Transgenic animal model for degenerative diseases of cartilage

A transgenic rodent whose genome comprises:

• (a) a nucleotide sequence encoding a constitutively enzymatically active MMP that cleaves Type II collagen selected from the group consisting of a constitutively enzymatically active human MMP and a constitutively enzymatically active mammalian MMP-13, wherein the nucleotide sequence encoding the MMP is operatively linked to a tetracycline-regulatable promoter;
• and
• (b) a nucleotide sequence encoding a repressor-activator fusion polypeptide that binds to the tetracycline regulatable promoter in the absence of tetracycline or a tetracycline analog and does not bind to the regulatable promoter in the presence of tetracycline or a tetracycline analog, which nucleotide sequence encoding the repressor-activator fusion polypeptide is operatively linked to a chondrocyte-specific promoter,
• wherein expression of the MMP is capable of being repressed in the rodent until adulthood, and wherein the MMP is capable of being expressed in the rodent during adulthood to a level sufficient to cause Type II collagen degradation in the joints of the rodent.

A transgenic rodent whose genome comprises:

• (a) a nucleotide sequence encoding a constitutively enzymatically active MMP that cleaves Type II collagen selected from the group consisting of a constitutively enzymatically active human MMP and a constitutively enzymatically active mammalian MMP- 13, wherein the nucleotide sequence encoding the MMP is operatively linked to a regulatable promoter;
• and
• (b) a nucleotide sequence encoding a transcription activator protein that binds to the regulatable promoter in the presence of a transcription activator protein-binding compound and does not bind to the regulatable promoter in the absence of the compound, which nucleotide sequence encoding the transcription activator protein is operatively linked to a chondrocyte-specific promoter;
• wherein expression of the MMP is capable of being repressed in the rodent until adulthood, and wherein the MMP is capable of being expressed in the rodent during adulthood to a level sufficient to cause Type II collagen degradation in the joints of the rodent.

A method for evaluating the potential of a composition to counteract degradation of Type II collagen in joints of a transgenic rodent, which degradation results in a phenotypic change selected from the group consisting of loss of proteoglycan, cleavage of Type II collagen into a TCA degradation product, a change in joint function, joint space narrowing, destruction of cartilage, a change in growth plate morphology, fibrillation and loss of articular cartilage, osteophyte formation, and combinations thereof, which method comprises:

• (a) providing a first and second transgenic rodent, whose genomes each comprise:
• (i) a nucleotide sequence encoding a constitutively enzymatically active MMP that cleaves Type II collagen selected from a group consisting of a constitutively enzymatically active human MMP and a constitutively enzymatically active mammalian MMP-13, wherein the nucleotide sequence encoding the MMP is operatively linked to a regulatable promoter;
• and
• (ii) a nucleotide sequence encoding a repressor-activator fusion polypeptide that binds to the regulatable promoter in the absence of a repressor-activator fusion polypeptide-binding compound and does not bind to the regulatable promoter in the presence of the compound, which nucleotide sequence encoding the repressor-activator fusion polypeptide is operatively linked to a chondrocyte-specific promoter,
• wherein expression of the MMP is capable of being repressed in the rodents until adulthood, and wherein the MMP is capable of being expressed in the rodents during adulthood to a level sufficient to cause Type II collagen degradation in the joints of the rodents;
• (b) activating expression of the MMP at the same age during adulthood of the transgenic rodents, wherein expression of the MMP results in a phenotypic change selected from the group consisting of loss of proteoglycan, cleavage of Type II collagen into a TCA degradation product, a change in joint function, joint space narrowing, destruction of cartilage, a change in growth plate morphology, fibrillation and loss of articular cartilage, osteophyte formation, and combinations thereof;
• (c) administering the composition to the first transgenic rodent;
• and
• (d) comparing the phenotype of the first transgenic rodent to which the composition was administered with the phenotype of the second transgenic rodent to which the composition is not administered,
• wherein any less extensive development in the nature or extent of the phenotype in the first transgenic rodent, or any increased length of time required for the phenotype to develop in the first transgenic rodent relative to the phenotype in the second transgenic rodent, indicates the potential of the composition to counteract degradation of Type II collagen in joints.