Tissue engineering of cartilage with the use of chitosan-gelatin complex scaffolds

Chitosan has been shown to be a promising scaffold for various applications in tissue engineering. In this study, a chitosan-gelatin complex was fabricated as a scaffold by a freezing and lyophilizing technique. Chitosan's structure and characteristics are similar to those of glycosaminoglycan (GAG) and its analogs, and possesses various biological activities, whereas gelatin can serve as a substrate for cell adhesion, differentiation, and proliferation. With the use of autologous chondrocytes isolated from pig's auricular cartilage and seeded onto the chitosan-gelatin scaffold, elastic cartilages have been successfully engineered at the porcine abdomen subcutaneous tissue. After 16 weeks of implantation, the engineered elastic cartilages have acquired not only normal histological and biochemical, but also mechanical properties. The tissue sections of the engineered elastic cartilages showed that the chondrocytes were enclosed in the lacuna, similar to that of native cartilage. The presence of elastic fibers in the engineered cartilages was also demonstrated by Vehoeff's staining, and immunohistochemical staining confirmed the presence of type II collagen in the engineered cartilages. Quantitatively, the GAG in the engineered cartilages reached 90% of the concentration in native auricular cartilage. Furthermore, biomechanical analysis demonstrated that the extrinsic stiffness of the engineered cartilages reached 85% of the level in native auricular cartilage when it was harvested at 16 weeks. Thus, this study demonstrated that the chitosan-gelatin complex may serve as a suitable scaffold for cartilage tissue engineering.     

整形外科常用软骨生物力学研究进展

肋软骨、耳软骨及鼻中隔软骨广泛应用于整形外科领域,肋软骨主要进行全耳再造及鼻整形,而耳软骨及鼻中隔软骨则应用于鼻整形术中,其术后效果及形态的维持与软骨生物力学特征密切相关。软骨主要由软骨细胞及细胞外基质组成,与生物力学相关的结构为蛋白多糖、胶原纤维以及软骨膜,而决定软骨生物力学性能的则是软骨的微观结构,主要为细胞外基质。主要关注肋软骨、耳软骨及鼻中隔软骨相关的生物力学特性及其微观结构研究结果,总结不同软骨包括组织工程耳软骨生物力学测试的基本数据。目前关于软骨生物力学研究有待于对测试方法进行标准化,同时可进一步推广有限元的研究思路,进而更好地指导临床诊治。     

Characteristics of tissue-engineered cartilage from human auricular chondrocytes

This study was done to define the mechanical and histological properties of tissue-engineered cartilage (TEC) derived from human chondrocytes and to compare these findings with those of native cartilage. Chondrocytes were obtained from 10 human auricular cartilages and seeded onto a biodegradable template of polyglycolic acid and poly L-lactic acid. Each template was shaped into a 1 cm x 2 cm rectangle. The templates were implanted in athymic mice for 8 weeks. Eight human auricular cartilages were used for comparison. Mechanical analysis with a tensile testing device provided values of ultimate tensile strength (UTS), stiffness, and resilience. Statistical analysis was performed with the Student's t-test. Histological assessment was done with hematoxylin-eosin staining along with other special stains. The TEC had UTS of 2.07 MPa, stiffness of 3.7 MPa, and resilience of 0.37 J/m3. The control specimens had UTS of 2.18 MPa, stiffness of 5.11 MPa, and resilience of 0.42 J/m3. No statistical difference was found between the experimental and control groups for each of the three parameters. Histological analysis showed mature cartilage with characteristic collagen, glycosaminoglycans, and elastin in the TEC. The neo-cartilage showed slightly smaller size and more irregular distribution of chondrocytes and unique fibrous capsule formation with peripheral infiltration of fibrous tissue. This study showed that the mechanical qualities of TEC from human chondrocytes are similar to those of native auricular cartilage. It suggests that the engineered cartilage from human chondrocytes may have sufficient strength and durability for clinical uses. The histological findings revealed some differences with neo-cartilage.     

Human fetal hyoid body origin revisited

The hyoid body is traditionally believed to have a dual origin from second and third arch mesenchyme, but this theory remains controversial. We examined paraffin-embedded sections from the hyoid region of 12 embryos and fetuses at 5-7 weeks of gestation (11-22 mm cranio-rump length). We found that the second (Reichert's cartilage) and third arch mesenchymal condensations did not reach the median area at the base of the tongue. Rather, a midline mesenchymal condensation was seen, and it separated from these arches at an early stage. This condensation was triangular and plate-like, and the cranial part was narrow between the bilateral Reichert's cartilages, while the caudal part was wide along the mediolateral axis between the bilateral primitive greater horns. We considered the midline mesenchymal condensation as the hyoid body anlage. At 7 weeks, a cartilaginous mass appeared in the midline condensation. The hypoglossal nerve changed its direction at the superolateral ends of the midline condensation. We propose that: (i) the hyoid body originates from the hypobranchial eminence via the midline condensation; (ii) the lesser horn originates from the caudal end of Reichert's cartilage; and (iii) the greater horn of the hyoid and the superior cornu of the thyroid cartilage originate from the third arch cartilage. The second and third arches may not regulate early hyoid body morphology.     

Association between the developing sphenoid and adult morphology: A study using sagittal sections of the skull base from human embryos and fetuses

The developing sphenoid is regarded as a median cartilage mass (basisphenoid [BS]) with three cartilaginous processes (orbitosphenoid [OS], ala temporalis [AT], and alar process [AP]). The relationships of this initial configuration with the adult morphology are difficult to determine because of extensive membranous ossification along the cartilaginous elements. The purpose of this study was therefore to evaluate the anatomical connections between each element of the fetal sphenoid and adult morphology. Sagittal sections from 25 embryos and fetuses of gestational age 6–34 weeks and crown-rump length 12–295 mm were therefore examined and compared with horizontal and frontal sections from the other 25 late-term fetuses (217–340 mm). The OS was identified as a set of three mutually attached cartilage bars in early fetuses. At all stages, the OS-post was continuous with the anterolateral part of the BS. The BS included the notochord and Rathke's pouch remnant in embryos and early fetuses. The dorsum sellae was absent from embryos, but it protruded from the BS in early fetuses before a fossa for the hypophysis became evident. Although not higher than the hypophysis at midterm, the dorsum sellae elongated superiorly after gestational age 25 weeks. In early fetuses, the AP was located on the side immediately anterior to the otic capsule. The AT developed on the side immediately posterior to the extraocular rectus muscles. At late term, the greater wing was formed by membranous bones from the AT and AP. The AT and AP formed a complex bridge between the BS and the greater wing. A small cartilage, future medial pterygoid process (PTmed) was located inferior to the AT in early fetuses. At midterm, one endochondral bone and multiple membranous bones formed the PTmed. The lateral pterygoid process (PTlat) was formed by a single membranous bone plate. Therefore, we connected fetal elements and the adult morphology as follows. (1) Derivative of the OS makes not only the lesser wing but also the anterior margin of the body of the sphenoid. (2) Derivatives of the BS are the body of the sphenoid including the sella turcica and the dorsum sellae. (3) Most of the greater wing including the foramen rotundum and the foramen oval originate from the AT and AP and multiple membranous bones. (4) The PTmed originate from endochondral bones and multiple membranous bones, while the PTlat derive from a single membranous bone.     

Reevaluation of the arterial blood supply of the auricle

The anatomical basis for auricular flaps used in multiple aesthetic and reconstructive procedures is currently based on a random distribution of the underlying arterial network. However, recent findings reveal a systematic pattern as opposed to the present concepts. Therefore, we designed this study to assess the arterial vascular pattern of the auricle in order to provide reliable data about the vascular map required for surgical interventions. Sixteen human auricles from eight body donors (five females/three males, 84.33 ± 9.0 years) were investigated using the unique ‘Spalteholz’ method. After arterial injection of silicone, a complete transparency of the tissue was achieved and the auricular arteries and branches were visible. Qualitative and quantitative evaluation of the arterial vascular pattern was performed. The superior and the inferior anterior auricular artery provided the vascular supply to the helical rim, forming an arcade, i.e. helical rim arcade. On the superior third of the helical rim another arcade was confirmed between the superior anterior auricular artery and the posterior auricular artery (PAA), i.e. the helical arcade. The perforators of the PAA were identified lying in a vertical line 1 cm posterior to the tragus, supplying the concha, inferior crus, triangular fossa, antihelix and the earlobe. The results of this study confirmed the constant presence of the helical rim arcade (Zilinsky‐Cotofana), consistent perforating branches of the PAA, and the helical arcade (Erdman), and will help and guide physicians performing auricular surgeries toward fast and simple procedures with optimal patient satisfaction.     

Bioengineering of elastic cartilage with aggregated porcine and human auricular chondrocytes and hydrogels containing alginate, collagen, and kappa-elastin.

Transplantation of isolated chondrocytes has long been acknowledged as a potential method for rebuilding small defects in damaged or deformed cartilages. Recent advances in tissue engineering permit us to focus on production of larger amounts of cartilaginous tissue, such as might be needed for reconstructive surgery of the entire auricle. In this report we describe modification of the basic techniques that lead to production of a large amount of elastic cartilage originated from porcine and human isolated chondrocytes. Small fragments of auricular cartilage were harvested from children undergoing ear reconstruction for microtia or extirpation of preauricular tags and from ears of juvenile pigs. Enzymatically isolated elastic chondrocytes were then agitated in suspension to form the chondronlike aggregates, which were further embedded in molded hydrogel constructs made of alginate and type I collagen augmented with kappa-elastin. The constructs were then implanted in nude mice and harvested 4 and 12 weeks after heterotransplantation. The resulting neocartilage closely resembled native auricular cartilage at the gross, microscopic, and ultrastructural levels. Immunohistochemistry and electron microscopy additionally confirmed that the newly produced cartilage contained the major components of the elastic cartilage-specific matrix, including collagen type II, proteoglycans, and well-assembled elastic fibers.     

Holmium laser in chondrology: potentials and prospects

To study the mechanism of simulation of a cartilage, to define the optimum parameters and laser radiation regimens, the authors made a complex of in vitro experiments on the cartilages of the nasal septum in man and domestic animals and in vivo experiments on those of the concha in rabbits and pigs. Holmium laser radiation is shown to be the most suitable tool for formation of a cartilage. Evidence is provided for the possibility of irreversibly altering the shape of a cartilage during laser radiation. A procedure has been developed for non-invasive correction of the septum of the nose for its curvature. Restored or improved nasal respiration was observed in more than two thirds of the patients. Laser surgery is not of age-limited application, it is noninvasive, can be performed in the outpatient settings and requires no drug treatment in the postoperative treatment.     

Glial Fibrillary Acidic Protein Immunoreactivity of Chondrocytes in Immature and Mature Teratomas

The immunoreactivity of chondrocytes for glial fibrillary acidic protein (GFAP), other intermediate filament proteins and S-100 protein was studied in formalin-fixed paraffin-embedded sections. A total of 95 cartilage specimens were examined from five immature teratomas, 12 mature teratomas, and a teratocarcinoma. GFAP-immunoreactive chondrocytes were abundant in immature cartilages, and as the cartilages maturated, these chondrocytes decreased and became distributed peripherally. Elastic cartilage had more GFAP-immunoreactive chondrocytes than non-elastic cartilage. GFAP-immunoreactive cartilage was often located close to central nervous tissue. lmmunostaining for vimentin and S-100 protein revealed extensive distribution of immunoreactive chondrocytes in immature and mature cartilages, but in mature cartilage, chondrocytes at the center had less vimentin immunoreactivity. GFAP-immunoreactive chondrocytes also showed apparent immunostaining for vimentin. There was no difference in immunohistochemical staining for the α and α subunits of S-100 protein. The immunoreactivities of teratoma cartilage specimens were quite similar to those of respiratory tract cartilage.     

Glial fibrillary acidic protein immunoreactivity of chondrocytes in immature and mature teratomas

The immunoreactivity of chondrocytes for glial fibrillary acidic protein (GFAP), other intermediate filament proteins and S-100 protein was studied in formalin-fixed paraffin-embedded sections. A total of 95 cartilage specimens were examined from five immature teratomas, 12 mature teratomas, and a teratocarcinoma. GFAP-immunoreactive chondrocytes were abundant in immature cartilages, and as the cartilages maturated, these chondrocytes decreased and became distributed peripherally. Elastic cartilage had more GFAP-immunoreactive chondrocytes than non-elastic cartilage. GFAP-immunoreactive cartilage was often located close to central nervous tissue. Immunostaining for vimentin and S-100 protein revealed extensive distribution of immunoreactive chondrocytes in immature and mature cartilages, but in mature cartilage, chondrocytes at the center had less vimentin immunoreactivity. GFAP-immunoreactive chondrocytes also showed apparent immunostaining for vimentin. There was no difference in immunohistochemical staining for the alpha and beta subunits of S-100 protein. The immunoreactivities of teratoma cartilage specimens were quite similar to those of respiratory tract cartilage.     

声门与小角结节及其相互关系的研究

对60具成人尸体喉标本进行了观察与测量,发现半数标本的双侧声带稍不对称,声带并非总是固定于尸状位.通过对声带、小角软骨和构状软骨及其相互关系的形态学分析,认为小角结节可能为声门运动的缓冲袋置,单侧小角结节病变,可引起两侧声带不在同一平面上闭合,双侧小结结节病变,可能导致喉接触性渍疡和声门闭合时后端出现三角形缝隙.     

Different expression of 25-kDa heat-shock protein (Hsp25) in Meckel's cartilage compared with other cartilages in the mouse

The 25-kDa heat-shock protein (Hsp25) is expressed in the cartilage of the growth plate and suggested to function in chondrocyte differentiation and degeneration. Using immunohistochemistry, we examined the temporal and spatial occurrence of Hsp25 in Meckel's cartilage in embryonic mice mandibles, and in other types of cartilage in both embryonic and adult mice. In adults, Hsp25 immunoreactivity was detected in the hypertrophic chondrocytes located in growth plates of long bones and in non-osteogenic laryngeal and tracheal cartilages. No chondrocytes in the resting or proliferating phase exhibited Hsp25 immunoreactivity. In the embryonic mandibles, resting and proliferating chondrocytes in the anterior and intermediate portions of Meckel's cartilage showed Hsp25 immunoreactivity from the 12th day of gestation (E12) through E15, whereas those in the posterior portion showed little or no immunoreactivity. After E16, the overall Hsp25 immunoreactivity in Meckel's cartilage substantially reduced in intensity, and little or no immunoreactivity was detected in the hypertrophic chondrocytes located in the degenerating portions of Meckel's cartilage. The antisense oligonucleotide for Hsp25 mRNA applied to the culture media of the mandibular explants from E10 embryos caused significant inhibition of the development of the anterior and middle portions of Meckel's cartilage. These results suggested that Hsp25 is essential for the development of Meckel's cartilage and plays different roles in Meckel's cartilage from those in the permanent cartilages and the cartilages undergoing endochondral ossification.     

Histogenesis of experimental open neural defects in the early chick embryo

The chick embryo is a useful experimental model for investigating neural dysraphism. Windowing at 26 h incubation is by itself teratogenic, resulting in predominantly neural tube defects. A histological study of a regular series of specimens between pre-neurulation and later stages was undertaken. Open brain defects occurred at every stage after the expected closure of the anterior neuropore, suggesting that they arose by non-closure, myeloschisis was preceded by a characteristic triangular shape of the rhomboid sinus. Serial sections revealed regular open defects, with separation between the neural plate and tail-bud sources of neural tissue, but continuity of the neural plate into the caudal region. These findings suggest that myeloschisis arises by nonclosure of the neural folds. The establishment of myeloschisis was followed by local separation of the notochord from an open area of neural tube, but not by overgrowth of neural tissue. Myelodysplasia appeared at about the time of expected closure of the rhomboid sinus. Serial sections revealed irregular open defects, with complete absence of neural plate material and formation of the cord tissue from tailbud material alone. The lesions were accompanied by extensive cystic and hemorrhagic changes in local mesoderm, with reduction in somite volume. There was no associated notochordal separation.     

The complex arrangement of an “aorto-jejunal paraduodenal” fossa, as revealed by dissection of human posterior parietal peritoneum

Peritoneal fossae derive from normal or anomalous coalescence of the peritoneum during fetal development, or from the course of retroperitoneal vessels. Clinically, internal abdominal hernias may be housed inside these fossae. In this report from an autopsy, a singular peritoneal fossa was delimited superiorly by an arcuate serous fold, raised up by the inferior mesenteric vein, and infero-posteriorly by two (right and left) avascular folds, extending from the abdominal aorta to the jejunum. The right fold reached the duodeno-jejunal flexure, which was located on the right side of the aorta. The left fold subdivided into two, anterior and posterior, secondary folds. The anterior fold reached the superior edge of the first jejunal loop, and the posterior fold turned medially to connect with the inferior edge of the proximal limb of the same loop. This fossa consisted of three recesses: superior, Located behind the subserous vascular arch, antero-inferior and postero-inferior, separated by interposition of the left posterior secondary fold, between the jejunum and aorta. The complex arrangement of this fossa suggests that it might have originated from a coalescence arising beyond the duodeno-jejunal flexure and including the first jejunal loop, and from the subserous course of the inferior mesenteric vein. Because of displacement to the right of the flexure, processes of coalescence in a location normally occupied by the ascending duodenum might have occurred in a similar pattern for the jejunum, involving the mesoduodenum and the proximal part of the mesentery. Labyrinthine fossae like this might cause strangulation of internal abdominal hernias and hinder intraoperative maneuvers.     

耳廓微血管网和血流分布特点

目的:观察耳廓微血管网和血流分布特点。方法:取新鲜成人尸体耳廓12例,明胶-氧化铅灌注铸型后行普通X平片及CT灌注血管成像,分析耳廓微血管网的构筑和分布特点。征召正常成人自愿者8例,用激光多普勒血流仪对其耳廓微循环血流进行测量,比较耳廓不同部位血流量的差异。结果:耳廓根部以进入耳廓的主干血管为主,微血管网主要分布在耳轮和对耳轮区域。耳轮和对耳轮区域的平均血流量(132.47±19.82PU)明显高于三角窝和耳甲艇区域的平均血流量(99.36±25.62PU),差异有统计学意义(t=4.70,P0.05)。结论:耳轮和对耳轮是耳廓微血管网和血流量最丰富区域,以该区域为蒂形成局部皮瓣具有良好的血供保障。     

基于多模态MRI图像的耳软骨模型构建

构建高保真的耳软骨支架一直是耳廓再造的研究核心。传统成像方法对耳软骨和周围组织的区分度较低,为探究可用于耳软骨成像的MRI扫描序列,为耳软骨3D生物打印提供高精度模型,提出超短回波时间(UTE)成像和3D_T2成像序列相结合的扫描方案。实验共收集40位健康志愿者单侧外耳廓数据。首先,两位有经验的评估者分别根据UTE图像逐层勾勒出耳软骨大致形状,并根据3D_T2图像进一步去除耳垂等其他组织,以此构建耳软骨模型。每名评估者独立重复3次。然后,分析评估者内和评估者间耳软骨分割结果的体积(Cg.V)、表面积(Cg.S)和厚度(Cg.Th)的相关性, 以评价不同评估者是否可以定义相同的感兴趣区域。结果显示,评估者内手动分割结果的精度误差分别为:Cg.V≤3.05%,Cg.S≤1.80%,Cg.Th≤3.43%,评估者间分别为:Cg.V=2.39%,Cg.S=3.75%,Cg.Th=3.37%;Cg.V、Cg.S和Cg.Th的组内相关性分别高于0.95、0.97、0.77,组间相关性分别为0.97、0.89和0.69;Dice相似性系数(DSC)均高于80%。这表明,超短回波时间和3D_T2成像序列结合能够表征耳软骨的形态学差异,是适合耳廓再造研究的扫描方案,可为3D生物打印提供高精度的耳软骨模型。     

Existence of vocal folds in the larynx of odontoceti (toothed whales)

Odontocetes (toothed whales) vocalize for communication and echolocation. The mechanisms of sound production, however, remain unclear. Their larynx has long been thought to lack vocal folds and, thus, was considered incapable of generating sounds. This study investigates internal anatomy of the odontocete larynx to: 1) describe the morphology of any folds found, 2) determine any structural homologies between these folds and the vocal folds of terrestrial mammals, and 3) assess their possible function in sound production. Larynges of 24 odontocetes representing ten genera (Delphinus, Stenella, Lagenorhynchus, Tursiops, Grampus, Delphinapterus, Globicephala, Kogia, Mesoplodon, and Phocoena) were studied post mortem. Nine specimens were cut midsagittally, and the remainder were dorsally opened to reveal internal anatomy. Results show that, contrary to established belief, vocal folds are consistently present. They are not isolated bands or "cords," but appear continuous with the internal laryngeal membrane. The attachments of these folds are the same as in terrestrial mammals, thus indicating homology with true mammalian vocal folds. These folds extend from the midline of the thyroid cartilage to the base of the arytenoid cartilages, sometimes to a discrete process. The vocal folds are elongated and oriented in a vertical plane, parallel to airflow direction. Vocal fold morphology varies, appearing as true bifurcated structures, a trifurcated fold, or a single midline fold. Laryngeal ventricles and vestibular folds are also consistently found lateral to the vocal folds. The vocal folds may divide the airstream within the larynx into three separate air currents. Fold vibrations may produce initial laryngeal sound used in echolocation or communication.     

The cartilage of the third eyelid: a comparative macroscopical and histological study in domestic animals.

The purpose of this comparative study was to evaluate morphological differences between the cartilages of the third eyelid in dogs, cats, pigs, cows, small ruminants and horses. For that reason a total of 83 third eyelids were investigated. By the aid of a modified maceration technique, the three-dimensional form of the cartilage could be demonstrated for the first time. Generally, the cartilage consists of a long narrow appendix which is followed by a variable crossbar. In dogs the appendix is cone shaped in the basal end and extends to form a triangular plate. The former is crescent-like in shape and has a marked bulge. The cartilage of the cat consists of an appendix which is enlarged in the proximal end as compared to the dog. The crossbar resembles a reverse s-form with ends tapering off to a point. In contrast pig and cow cartilage possess a typical anchorform whereas the cartilage of small ruminants starts with a thin rod which extends in a slightly curved form ending in an oval plate. The crossbar is crescent-like in these animals. In the horse the base of the cartilage is surrounded by a massive fatty tissue and the crossbar has a characteristic hook-form. Moreover, there are significant differences in regard to the quality of the cartilage, especially concerning the presence and distribution of elastic fibres. In cats and horses the elastic fibres of the adjacent connective tissue penetrate the perichondrium. Additionally, the centre of the cartilage shows a very dense network consisting of fine elastic fibres. In dogs, pigs, cows and small ruminants the cartilage consists of hyaline quality and only in the neighbouring connective tissue are some elastic fibres detectable.     

Expression of matrix metalloproteinases in normal and damaged articular cartilage from human knee and ankle joints

The objectives of this study were the following: (a) describe the appearance of histopathologic changes observed in human articular cartilage from the knee and ankle joints of organ donors with no symptomatic joint disease; (b) compare by in situ hybridization mRNA expression of six matrix metalloproteinases (MMP) in these cartilages; (c) compare MMP mRNA expression with the histology of the cartilage; and (d) test whether the effect of interleukin-1beta (IL-1beta) on the MMP mRNA expression could be detected with in situ hybridization. Human articular cartilages from the knee (tibiofemoral) and ankle (talocrural) joints of 41 different donors (aged 18 to 84 years) were obtained through the Regional Organ Bank of Illinois. The microscopic appearance of the cartilages was graded on a histopathologic scale from 0 to 13 with the highest grade representing severely damaged cartilage. In situ hybridization was performed using oligonucleotide probes to three collagenases (MMP-1, MMP-8, MMP-13), gelatinase A (MMP-2), stromelysin (MMP-3), and matrix type-1 metalloproteinase (MMP-14). Cartilages from some donors were cultured with IL-1beta and then analyzed for MMP expression using in situ hybridization. The histopathology grades of the cartilages from the asymptomatic donors covered the entire scale even in the ankle. Based on their grades, the cartilages were described as either normal (grades 0 to 5) or damaged (grades 6 to 13). The cartilages contained message for all six MMP tested with no detectable differences in expression of MMP-1, -2, -13, and -14 between the normal and damaged cartilages. However the expression of MMP-3 and MMP-8 was elevated in the damaged cartilages. In normal knee cartilage, mRNA expression of MMP-3 and MMP-8 was low, whereas in normal ankle cartilage, MMP-8 expression was below the detection limit. MMP-3 and MMP-8 message was up-regulated in the damaged cartilage from both joints, or if the tissue was cultured in the presence of IL-1beta. From this study we conclude the following: (a) similar histopathologic changes occur in both knee and ankle cartilages; (b) MMP-1, -2, -13, and -14 are constitutively expressed in adult human cartilage; and (c) only up-regulation of mRNA expression of MMP-3 and MMP-8 could be detected with naturally occurring cartilage damage and IL-1beta induction.