Hyalgan has a dose-dependent differential effect on macrophage proliferation and cell death

Effects of Streptococcus thermophilus on anterior cruciate ligament transection-induced early osteoarthritis in rats

Osteoarthritis (OA) is the most common joint disorder and is classically defined as a progressively degenerative disease of articular cartilage. It manifests as joint pain and disability and currently has no comprehensive treatments. The primary purpose of the present study was to test the effects of probiotics, Streptococcus thermophilus (TCI633), on anterior cruciate ligament transection (ACLT)-induced experimental osteoarthritis (OA) in rats. In the current study, the experimental groups were given TCI633 (5x10⁹, 5x10¹⁰ and 5x10¹¹ CFU/kg/day) and glucosamine sulfate (250 mg/kg) between week 8 and 20 following ACLT. The results showed that oral administration of TCI633 and glucosamine had significant therapeutic effects on pain behaviors and knee swelling. Dose-dependent effects of TCI633 were also observed in ACLT-treated rats. Histopathological analysis demonstrated that ACLT+TCI633 (5x10⁹, 5x10¹⁰ and 5x10¹¹ CFU/kg/day) improved the synovial inflammation and cartilage damage of ACLT rats. Histology evaluation using the Osteoarthritis Research Society International system and synovial inflammatory score analysis showed the dose-dependent inhibition of TCI633 on synovial inflammation and cartilage damage. Immunohistochemical staining and TUNEL apoptosis staining showed that TCI633 could effectively increase the expression of type II collagen and reduce the amount of chondrocyte apoptosis in cartilage. Therefore, the present study demonstrated that oral intake of TCI633 could significantly suppressing pain behavior, reduce joint swelling and synovial tissue inflammation and increase type II collagen expression in cartilage. There was also a reduction in chondrocyte apoptosis and decreased progression of OA in ACLT-treated rats.

Addition of High Molecular Weight Hyaluronic Acid to Fibroblast-Like Stromal Cells Modulates Endogenous Hyaluronic Acid Metabolism and Enhances Proteolytic Processing and Secretion of Versican

We have examined the effect of exogenous linear chain high molecular weight hyaluronic acid (HMW HA) on endogenously synthesized hyaluronic acid (HA) and associated binding proteins in primary cultures of fibroblast-like stromal cells that were obtained by collagenase digestion of the murine peripatellar fat pad. The cultures were expanded in DMEM that was supplemented with fetal bovine serum and basic fibroblast growth factor (bFGF) then exposed to macrophage-colony-stimulating factor (MCSF) to induce macrophage properties, before activation of inflammatory pathways using E. coli lipopolysaccharide (LPS). Under all culture conditions, a significant amount of endogenously synthesized HA localized in LAMP1-positive lysosomal vesicles. However, this intracellular pool was depleted after the addition of exogenous HMW HA and was accompanied by enhanced proteolytic processing and secretion of de novo synthesized versican, much of which was associated with endosomal compartments. No changes were detected in synthesis, secretion, or proteolytic processing of aggrecan or lubricin (PRG4). The addition of HMW HA also modulated a range of LPS-affected genes in the TLR signaling and phagocytosis pathways, as well as endogenous HA metabolism genes, such as Has1, Hyal1, Hyal2, and Tmem2. However, there was no evidence for association of endogenous or exogenous HMW HA with cell surface CD44, TLR2 or TLR4 protein, suggesting that its physiochemical effects on pericelluar pH and/or ionic strength might be the primary modulators of signal transduction and vesicular trafficking by this cell type. We discuss the implications of these findings in terms of a potential in vivo effect of therapeutically applied HMW HA on the modification of osteoarthritis-related joint pathologies, such as pro-inflammatory and degradative responses of multipotent mesenchymal cells residing in the synovial membrane, the underlying adipose tissue, and the articular cartilage surface.

Anti-Inflammatory Effects of Intra-Articular Hyaluronic Acid: A Systematic Review

OBJECTIVE

Osteoarthritis (OA) is one of the leading causes of disability in the adult population. Common nonoperative treatment options include nonsteroidal anti-inflammatory drugs (NSAIDs), intra-articular corticosteroids, and intra-articular injections of hyaluronic acid (HA). HA is found intrinsically within the knee joint providing viscoelastic properties to the synovial fluid. HA therapy provides anti-inflammatory relief through a number of different pathways, including the suppression of pro-inflammatory cytokines and chemokines.

METHODS

We conducted a systematic review to summarize the published literature on the anti-inflammatory properties of hyaluronic acid in osteoarthritis. Included articles were categorized based on the primary anti-inflammatory responses described within them, by the immediate cell surface receptor protein assessed within the article, or based on the primary theme of the article. Key findings aimed to describe the macromolecules and inflammatory-mediated responses associated with the cell transmembrane receptors.

RESULTS

Forty-eight articles were included in this systematic review that focused on the general anti-inflammatory effects of HA in knee OA, mediated through receptor-binding relationships with cluster determinant 44 (CD44), toll-like receptor 2 (TLR-2) and 4 (TLR-4), intercellular adhesion molecule-1 (ICAM-1), and layilin (LAYN) cell surface receptors. Higher molecular weight HA (HMWHA) promotes anti-inflammatory responses, whereas short HA oligosaccharides produce inflammatory reactions.

CONCLUSIONS

Intra-articular HA is a viable therapeutic option in treating knee OA and suppressing inflammatory responses. HMWHA is effective in suppressing the key macromolecules that elicit the inflammatory response by short HA oligosaccharides.

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.

Click-crosslinked injectable hyaluronic acid hydrogel is safe and biocompatible in the intrathecal space for ultimate use in regenerative strategies of the injured spinal cord

Traumatic spinal cord injury (SCI) causes damage and degeneration at and around the lesion site resulting in a loss of function. SCI presents a complex regenerative problem due to the multiple aspects of growth inhibition and the heterogeneity in size, shape and extent of injury. Currently, there is no widely accepted treatment strategy available and delivering biomolecules to the central nervous system remains a challenge. With a view towards achieving local release, we designed a hydrogel that can be injected into the intrathecal space. Here we describe the synthesis and characterization of a click-crosslinked hyaluronic acid hydrogel and demonstrate controlled in vitro release of bioactive brain derived neurotrophic factor. Importantly, we demonstrate that this new hydrogel is both biocompatible in the intrathecal space based on immunohistochemistry of the host tissue response and safe based on behavioral analysis of locomotor function.

Glycosaminoglycans and neuroprotection

Glycosaminoglycans (GAGs) are basic building blocks of the ground substance of the extracellular matrix and present at the cellular level as an important component of the glycocalyx covering the cell membrane. In addition to the general role of GAGs in maintaining the integrity of the cell and extracellular matrix by retaining water, certain GAGs exhibit anticoagulant and neuroprotective properties and serve as cell-surface receptors for various molecules. Although heparin, a highly sulfated GAG, has been used as a drug for more than 70 years due to its anticoagulant attributes, the neuroprotective properties of GAGs came into focus only in recent years. The discovery of some of the roles GAGs play in the pathomechanism of numerous neurodegenerative disorders as well as shedding light on the neuroprotective properties of these compounds in animal studies raised the possibility that GAGs may provide an entirely new avenue in the treatment of neurodegenerative diseases. Indeed, some GAGs were successfully used to improve the cognitive function of patients with various neurodegenerative conditions (Ban et al. (1991, 1992); Conti et al. (1989a, b); Passeri and Cucinotta, (1989); Santini (1989). Although the mechanism by which the GAGs exhibit neuroprotective properties is not entirely clear, there is a general consensus that the major factors of the neuroprotective attributes of GAGs include the impact of GAGs on amyloidogenesis and the regulatory action of GAGs in the apoptotic pathway.

Low molecular weight hyaluronic acid effects on murine macrophage nitric oxide production

Hyaluronic acid (HA) is increasingly used for a number of medical device applications. Since the chemical structure of HA is identical no matter its bacterial or animal origin, it should be the ideal biomaterial. However, short term transient inflammatory reactions are common, while rare long-term adverse events may correlate with subclinical chronic inflammation. Concern has been raised that low molecular weight components or degradation fragments from implanted HA may directly stimulate inflammatory reactions. This study examined a panel of HA molecular weights from the unitary disaccharide up to 1.7 x 10(6) Dalton lengths, in which endotoxin was assayed at a very low level (less than 0.03 EU/mg). The murine cell line RAW 264.7, rat splenocytes, and rat adherent differentiated primary macrophages were assayed for nitric oxide production under a variety of inflammatory conditions plus or minus HA. Under the highest inflammatory states, nitric oxide production was mildly suppressed by HMW-HA while slightly augmented by LMW-HA at mg/mL concentrations. However, at micromolar concentrations fragments below 5000 Daltons, thought to have drug-like qualities, were without effect. These data support the hypothesis that if endotoxin is reduced to an extremely low level, LMW-HA may not directly provoke normal tissue macrophage-mediated inflammatory reactions.

Effects of chondroitin sulfate and sodium hyaluronate on chondrocytes and extracellular matrix of articular cartilage in dogs with degenerative joint disease

Samples of articular cartilage of femur, tibia and patella of 15 dogs with experimentally induced degenerative joint disease (DJD) were microscopically analyzed. Animals were distributed into three groups (n=5): the control group received no medication; the second group was treated with chondroitin sulfate and the third received sodium hyaluronate. Samples were processed and stained with HE and toluidine blue for morphological evaluation. The metabolic and proliferative activity of the chondrocytes was evaluated by the measurement of nucleolar organizer regions (NORs) after impregnation by silver nitrate. Significant differences were not observed (P>0.05) in the morphology among the groups, however, the group treated with sodium hyaluronate had a higher score suggesting a trend to a greater severity of the lesions. Significant differences were not observed (P>0.05) in the measurement of NORs, cells and NORs/cells among the groups. Although differences were not significant, sodium hyaluronate group showed higher NOR and cell counts which suggested an increase of the proliferation rate of chondrocytes. In addition, a higher NOR/cell ratio in the group treated with chondroitin sulfate suggested that this drug may have stimulated the metabolic activity of the chondrocytes, minimizing the lesions resulting from DJD.

Modeling the effects of treating diabetic wounds with engineered skin substitutes

In this paper, a novel mathematical model of wound healing in both normal and diabetic cases is presented, focusing upon the effects of adding two currently available commercial engineered skin substitute therapies to the wound (Apligraf) and Dermagraft). Our work extends a previously developed model, which considers inflammatory and repair macrophage dynamics in normal and diabetic wound healing. Here, we extend the model to include equations for platelet-derived growth factor concentration, fibroblast density, collagen density, and hyaluronan concentration. This enables us to examine the variation of these components in both normal and diabetic wound healing cases, and to model the treatment protocols of these therapies. Within the context of our model, we find that the key component to successful healing in diabetic wounds is hyaluronan and that the therapies work by increasing the amount of hyaluronan available in the wound environment. The time-to-healing results correlate with those observed in clinical trials and the model goes some way to establishing an understanding of why diabetic wounds do not heal, and how these treatments affect the diabetic wound environment to promote wound closure.

[Reduction of arthrosis associated knee pain through a single intra-articular injection of synthetic hyaluronic acid]

AIM

Conventional hyaluronic acids need three to five injections for therapeutic success, whereas Durolane), a synthetic hyaluronic acid, needs only a single injection. Clinical outcome using Durolane should be compared with the results of studies using hyaluronic acids or glucocorticoids.

METHOD

Fifty patients with primary gonarthrosis stages I-III (Kellgren Score) were investigated for knee function, pain intensity, and quality of life. The knee and osteoarthritis outcome score (KOOS), visual analogue scale (VAS), and European quality of live score (EQ-5D), as well as motion of the knee were measured. Patients were investigated before, and 2, and 24 weeks after injection.

RESULTS

Two weeks after injection, the subjective function of knee and quality of life had increased significantly. In the following 22 weeks, all parameters increased significantly (quality of life and activity +19%; range of motion active 109 vs. 115 degrees ; pain, 55 vs. 41 mm (VAS); all p<0.01).

CONCLUSION

We conclude that a single injection of Durolane can reduce arthrosis associated knee pain sufficiently. Our data are comparable with those published in clinical studies using other hyaluronic acids. The effects of Durolane are delayed but more sustained compared than those found for glucocorticoids. Because of the single injection, we see an advantage in using Durolane compared to other conventional hyaluronic acids and glucocorticoids.

Intrathecal drug delivery strategy is safe and efficacious for localized delivery to the spinal cord

Neuroprotective and neuroregenerative strategies for spinal cord injury repair are limited in part by poor delivery techniques. A novel drug delivery system is being developed in our laboratory that can provide localized release of therapeutically relevant molecules from an injectable hydrogel. Design criteria were established for the hydrogel to be--injectable, fast-gelling, biocompatible, biodegradable and able to release biologically active therapeutics when injected into the intrathecal space that surrounds the spinal cord. This novel way of localized drug delivery to the spinal cord was tested first with a collagen gel and then with a new hydrogel blend of hyaluronan and methylcellulose (HAMC). The underlying principle that this novel methodology is both safe and able to provide localized delivery was proven with a fast gelling collagen solution. Using a recombinant human epidermal growth factor, rhEGF, dispersed in collagen, we demonstrated localized release to the injured spinal cord. We extended this technology to other fast-gelling systems and found that HAMC was injectable due to the shear thinning property of hyaluronan (HA), biocompatible and had some therapeutic benefit when injected into the intrathecal space using a compression injury model in rats.

High-molecular-weight hyaluronan inhibits macrophage proliferation and cytokine release in the early wound of a preclinical postlaminectomy rat model

BACKGROUND CONTEXT

Failed back syndrome, a condition that affects 3-14% of postoperative spine patients, is characterized by the recurrence of radicular pain after spinal decompression. The source of this pain in some patients is thought by many investigators to be the result of epidural scarring and nerve root tethering, but this is controversial. We have previously demonstrated that in a disc-injury model the untreated postlaminectomy rats develop a significant proliferative fibrous response at 8 weeks with spinal nerve scarring to the disc and adjacent pedicle, and increased sensitivity to tactile allodynia testing in the related sensory dermatome. Topical high-molecular-weight hyaluronan (HMW HA) moderates both the proliferative fibrosis and the behavioral pain response.

PURPOSE

Our purpose is to study the time-related changes in the proinflammatory cytokine and monocyte/macrophage profiles in the epidural space in the early postlaminectomy untreated and HMW HA gel treated groups.

STUDY DESIGN/SETTING

A modified rat laminectomy with disc injury model was employed to assess epidural fibrosis between and around the spinal nerves using a quantitative immunohistochemistry assessment approach along with correlative enzyme-linked immunosorbent assay analysis.

METHODS

Lumbar laminectomies at L5 and L6 with a L5-L6 disc injury were performed on 120 adult male Sprague-Dawley rats. The rats were then randomized into one of two groups: untreated and treated. The treatment group received a one-time topical application of 0.1 cc of HMW HA gel directly to the laminectomy site just before wound closure. The rats were then randomly subdivided into survival periods of 24 hours, 72 hours, and 7 days. Immunohistochemistry was performed on fresh frozen sections and stained for interleukin-1 beta (IL-1beta) and monocytes/macrophages (ED-1) using monoclonal antibodies and 3, 3' diaminobenzidine (DAB) chromogen. The amount of stain in each specimen was then quantified using the National Institutes of Health computer imaging analysis system.

RESULTS

The semiquantified data from the histological specimens demonstrated significant decreases in the IL-1beta and IL-6 infiltration observed at 24 hours in the epidural space and around the right nerve root (p=.0296 and 0.0195, respectively) in the HA gel treated group. Additionally, significant decreases in the monocyte/macrophage infiltration were observed at 72 hours in the epidural space around the left nerve root (p=.0039) and right nerve root (p=.0072) in the HA gel treated group. At 7 days, IL-1beta, IL-6, and macrophage infiltration of the wound had declined in both the HA gel and the untreated groups. The enzyme-linked immunosorbent assay data support the same pattern as seen in the histological results.

CONCLUSION

These results demonstrate that treatment of postlaminectomy wounds with HMW HA gel decreases the number of monocytes and macrophages and the concentration of certain cytokines in the early inflammatory phase of healing. There are several plausible explanations for this effect. First, the HMW HA may block the interaction of short-chain low-molecular-weight HA with proinflammatory cell surface receptors. The interaction of these short-chain oligo-HA fragments, upon cell-surface receptor binding, induces changes in inflammatory cells that lead to increased cell motility and migration into the wound area. Second, the addition of exogenous HMW HA may cause a dilution effect in the wound, thereby decreasing the concentration of inflammatory cells in the extracellular matrix of the region of injury. Finally, the migration of inflammatory cells may be decreased in the viscous environment of the HMW HA. The first explanation is believed by the authors of this paper to be the more likely mechanism. HMW HA probably mutes the proinflammatory effects of the low-molecular weight fragments, leading to decreased inflammation, and thus decreased fibrosis and scar formation noted in the chronic model.

Hyaluronic acid attenuates osteoarthritis development in the anterior cruciate ligament-transected knee: Association with excitatory amino acid release in the joint dialysate

We previously reported increased release of the excitatory amino acid (EAA) neurotransmitters, glutamate and aspartate, during the early stage of experimental osteoarthritis (OA). Our present objective was to study the effect of intraarticular injection of hyaluronic acid (HA) on OA development, and to analyze concomitant changes in EAA levels in dialysates of anterior cruciate ligament-transected (ACLT) knee joints. OA was induced in Wistar rats by ACLT of one hindlimb; the knee of the other hindlimb was used as the sham-operated control. HA group (n = 12) were injected intraarticularly in the ACLT knee with 1 mg of HA once a week for 5 consecutive weeks, starting at 8 weeks after surgery. Saline group (n = 12) were injected as above with normal saline. The sham-operated group, underwent arthrotomy, but not ACLT, and received no treatment (n = 14). Twenty weeks after surgery, knee joint dialysates were collected by microdialysis and EAA levels assayed by high-performance liquid chromatography, and gross morphological examination and histopathological evaluation were performed on the medial femoral condyles and synovia. Rats receiving intraarticular HA injections showed a significantly lower degree of cartilage degeneration on the medial femoral condyle at both the macroscopic level and on the Mankin grading scale than rats receiving saline injections. Intraarticular HA treatment also suppressed synovitis. Moreover, glutamate and aspartate levels were significantly reduced in the HA group compared to the saline group. Intraarticular injection of HA limits articular cartilage and synovium damage and OA formation, and, in parallel, reduces EAA levels in ACLT joint dialysates. This study suggests that the underlying mechanism of the anti-inflammatory effect of HA is to inhibit glutamate and aspartate release in ACLT knee joints, which attenuates the early development of OA.

Fast-gelling injectable blend of hyaluronan and methylcellulose for intrathecal, localized delivery to the injured spinal cord

Strategies for spinal cord injury repair are limited, in part, by poor drug delivery techniques. A novel drug delivery system (DDS) is being developed in our laboratory that can provide localized release of growth factors from an injectable gel. The gel must be fast-gelling, non-cell adhesive, degradable, and biocompatible as an injectable intrathecal DDS. A gel that meets these design criteria is a blend of hyaluronan and methylcellulose (HAMC). Unlike other injectable gels, HAMC is already at the gelation point prior to injection. It is injectable due to its shear-thinning property, and its gel strength increases with temperature. In vivo rat studies show that HAMC is biocompatible within the intrathecal space for 1 month, and may provide therapeutic benefit, in terms of behavior, as measured by the Basso, Beattie and Bresnahan (BBB) locomotor scale, and inflammation. These data suggest that HAMC is a promising gel for localized delivery of therapeutic agents to the injured spinal cord.

Formation of a new enthesis after attachment of the supraspinatus tendon: A quantitative histologic study in rabbits

PURPOSE

To quantify in a longitudinal study non-chondrocytic cells and chondrocytes, tissular architecture as well as extracellular matrix restoration during the formation of an enthesis following supraspinatus tendon attachment to the humerus.

METHODS

In 89 rabbits, one supraspinatus fibrocartilaginous enthesis was resected and the tendon either attached to the greater tuberosity (n=75) or not attached (n=14). The animals were sacrificed after 2, 6, 8, 12 or 24 weeks. The operated and contralateral shoulders were processed for histologic sections. Number of non-chondrocytes, chondrocytes and alignment of chondrocytes in rows were assessed histologically. Extracellular matrix restoration was measured based on (1) area of toluidine blue metachromasia indicating proteoglycan content and (2) on area of diffracted polarized light indicating spatial collagen fiber alignment.

RESULTS

In the attached tendon, the number of non-chondrocytic cells sharply increased at 2 weeks, progressively decreased thereafter but remained higher than controls at all time points. Chondrocytes appeared at 2 weeks and their number reached control levels by 6 weeks (136+/-14 vs 144+/-15 controls, p>.05). The percentage of chondrocytes aligned in rows increased from 19+/-4% at 2 weeks to reach near normal values at 24 weeks (71+/-3% vs 78+/-2% controls, p>.05). Area of metachromasia increased from 0.1+/-0.1 mm(2) at 2 weeks to 3.8+/-0.3 mm(2) at 24 weeks, still below contralateral enthesis levels (4.6+/-0.1 mm(2), p<.05). Area of diffracted polarized light enlarged from 12+/-2 x 10(3) microm(2) at 2 weeks to 151+/-19 x 10(3) microm(2) at 24 weeks, still significantly smaller than contralateral levels (177+/-13 x 10(3) microm(2), p<.05). Neither chondrocytes nor metachromasia were observed in the non-attached tendons.

CONCLUSION

A new enthesis was formed after attachment of the supraspinatus tendon into bony trough. Histomorphometry allowed to document extensive non-chondrocytic proliferation that was followed by appearance of chondrocytes and their spatial organization, a process was complete by 24 weeks. Extracellular matrix formation as well as spatial alignment of collagen fibers were delayed and not complete by 24 weeks. This first longitudinal investigation on the formation of the supraspinatus enthesis using quantitative outcome measures cautions against too early and too aggressive a rehabilitation program.

Topical high molecular weight hyaluronan reduces radicular pain post laminectomy in a rat model

BACKGROUND CONTEXT

A controversy exists about the mechanism of causation of the post-laminectomy pain syndrome. Some believe that epidural scarring, and attendant spinal nerve and nerve root scarring and tethering to the disc or pedicle at the site of surgery contributes to post-laminectomy pain in such patients. However, clinical outcome studies on this question are inconclusive and the assertion remains controversial. Definitive studies to help resolve the question are needed. Previously our laboratory has reported on a preclinical post-laminectomy model that mimics the postoperative proliferative fibrotic response grossly, as well as by biochemical assessment of the collagen content within the spinal canal. The post-laminectomy fibrotic response was attenuated in that study by application of a topical antifibrotic (high molecular weight hyaluronan gel) or by insertion of an absorbable roofing barrier (0.2-mm-thick Macropore sheet material) over the laminectomy defect before wound closure. The question remains of relevance of the attenuation of the fibrotic response to post-laminectomy chronic pain syndromes.

PURPOSE

The purpose of this study is to evaluate the effect of therapeutic attenuation of proliferative scar within the spinal canal post laminectomy on the pain-related behavioral response in a preclinical rat model.

STUDY DESIGN/SETTING

An established L5-L6 rat laminectomy model with a unilateral L5-6 disc injury was employed to assess postoperative proliferative fibrosis of the L5 spinal nerves using quantitative biochemical hydroxyproline assessment of the collagen content in four experimental groups. These observations were correlated with gross descriptions of spinal nerve scarring or tethering. Associated manifestations of a sensory pain-related response in the L5 spinal nerve receptor area of the hind paws was studied using standard tactile allodynia assessment with the von Frey hair technique. The tactile allodynia findings were supplemented by weekly descriptors of behavioral pain manifestations.

METHODS

Bilateral laminectomies at L5 and L6 and a unilateral right disc injury (L5-6) were performed on 35 male adult Sprague-Dawley rats, weighing 400+ grams (approved by the VA Institutional Animal Care Use Committee). The study consisted of four groups: 1) normal nonoperative control; 2) a sham-operated group; 3) an untreated laminectomy-disc injury group; and 4) a laminectomy-disc injury treatment group in which 0.1 cc topical high molecular weight hyaluronan (HMW HA) gel was layered over the dura and into the laminectomy canal before closure. Before animals were entered into the study, they were checked for the presence of abnormal response to the tactile testing procedure of the L5 sensory receptor area. Animals exhibiting anomalous responses were excluded from the study. Behavioral testing for tactile allodynia was performed at weekly intervals post laminectomy beginning at 3 weeks. Pain-related behavior was characterized at weekly intervals. A behavioral test cage with a wire mesh floor allowed for tactile allodynia testing. Graduated von Frey hairs whose stiffness increased logarithmically from 0.41 to 15 g were used for tactile allodynia tests. The animals were killed 8 weeks postoperatively for analysis. The dissected spinal nerve and nerve root specimens were studied biochemically for hydroxyproline content to estimate total collagen in and around the L5 neural structures. Statistical analyses were performed using analysis of variance and a Fisher comparison t test.

RESULTS

The major observations on the untreated preclinical post-laminectomy rat model previously described by this laboratory were confirmed. All untreated animals developed a tail contracture concave toward the right (disc injury side) consistent with asymmetrical lumbar muscle spasm. Only one animal in the HA gel treatment group had a tail contracture. It was of mild degree and occurred in an animal that demonstrated slightly increased right L5 tactile sensitivity. Gross inspection of the dissected specimens demonstrated spinal nerve scarring and tethering to the disc and pedicle greater on the right than the left in untreated animals, findings that were markedly reduced in the treatment group. Collagen content of the L5 spinal nerve and nerve roots with attached scar were significantly lower in the HA gel treatment group than in the untreated laminectomy group (p=.0014). Pain behavioral testing of the L5 receptor area of the right hind paw in the untreated laminectomy group showed markedly increased sensitivity to tactile allodynia testing compared with the corresponding limb of the control group (p=.0001), to the corresponding limb of the sham group (p=.0001), and compared with the HMW HA gel treatment group (p=.0010). Comparisons of the pain behavioral data between the sham and the post-laminectomy HA gel treatment group and the control animals lacked statistical significance.

CONCLUSION

This study supports the concept of a relationship between perineural fibrosis and radicular neuropathy in the model described, and emphasizes the role of disc injury and spinal nerve retraction in the post-laminectomy fibrotic process. Furthermore, it shows promise for preliminary assessment of interventions with other anti-inflammatory agents, for characterization of the neurochemical profile of the post-laminectomy pain state, and for exploration of newer pharmaceutical agents potentially useful in the prevention or management of the post-laminectomy syndrome. Post-laminectomy scar is but one of many potential causes of the post-laminectomy pain syndrome. Furthermore, a cautionary note must be emphasized as in all studies using preclinical models, conclusions drawn from the studies cannot be extended directly to patients without confirmatory clinical follow-up studies.

Sodium hyaluronate regulating angiogenesis during Achilles tendon healing

The aim of this study was to evaluate the effect of SH (sodium hyaluronate-NaHA) on vascular endothelial growth factor (VEGF) and type IV collagen expression during the Achilles-tendon healing process. Adult New Zealand white rabbits (n=32) aged 4 months and weighing 2.7-3.9 kg were used. The rabbits were randomly divided into two groups, and each group was divided into two subgroups and monitored for 6 and 12 weeks. Tendo calcanei were incised transversely and repaired. An injection of 0.5 ml NaHA (15 mg/ml) was administered between the tendon and paratenon of the right leg and repeated twice at one-week intervals. Equal numbers of animals were sacrificed at the 6th and 12th weeks, and the repaired tissue was examined macroscopically and histologically for the presence of VEGF and type IV collagen expression every week. The decrease in the amount of adhesion tissue and the acceleration of tendon healing in the NaHA group were significantly high when compared with control groups at 6 and 12 weeks (p<0.001, p<0.05). In the NaHA group, due to vascular proliferation VEGF immunostaining was strongly positive in the 6th week (p<0.05), and remained positive in the 12th week (p<0.05). Similar immunostaining findings were detected for type IV collagen in the 6th week. However, there was a significant decline in immunostaining rate in the 12th week (p<0.05). The increases in VEGF and type IV collagen expression following SH administration might be an indication that SH may partly be involved in regulation of angiogenesis.

Hyaluronic acid of high molecular weight inhibits proliferation and induces cell death in U937 macrophage cells

Hyaluronic acid (HA), a major glycosaminoglycan component of the extracellular matrix, has regulatory influences on cells and cellular activities. To explore the effects of a high concentration (1 mg/mL) of high molecular weight HA (500-730 kD) on U937 macrophage growth dynamics, three factors that influence overall cellular growth, namely proliferation, apoptosis, and cell death, were examined. Cells were cultured with HA and were analyzed by flow cytometry every 24 hours during a 168-hour period for proliferation and the presence of apoptotic and dead cells. These analyses demonstrated that HA inhibits U937 macrophage proliferation in a time-dependent manner. Through the first 72 hours, cells exhibited slowed proliferation. However, no evidence of cell division arrest or reduced cell viability was observed. Thereafter, HA continued to diminish proliferation, but induced apoptosis. This data is consistent with regulatory influences secondary to HA binding to CD44 and/or RHAMM cell surface receptors, both of which were shown to be expressed on U937 macrophages. This study demonstrates that a high concentration of high molecular weight HA greatly inhibits macrophage population growth by the dual actions of impeding cell proliferation and inducing apoptosis.