartilage and bone formation has been partially elucidated. Both BMP and TGF&bgr; molecules bind to cell surface receptors (the BMP/TGF&bgr; receptors), which initiates a cascade of signals to the nucleus that promotes proliferation, differentiation to cartilage, and/or differentiation to bone (Massague
Cell
85: 947-950, 1996).
In 1984, Urist described a substantially pure, but not recombinant BMP, combined with a biodegradable polylactic acid polymer delivery system for bone repair (U.S. Pat. No. 4,563,489). This system blends together equal quantities of BMP and polylactic acid (PLA) powder (100 &mgr;g of each) and decreases the amount of BMP required to promote bone repair.
Hunziker (U.S. Pat. Nos. 5,368,858; 5,206,023) describes a cartilage repair composition consisting of a biodegradable matrix, a proliferation and/or chemotactic agent, and a transforming factor. A two stage approach is used where each component has a specific function over time. First, a specific concentration of proliferation/chemotactic agent fills the defect with repair cells. Secondly, a larger transforming factor concentration transforms repair cells into chondrocytes. Thereby the proliferation agent and the transforming agent may both be TGF&bgr; differing in concentration only. In addition, the patent discloses a liposome encapsulation method for delivering TFG&bgr;-1 serving as transformation agent.
Hattersley et al. (WO 96/39170) disclose a two factor composition for inducing cartilaginous tissue formation using a cartilage formation-inducing protein and a cartilage maintenance inducing protein. Specific recombinant cartilage formation inducing protein(s) are specified as BMP-13, MP-52, and BMP-12, and cartilage maintenance-inducing protein(s) are specified as BMP-9. In one embodiment, BMP-9 is encapsulated in a resorbable polymer system and delivered to coincide with the presence of cartilage formation inducing protein(s).
Laurencin et al., (U.S. Pat. No. 5,629,009) disclose a chondrogenesis-inducing device, consisting of a polyanhydride and polyorthoester, that delivers water soluble proteins derived from demineralized bone matrix, TGF&bgr;, EGF, FGF, or PDGF.
The results of the approaches to cartilage repair as cited above are encouraging but they are not satisfactory. In particular, the repair tissue arrived at is not fully hyaline in appearance and/or it does not contain the proper chondrocyte organization. Furthermore, previous approaches to cartilage repair have been addressed to very small defects and have not been able to solve problems associated with repair of large, clinically relevant defects.
One reason that previous approaches failed to adequately repair cartilage may be that they were not able to recapitulate natural cartilage ontogeny faithfully enough, this natural ontogeny being based on a very complicated system of different factors, factor combinations and factor concentrations with temporal and local gradients. A single recombinant growth factor or two recombinant growth factors may lack the inductive complexity to mimic cartilage development to a sufficient degree and/or the delivery systems used may not have been able to mimic the gradient complexity of the natural system to a satisfactory degree.
Previous approaches may also have failed because growth factor concentrations were not able to be maintained over a sufficient amount of time, which would prevent a full and permanent differentiation of precursor cells to chondrocytes. The loss of growth factor could be caused by diffusion, degradation, or by cellular internalization that bypasses the BMP/TGF&bgr; receptors. Maintaining a sufficient growth factor concentration becomes particularly important in repair of large sized defects that may take several days or several weeks to fully repopulate with cells.
The object of this invention is to create a composition for improved cartilage repair in vivo. The inventive composition is to enable in vivo formation of repair cartilage tissue which tissue resembles endogenous cartilage (in the case of articular cartilage with its specific chondrocyte spatial organization and superficial, intermediate, and deep cartilage zones) more closely than repair tissue achieved using known compositions for inducing cartilage repair. A further object of the invention is to create a device for cartilage repair which device contains the inventive composition.
This object is achieved by the composition and the device as defined by the claims.
BRIEF DESCRIPTION OF THE INVENTION
The inventive composition basically consists of a naturally derived osteoinductive and/or chondroinductive mixture of factors (e.g. derived from bone) or of a synthetic mimic of such a mixture combined with a nanosphere delivery system. A preferred mixture of factors is the combination of factors isolated from bone, known as BP and described by Poser and Benedict (WO 95/13767). The nanosphere delivery system consists of nanospheres defined as polymer particles of less than 1000 nm in diameter (whereby the majority of particles preferably ranges between 200-400 nm) in which nanospheres the combination of factors is encapsulated. The nanospheres are loaded with the mixture of factors in a weight ratio of 0.001
Atkinson Brent
Benedict James J.
Bittmann Pedro
Chickering Donald
Ranieri John
Phan Hieu
Sheridan & Ross P.C.
Sulzer Innotec AG
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