Gene expression of single articular chondrocytes.

Although previous studies in the field of tissue engineering have provided important information about articular cartilage, their conclusions are based on population averages and do not account for variations in cell subpopulations. To obtain a precise understanding of chondrocytes, we investigated the effects of cartilage zone and seeding duration on single chondrocyte gene expression to select an optimal zone for tissue engineering (Phase I), followed by an evaluation of growth factor exposure on the zone selected in Phase I (Phase II). In Phase I, superficial and middle/deep bovine articular chondrocytes were seeded in monolayers for 3 or 18 h.

Growth factor effects on passaged TMJ disk cells in monolayer and pellet cultures.

Objectives: Previously, we demonstrated rapid changes in temporomandibular joint (TMJ) disk gene expression during monolayer expansion. This study's objective was to investigate the ability of pellet culture and growth factors to rescue TMJ disk gene expression changes.

Design: Temporomandibular joint disk cells were isolated from mature porcine tissue and passaged up to five times.

Comparison of mechanical debridement and radiofrequency energy for chondroplasty in an in vivo equine model of partial thickness cartilage injury.

Objective: The purpose of this study was to develop a long-term model of cartilage injury that could be used to compare the effects of radiofrequency energy (RFE) and mechanical debridement as a treatment.

Methods: Partial thickness fibrillation of patellar cartilage was created in 16 mature ponies. Three months after the initial surgery all injured patellae were randomly selected to receive one of the four treatments (n = 8/treatment): (1) control, (2) mechanical debridement with a motorized shaver, (3) TAC-CII RFE probe, and (4) CoVac 50 RFE probe.

A direct compression stimulator for articular cartilage and meniscal explants.

This paper describes the development and use of a direct compression stimulator for culturing explants from the meniscus of the knee and articular cartilage. Following design and fabrication of the instrument along with its data acquisition system, the function of the machine was verified by both mechanical means and tissue effect. The loading chamber can hold up to 45 5 mm diameter samples.

The effects of TGF-beta1 and IGF-I on the biomechanics and cytoskeleton of single chondrocytes.

Objective: Ascertaining how mechanical forces and growth factors mediate normal and pathologic processes in single chondrocytes can aid in developing strategies for the repair and replacement of articular cartilage destroyed by injury or disease. This study examined effects of transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor-I (IGF-I) on the biomechanics and cytoskeleton of single zonal chondrocytes.

Method: Superficial and middle/deep bovine articular chondrocytes were seeded on tissue culture treated plastic for 3 and 18 h and treated with TGF-beta1 (5 ng/mL), IGF-I (100 ng/mL), or a combination of TGF-beta1 (5 ng/mL)+IGF-I (100ng/mL).

Effects of ascorbic acid concentration on the tissue engineering of the temporomandibular joint disc.

The temporomandibular joint (TMJ) disc is a specialized fibrocartilaginous tissue. When the disc becomes an obstacle and becomes damaged, surgeons have no choice but to perform a discectomy. Tissue engineering may provide a novel treatment modality for TMJ disorder patients who undergo discectomy.

Effects of ageing on the biomechanical properties of rat articular cartilage.

Previous studies have demonstrated that male Sprague Dawley (SD) rats experience age-related bone loss with the same characteristics as that in ageing men. As articular cartilage, like bone, is a critical component of the health and function of the musculoskeletal system, the authors hypothesized that articular cartilage in the untreated male SD rats could be a suitable model for studying the age-related deterioration of articular cartilage in men. To test this hypothesis, male SD rats were killed at between 6 and 27 months.

The effects of intermittent hydrostatic pressure on self-assembled articular cartilage constructs.

To date, static culture for the tissue engineering of articular cartilage has shown to be inadequate in conferring functionality to constructs. Various forms of mechanical stimuli accompany articular cartilage development in vivo, and one of these is hydrostatic pressure. This study used histology, biochemistry, and biomechanics to examine the effects of intermittent hydrostatic pressure, applied at 10 MPa and 1 Hz for 4 h per day for 5 days per week for up to 8 weeks on self-assembled chondrocyte constructs.

Effects of hydrostatic pressure on TMJ disc cells.

The effects of mechanical stimuli on TMJ disc cells have yet to be investigated. This study examined for the first time the effect of constant and intermittent hydrostatic pressure (HP) on TMJ disc cells. Guided by studies on articular chondrocytes, the chosen amplitude was 10 MPa, the frequency was 1 Hz for intermittent HP, and the duration was 4 h.

Tissue Engineering of the TMJ disc: a review.

The potential impact of a tissue-engineered temporomandibular joint (TMJ) disc is immense. Currently, patients suffering from a severely dysfunctional TMJ have few options. Facing the general lack of safe, effective TMJ disc implants, many patients undergo discectomy, a procedure that removes the injured TMJ disc in hopes of reducing debilitating symptoms associated with severe TMJ disorders.

Chondrocytes from different zones exhibit characteristic differences in high density culture.

Superficial and middle/deep zone chondrocytes were isolated from goat femoral cartilage by a zonal abrasion method. The cells were expanded 100-fold through two passages, then seeded into agarose wells to form high-density constructs through a self-assembling process. After 4 weeks in culture, the superficial zone constructs contracted into a dense cell mass, while middle/deep zone chondrocytes formed constructs with four distinct regions.

A self-assembling process in articular cartilage tissue engineering.

Current therapies for articular cartilage defects often result in fibrocartilaginous tissue. To achieve regeneration with hyaline articular cartilage, tissue-engineering approaches employing cell-seeded scaffolds have been investigated. However, limitations of scaffolds include phenotypic alteration of cells, stress-shielding, hindrance of neotissue organization, and degradation product toxicity.

Effect of diabetes mellitus on the material properties of the distal tibia.

This investigation evaluates the effects of diabetes on the mechanical properties of human bone, specifically, the tibia. Seven diabetic and seven nondiabetic human (male) cadaveric distal tibiae were used in this study. The average age of the diabetic cadaveric samples was 51 years (range, 46-61 years), and the average age of the nondiabetic cadaveric samples was 75 years (range, 67-85 years).

In vivo study on the short-term effect of radiofrequency energy on chondromalacic patellar cartilage and its correlation with calcified cartilage pathology in an equine model.

Chondromalacia can cause joint pain and synovial effusion with the potential for developing into osteoarthritis. Thermal chondroplasty using radiofrequency energy (RFE) has been reported to be superior to mechanical debridement for treating chondromalacia. We compared short-term changes in biomechanical properties of articular cartilage after treatment with monopolar (mRFE) or bipolar RFE (bRFE) or mechanical debridement (MD) on experimentally created grade II chondromalacia patellae.

Strain-dependent recovery behavior of single chondrocytes.

One of the challenges facing researchers studying chondrocyte mechanobiology is determining the range of mechanical forces pertinent to the problems they study. One possible way to deal with this problem is to quantify how the biomechanical behavior of cells varies in response to changing mechanical forces. In this study, the compressibility and recovery behaviors of single chondrocytes were determined as a function of compressive strains from 6 to 63%.

Cell type and distribution in the porcine temporomandibular joint disc.

Purpose: Surprisingly little is known about the cellular composition of the temporomandibular joint (TMJ) disc, which is a crucial piece of the puzzle in tissue engineering efforts. Toward this end, cell types were identified and quantified regionally in the TMJ disc.

Materials And Methods: Porcine TMJ discs were examined by histology, electron microscopy, and immunohistochemistry.

Viscoelastic characterization of the porcine temporomandibular joint disc under unconfined compression.

Pathophysiology of the temporomandibular joint (TMJ) disc is central to many orofacial disorders; however, mechanical characterization of this tissue is incomplete. In this study, we identified surface-regional mechanical variations in the porcine TMJ disc under unconfined compression. The intermediate zone, posterior, anterior, lateral, and medial regions of eight TMJ discs were sectioned into inferior and superior surface samples.

Tensile and compressive properties of the medial rabbit meniscus.

Quantification of the material properties of the meniscus is of paramount importance, creating a 'gold-standard' reference for future tissue engineering research. The purpose of this study was to determine the compressive and circumferential tensile properties in the rabbit meniscus. Creep and recovery indentation experiments were performed on the meniscus using a creep indentation apparatus and analysed via a finite element optimization method to determine the compressive material properties at six topographical locations.

Use of a rotating bioreactor toward tissue engineering the temporomandibular joint disc.

This objective of this study was to determine the effects of a rotating bioreactor in temporomandibular joint (TMJ) disc tissue engineering. Porcine TMJ disc cells were seeded at a density of 20 million cells/mL onto nonwoven poly(glycolic acid) (PGA) scaffolds in spinner flasks for 1 week and then cultured either under static conditions or in a rotating bioreactor for a period of 6 weeks. A series of analyses was performed, including mechanical testing, measurement of cellularity, quantification of matrix biosynthesis with a hydroxyproline assay and enzyme-linked immunosorbent assays, and observation of matrix distribution with immunohistochemistry.

Effects of growth factors on meniscal fibrochondrocytes.

To tissue engineer the knee meniscus, our laboratory follows a paradigm that includes biomaterial scaffolding, mechanical stimulation, and growth factor addition. The aim of this study was to study extracellular matrix (ECM) component uptake by meniscal fibrochondrocytes when stimulated with platelet-derived growth factor AB, transforming growth factor beta(1) (TGF-beta(1)), insulin-like growth factor type I, and basic fibroblast growth factor at various concentrations (low, medium, and high levels for each). Growth factors were applied to monolayer cultures for 3 weeks in a soluble form as part of the culture medium.

Comparison of scaffolds and culture conditions for tissue engineering of the knee meniscus.

The menisci of the knee are semilunar fibrocartilaginous structures critical in load bearing, shock absorption, stability, and lubrication. In this study, two commonly used biomaterials, a hydrogel (agarose) and a nonwoven mesh polymer [poly(glycolic acid); PGA], were compared for suitability as scaffold materials for tissue engineering the knee meniscus. In addition, a rotating wall bioreactor culture of both scaffold materials was compared with static cultures.

Growth factors and fibrochondrocytes in scaffolds.

Four growth factors, transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor-AB (PDGF-AB), insulin-like growth factor I (IGF-I), and basic fibroblastic growth factor (bFGF), were tested at different concentrations for their effects on extracellular matrix (ECM) production in three-dimensional cultures of meniscal fibrochondrocytes. Cells from New Zealand white rabbits were seeded on poly-glycolic acid (PGA) scaffolds and were stimulated with growth factors for three weeks. (3)H-proline and (35)S-sulfate labels were used to measure uptake of collagen and glycosaminoglycan (GAG) components, respectively.

Wear and biomechanical characteristics of a novel shear-reducing insole with implications for high-risk persons with diabetes.

Objective: This study was designed to measure pressure and shear reduction of a novel insole design.

Methods: We compared three multilayer viscoelastic insoles to a novel insole design (Glide-Soft, Xilas Medical, Inc., San Antonio, TX).

Evaluation of three growth factors in combinations of two for temporomandibular joint disc tissue engineering.

Tissue engineering of the temporomandibular joint disc could be a great value in treatments that require discectomy. Potential benefit has been found in the use of three growth factors: insulin-like growth factor-I, basic fibroblast growth factor and transforming growth factor-beta1 in maintaining disc-like tissue in culture. In the present study, these three growth factors were combined in pairs and tested at two different concentrations over a 6-week period.

A surface-regional and freeze-thaw characterization of the porcine temporomandibular joint disc.

The temporomandibular joint (TMJ) disc is a central element in several TMJ disorders. Tissue-engineered TMJ disc replacements may alleviate discomfort associated with TMJ disorders; however, prior to developing a replacement, a thorough understanding of the native disc must be attained. Toward this end, we developed an unconfined compression, incremental stress relaxation viscoelastic model which simultaneously incorporates the strain increment magnitude and total deformation in the stress relaxation solution.