In vitro characterization of chondrocytes isolated from naturally occurring osteochondrosis lesions of the humeral head of dogs

Tissue Engineering of Canine Cartilage from Surgically Debrided Osteochondritis Dissecans Fragments

This study in dogs explored the feasibility of using cartilage fragments removed and discarded during routine palliative surgery for osteochondritis dissecans (OCD) as a source of primary chondrocytes for scaffold-free cartilage tissue-engineering. Primary chondrocytes were obtained from three OCD donors and one age-matched healthy articular cartilage (HAC) donor. After monolayer expansion of primary cells, a three-dimensional spherical suspension culture was implemented. Following this stage, cells were seeded at a high density into custom-made agarose molds that allowed for size and shape-specific constructs to be generated via a method of cellular self-assembling in a scaffold-free environment. Fifty-eight neocartilage constructs were tissue-engineered using this methodology. Neocartilage constructs and native cartilage from shoulder joint were subjected to histological, mechanical, and biochemical testing. OCD and HAC chondrocytes-sourced constructs had uniformly flat morphology and histology consistent with cartilage tissue. Constructs sourced from OCD chondrocytes were 1.5-times (32%) stiffer in compression and 1.3 times (23%) stronger in tension than constructs sourced from HAC chondrocytes and only 8.7-times (81%) less stiff in tension than native tissue. Constructs from both cell sources consistently had lower collagen content than native tissue (22.9%/dry weight [DW] for OCD and 4.1%/DW for HAC vs. 51.1%/DW native tissue). To improve the collagen content and mechanical properties of neocartilage, biological and mechanical stimuli, and thyroid hormone (tri-iodothyronine) were applied to the chondrocytes during the self-assembling stage in two separate studies. A 2.6-fold (62%) increase in compressive stiffness was detected with supplementation of biological stimuli alone and 5-fold (81%) increase with combined biological and mechanical stimuli at 20% strain. Application of thyroid hormone improved collagen content (1.7-times, 33%), tensile strength (1.8-times, 43%), and stiffness (1.3-times, 21%) of constructs, relative to untreated controls. Collectively, these data suggest that OCD chondrocytes can serve as a reliable cell source for cartilage tissue-engineering and that canine chondrocytes respond favorably to biological and mechanical stimuli that have been shown effective in chondrocytes from other animal species, including humans.

Viability of Pathologic Cartilage Fragments as a Source for Autologous Chondrocyte Cultures

OBJECTIVE

To study if a culture of chondrocytes can be obtained from pathologic hyaline cartilage (PHC) fragments.

DESIGN

Twenty-five men and 9 women with osteochondritis dissecans (OCD) in 11 cases, arthrosis in 13 patients, and trauma in the remaining 10 cases were included. The PHC fragments and a small sample of the next healthy cartilage were extracted by arthroscopy. According to the appearance, the PHC samples were divided into fixed (3 cases), flapped (6 patients), or loose bodies (25 cases), depending on the attachment degree of the cartilage to the subchondral bone. Approximately half of each pathologic sample and the whole healthy one were digested to isolate the cells trying to establish the cell culture.

RESULTS

We were able to establish a cell culture in 7 out of 34 (20.6%) PHC samples (positive samples), whereas in the remaining 27 (79.4%) no cell growth was observed (negative samples). Most of the negative samples were loose bodies (P = 0.005) taken from patients with OCD or arthrosis (P = 0.001) with an evolution time of more than 1 year (P < 0.001). The best binary logistic regression model (P < 0.001) showed that the only factor affecting the establishment of cell culture was the evolution time (P = 0.044).

CONCLUSION

It is possible to culture chondrocytes from osteochondral fragments if they are traumatic, within a year of injury and not from fragments due to arthrosis or OCD.

A genome-wide association study of osteochondritis dissecans in the Thoroughbred

Osteochondrosis is a developmental orthopaedic disease that occurs in horses, other livestock species, companion animal species, and humans. The principal aim of this study was to identify quantitative trait loci (QTL) associated with osteochondritis dissecans (OCD) in the Thoroughbred using a genome-wide association study. A secondary objective was to test the effect of previously identified QTL in the current population. Over 300 horses, classified as cases or controls according to clinical findings, were genotyped for the Illumina Equine SNP50 BeadChip. An animal model was first implemented in order to adjust each horse's phenotypic status for average relatedness among horses and other potentially confounding factors which were present in the data. The genome-wide association test was then conducted on the residuals from the animal model. A single SNP on chromosome 3 was found to be associated with OCD at a genome-wide level of significance, as determined by permutation. According to the current sequence annotation, the SNP is located in an intergenic region of the genome. The effects of 24 SNPs, representing QTL previously identified in a sample of Hanoverian Warmblood horses, were tested directly in the animal model. When fitted alongside the significant SNP on ECA3, two of these SNPs were found to be associated with OCD. Confirmation of the putative QTL identified on ECA3 requires validation in an independent sample. The results of this study suggest that a significant challenge faced by equine researchers is the generation of sufficiently large data sets to effectively study complex diseases such as osteochondrosis.

In vitro phenotypic modulation of chondrocytes from knees of patients with osteochondritis dissecans: implications for chondrocyte implantation procedures

We attempted to characterise the biological quality and regenerative potential of chondrocytes in osteochondritis dissecans (OCD). Dissected fragments from ten patients with OCD of the knee (mean age 27.8 years (16 to 49)) were harvested at arthroscopy. A sample of cartilage from the intercondylar notch was taken from the same joint and from the notch of ten patients with a traumatic cartilage defect (mean age 31.6 years (19 to 52)). Chondrocytes were extracted and subsequently cultured. Collagen types 1, 2, and 10 mRNA were quantified by polymerase chain reaction. Compared with the notch chondrocytes, cells from the dissecate expressed similar levels of collagen types 1 and 2 mRNA. The level of collagen type 10 message was 50 times lower after cell culture, indicating a loss of hypertrophic cells or genes. The high viability, retained capacity to differentiate and metabolic activity of the extracted cells suggests preservation of the intrinsic repair capability of these dissecates. Molecular analysis indicated a phenotypic modulation of the expanded dissecate chondrocytes towards a normal phenotype. Our findings suggest that cartilage taken from the dissecate can be reasonably used as a cell source for chondrocyte implantation procedures.

Are ankle chondrocytes from damaged fragments a suitable cell source for cartilage repair?

OBJECTIVE

To characterize the post-expansion cartilage-forming capacity of chondrocytes harvested from detached fragments of osteochondral lesions (OCLs) of ankle joints (Damaged Ankle Cartilage Fragments, DACF), with normal ankle cartilage (NAC) as control.

DESIGN

DACF were obtained from six patients (mean age: 35 years) with symptomatic OCLs of the talus, while NAC were from 10 autopsies (mean age: 55 years). Isolated chondrocytes were expanded for two passages and then cultured in pellets for 14 days or onto HYAFF-11 meshes (FAB, Italy) for up to 28 days. Resulting tissues were assessed histologically, biochemically [glycosaminoglycan (GAG), DNA and type II collagen (CII)] and biomechanically.

RESULTS

As compared to NAC, DACF contained significantly lower amounts of DNA (3.0-fold), GAG (5.3-fold) and CII (1.5-fold) and higher amounts of type I collagen (6.2-fold). Following 14 days of culture in pellets, DACF-chondrocytes generated tissues less intensely stained for Safranin-O and CII, with significantly lower GAG contents (2.8-fold). After 28 days of culture onto HYAFF((R))-11, tissues generated by DACF-chondrocytes were less intensely stained for Safranin-O and CII, contained significantly lower amounts of GAG (1.9-fold) and CII (1.4-fold) and had lower equilibrium (1.7-fold) and dynamic pulsatile modulus (3.3-fold) than NAC-chondrocytes.

CONCLUSION

We demonstrated that DACF-chondrocytes have inferior cartilage-forming capacity as compared to NAC-chondrocytes, possibly resulting from environmental changes associated with trauma/disease. The study opens some reservations on the use of DACF-derived cells for the repair of ankle cartilage defects, especially in the context of tissue engineering-based approaches.

Viability of loose body fragments in osteochondritis dissecans of the knee. A series of cases

The purpose of this study was to determine if the cartilage from loose osteochondral fragments remains viable. Five patients with OCD of the knee who had undergone surgical treatment (arthroscopic reduction and internal fixation of the loose body) were included. The average age of patients was 13 years (range 10-14 years). Cartilage samples were obtained from the loose body fragments before reattachment was performed (study group) and from the healthy native cartilage (intercondyle area, control group) from each of the five patients. Tissue viability was assessed using live-dead assay in both groups. All five loose osteochondral fragments showed similar viability to the healthy native cartilage group, with 88% cell viability (95% CI 50-100) in loose body fragments versus 92% viability (95% CI 50-100) from healthy cartilage. This study showed that cartilage from detached OCD fragments remains viable before reattachment is performed.

Chondrocytes harvested from osteochondritis dissecans cartilage are able to undergo limited in vitro chondrogenesis despite having perturbations of cell phenotype in vivo

Our objective was to characterize the variation in gene expression for key genes associated with chondrogenic phenotype of osteochondrosis (OC)-affected and normal chondrocytes, and to identify whether OC chondrocytes can redifferentiate and regain a phenotype similar to normal chondrocytes if appropriate chondrogenic signals are given. Equine articular cartilage removed at surgery to treat clinically significant OC lesions was collected (n = 10), and the gene expression evaluated and compared to aged-matched normal samples (n = 10). Cartilage was harvested from normal (n = 4) and OC (n = 3) joints from horses at necropsy. Chondrogenic pellet cultures were established following monolayer proliferation. After 14 days in culture, the pellets were assessed by histochemical and pellet weight analysis, assay of glycosaminoglycan (GAG) content, and gene expression. Chondrocytes from OC cartilage expressed significantly more Coll-I, -II, -III, and -X than chondrocytes from normal cartilage (all p < 0.0001). Furthermore, OC chondrocytes expressed significantly more MMP-13, ADAMTS-4 (both p < 0.0001), and TIMP-1 (p < 0.001) and significantly less TIMP-2 and TIMP-3. Pellets created from OC chondrocytes contained significantly less GAG (p = 0.0069) and expressed significantly less Sox9 and significantly more superficial zone protein (SZP) (p = 0.0105) than pellets created from normal cartilage. The results suggest that chondrocytes from OC cartilage at the time of surgical treatment have perturbations in phenotype compared to cells from normal cartilage. Despite these differences, following monolayer expansion and pellet culture under chondrogenic conditions, chondrocytes derived from OC cartilage retain some ability to undergo chondrogenic differentiation and synthesize an appropriate cartilage-like matrix. However, this chondrogenic differentiation potential is inferior to that seen in aged-matched normal chondrocytes.

Histological and cell biological characterization of dissected cartilage fragments in human osteochondritis dissecans of the femoral condyle

INTRODUCTION

Osteochondritis dissecans (OCD) within the weight-bearing femoral condyle carries a high risk of osteoarthritis. The definitive pathogenetic cause is unclear. Therefore biochemical and cellular features of OCD were analyzed and compared to macroscopically normal cartilage of the same joint surface.

MATERIALS AND METHODS

Dissected fragments from 14 patients and biopsies of normal cartilage from the intercondylar notch as controls were harvested at arthroscopy. Staining with safranin O to monitor proteoglycan content, alkaline phosphatase activity, and immunohistochemistry with mouse monoclonal antibodies to collagen types I, II, and X. Chondrocytes were isolated for RT-PCR to detect GAPDH, collagen types I, II, X, aggrecan, TGF-beta, BMP-7, bFGF, VEGF and IL-1.

RESULTS

The dissected cartilage displayed significant variability. Apart from normal cartilage matrix components also atypical molecules such as collagen type X and alkaline phosphatase were detected at the tidemark but also across the entire dissecate, suggesting chondrocyte hypertrophy. Extended fibrous degeneration associated with collagen type I deposition was observed at the surface and may indicate chondrocyte dedifferentiation. Viable cells could be extracted from OCD and notch. Both expressed similar mRNA levels for matrix molecules, growth factors, and interleukin-1 (IL-1), however significantly more Col X mRNA was detected in dissecates.

CONCLUSION

Histology suggests focal alteration of cartilage matrix originating from the basis of the joint cartilage, potentially the mineralized layer or subchondral bone. The molecular analysis indicates a disorganization of cartilage homeostasis across the joint accompanied by embryogenetic processes. The surprisingly high viability and quality of the extracted cells suggests a still preserved intrinsic repair capacity of those vital dissecates.

Characterizing osteochondrosis in the dog: potential roles for matrix metalloproteinases and mechanical load in pathogenesis and disease progression

OBJECTIVE

To address possible roles of matrix metalloproteinases (MMPs) and mechanical stress in the pathogenesis of osteochondrosis (OC).

METHODS

Naturally-occurring canine OC lesions (n=50) were immunohistochemically analyzed for MMP-1, -3, and -13, and normal canine articular cartilage explants (n=6) cultured under 0-, 2-, or 4-MPa compressive loads (0.1 Hz, 20 min every 8 h up to 12 days) were compared to OC samples (n=4) biochemically and molecularly.

RESULTS

MMP-1 and -3 immunoreactivities were readily detected in both OC samples and control tissues obtained from age-matched dogs (n=11) whereas MMP-13 was only detectable in OC samples. MMP-13 gene expression as determined by real-time reverse transcription polymerase chain reaction was elevated in OC samples and cartilage explants cultured without mechanical stimuli (0 MPa groups) compared to normal cartilage (day 0 controls). Glycosaminoglycan content (per weight) in cartilage explants cultured under no load was significantly (P<0.05) lower on day 12 than in the day 0 controls. Gene expression levels of aggrecan and type II collagen in OC samples were lower than those in the day 0 controls. High levels of aggrecan and collagen II expression were seen in the 2 MPa groups.

CONCLUSIONS

These findings imply that impaired biochemical characteristics in OC-affected cartilage may be attributable to decreased extracellular matrix production that may stem from disruption of normal weight bearing forces.