Extracellular matrix recovery by human articular chondrocytes after treatment with hyaluronan hexasaccharides or Streptomyces hyaluronidase

Hyaluronan Pericellular Matrix: Particle Exclusion Assay

Particle exclusion assays are used to visualize pericellular envelopes with a high content of hyaluronan. Pericellular hyaluronan is basally abundant in certain cell types while in others it is deposited in a highly dynamic manner in response to specific conditions and its presence may indicate cellular status. This assay, described here, is a quick semiquantitative approach to detecting pericellular hyaluronan using the hyaluronan-binding proteoglycan, aggrecan, to stabilize and amplify the surface matrix. Hyaluronan matrix can then be observed and quantified by microscopic image analysis of clear zones around individual cells, from which exogenously added fixed red blood cell particles are excluded.

CRISPR/Cas9 knockout of HAS2 in rat chondrosarcoma chondrocytes demonstrates the requirement of hyaluronan for aggrecan retention

Hyaluronan (HA) plays an essential role in cartilage where it functions to retain aggrecan. Previous studies have suggested that aggrecan is anchored indirectly to the plasma membrane of chondrocytes via its binding to cell-associated HA. However, reagents used to test these observations such as hyaluronidase and HA oligosaccharides are short term and may have side activities that complicate interpretation. Using the CRISPR/Cas9 gene editing approach, a model system was developed by generating HA-deficient chondrocyte cell lines. HA synthase-2 (Has2)-specific single guide RNA was introduced into two different variant lines of rat chondrosarcoma chondrocytes; knockout clones were isolated and characterized. Two other members of the HA synthase gene family were expressed at very low relative copy number but showed no compensatory response in the Has2 knockouts. Wild type chondrocytes of both variants exhibited large pericellular matrices or coats extending from the plasma membrane. Addition of purified aggrecan monomer expanded the size of these coats as the proteoglycan became retained within the pericellular matrix. Has2 knockout chondrocytes lost all capacity to assemble a particle-excluding pericellular matrix and more importantly, no matrices formed around the knockout cells following the addition of purified aggrecan. When grown as pellet cultures so as to generate a bioengineered neocartilage tissue, the Has2 knockout chondrocytes assumed a tightly-compacted morphology as compared to the wild type cells. When knockout chondrocytes were transduced with Adeno-ZsGreen1-mycHas2, the cell-associated pericellular matrices were restored including the capacity to bind and incorporate additional exogenous aggrecan into the matrix. These results suggest that HA is essential for aggrecan retention and maintaining cell separation during tissue formation.

The mechanism of action for hyaluronic acid treatment in the osteoarthritic knee: a systematic review

BACKGROUND

Knee osteoarthritis (OA) is one of the leading causes of disability within the adult population. Current treatment options for OA of the knee include intra-articular (IA) hyaluronic acid (HA), a molecule found intrinsically within the knee joint that provides viscoelastic properties to the synovial fluid. A variety of mechanisms in which HA is thought to combat knee OA are reported in the current basic literature.

METHODS

We conducted a comprehensive literature search to identify currently available primary non-clinical basic science articles focussing on the mechanism of action of IA-HA treatment. Included articles were assessed and categorized based on the mechanism of action described within them. The key findings and conclusions from each included article were obtained and analyzed in aggregate with studies of the same categorical assignment.

RESULTS

Chondroprotection was the most frequent mechanism reported within the included articles, followed by proteoglycan and glycosaminoglycan synthesis, anti-inflammatory, mechanical, subchondral, and analgesic actions. HA-cluster of differentiation 44 (CD44) receptor binding was the most frequently reported biological cause of the mechanisms presented. High molecular weight HA was seen to be superior to lower molecular weight HA products. HA derived through a biological fermentation process is also described as having favorable safety outcomes over avian-derived HA products.

CONCLUSIONS

The non-clinical basic science literature provides evidence for numerous mechanisms in which HA acts on joint structures and function. These actions provide support for the purported clinical benefit of IA-HA in OA of the knee. Future research should not only focus on the pain relief provided by IA-HA treatment, but the disease modification properties that this treatment modality possesses as well.

Hyaluronan oligosaccharide treatment of chondrocytes stimulates expression of both HAS-2 and MMP-3, but by different signaling pathways

OBJECTIVE

Small hyaluronan (HA) oligosaccharides displace HA from the cell surface and induce cell signaling events. In articular chondrocytes this cell signaling is mediated by the HA receptor CD44 and includes stimulation of genes involved in matrix degradation such as matrix metalloproteinases (MMPs) as well as matrix repair genes including collagen type II, aggrecan and HA synthase-2 (HAS-2). The objective of this study was to determine whether stimulation of HAS-2 and MMP-3 by HA oligosaccharides is due to the activation of a single, cascading pathway or multiple signaling pathways.

METHOD

Bovine articular chondrocytes were pre-treated with a variety of inhibitors of major signaling pathways prior to the addition of HA oligosaccharides. Changes in HA were monitored by real time reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of HAS-2 mRNA, HA ELISA and HA accumulation at the cell surface. A 1900 base pair sequence containing the proximal promoter of HAS-2 was inserted into a luciferase reporter construct, transfected into human immortalized chondrocytes and assayed in a similar fashion.

RESULTS

While our previous studies demonstrated that HA oligosaccharides stimulate MMP-13 activity via activation of p38 MAP kinase and NF-kappaB, inhibitors of these pathways did not affect the stimulation of HAS-2 mRNA expression. However, inhibiting the phosphatidylinositol-3-kinase pathway blocked HA oligosaccharide-mediated stimulation of HAS-2 yet had no effect on MMP-3. Wortmannin and LY294002 also blocked HA oligosaccharide-induced serine and threonine Akt phosphorylation. Treatment of transfected immortalized chondrocytes with HA oligosaccharides resulted in stimulation of HAS-2 mRNA, activation of Akt and enhanced luciferase activity-activity that was blocked by inhibitors of Akt phosphorylation.

CONCLUSIONS

Changes in chondrocyte-matrix interactions by HA oligosaccharides induce altered matrix metabolism by the activation of least two distinct signaling pathways.

Hyaluronan oligosaccharides inhibit tumorigenicity of osteosarcoma cell lines MG-63 and LM-8 in vitro and in vivo via perturbation of hyaluronan-rich pericellular matrix of the cells

Numerous studies have demonstrated a correlation between hyaluronan expression and the malignant properties of various kinds of cancer, and inhibition of hyaluronan production causes decreased tumor growth. Hyaluronan oligosaccharides have been shown to inhibit several tumor cell types via disruption of receptor-hyaluronan interaction. However, few studies have addressed hyaluronan with respect to osteosarcoma. In this study, we examined the effects of exogenously added hyaluronan oligosaccharides on tumorigenicity of murine osteosarcoma cells, LM-8, and human osteoblastic osteosarcoma cells, MG-63. Moreover, the critical size of oligomers needed to inhibit malignant properties was defined. Fluorescent hyaluronan oligosaccharides accumulated both on the surface of cells and in the cytoplasm, and this retention was blocked by pretreatment with an anti-CD44 monoclonal antibody. Hyaluronan octasaccharides significantly inhibited cell viability and induced apoptosis as defined by cell proliferation and terminal deoxynucleotidyl transferase dUTP nick-end labeling assays, respectively. Octasaccharides also abrogated functional cell-associated matrices and significantly reduced the retention of endogenous hyaluronan. Further, octasaccharide treatment affected an inhibition of cell motility as well as cell invasiveness. Pretreatment of the cells with anti-CD44 antibody reduced the antitumor effect of the octasaccharides. In vivo, intratumoral injection of hyaluronan octasaccharides reduced the hyaluronan accumulation in local tumors, resulting in significant suppression of the formation of distant lung metastasis. Together these data suggest that hyaluronan oligosaccharides have potent antitumor effects functioning in part by the abrogation of hyaluronan-rich cell-associated matrices.

Hyaluronan fragments activate nitric oxide synthase and the production of nitric oxide by articular chondrocytes

Chondrocyte CD44 receptors anchor hyaluronan to the cell surface, enabling the assembly and retention of proteoglycan aggregates in the pericellular matrix. Hyaluronan-CD44 interactions also provide signaling important for maintaining cartilage homeostasis. Disruption of chondrocyte-hyaluronan contact alters CD44 occupancy, initiating alternative signaling cascades. Treatment with hyaluronan oligosaccharides is one approach to uncouple CD44 receptors from its native ligand, hyaluronan. In bovine articular chondrocytes, treatment with hyaluronan oligosaccharides or purified hyaluronan hexasaccharides induced the production of nitric oxide that mirrored nitric oxide production following interleukin-1 treatment. In contrast, 120 and 1,260 kDa hyaluronan did not induce production of nitric oxide. Human chondrocytes responded similarly to treatment with hyaluronan or hyaluronan oligosaccharides. Nitric oxide production from chondrocytes was mediated by activation of the inducible nitric oxide synthase, as confirmed by mRNA expression and inhibition of nitric oxide production by diphenyleneiodonium. Co-treatment of chondrocytes with hyaluronan oligosaccharides and interleukin-1 did not demonstrate additive effects. Blocking interleukin-1 receptors with an antagonist did not abolish the production of nitric oxide induced by treatment with hyaluronan oligosaccharides. Moreover, only COS-7 following transfection with a pCD44, not the CD44-null parental cells, responded to treatment with hyaluronan oligosaccharides by releasing nitric oxide. This study demonstrates a novel signaling potential by hyaluronan fragments, in lieu of endogenous hyaluronan-chondrocyte interactions, resulting in the activation of inducible nitric oxide synthase.

Hyaluronan oligosaccharide-induced activation of transcription factors in bovine articular chondrocytes

OBJECTIVE

To document the activity profile of transcription factors following chondrocyte stimulation with hyaluronan (HA) hexasaccharides (HA(6)) and to determine the expression of genes whose transcriptional activation is tightly associated with the transcription factors.

METHODS

Nuclear extracts from bovine articular chondrocytes treated with HA(6) were subjected to transcription factor protein-DNA array analysis. Electrophoretic mobility shift assay (EMSA) analyses were performed to confirm the results of protein-DNA array. The gene expressions of matrix metalloproteinase 3 (MMP-3), type II collagen, and cartilage oligomeric matrix protein (COMP) were examined by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), and protease activity was assessed by casein zymography.

RESULTS

In the protein-DNA array analysis, 12 transcription factors were up-regulated and 2 transcription factors were down-regulated in the chondrocytes treated with HA(6). The transcription factors retinoic acid receptor (RAR), retinoid X receptor (RXR), and Sp-1 exhibited >2-fold increased activity by HA(6) treatment, as confirmed by EMSA. RT-PCR analysis showed that the expression levels of MMP-3, type II collagen, and COMP messenger RNA, which are tightly associated with the activation of RAR, RXR, or Sp-1, were up-regulated by treatment with HA(6). Addition of high molecular mass HA after HA(6) treatment resulted in abrogation of the MMP-3 induction.

CONCLUSION

These results suggest that HA(6) increase the activity of multiple transcription factors in chondrocytes and signal the enhanced expression of key genes involved in cartilage-matrix remodeling and turnover. The data also demonstrate that high molecular mass HA has a potential to suppress the signaling activated by HA(6).

Osteogenic Protein-1 inhibits matrix depletion in a hyaluronan hexasaccharide-induced model of osteoarthritis

OBJECTIVE

To examine the capacity of recombinant osteogenic protein-1 (OP-1) to inhibit the cartilage extracellular matrix damage that follows treatment with hyaluronan hexasaccharides (HA6).

DESIGN

The effects of OP-1 were examined on isolated human chondrocytes grown in alginate beads as well as articular cartilage slices treated with hyaluronan hexasaccharides. Changes in the relative expression of messenger RNA for hyaluronan synthase- 2, aggrecan and CD44 were determined by competitive quantitative reverse transcriptase-polymerase chain reaction. Cartilage proteoglycan biosynthesis was examined by a (35)S-sulfate incorporation assay. Cell-associated matrix of human chondrocytes was visualized by the use of particle exclusion assay, and alcian blue staining. Cartilage slices were examined for accumulation of proteoglycan by Safranin-O, and hyaluronan by a specific biotinylated probe.

RESULTS

Combined OP-1 and HA6 treatment resulted in enhanced expression of mRNA for aggrecan and HAS-2, compared to the treatment with HA6 only. This increased expression of aggrecan mRNA was paralleled by an increased synthesis of cartilage proteoglycan especially retained in the cell-associated matrix. Co-treatment with OP-1 inhibited the HA6-induced depletion of cell-associated matrices as well as HA6-induced depletion of hyaluronan and proteoglycan within cartilage tissue slices.

CONCLUSIONS

These results demonstrate that OP-1 can abrogate the catabolic events associated with a HA6-induced matrix depletion model of osteoarthritis. The mRNA levels of two major cartilage extracellular matrix components, aggrecan and hyaluronan synthase-2 are enhanced above values obtained by either OP-1 or HA6 treatments alone.