PubMed Health⌕ Search

Biomedical subjects

L J Bonassar

Publications and source records attributed to L J Bonassar.

At least 19 recordsLinked to original sources
PubMed2001

Injection molding of chondrocyte/alginate constructs in the shape of facial implants.

Over one million patients per year undergo some type of procedure involving cartilage reconstruction. Polymer hydrogels, such as alginate, have been shown to be effective carriers for chondrocytes in subcutaneous cartilage formation. The goal of our current study was to develop a method to create complex structures (nose bridge, chin, etc.) with good dimensional tolerance to form cartilage in specific shapes. Molds of facial implants were prepared using Silastic ERTV. Suspensions of chondrocytes in 2% alginate were gelled by mixing with CaSO(4) (0.2 g/mL) and injected into the molds. Constructs of various cell concentrations (10, 25, and 50 million/mL) were implanted in the dorsal aspect of nude mice and harvested at times up to 30 weeks. Analysis of implanted constructs indicated progressive cartilage formation with time. Proteoglycan and collagen constructs increased with time to approximately 60% that of native tissue. Equilibrium modulus likewise increased with time to 15% that of normal tissue, whereas hydraulic permeability decreased to 20 times that of native tissue. Implants seeded with greater concentrations of cells increased proteoglycan content and collagen content and equilibrium and decreased permeability. Production of shaped cartilage implants by this technique presents several advantages, including good dimensional tolerance, high sample-to-sample reproducibility, and high cell viability. This system may be useful in the large-scale production of precisely shaped cartilage implants.

Absorbable Implants↗
PubMed2001

The effect of dynamic compression on the response of articular cartilage to insulin-like growth factor-I.

Articular cartilage is routinely subjected to mechanical forces and to cell-regulatory molecules. Previous studies have shown that mechanical stimuli can influence articular chondrocyte metabolic activity, and biochemical studies have shown that growth factors and cytokines control many of the same cell functions. Little is known, however, of the relationships or interplay, if any, between these two key components of the articular environment. This study investigated the comparative and interactive effects of low amplitude, sinusoidal, dynamic compression and insulin-like growth factor-I (IGF-I), a polypeptide in synovial fluid that is anabolic for cartilage. In bovine patellofemoral cartilage explants, IGF-I increased protein and proteoglycan synthesis 90% and 120%, respectively while dynamic compression increased protein and proteoglycan synthesis 40% and 90%, respectively. Stimulation by IGF-I was significantly greater than by dynamic compression for both protein and proteoglycan synthesis. When applied together, the two stimuli enhanced protein and proteoglycan synthesis by 180% and 290%, respectively, a degree greater than that achieved by either stimulus alone. IGF-I augmented protein synthesis with a time constant of 12.2 h. Dynamic compression increased protein synthesis with a time constant of 2.9 h, a rate significantly faster than that of IGF-I, suggesting that these signals act via distinct cell activation pathways. When used together, dynamic compression and IGF-I acted with a time constant of 5.6 h. Thus, dynamic compression accelerated the biosynthetic response to IGF-I and increased transport of IGF-I into the articular cartilage matrix, suggesting that, in addition to independently stimulating articular chondrocytes, cyclic compression may improve the access of soluble growth factors to these relatively isolated cells.

Animals↗
PubMed2001

A biomechanical analysis of an engineered cell-scaffold implant for cartilage repair.

This study evaluated the biomechanical and physical properties of newly formed cartilage engineered from isolated chondrocytes in combination with matrix components. Four groups of constructs were studied. Group A consisted of lyophilized articular cartilage chips mixed with a cell-fibrinogen solution and thrombin to obtain constructs made of fibrin glue, chondrocytes, and cartilage chips. Group B constructs were prepared using fibrin glue and cartilage chips without cells. Group C contained chondrocytes in fibrin glue without chips, and group D comprised constructs of fibrin glue alone. Specimens were implanted in the subcutaneous tissue of nude mice for 9 weeks. At necropsy the specimens were examined grossly, physically, biomechanically, and histologically. The original, preimplantation mass of the constructs was retained only in experimental group A. Histological analysis of specimens in experimental groups A and C demonstrated the presence of newly formed cartilaginous matrix, whereas only fibrotic tissue was observed in control groups B and D. Biomechanical analysis demonstrated higher mean values of equilibrium modulus in the experimental samples of group A with respect to all control groups. This study demonstrated that adding lyophilized cartilage chips to a fibrin glue-engineered cartilage construct maintains the biomechanical properties and the original mass after medium-/long-term in vivo transplantation.

Animals↗
PubMed2000

Mechanical and physicochemical regulation of the action of insulin-like growth factor-I on articular cartilage.

The development and maintenance of healthy joints is a complex process involving many physical and biological stimuli. This study investigates the interaction between insulin-like growth factor-I (IGF-I) and static mechanical compression in the regulation of articular cartilage metabolism. Bovine cartilage explants were treated with concentrations of IGF-I from 0 to 300 ng/ml in the presence or absence of 0-50% static compression, and the transient and steady-state incorporation of [(3)H]proline and [(35)S]sulfate into matrix components were measured. In parallel studies, cartilage explants were treated with 0-300 ng/ml IGF-I at media pH ranging from 6.4 to 7.2 and the steady-state incorporation of [(3)H]proline and [(35)S]sulfate was measured. The effect of 50% static compression on IGF-I transport was determined by measuring the uptake of (125)I-labeled IGF-I into cartilage explants. Static compression decreased both [(3)H]proline and [(35)S]sulfate incorporation in a dose-dependent manner in the presence or absence of IGF-I. IGF-I increased [(3)H]proline and [(35)S]sulfate incorporation in a dose-dependent manner in the presence or absence of compression, but the anabolic effect of the growth factor was lessened when the tissue was compressed by 50%. The response of cartilage explants to IGF-I was similarly lessened in unstrained tissue cultured in media at pH 6.4, a condition which results in a similar intratissue pH to that when cartilage is compressed by 50%. The characteristic time constant (tau) for IGF-I stimulation of cartilage explants was approximately 24 h, while tau for inhibition of biosynthesis by static compression was approximately 2 h. Samples which were both compressed and treated with IGF-I demonstrated an initial decrease in biosynthetic activity at 2 h, followed by an increase at 24 h. Static compression did not alter tau for (125)I-labeled IGF-I transport into cartilage but decreased the concentration of (125)I-labeled IGF-I in the tissue at equilibrium.

Animals↗
PubMed2000

Minimally invasive technique of auricular cartilage harvest for tissue engineering.

Tissue engineered human cartilage is presently being utilized in clinical research programs in a variety of medical disciplines including otolaryngology, urology, and orthopedics. In this study, we present a new methodology for auricular cartilage harvest that can be applied to tissue engineering. Eight 16-week-old pigs were subjected to a traditional open cartilage harvest technique involving suture closure, while the other ear was subjected to the closed stitchless cartilage harvest, using a 12-gauge core biopsy needle. Surgical time was significantly (p < 0.0001) shorter (3.5 +/- 2.8 min for closed vs. 14.4 +/- 5 min for open), and no sutures where utilized in the closed technique. Sample weights were significantly (p < 0.00001) greater (0.115 +/- 0.028 g vs. 0.045 +/- 0.005 g) for the closed techniques. However, the minimally invasive closed technique had fewer incidents of bruising, hematoma, long-term stitch abscess, and scarring. Cell culture data shows no disadvantage to either technique with regards to cell growth characteristics. Final histological data from donor ears indicates favorable results with the minimally invasive technique. This technique preserves cell viability and isolation efficiency while decreasing surgical time and lessening postoperative complications.

Animals↗
PubMed1999

Biomechanical analysis of a chondrocyte-based repair model of articular cartilage.

The objective of this study was to evaluate the biomechanical properties of newly formed cartilaginous tissue synthesized from isolated chondrocytes. Cartilage from articular joints of lambs was either digested in collagenase to isolated chondrocytes or cut into discs that were devitalized by multiple freeze-thaw cycles. Isolated cells were incubated in suspension culture in the presence of devitalized cartilage matrix for 3 weeks. Multiple chondrocyte/matrix constructs were assembled with fibrin glue and implanted subcutaneously in nude mice for up to 6 weeks. Testing methods were devised to quantify integration of cartilage pieces and mechanical properties of constructs. These studies showed monotonic increase with time in tensile strength, fracture strain, fracture energy, and tensile modulus to values 5-10% of normal articular cartilage by 6 weeks in vivo. Histological analysis indicated that chondrocytes grown on dead cartilage matrix produced new matrix that integrated individual cartilage pieces with mechanically functional tissue.

Animals↗
PubMed1999

An overview of tissue engineered bone.

Numerous important developments in tissue engineering of new bone during the last 10 years are reviewed. Early efforts to combine cells with biocompatible materials are described and applications of this technology are presented with particular focus on uses in orthopaedics and maxillofacial surgery. Basic principles of tissue engineering focusing on cell biology and materials science as used currently in the field are presented. Finally, future challenges are outlined from the perspective of integrating technologies from medicine, biology, and engineering in hopes of translating tissue engineering to clinical applications.

Animals↗
PubMed1999

Temporal bone fractures: otic capsule sparing versus otic capsule violating clinical and radiographic considerations.

OBJECTIVE: To assess the practicality and utility of the traditional classification system for temporal bone fracture (transverse vs. longitudinal) in the modern Level I trauma setting and to determine whether a newer system of designation (otic capsule sparing vs. otic capsule violating fracture) is practical from a clinical and radiographic standpoint. METHODS: The University of Massachusetts Medical Center Trauma Registry was reviewed for the years 1995 to 1997. Patients identified as sustaining closed head injury were reviewed for basilar skull fracture and temporal bone fracture. Clinical and radiographic records were evaluated by using the two classification schemes. RESULTS: A total of 2,977 patients were treated at the trauma center during this time. Ninety (3%) patients sustained a temporal bone fracture. The classic characterization of transverse versus longitudinal fracture (20% vs. 80%, respectively) was unable to be determined in this group; therefore, clinical correlation to complications using that paradigm was not possible. By using the otic capsule violating versus sparing designation, an important difference in clinical sequelae and intracranial complications became apparent. Compared with otic capsule sparing fractures, patients with otic capsule violating fractures were approximately two times more likely to develop facial paralysis, four times more likely to develop CSF leak, and seven times more likely to experience profound hearing loss, as well as more likely to sustain intracranial complications including epidural hematoma and subarachnoid hemorrhage. CONCLUSION: The use of a classification system for temporal bone fractures that emphasizes violation or lack of violation of the otic capsule seems to offer the advantage of radiographic utility and stratification of clinical severity, including severity of Glasgow Coma Scale scores and intracranial complications such as subarachnoid hemorrhage and epidural hematoma.

Cerebrospinal Fluid Otorrhea↗
PubMed1998

Tissue engineering: the first decade and beyond.

This article reviews the important developments in the field of tissue engineering over the last 10 years. Research in the area of biomaterials is examined from the perspective of providing the foundation for the development of tissue engineering. Early efforts combining cells with biocompatible materials are described and applications of this technology presented, with particular focus on uses in orthopaedics and maxillofacial surgery. The basic principles of tissue engineering and state-of-the-art technology in cell biology and materials science as used currently in the field are presented. Finally, futures challenges are outlined from the perspective of integrating technologies from medicine, biology, and engineering, in hopes of translating tissue engineering to clinical applications.

Animals↗
PubMed1997

Inhibition of cartilage degradation and changes in physical properties induced by IL-1beta and retinoic acid using matrix metalloproteinase inhibitors.

Bovine cartilage explants were treated with 100 ng/ml recombinant human interleukin-1beta (IL-1beta) or 1 microM all-trans retinoic acid (RA) and changes in biochemical, biomechanical, and physicochemical properties were assessed. Additionally, samples cultured with IL-1beta or RA were treated with 4 microM recombinant human tissue inhibitor of metalloproteinases-1 (TIMP-1) or a synthetic metalloproteinase inhibitor (L-758,354) to inhibit this degradation. Treatment with IL-1beta or RA each resulted in >90% GAG loss after 8 days in culture. Addition of TIMP or L-758,354 to the culture media inhibited IL-1beta-induced loss of tissue GAG by 40 and 65%, respectively, and inhibited RA-induced GAG loss by 35 and 65%, respectively. Analysis of degradation products in the culture media using a G1 antibody indicated that IL-1beta- and RA-treated plugs released 68-kDa fragments of aggrecan, corresponding to a segment of the aggrecan core protein from the G1 domain to the C-terminus NITEGE, consistent with "aggrecanase" activity. Release of the G1 fragment was inhibited by treatment with L-758,354. Both IL-1beta and RA induced significant loss of hyaluronan from cartilage explants after 8 days of exposure and HA loss was also inhibited by addition of L-756,354 to the culture media. IL-1beta, but not RA, induced a significant increase in swelling ratio (wet weight in 0.01 M NaCl normalized to wet weight in DMEM) after 8 days in culture, consistent with degradation of the collagen network, and the increase in tissue swelling was inhibited by treatment with TIMP-1 or L-758,354. Exposure to IL-1beta or RA resulted in significant changes in cartilage physical properties including streaming potential, equilibrium modulus, hydraulic permeability, and electrokinetic coupling coefficient after 8 days in culture, and these changes were inhibited by 40-90% by exposure to TIMP and by 50-90% by exposure to L-758,354. Measurement of dynamic streaming potential showed that changes due to treatment with IL-1beta alone were highly dependent in compression frequency, with dramatic changes seen at high frequency prior to changes in mechanical properties, and little initial change seen at low frequency. Streaming potential and equilibrium modulus of explants treated with RA decreased to 10% of their initial values after 8 days in culture, but decreased to only 40 and 90%, respectively, when treated with RA plus TIMP-1.

Aggrecans↗
PubMed1997

Interaction of epidermal growth factor and insulin-like growth factor-I in the regulation of growth plate chondrocytes.

The action of growth factors on the cells of the epiphyseal growth plate is an important mechanism in the regulation of skeletal growth. Insulin-like growth factor-I (IGF-I) is known to play a central role in the regulation of bone growth. In contrast, the role, if any, of epidermal growth factor (EGF) is not yet clear. In these studies, we tested the hypothesis that EGF interacts with IGF-I in the regulation of growth plate chondrocyte mitotic and metabolic activities. Chondrocytes isolated from bovine radioulnar growth plates and incubated in suspension culture were analyzed for their responsiveness to EGF with respect to synthesis of DNA, proteins, and proteoglycans, responsiveness to IGF-I, and ability to specifically bind [125I]IGF-I. Treatment of growth plate chondrocytes with maximally effective concentrations (10-100 ng/ml) of EGF produced a 16-27% increase in specific binding of [125I]IGF-I. Scatchard analysis indicated that this increase in specific binding was due to an increase in the number of receptors/cell with no change in receptor affinity. EGF stimulated protein synthesis by 30-35%. Pretreatment with EGF increased the responsiveness of chondrocytes to IGF-I, resulting in 90 and 60% augmentation of IGF-I-stimulated mitotic activity and proteoglycan synthesis, respectively. Given the prominent role of IGF-I in skeletal development and the presence of EGF in the growth plate, this study suggests an important role for interactions between these growth factors in the regulation of skeletal growth.

Animals↗
PubMed1997

Detection of interleukin-1 in the cartilage of patients with osteoarthritis: a possible autocrine/paracrine role in pathogenesis.

The interleukin-1 (IL-1) cytokines stimulate the synthesis of degradative enzymes in joint tissues and may play a role in the pathological joint destruction in osteoarthritis (OA). In this study, we have used immunohistochemistry and Western blot analysis to identify IL-1 in human OA cartilage. IL-1 alpha and IL-1 beta were evident in chondrocytes at the articular surface, as well as distributed throughout the cartilage. In many specimens, IL-1 beta but not IL-1 alpha was detected as a diffuse staining of the extracellular matrix especially surrounding superficial zone chondrocytes. Although chondrocyte-associated IL-1 alpha and IL-1 beta were detected in most specimens, cartilages exhibiting early osteoarthritic changes had the highest intensity of staining and the highest frequency of positive cells. Western blot analysis revealed intense immunoreactive bands corresponding to the 35 kDa precursor form of IL-1 alpha in all four chondrocyte lysates tested. The processed 18 kDa IL-1 beta species was present in only one of four chondrocyte lysates, and there was no clear evidence of precursor form within these cells. The results of this study indicate increased IL-1 alpha in cartilage showing early degenerative changes, suggesting an autocrine/paracrine role for this cytokine in OA pathogenesis.

Adult↗
PubMed1996

Activation and inhibition of endogenous matrix metalloproteinases in articular cartilage: effects on composition and biophysical properties.

Bovine cartilage explants were cultured with 1 mM 4-aminophenylmercuric acetate (APMA) to activate endogenous matrix metalloproteinases (MMPs) and changes in biochemical, biomechanical, and physicochemical properties were assessed. Additionally, graded levels of either rhTIMP-1 (recombinant human tissue inhibitor of metalloproteinases-1) or L-696-418 (a synthetic metalloproteinase inhibitor) were used to inhibit degradation induced by APMA. Treatment with APMA resulted in as much as 80% loss in tissue GAG content, a greater than threefold increase in denatured type II collagen as determined by the presence of CB11B epitope, and complete loss of biosynthetic activity after 3 days in culture. Physicochemical studies revealed that APMA treatment resulted in a significant increase in tissue swelling response, consistent with damage to the collagen network. Activation of MMPs by APMA also resulted in > 80% decrease in equilibrium modulus, dynamic stiffness, and streaming potential and > 50% decrease in electrokinetic coupling coefficient. The addition of 4 microM, 400 nM, and 40 nM TIMP inhibited PG loss by 95, 50, and 20%, respectively, and all doses effectively inhibited swelling response. The addition of 4 microM and 400 nM L-696-418 inhibited PG loss by 95% while 40 nM L-696-418 inhibited PG loss by 60%, and all doses effectively inhibited swelling response. The inhibition of APMA-induced GAG loss by 4 microM TIMP was accompanied by maintenance of streaming potential, electrokinetic coupling coefficient, dynamic stiffness, and equilibrium modulus.

Animals↗
PubMed1995

Changes in cartilage composition and physical properties due to stromelysin degradation.

OBJECTIVE: To determine the effects of stromelysin treatment on biochemical, histologic, and swelling characteristics of intact cartilage explants and to correlate these effects with changes in the functional physical properties of the tissue. METHODS: Bovine articular cartilage explants were cultured for up to 3 days in the presence or absence of recombinant human stromelysin (SLN). Damage to matrix proteoglycans and collagens was assessed and characterized by N-terminal sequencing and Western blot analysis, respectively. Explants were mechanically tested to assess the ability of the tissue to withstand cyclic and static compressive loads. RESULTS: Treatment with SLN resulted in a time- and dose-dependent loss of proteoglycans from cartilage explants, with significant loss seen after 3 days of exposure to 20 nM SLN: Histology indicated that initial loss of proteoglycans occurred in regions near the tissue surface and proceeded inward with increasing time of SLN exposure. SLN treatment resulted in degradation of matrix collagen types IX and II, and a concomitant increase in tissue swelling. This matrix degradation resulted in severe alterations in functional physical properties of the tissue, including compressive stiffness. The initial, focal loss of proteoglycans that resulted from SLN treatment was most accurately detected with high-frequency streaming potential measurements. CONCLUSION: Exposure of intact cartilage to SLN caused specific, molecular-level degradation of matrix molecules, which resulted in changes in the swelling behavior and marked deterioration of functional physical properties of the tissue.

Amino Acid Sequence↗
PubMed1995

In vivo effects of stromelysin on the composition and physical properties of rabbit articular cartilage in the presence and absence of a synthetic inhibitor.

OBJECTIVE: To characterize the effects of intraarticular injection of recombinant human stromelysin (SLN) on the matrix composition and physical properties of cartilage from lapine stifle joints and the modulation of these effects by the systemic administration of an N-carboxyalkyl synthetic matrix metalloproteinase inhibitor, L-696,418. METHODS: Female 6-8-week-old New Zealand white rabbits received an intraarticular injection of 100 micrograms activated SLN in 1 stifle joint and buffer in the contralateral control knee; these animals were killed after 1 hour. A separate group of animals received an intravenous injection of either 30 mg/kg L-696,418 or buffer prior to intraarticular injection of SLN. Joints were dissected and analyzed for proteoglycan (PG) loss into joint fluid, tissue biochemical composition, and histology by toluidine blue or anti-VDIPEN antibody staining, or were frozen for physical property analysis. Disks of femoropatellar groove cartilage were harvested from the stifle joint and tested in uniaxially confined compression for determination of electromechanical and mechanical properties. RESULTS: Lapine stifle joints that received injection of SLN without systemic administration of L-696,418 showed a 13-fold increase in loss of PG into synovial fluid. Cartilage from these joints showed significant decreases in streaming potential at 1 Hz and electrokinetic coupling coefficient, but no change in equilibrium modulus, dynamic stiffness, or hydraulic permeability. Systemic treatment with L-696,418 resulted in a significant decrease in loss of PG into joint fluid and elimination of changes in cartilage high-frequency streaming potential and coupling coefficient in joints that were injected with SLN. CONCLUSION: The 1-hour exposure to SLN in vivo resulted in loss of PG and exposure of the VDIPEN epitope of the aggrecan core protein in the superficial region of the tissue near the articular surface. This highly localized degradation resulted in electromechanical behavior changes, but little or no change occurred in mechanical properties. Systemic administration of L-696,418 significantly decreased loss of PG from cartilage and prevented the highly localized tissue degradation and the resultant changes in electromechanical behavior caused by intraarticular SLN injection.

Animals↗
PubMed1995

The role of cartilage streaming potential, fluid flow and pressure in the stimulation of chondrocyte biosynthesis during dynamic compression.

The effects of streaming potential, fluid flow and hydrostatic pressure on chondrocyte biosynthesis were studied by comparing the spatial profiles of these physical stimuli to the profiles of biosynthesis within cartilage disks subjected to dynamic unconfined compression. The radial streaming potential was measured using compression frequencies and disk sizes relevant to studies of physical modulation of cartilage metabolism; a general analytical solution to the unconfined compression of a poroelastic cylinder with impermeable, rigid, adhesive platens was derived using potential theory. The solution with adhesive platen boundary conditions, using measured values of cartilage material properties, predicted streaming potentials that were much closer to experimental results between 0.001 and 1 Hz than a solution using frictionless platen boundary conditions. The predicted radial profiles of streaming potential gradient and fluid velocity (but not hydrostatic pressure) were similar to the previously reported radial dependence of proteoglycan synthesis induced by dynamic unconfined compression. Changes in stiffness associated with reduction of disk diameter suggested that the relative contributions of collagen and proteoglycans to cartilage mechanical properties may be a function of loading frequency in unconfined compression; such anisotropies may explain the remaining discrepencies between measured stiffness and stiffness predicted by the present model.

Biomechanical Phenomena↗