DOI: The drying of open living animal joints by laminar airflow subsequently causes deleterious changes to cartilage and in situ chondrocytes. This leads to cartilage degeneration which has the characteristics of osteoarthritis OA. Properties of cartilage were studied by histology and modified Mankin score, and in situ fluorescently-labelled chondrocytes by confocal laser scanning microscopy CLSM. Some of the changes observed resembled the degeneration that occurs during early osteoarthritis. The results strongly suggest that limiting cartilage drying by maintaining effective cartilage hydration is crucial so as to minimise the damaging effect of laminar airflow on joint health.
This is the first study demonstrating the effect of open joint drying by laminar airflow on the properties of cartilage and chondrocytes in an in vivo animal model. The model cannot precisely mimic the changes occurring during open human orthopaedic surgery.
- Georges-Louis Leclerc, Comte de Buffon - Wikipedia.
- THE SPIRIT WORLD;
- Degenerative Myelopathy (DM) Test.
- Login using!
- 2. The ocean quahog.
Nevertheless, it is highly likely that the deleterious changes to cartilage and chondrocytes reported here may occur in human cartilage unless adequate cartilage hydration is maintained under laminar airflow. The effects of drying on articular cartilage are of relevance during commonly performed orthopaedic procedures such as the treatment of intra-articular fractures or unicompartmental joint arthroplasties. The majority of fractures, especially those in larger joints such as the shoulder, elbow, hip, and knee, require open surgery for the restoration of articular surface congruity.
These procedures can be complex and lengthy, and the native articular cartilage is exposed to allow visual inspection and reconstruction. In many orthopaedic theatres, the tissue is typically exposed to a constant laminar airflow of approximately 0. There is a well-defined association between intra-articular fractures and secondary development of degenerative disorders within synovial joints. Knee arthroplasty surgery for OA is now exclusively performed under laminar airflow and it is common practice to leave parts of the knee joint intact during surgery. For instance, during total knee arthroplasty TKA while the tibiotalar compartment is replaced, the patellar cartilage in the patellofemoral joint is often not resurfaced.
Similarly, during partial knee arthroplasty the medial compartment of the knee joint is replaced but the lateral compartment and patellofemoral compartments are left intact. TKA surgery can last one to two hours and thus the native cartilage that is not replaced may be exposed to prolonged airflow. Inferior outcomes following TKA have been attributed to patellofemoral pain, 4 and following partial knee arthroplasty to OA progression in the unresurfaced lateral compartment.
For example, Mitchell and Shepard 7 reported changes to matrix constituents and chondrocyte 3 H-proline labelling of rabbit cartilage exposed to static air. Chondrocyte necrosis and histological changes to cartilage have also been described after exposure of rabbit knees to static air causing drying. Pun et al 10 reported that chondrocyte death within human osteochondral explants correlated with length of exposure to static air and cartilage depth, and noted the particular sensitivity of superficial zone SZ chondrocytes.
Recently, Paterson et al 12 reported that chondrocytes at the cut edge of bovine or human cartilage were more sensitive to drying by laminar airflow than those distant from the edge. In addition, whereas rehydration could restore the normal appearance of cartilage, the extent of chondrocyte death was unaltered. Chondrocyte death arising from cartilage drying is a particular concern as cell division is absent in healthy articular cartilage.
Articular cartilage has a very limited capacity for repair and the fibro-cartilaginous matrix produced is mechanically incompetent. The aim of this investigation was therefore to test the hypothesis that the drying of exposed living animal joints would subsequently lead to degenerative changes in articular cartilage. Accordingly, to standardise the amount of synovial fluid, excess synovial fluid was absorbed by gently swabbing with Melgisorb Tendra , Gothenburg, Sweden.
Control sham operations were performed in which the patella was displaced laterally, excess synovial fluid removed and the patella relocated without cartilage drying.
Development of Animal Models of Local Retinal Degeneration.
Rats were given buprenorphine 0. Rats were randomly assigned to the experimental groups four in each group and were killed either immediately after surgery week 0 or at four to eight weeks after surgery, and knee joints dissected. Rats were maintained under standard conditions of housing and husbandry. Cartilage degeneration was assessed using the modified Mankin score in which cartilage structure, cellular appearance and intensity of matrix staining were assessed and scored. We therefore thought it would be more appropriate for the sham and dried cartilage to be scored by separate assessors.
Accordingly, one assessor NE scored the sham-operated cartilage samples, while a different researcher SP independently scored the cartilage-dried samples using the same criteria, and the results were then collated. A semi-automated protocol was then used to identify CMFDA- green and PI- red labelled cells and nuclei based on size and relative intensity. Chondrocyte density was determined as the total number of chondrocytes i.
Animal behaviour was monitored routinely throughout the experimental periods as required for Home Office regulations. Pain behavioural signs such as curling toes, eversion of the foot, non-weight bearing, guarding and avoiding contact with the limb were observed following surgical procedures. Animals were also closely monitored for wound healing and development of any inflammatory signs such as redness, swelling, abnormal gait and reduced spontaneous activity.
Prior to sacrifice of animals at the different experimental points, joints were carefully examined, and there was no evidence of ulcerations, tenderness, swelling or redness in any of the animals. Following visual inspection of exposed sham-operated joints, no macroscopic fibrillations were observed, however, in dried joints fibrillations were present in one of four joints following four weeks of recovery, and in three of four joints following eight weeks of recovery from surgery.
However, degeneration was observed in all recovered joints at four and eight weeks with examples shown in Figure 1 A d-f. After four weeks, the cartilage surface appeared uneven and there was loss of superficial zone SZ structure and the presence of empty lacunae, indicating chondrocyte loss. The modified Mankin score increased significantly to six Fig. By eight weeks, the SZ had almost completely disappeared with additional loss of the mid zone MZ , there were deep fibrillations, and there was a further significant increase in the modified Mankin score.
No change to histological grading of the sham controls was observed over the eight-week period Fig. There was a significant and progressive increase in cartilage thickness following the surgical procedure Fig.
A year-old shark is the latest animal discovery to reveal the secrets of long life
Thus at week four, thickness increased 1. There was no significant change to the cartilage thickness of the sham controls over this period Fig. Full-depth cartilage thickness was determined microscopically on histological sections obtained from decalcified joints as described in Materials and Methods. Drying cartilage had marked effects on the viability and density of chondrocytes Fig.
For the sham control, no PI-labelled chondrocytes were observed Fig. In contrast, following cartilage drying, there were no CMFDA-labelled chondrocytes, and the chondrocytes were labelled with PI, indicating that all the cells were dead Fig. A Labelled in situ chondrocytes in cartilage explants from the patellar groove were imaged by CLSM axial view in sham controls Sham , at the initial time point of the experiments week 0 , and then following surgical recovery after four or eight weeks. Figure 4 A shows axial images of fluorescently-labelled chondrocytes within the patellar groove in sham-operated control joints Figs 4 A a-c , and after eight weeks at either the non-fibrillated Fig.
Chondrocyte volume and distribution appeared normal in cartilage of sham-operated joints, however, at eight weeks there were significantly fewer single chondrocytes but a significantly greater proportion of pairs and clusters Fig. Chondrocyte volume also appeared to be larger compared with the images obtained in the sham control. As noted in histological sections Fig. Note that despite the dye being present, no PI-labelled chondrocytes were observed. Chondrocyte volume within dried cartilage eight weeks after recovery increased significantly Fig. Chondrocyte morphology and distribution.
A a—c , examples of CLSM images from sham-operated joints, d-f , cartilage in vivo dried 60 minutes , then visualised after eight weeks in regions that were distant from, and g-i at fibrillated areas broken lines. Control three joints; cells , week 8 four joints; cells. Sham-operated control data or that from joints dried following eight weeks of recovery, were obtained from confocal laster scanning microscopy CLSM images of 5-chloromethylfluorescein diacetate CMFDA -labelled chondrocytes as described see Materials and Methods. In vivo drying of an exposed animal joint several weeks following surgery had profound effects on the joint cartilage and its chondrocytes.
Georges-Louis Leclerc, Comte de Buffon
While we did not observe any obvious external changes to the animals, histology and cartilage grading showed that degeneration was evident Figs 1 A and 1 B. The thickness of cartilage Fig. There was then a significant increase at eight weeks, but cell density was still less than that for sham-operated joints Fig. These results highlighted the damaging effect of laminar airflow and raise questions as to why joint drying had such a marked effect on cartilage and chondrocytes.
Swabbing the open joint to remove excess synovial fluid was performed in an attempt to limit variability and standardise the experimental conditions. However, this procedure would not occur during orthopaedic surgery and instead any protective properties of synovial fluid could be washed away by irrigating saline, potentially increasing the sensitivity of the cartilage and chondrocytes to subsequent drying. It is also important to note that the whole open joint was exposed to laminar airflow and it was not possible for this to be focused solely on the cartilage.
Thus, neighbouring tissues synovium, tendons, ligaments would also have dried, perhaps in a way similar to that which occurs during orthopaedic surgery.
However, we do not know if this had a permanent effect and influenced overall joint function, and cartilage properties in particular. While it is possible that these tissues may be capable of some repair and replacement of dead cells, this would not be the case for articular cartilage which has poor repair potential. Additionally, during joint dissection, we did not observe any macroscopic deleterious changes to the soft tissues surrounding the joints or any evidence of inflammation. It may be that the whole exposed area was dried and damaged, but that the soft tissues recovered whereas the cartilage did not.
Therefore it is possible that cartilage was the most sensitive tissue and that the other tissues were protected against the damaging effect of airflow, perhaps by their vascularised nature. The data on chondrocyte density showed an initial decrease followed by a rise Fig. This might be because the remains of dead chondrocytes were removed, e. Additionally, enzymes in serum can degrade nucleic acids and the remains of any dead cells would be removed, also leading to a lack of DNA labelling by PI. It should also be noted that as these were axial CLSM images, it is possible that the reduced cell density at four weeks was due to the loss of chondrocytes within the SZ Fig.
However, at eight weeks this zone may have disappeared see Fig. It has been proposed that injuries causing chondrocyte death may stimulate the emergence and homing of chondrogenic progenitor cells CPCs. It is also possible that the rate of cartilage failure was too rapid for CPCs to play any effective role in repair. Cartilage degeneration, as occurs in OA, is complex and results from risk factors such as age, genetic predisposition, obesity, anatomical abnormalities and excessive load or joint injury.
Our overall assessment of cartilage properties showed an increase in the modified Mankin score Fig. The effects we observed were very rapid compared with the time course of human OA development. At present, it is unknown how in vivo joint drying subsequently leads to these deleterious effects. Cartilage drying could cause chondrocyte damage or death, irreparable damage to the extracellular matrix, or a combination of these factors.
The injury or death of chondrocytes is implicated in OA development. Simon et al, 44 investigating the effects of localised freezing on in vivo rabbit cartilage, reported that at six months the cartilage was apparently intact, but there were no stainable chondrocytes. However, at 12 months there was cartilage softening and fibrillations with chondrocyte clustering and other features resembling OA. While this does not rule out a role for freezing damage to the cartilage matrix, the injury is more focused than drying and suggests that chondrocyte death is important.
It is firmly established that chondrocyte death, whether by apoptosis, necrosis, autophagy, 45 chondroptosis, 46 or a combination of these processes, 28 is a crucial element in the process of cartilage degeneration. What is less clear is whether chondrocyte death precedes cartilage failure or is a consequence of it. In summary, drying an exposed animal joint in vivo by laminar airflow leads to marked changes in cartilage and chondrocyte properties, the characteristics of which show some similarities to early OA.
While the sequence of events following drying and its effects on cartilage integrity and chondrocyte viability are unclear, the results emphasise the critical importance of maintaining cartilage hydration during surgery.
Lee Alan Dugatkin
We thank Dr A. None declared. Transgenic pigs as models for translational biomedical research Genetically modified animal models Mouse model of human disease by forward and reverse genetics Animal models of neonatal seizures Animal models for the study of neonatal disease Animal models of fetal programming Animal models of human viral diseases Animal models of breast cancer Animal models of systemic sclerosis: past, present, and perspective Animal models of multiple sclerosis Animal Models of Mood Disorders Pigs in Behaviour Models Models of Alzheimer's disease MPTP-induced animal models for Parkinson's disease Animal Models of Neurodegenerative Disease Animal models of mania Animal Models of Stress Coping and Resilience.
He is The Robert C. After receiving a B. In , he became Professor and Head of Pharmacology at the University of Iowa College of Medicine, a position he held for eleven years. Conn is known for his research in the area of the cellular and molecular basis of action of gonadotropin releasing hormone action in the pituitary and therapeutic approaches that restore misfolded proteins to function. His work has led to drugs that have benefitted humans and animals. Most recently, he has identified a new class of drugs, pharmacoperones, which act by regulating the intracellular trafficking of receptors, enzymes and ion channels.
He has authored or co-authored over publications in this area and written or edited over books, including texts in neurosciences, molecular biology and endocrinology. Conn served on the National Board of Medical Examiners, including two years as chairman of the reproduction and endocrinology committee. He is the co-author of The Animal Research War and many articles for the public and academic community on the value of animal research and the dangers posed by animal extremism.
Conn consults with organizations that are influenced by animal extremism and with universities and companies facing challenges from these groups. We are always looking for ways to improve customer experience on Elsevier. We would like to ask you for a moment of your time to fill in a short questionnaire, at the end of your visit. If you decide to participate, a new browser tab will open so you can complete the survey after you have completed your visit to this website.
Thanks in advance for your time. Skip to content. About Elsevier. Search for books, journals or webpages All Pages Books Journals. View on ScienceDirect. Editors: P. Michael Conn. Hardcover ISBN: Imprint: Academic Press. Published Date: 28th June Page Count: Sorry, this product is currently out of stock. Flexible - Read on multiple operating systems and devices.