in accordance with the present invention , particulate cartilage compositions for stimulating chondrogenesis and producing cartilage regeneration comprise non - demineralized particulate articular cartilage . articular cartilage may be obtained from the articular surfaces of joints , such as from distal femurs , proximal tibias , acetabulums , heads of femurs , and / or heads of radiuses . the cartilage may be removed , for example , with a scalpel blade and is preferably removed down to subchondral bone , without removing bone . the articular cartilage for use in the present invention may include articular hyaline cartilage and / or fibrocartilage and may comprise allogeneic and / or xenogeneic cartilage . the articular cartilage is preferably non - demineralized . preferably , the cartilage is not subjected to harsh chemical treatments , which can alter the inherent natural properties of material within the cartilage . for example , the cartilage is preferably not subjected to demineralization treatments such as treatment with hydrochloric acid , ethylene diamine , and / or other demineralization agents . in some embodiments , the non - demineralized articular cartilage may be subjected to microbiological testing or subjected to other testing protocols that do not deleteriously alter the cartilage . additionally , the articular cartilage is not subjected to any physical treatments that may demineralize and / or alter the inherent natural properties of the cartilage . for example , the articular cartilage is preferably not subjected to elevated temperatures , e . g ., temperatures greater than about 50 ° c ., that may diminish the chondrogenic activity of the cartilage . however , the articular cartilage may be preserved , e . g ., freeze - dried , frozen , and / or dried , after being removed from the joint . one preferred method of preserving articular cartilage is freeze - drying . the composition includes non - demineralized cartilage particles preferably having a distribution of particle sizes . the articular cartilage particles may have sizes distributed within the range of from about 60 microns to about 500 microns , more preferably distributed in the range of from about 60 microns to about 250 microns . some compositions , according to the present invention , may include cartilage particles having particle sizes of less than about 250 microns , i . e ., cartilage powder . some compositions may include cartilage particles having a distribution of particle sizes in the range of from about 250 microns to about 500 microns , i . e ., cartilage granules . in some embodiments , the composition may comprise a combination of cartilage powder and cartilage granules . cartilage compositions according to the present invention may be produced by grinding non - demineralized articular cartilage to produce particles having the preferred distribution of particle sizes . the cartilage may be in the form of dry cartilage , freeze - dried cartilage , frozen cartilage , wet cartilage or mixtures thereof . in one preferred embodiment , the cartilage is freeze - dried . for example , pieces of cartilage obtained from the articular surface of one or more joints is washed in several changes of normal saline , blotted dry , and frozen rapidly , e . g ., at 10 ° c ./ min or faster , in the vapor phase of liquid nitrogen ( about − 150 ° c .) or alternatively in the liquid phase of liquid nitrogen ( about − 196 ° c .). after being frozen , the cartilage is preferably rapidly placed directly on the shelves of a freeze - drying apparatus maintained at about − 40 ° c . to about − 50 ° c . ( the condenser being cooled to from about − 70 ° c . to about − 80 ° c .). a vacuum level of less than about 100 millitorr is preferably maintained in the freeze - drying chamber during the freeze - drying cycle . the freeze - drying cycle may last an average of about 5 days . during the initial 30 - 45 minutes of the cycle , the cartilage warms from the initial frozen temperature ( e . g ., about − 150 ° c .) to the temperature of the freeze - drying chamber ( e . g ., about − 40 ° c . ), after which it is maintained at about − 40 ° c . for the remainder of the cycle . preferably , the moisture content of the cartilage is reduced to from about 4 to about 5 %. overdrying is preferably avoided , as this may result in the irreversible alterations of collagen and proteoglycan structures . at the end of the freeze - drying cycle , the chamber is warmed to room temperature , the vacuum released and the freeze - dried cartilage is removed . the non - demineralized articular cartilage may be ground using any suitable grinding apparatus . for example , any grinding apparatus capable of grinding dry , hard , brittle material in seconds , such as turbo mills , disc mills , toothed disc mills , jet mills or other similar apparatuses are suitable . preferably , grinding is performed under conditions that preclude raising the temperature of the non - demineralized articular cartilage to a level that may diminish the chondrogenic activity of the composition . for example , grinding is preferably performed without raising the temperature of the articular cartilage above about 50 ° c . in some embodiments , grinding is preferably performed without raising the temperature of the cartilage above about 40 ° c . the temperature of the articular cartilage may be measured in any suitable manner . for example , thermocouples may be used to monitor the temperature of the cartilage directly , e . g ., by measuring the temperature of the cartilage immediately after grinding , or indirectly , e . g ., by measuring the temperature of the metal in the grinding mill . continuous grinding in conventional grinding mills for 3 - 5 minutes can raise the temperature of the material to 70 ° c . or above . however , operating a grinding mill intermittently may preclude an undesirable rise in temperature . in one embodiment , freeze - dried pieces of cartilage , 1 - 4 mm in size , may be ground in a grinding mill operating intermittently for 20 - 30 second intervals . after each grinding cycle , the cartilage may be sieved . the cartilage may be sieved through sieves of 100 to 500 microns . sieving may be used to separate cartilage into cartilage powder ( i . e ., particle sizes of less than 250 microns ) and cartilage granules ( i . e ., particle sizes of 250 to 500 microns ). grinding may be repeated until the desired distribution of particles sizes is obtained . the present invention also provides a method for regenerating articular cartilage . therapeutically effective amounts of cartilage composition comprising non - demineralized articular cartilage having particle sizes distributed within the range of from about 60 microns to about 500 microns may be administered at the site of a cartilage defect . the cartilage composition may be implanted at the articular surface and packed into the defect . advantageously , in some embodiments , the cartilage composition may be packed into the defect with the use of an overlying cover . without wishing to be bound to any theory , it is believed that compositions , according to the invention , including non - demineralized particulate cartilage , release cartilage growth factor ( s ) or other substances that induce regeneration of articular cartilage . the three - dimensional shape of the particles and multiple surfaces , as well as the inventive particle sizes and distributions , enhance diffusion of the cartilage growth factor ( s ) or other substances from the particles . furthermore , the absence of harsh chemical treatments and avoidance of elevated temperatures during processing facilitates the production of particles having high chondrogenic activity . the following example further illustrates the invention but , of course , should not be construed as in any way limiting its scope . this example demonstrates the chondrogenic activity of the inventive composition in frilly immunocompetant non - human primates . full thickness cartilage defects measuring 10 mm × 10 mm were created in the medial condyles of the animals . the defects were densely packed with the cartilage composition according to the present invention and were compacted with a tamp . the animals were examined two , six , and sixteen weeks post transplantation and the joints were re - explored . fig1 a - 1 c are photographs taken at two , six , and sixteen weeks , respectively . specimens were also taken and were fixed in 10 % formalin - earle &# 39 ; s balanced salt solutions . paraffin sections were cut and stained with homotoxylin and eosin , pas , romanowski - giemsa and safranin - o stains . fig2 a and 2 b illustrate the specimens taken ( 100 ×) at six and sixteen weeks , respectively . as seen in fig1 a , at two weeks post transplantation , granulation tissue is present in the center of the defect and new cartilage is present at the edge of the defect . at six weeks post transplantation ( fig1 b ), new cartilage is formed from the edges of the defect and granulation tissue is no longer present . fig1 b also shows the inventive cartilage composition covered with a translucent membrane in the center of the defect . fig2 a further illustrates the normal morphology of the hyaline cartilage at six weeks . at sixteen weeks post transplantation , as seen in fig1 c , the defect is completely healed and covered with congruous normal appearing cartilage . a section of the newly formed cartilage taken at sixteen weeks is shown in fig2 b , and the normal appearing hyaline cartilage can be seen . as a comparison , fig1 d illustrates a control , where the defect was left untreated . as seen in the figure , no evidence of healing is visible and the defect has become larger due to additional fragmentation of the cartilage . all references , including publications , patent applications , and patents , cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein . the use of the terms “ a ” and “ an ” and “ the ” and similar referents in the context of describing the invention ( especially in the context of the following claims ) are to be construed to cover both the singular and the plural , unless otherwise indicated herein or clearly contradicted by context . recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range , unless otherwise indicated herein , and each separate value is incorporated into the specification as if it were individually recited herein . all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context . the use of any and all examples , or exemplary language ( e . g ., “ such as ”) provided herein , is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed . no language in the specification should be construed as indicating any non - claimed element as essential to the practice of the invention . preferred embodiments of this invention are described herein , including the best mode known to the inventor for carrying out the invention . of course , variations of those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description . the inventor expects skilled artisans to employ such variations as appropriate , and the inventor intends for the invention to be practiced otherwise than as specifically described herein . accordingly , this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law . moreover , any combination of the - above - described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context .
particulate cartilage compositions for stimulating chondrogenesis and producing cartilage regeneration and processes for their preparation are disclosed . methods for regenerating articular cartilage are also disclosed .