Effects of dynamic compressive load on collagen-based scaffolds seeded with fibroblast-like synoviocytes

Endogenous production of hyaluronan, PRG4, and cytokines is sensitive to cyclic loading in synoviocytes

Synovial fluid is composed of hyaluronan and proteoglycan-4 (PRG4 or lubricin), which work synergistically to maintain joint lubrication. In diseases like osteoarthritis, hyaluronan and PRG4 concentrations can be altered, resulting in lowered synovial fluid viscosity, and pro-inflammatory cytokine concentrations within the synovial fluid increase. Synovial fibroblasts within the synovium are responsible for contributing to synovial fluid and can be targeted to improve endogenous production of hyaluronan and PRG4 and to alter the cytokine profile. We cyclically loaded SW982 synoviocytes to 0%, 5%, 10%, or 20% strain for three hours at 1 Hz. To assess the impact of substrate stiffness, we compared the 0% strain group to cells grown on tissue culture plastic. We measured the expression of hyaluronan turnover genes, hyaluronan localization within the cell layer, hyaluronan concentration, PRG4 concentration, and the cytokine profile within the media. Our results show that the addition of cyclic loading increased HAS3 expression, but not in a magnitude-dependent response. Hyaluronidase expression was impacted by strain magnitude, which is exemplified by the decrease in hyaluronan concentration due to cyclic loading. We also show that PRG4 concentration is increased at 5% strain, while higher strain magnitude decreases overall PRG4 concentration. Finally, 10% and 20% strain show a distinct, more pro-inflammatory cytokine profile when compared to the unloaded group. Multivariate analysis showed distinct separation between certain strain groups in being able to predict strain group, hyaluronan concentration, and PRG4 concentration from gene expression or cytokine concentration data, highlighting the complexity of the system. Overall, this study shows that cyclic loading can be used tool to modulate the endogenous production of hyaluronan, PRG4, and cytokines from synovial fibroblasts.

Spectral characterization of cell surface motion for mechanistic investigations of cellular mechanobiology

Understanding the specific mechanisms responsible for anabolic and catabolic responses to static or dynamic force are largely poorly understood. Because of this, most research groups studying mechanotransduction due to dynamic forces employ an empirical approach in deciding what frequencies to apply during experiments. While this has been shown to elucidate valuable information regarding how cells respond under controlled provocation, it is often difficult or impossible to determine a true optimal frequency for force application, as many intracellular complexes are involved in receiving, propagating, and responding to a given stimulus. Here we present a novel adaptation of an analytical technique from the fields of civil and mechanical engineering that may open the door to direct measurement of mechanobiological cellular frequencies which could be used to target specific cell signaling pathways leveraging synergy between outside-in and inside-out mechanotransduction approaches. This information could be useful in identifying how specific proteins are involved in the homeostatic balance, or disruption thereof, of cells and tissue, furthering the understanding of the pathogenesis and progression of many diseases across a wide variety of cell types, which may one day lead to the development of novel mechanobiological therapies for clinical use.

Effect of Cyclic Dynamic Compressive Loading on Chondrocytes and Adipose-Derived Stem Cells Co-Cultured in Highly Elastic Cryogel Scaffolds

In this study, we first used gelatin/chondroitin-6-sulfate/hyaluronan/chitosan highly elastic cryogels, which showed total recovery from large strains during repeated compression cycles, as 3D scaffolds to study the effects of cyclic dynamic compressive loading on chondrocyte gene expression and extracellular matrix (ECM) production. Dynamic culture of porcine chondrocytes was studied at 1 Hz, 10% to 40% strain and 1 to 9 h/day stimulation duration, in a mechanical-driven multi-chamber bioreactor for 14 days. From the experimental results, we could identify the optimum dynamic culture condition (20% and 3 h/day) to enhance the chondrocytic phenotype of chondrocytes from the expression of marker (Col I, Col II, Col X, TNF-α, TGF-β1 and IGF-1) genes by quantitative real-time polymerase chain reactions (qRT-PCR) and production of ECM (GAGs and Col II) by biochemical analysis and immunofluorescence staining. With up-regulated growth factor (TGF-β1 and IGF-1) genes, co-culture of chondrocytes with porcine adipose-derived stem cells (ASCs) was employed to facilitate chondrogenic differentiation of ASCs during dynamic culture in cryogel scaffolds. By replacing half of the chondrocytes with ASCs during co-culture, we could obtain similar production of ECM (GAGs and Col II) and expression of Col II, but reduced expression of Col I, Col X and TNF-α. Subcutaneous implantation of cells/scaffold constructs in nude mice after mono-culture (chondrocytes or ASCs) or co-culture (chondrocytes + ASCs) and subject to static or dynamic culture condition in vitro for 14 days was tested for tissue-engineering applications. The constructs were retrieved 8 weeks post-implantation for histological analysis by Alcian blue, Safranin O and Col II immunohistochemical staining. The most abundant ectopic cartilage tissue was found for the chondrocytes and chondrocytes + ASCs groups using dynamic culture, which showed similar neo-cartilage formation capability with half of the chondrocytes replaced by ASCs for co-culture. This combined co-culture/dynamic culture strategy is expected to cut down the amount of donor chondrocytes needed for cartilage-tissue engineering.

BM-MSCs and Bio-Oss complexes enhanced new bone formation during maxillary sinus floor augmentation by promoting differentiation of BM-MSCs

Bone marrow-derived mesenchymal stem cells (BM-MSCs) have been recognized as a new strategy for maxillary sinus floor elevation. However, little is known concerning the effect of the biomechanical pressure (i.e., sinus pressure, masticatory pressure, and respiration) on the differentiation of BM-MSCs and the formation of new bone during maxillary sinus floor elevation. The differentiation of BM-MSCs into osteoblasts was examined in vitro under cyclic compressive pressure using the Flexcell® pressure system, and by immunohistochemical analysis, qRT-PCR, and Western blot. Micro-CT was used to detect bone formation and allow image reconstruction of the entire maxillary sinus floor elevation area. Differentiation of BM-MSCs into osteoblasts was significantly increased under cyclic compressive pressure. The formation of new bone was enhanced after implantation of the pressured complex of BM-MSCs and Bio-Oss during maxillary sinus floor elevation. The pressured complex of BM-MSCs and Bio-Oss promoted new bone formation and maturation in the rabbit maxillary sinus. Stem cell therapy combined with this tissue engineering technique could be effectively used in maxillary sinus elevation and bone regeneration.

Hyaluronic acid secretion by synoviocytes alters under cyclic compressive load in contracted collagen gels

Knee osteoarthritis is a degenerative disease of diarthrodial joints. Biomechanical factors are considered as risk factors for the disease, the knee joint being normally subject to pressure. Some studies have examined the biomechanical environment of the knee joint in vitro. The aim of this study was to establish a culture model to mimic the knee joint environment. As a first step, synoviocytes induced contraction of three-dimensional collagen gels. Next, contracted collagen gels containing synoviocytes underwent cyclical compression ranging from 0 to 40 kPa at a frequency of 1.0 Hz for 1.5, 3, 6 and 12 h using the FX-4000C™ Flexercell(®) Compression Plus™ System. RNA in collagen gels was extracted immediately after compression and mRNA expression levels of HAS genes were analyzed by quantitative RT-PCR. Culture medium was collected 48 h after compression and analyzed by agarose gel electrophoresis and cellulose acetate electrophoresis. Synoviocytes in contracted collagen gels were stimulated by cyclic compressive load. Long-term compressive stimulation led to the production of higher molecular weight hyaluronic acid, whereas, short-term, compressive stimulation increased the total amount of hyaluronic acid. Furthermore, mRNA expression levels of both HAS-1 and HAS-2 were significantly higher than without compression. Taken together, using this gel culture system, synoviocytes synthesized higher molecular weight hyaluronic acid and produced large quantities of hyaluronic acid through up-regulation of HAS gene expression. Therefore, the contracted collagen gel model will be a useful in vitro three-dimensional model of the knee joint.

Culture of canine synoviocytes on porcine intestinal submucosa scaffolds as a strategy for meniscal tissue engineering for treatment of meniscal injury in dogs

Meniscal injury is a common cause of canine lameness. Tissue engineered bioscaffolds may be a treatment option for dogs suffering from meniscal damage. The aim of this study was to compare in vitro meniscal-like matrix formation and biomechanical properties of porcine intestinal submucosa sheets (SIS), used in canine meniscal regenerative medicine, to synoviocyte-seeded SIS bioscaffold (SSB), cultured with fetal bovine serum (SSBfbs) or chondrogenic growth factors (SSBgf). Synoviocytes from nine dogs were seeded on SIS and cultured for 30days with 17.7% fetal bovine serum or recombinant chondrogenic growth factors (IGF-1, TGFβ1 and bFGF). The effect on fibrochondrogenesis was determined by comparing mRNA expression of collagen types Iα and IIα, aggrecan, and Sry-type homeobox protein-9 (SOX9) as well as protein expression of collagens I and II, glycosaminoglycan (GAG), and hydroxyproline. The effect of synoviocyte seeding and culture conditions on biochemical properties was determined by measuring peak load, tensile stiffness, resilience, and toughness of bioscaffolds. Pre-culture SIS contained 13.6% collagen and 2.9% double-stranded DNA. Chondrogenic growth factor treatment significantly increased SOX9, collagens I and IIα, aggrecan gene expression (P<0.05), and histological deposition of fibrocartilage extracellular matrix (GAG and collagen II). Culture with synoviocytes increased SIS tensile peak load at failure, resilience, and toughness of bioscaffolds (P<0.05). In conclusion, culturing SIS with synoviocytes prior to implantation might provide biomechanical benefits, and chondrogenic growth factor treatment of cultured synoviocytes improves in vitro axial meniscal matrix formation.

Cell-based meniscal tissue engineering: a case for synoviocytes

BACKGROUND

Avascular meniscal injuries are largely incapable of healing; the most common treatment remains partial meniscectomy despite the risk of subsequent osteoarthritis. Meniscal responses to injury are partially mediated through synovial activity and strategies have been investigated to encourage healing through stimulating or transplanting adjacent synovial lining. However, with their potential for chondrogenesis, synovial fibroblast-like stem cells hold promise for meniscal cartilage tissue engineering.

QUESTIONS/PURPOSES

Thus, specific purposes of this review were to (1) examine how the synovial intima and synoviomeniscal junction affect current meniscal treatment modalities; and (2) examine the components of tissue engineering (cells, scaffolds, bioactive agents, and bioreactors) in the specific context of how cells of synovial origin may be used for meniscal healing or regeneration.

METHODS

An online bibliographic search through PubMed was performed in March 2010. Studies were subjectively evaluated and reviewed if they addressed the question posed. Fifty-four resources were initially retrieved, which offered information on the chondrogenic potential of synovial-based cells that could prove valuable for meniscal fibrocartilage engineering.

RESULTS

Based on the positive effects of adjoining synovium on meniscal healing as used in some current treatment modalities, the chondrogenic potential of fibroblast-like stem cells of synovial origin make this cell source a promising candidate for cell-based tissue engineering strategies.

CONCLUSIONS

The abundance of autologous synovial lining, its ability to regenerate, and the potential of synovial-derived stem cells to produce a wide spectrum of chondral matrix components make it an ideal candidate for future meniscal engineering investigations.

Bioreactor for Biaxial Mechanical Stimulation to Tissue Engineered Constructs

The complex structure and properties of biological tissues as well as their in situ environment often make it difficult to self-heal. A suitable replacement tissue may be created in vitro through tissue engineering approaches and mechanical stimulation of tissue constructs. A new biaxial bioreactor was designed, constructed, and evaluated for the purposes of developing constructs with specific functional characteristics. Once constructed and assembled, the bioreactor was tested for position accuracy and application of strain. Additionally, a tissue construct was tested in the chamber and compared with a nonstimulated construct. Results showed high position accuracy, but some loss between applied strain via grip movement and strain experienced by the scaffold. The tested construct exhibited an increase in cells and matrix deposition in comparison to the nonstimulated construct. This biaxial bioreactor will be useful for mechanically stimulating tissue constructs in two perpendicular directions to create implants for tissues requiring preferred compressive and tensile resistances.

In vitro and in vivo comparison of five biomaterials used for orthopedic soft tissue augmentation

OBJECTIVE

To compare biomaterials used in orthopedics with respect to in vitro cell viability and cell retention and to in vivo tissue healing and regeneration.

ANIMALS

65 adult female Sprague-Dawley rats and synovium, tendon, meniscus, and bone marrow specimens obtained from 4 adult canine cadavers.

PROCEDURES

Synovium, tendon, meniscus, and bone marrow specimens were used to obtain synovial fibroblasts, tendon fibroblasts, meniscal fibrochondrocytes, and bone marrow-derived connective tissue progenitor cells for culture on 5 biomaterials as follows: cross-linked porcine small intestine (CLPSI), non-cross-linked human dermis, cross-linked porcine dermis, non-cross-linked porcine small intestine (NCLPSI), and non-cross-linked fetal bovine dermis. After 1 week of culture, samples were evaluated for cell viability, cell density, and extracellular matrix production. Biomaterials were evaluated in a 1-cm(2) abdominal wall defect in rats. Each biomaterial was subjectively evaluated for handling, suturing, defect fit, and ease of creating the implant at the time of surgery, then grossly and histologically 6 and 12 weeks after surgery.

RESULTS

All biomaterials allowed for retention of viable cells in culture; however, CLPSI and NCLPSI were consistently superior in terms of cell viability and cell retention. Cell infiltration for NCLPSI was superior to other biomaterials. The NCLPSI appeared to be replaced with regenerative tissue most rapidly in vivo and scored highest in all subjective evaluations of ease of use.

CONCLUSIONS AND CLINICAL RELEVANCE

These data suggested that NCLPSI and CLPSI have favorable properties for further investigation of clinical application in orthopedic tissue engineering.