Kaplan Lab - Recent Projects

Kaplan Laboratory: Recently Completed Projects

Temporal Effects of Cytoprotective Agents (IgF-1 and JNK-II) on Articular Cartilage Undergoing Mechanical Chondroplasty. Poster presentation at the Orthopedic Research Society (ORS), San Diego, CA, February, 2007.

Partial thickness articular cartilage lesions are a common pathology in sports medicine and usually are encountered as a consequence of trauma from a sports injury. Mechanical chondroplasty is one technique used to smooth damaged articular cartilage but it may also induce metabolic damage to the surrounding cartilage. The ability to supplement metabolism at a time of chondrocyte stress has potential clinical implications. Growth factors such as insulin-like growth factor (IgF-1) help regulate cartilage homeostasis due to their ability to stimulate chondrocyte anabolic activity. IgF-1 is found in articular cartilage and synovial fluid and is thought to be a major stimulator of chondrocyte proteoglycan synthesis in serum and synovial fluid. The c-Jun N-terminal kinase or stress-activated protein kinase pathway is considered one of the major signal transduction pathways for converting stress signals to programmed cell death or apoptosis. The addition of JNK-II inhibitor may inhibit this cascade and decrease catabolism. The hypothesis for our study was that IgF-1 and/or JNK-II inhibitor will provide cellular support to the surrounding cartilage and enhance metabolic activity, if administered before and/or after mechanical chondroplasty.

Hip Vs Knee Cartilage: Proliferation and Metabolic Activity. Podium presentation at the International Cartilage Research Society (ICRS) San Diego, CA , January, 2006.

Human articular cartilage research has been a rapidly growing field in recent years. Research labs evaluate different types of culture methods, signaling mechanisms, and therapeutic interventions in cartilage damage. This growth has increased demand on different sources of cartilage for research. One convenient source of cartilage is from specimens following joint arthroplasty. Due to the prevalence of knee arthroplasty procedures, many labs have focused on harvesting articular cartilage from femoral condyles. This has been especially efficacious due to the typical pressures of relatively uninvolved cartilage on the posterior surfaces of the femoral condyles. The demand for this tissue may outweigh the availability of knee specimens, in turn limiting research capabilities. One potential source of additional articular cartilage would be femoral head specimen from hip arthroplasty. Most research institutions that perform knee arthroplasty also perform hip arthroplasty, allowing ready access to this tissue. The tissue harvested from the hip should theoretically be amenable to the different techniques used in cartilage research. The objective of this project was to analyze and compare the metabolic and proliferative activity of hip and knee articular cartilage in both ex vivo (explants) and in vitro (culture) models. The ex vivo model allows investigation of the activity of the chondrocytes and their natural matrix. The explants were analyzed for cellularity and proteoglycan synthesis. Chondrocytes were analyzed in monolayer culture. These techniques allowed for investigation of both proteoglycan synthesis and proliferative ability of the chondrocytes.

Development of Partial Thickness Articular Cartilage Injury in an Ovine Model recently published in Journal of Orthopaedic Research 24(10):1974-1982, 2006.

Partial thickness articular cartilage (PARC) lesions are commonly encountered in orthopedics surgery. These lesions do not have the ability to heal themselves, due to lack of vascular supply and the reliance on synovial nutrition. However, Hunziker et al demonstrated that the failure of PARC lesions to heal is not exactly due to lack of access to mesenchymal cells in perivascular tissue, although their experiments still did not yield repair cartilage. The clinical quandary presented by partial thickness articular cartilage lesions is one with no clear answer. Surgical techniques and options have focused on stabilization of PARC lesions to halt further degeneration. These techniques include mechanical and thermal chondroplasty. The use of thermal energy, whether laser or radiofrequency-generated, has been controversial. The primary issue is the viability and denaturation of the remaining articular cartilage and thermal treatment. Mechanical chondroplasty techniques utilizing shavers have been the “time tested technique” for many decades. It has been suggested that using this technique is superior to the newer usage of thermal energy in that the long term consequences of this treatment have been minimal. Several other studies have shown that the remaining surface of the cartilage is smoother if treated with thermal chondroplasty. Recently, there has been increased focus on the various techniques used to evaluate the cartilage after treatment. This has included histological techniques such as H&E staining and confocal laser microscopy. The utilization of metabolic techniques may add significant information about the cellular chondrocytes activity. A combination of all available technique for cartilage evaluation should provide the most accurate assessment of treatment modalities. Basic science about the natural history of PARC lesions is necessary to fully evaluate current and future treatments. Therefore, an in vivo animal model would provide important information with clinical applicability. To date, the literature on articular cartilage lesions has focused primarily on full-depth lesions, with only a few studies methodically addressing partial-thickness lesions. The purpose of this study was to create a more precisely-controlled PARC lesion, which would be evaluated by morphology, histology, cell viability and metabolism over time. This study will serve the orthopedic community by establishing a natural history of PARC lesions and provide a novel, well-characterized model for testing current and future treatments options.

Mechanical Chondroplasty: Early Metabolic Consequences In Vitro recently published in Arthroscopy; The Journal of Arthroscopic and Related Surgery (23(9):923-929, 2007.

Chondroplasty is routinely used in arthroscopic surgery to debride and smooth articular cartilage lesions. The use of mechanical debridement has been used without some of the concerns which have preoccupied radiofrequency chondroplasty. These issues are resultant depth of penetration, metabolic consequence and chondrocyte death. As of yet these issues have not been as thoroughly investigated in mechanical chondroplasty when compared to radiofrequency chondroplasty. Arthroscopic mechanical debridement was first described by Johnson in the 1980’s. Partial and full thickness articular lesions are commonly encountered in arthroscopy. Curl et al. evaluated 31,516 arthroscopies and found 53,569 hyaline cartilage lesions in 19,827 patinets over a four year duration. The pain experienced with chondral lesions is believed to stem from the nerve endings in the exposed subchondral bone and knee effusions caused by articular debris. Loose articular cartilage flaps and exposed subchondral bone have been a cause of significant disability in the knee joint. The goal of chondroplasty is to attempt to halt progression of the articular lesion, smooth the remaining surface and prevent debris from becoming an irritant within the joint. Mechanical shavers and radiofrequency devices are commonly utilized to perform chondroplasty. Radiofrequency devices have been scrutinized closely with focus being on depth of penetration and resultant cartilage damage and/or death. Mechanical chondroplasty is widely used, yet the consequences of their use have not been clearly delineated. The purpose of this study was to determine the depth of penetration and metabolic consequences of mechanical chondroplasty in vitro. Evaluation was done by looking at the metabolic consequence to the remaining articular cartilage and depth of penetration of shaver and damaged tissue.

Mechanical Chondroplasty: Effect of Pressure on Depth of Penetration, Cell Death and Metabolism. Poster presentation Orthopedic Research Society (ORS), San Diego, CA, February, 2007.

A partial thickness articular cartilage lesion is often caused by trauma from a sport injury and the usual treatment is debridement. Mechanical and thermal (radiofrequency energy) chondroplasty are the two choices for debridement. Neither mechanical nor radiofrequency chonroplasty is a benign procedure. Radiofrequency energy (RFE) creates a smooth cartilage surface at the expense of collagen denaturation and dose-dependent chondrocyte death especially in the superficial layer. The factors that influence the depth of debridement and underlying cell death include the instrument power setting, design, speed, number of passes and force applied. Mechanical chondroplasty has been used for many decades without some of the concerns that have preoccupied radiofrequency chondroplasty. Currently, mechanical chondroplasty is routinely used to smooth and debride articular cartilage but it also induces damage to the surrounding cartilage. In this study, we tested the hypothesis that there will be a proportional increase in the depth of instrument penetration and cell death and reduction of metabolic activity (proteoglycan synthesis) with increased pressure (added weight).

Evaluation of Articular Cartilage from Osteoarthritic Femoral Heads using the OARSI Grading System. Poster presentation at the Osteoarthritis Research Society International (OARSI), Prague, Czech Republic, December, 2006.

The grading of osteoarthritic cartilage has been based on a limited grading systems and imaging techniques. The newly developed OARSI grading system (Osteoarthritis Research Society International) has the capacity to differentiate between all levels of osteoarthritic changes in cartilage. A modified OARSI system was used in this study to grade femoral head cartilage for an exploration of a consistent pattern of degradation in osteoarthritis and to investigate areas where healthy cartilage can be found for research and clinical purposes.

Metabolic Decay of Articular Cartilage and Response to Growth Factors.

Culturing articular cartilage in vitro has been utilized for many decades to quantify the metabolic effects of chondrocytes after treatments with various agents. Cutting of articular cartilage from the bone for these cultures is a traumatic event for the cartilage cells which will significantly affects chondrocyte metabolism. Due to the avascular nature of cartilage, the amount of time that the cartilage remains on the bone may be critical to optimize cell viability. This study was designed to quantify the metabolic activity articular cartilage as measured by proteoglycan synthesis (1) when the cartilage was removed from the subcondral bone immediately after surgery (day 0) or on day 1, 2 or 3 and (2) determine the optimum “recovery time” for articular cartilage after it is removed from the subcondral bone.

Effect of Neuropeptides on the Growth and Proliferation of Bovine Articular Cartilage. Poster presentation at the Orthopedic Research Society (ORS), February, 2007.

The repair of cartilage is a central issue in orthopedic care. Because cartilage lacks regenerative ability, treatment for cartilage disease is primarily analgesic or surgical. Neuropeptides play a role in the proliferative and reparative processes of many tissue types, including fibroblasts, which arise from the same progenitor cells as chondrocytes (1). There is also some evidence that neuropeptides have a direct effect on articular chondrocytes (2,3). This project aims to investigate the effect of four candidate neuropeptides (neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), substance P (SP), or VIP) on bovine articular chondrocyte proliferation.