Denervation impairs healing of the rabbit medial collateral ligament

Arthroscopic scaphocapitate fusion without bone graft; clinical and radiological outcomes

PURPOSE

Scaphocapitate fusion (SCF) is an important surgical option for carpal pathologies, which are difficult to manage as Kienböck's disease. With the advantages of arthroscopy combined with percutaneous fixation techniques, arthroscopic scaphocapitate fusion can have the best outcome for the patient from a functional perspective. This study aims to evaluate the clinical, radiological, and functional results of arthroscopic SCF.

METHODS

The study included thirty patients with stage IIIB and IIIC Kienböck's disease. The articular surfaces were prepared using arthroscopic burr then fixed by Herbert screw. The mean follows up period was about 29 months.

RESULTS

SCF was achieved in approximately seven weeks. There was a statistically significant difference in pre- and post-operative grip strength and Mayo wrist score.

CONCLUSION

According to our study findings, arthroscopic SCF may be performed with significant improvements and satisfactory clinical and functional results in patients with stage IIIB and IIIC Kienböck's disease.

The effect of local sympatholysis on bone-tendon interface healing in a murine rotator cuff repair model

Background

Although neuroregulation plays an important role in tissue healing, the key neuroregulatory pathways and related neurotransmitters involved in bone-tendon interface (BTI) healing are still unknown. It is reported that sympathetic nerves can regulate cartilage and bone metabolism, which are the basic aspects of BTI repair after injury, through the release of norepinephrine (NE). Thus, the purpose of this study was to explore the effect of local sympatholysis (LS) on BTI healing in a murine rotator cuff repair model.

Methods

Specifically, C57BL/6 mice underwent unilateral supraspinatus tendon (SST) detachment and repair was established on a total of 174 mature C57BL/6 mice (12 weeks old): 54 mice were used to examine the sympathetic fibers and its neurotransmitter NE for the representation of sympathetic innervation of BTI, while the rest of them were randomly allocated into (LS) group and control group to verify the effect of sympathetic denervation during BTI healing. The LS group were intervened with fibrin sealant containing 10 ​ng/ml guanethidine, while the control group received fibrin sealant only. Mice were euthanized at postoperative 2, 4 and 8 weeks for immunofluorescent, qRT-PCR, ELISA, Micro-computed tomography (CT), histology and biomechanical evaluations.

Results

Immunofluorescence, qRT-PCR and ELISA evaluations indicated that there were the expression of tyrosine hydroxylase (TH), NE and β2-adrenergic receptor (β2-AR) at the BTI site. All the above showed a trend of increasing at the early postoperative stage and they started to decrease with the healing time after a significant peak. Meanwhile, local sympathetic denervation of BTI was achieved after the use of guanethidine as shown in the NE ELISA outcomes in two groups. QRT-PCR analysis revealed that the healing interface in the LS group expressed more transcription factors, such as Runx2, Bmp2, Sox9, and Aggrecan, than the control group. Further, radiographic data showed that the LS group significantly possessed higher bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and lower trabecular spacing (Tb.Sp) than the control group. Also, histological test results showed that there was more fibrocartilage regenerated at the healing interface in the LS group compared with the control group. Mechanical testing results demonstrated that the failure load, ultimate strength and stiffness in the LS group were significantly higher at postoperative week 4 (P ​< ​0.05), but not at postoperative week 8 (P ​> ​0.05), compared to the control group.

Conclusion

The regulation of sympathetic innervation was involved in the healing process of injured BTI, and local sympathetic denervation by using guanethidine was beneficial for BTI healing outcomes.The translational potential of this article: This is the first study to evaluate the expression and specific role of sympathetic innervation during BTI healing. The findings of this study also imply that the antagonists of β2-AR could serve as a potential therapeutic strategy for BTI healing. Also, we firstly successfully constructed a local sympathetic denervation mouse model by using guanethidine loaded fibrin sealant, which provided a new effective methodology for future neuroskeletal biology study.

Cruciate ligament healing and injury prevention in the age of regenerative medicine and technostress: homeostasis revisited

PURPOSE

This clinical concepts paper discusses the essential elements of cruciate ligament recuperation, micro-trauma repair, and remodeling.

METHODS

Cruciate ligament mechanobiology and tissue heterogeneity, anatomy and vascularity, and synovial membrane and fluid functions are discussed in relationship to deficiency-induced inflammatory responses, nervous and immune system function, recuperation, repair and remodeling, and modern threats to homeostasis.

RESULTS

Cruciate ligament surgical procedures do not appreciate the vital linked functions of the central, peripheral, and autonomic nervous systems and immune system function on knee ligament injury recuperation, micro-trauma repair, and remodeling. Enhanced knowledge of these systems could provide innovative ways to decrease primary non-contact knee injury rates and improve outcomes following reconstruction or primary repair.

CONCLUSIONS

Restoration of knee joint homeostasis is essential to cruciate ligament recuperation, micro-trauma repair, and remodeling. The nervous and immune systems are intricately involved in this process. Varying combinations of high-intensity training, under-recovery, technostress, and environmental pollutants (including noise) regularly expose many athletically active individuals to factors that abrogate the environment needed for cruciate ligament recuperation, micro-trauma repair, and remodeling. Current sports training practice, lifestyle psychobehaviors, and environmental factors combine to increase both primary non-contact knee injury risk and the nervous and immune system dysregulation that lead to poor sleep, increased anxiety, and poorly regulated hormone and cytokine levels. These factors may create a worst-case scenario leading to poor ligament recuperation, micro-trauma repair, and remodeling. Early recognition and modification of these factors may decrease knee ligament injury rates and improve cruciate ligament repair or reconstruction outcomes.

LEVEL OF EVIDENCE

V.

The peripheral neuronal phenotype is important in the pathogenesis of painful human tendinopathy: a systematic review

BACKGROUND

The pathogenesis of tendinopathy is complex and incompletely understood. Although significant advances have been made in terms of understanding the pathological changes in both the extracellular matrix and the cells involved, relatively little is known about the role of neuronal regulation in tendinopathy. The frequent mismatch between tendon pathology and pain may be explained, in part, by differences in the peripheral neuronal phenotype of patients.

QUESTIONS/PURPOSES

The primary purpose of this review was to determine whether evidence exists of changes in the peripheral neuronal phenotype in painful human tendinopathy and, if so, to identify the associated histological and molecular changes. The secondary purpose was to determine if any changes in the peripheral neuronal phenotype reported correlate with pain symptoms.

METHODS

We conducted a systematic review of the scientific literature using the PRISMA and Cochrane guidelines. The Medline and Embase databases were searched using specific search criteria. Only studies analyzing the peripheral tissue of patients with the clinical diagnosis of tendinopathy were included. Inclusion was agreed on by two independent researchers on review of abstracts or full text.

RESULTS

Overall in the 27 included studies, there was clear evidence of changes in the peripheral neuronal phenotype in painful human tendinopathy. The excitatory glutaminergic system was significantly upregulated in seven studies, there was a significant increase in sensory neuropeptide expression in four studies, and there were significant changes in the molecular morphology of tenocytes, blood vessels, and nerves. In rotator cuff tendinopathy, substance P has been shown to correlate with pain and the neural density in the subacromial bursa has been shown to correlate with rest pain.

CONCLUSIONS

The peripheral neuronal phenotype is an important factor in the pathogenesis of painful human tendinopathy. Further research in this area specifically correlating tissue changes to clinical scores has great potential in further developing our understanding of the disease process.

Neuronal regulation of tendon homoeostasis

The regulation of tendon homoeostasis, including adaptation to loading, is still not fully understood. Accumulating data, however, demonstrates that in addition to afferent (sensory) functions, the nervous system, via efferent pathways which are associated with through specific neuronal mediators plays an active role in regulating pain, inflammation and tendon homeostasis. This neuronal regulation of intact-, healing- and tendinopathic tendons has been shown to be mediated by three major groups of molecules including opioid, autonomic and excitatory glutamatergic neuroregulators. In intact healthy tendons the neuromediators are found in the surrounding structures: paratenon, endotenon and epitenon, whereas the proper tendon itself is practically devoid of neurovascular supply. This neuroanatomy reflects that normal tendon homoeostasis is regulated from the tendon surroundings. After injury and during tendon repair, however, there is extensive nerve ingrowth into the tendon proper, followed by a time-dependent emergence of sensory, autonomic and glutamatergic mediators, which amplify and fine-tune inflammation and regulate tendon regeneration. In tendinopathic condition, excessive and protracted presence of sensory and glutamatergic neuromediators has been identified, suggesting involvement in inflammatory, nociceptive and hypertrophic (degenerative) tissue responses. Under experimental and clinical conditions of impaired (e.g. diabetes) as well as excessive (e.g. tendinopathy) neuromediator release, dysfunctional tendon homoeostasis develops resulting in chronic pain and gradual degeneration. Thus there is a prospect that in the future pharmacotherapy and tissue engineering approaches targeting neuronal mediators and their receptors may prove to be effective therapies for painful, degenerative and traumatic tendon disorders.

A multipotent clonal human periodontal ligament cell line with neural crest cell phenotypes promotes neurocytic differentiation, migration, and survival

Repair of injured peripheral nerve is thought to play important roles in tissue homeostasis and regeneration. Recent experiments have demonstrated enhanced functional recovery of damaged neurons by some types of somatic stem cells. It remains unclear, however, if periodontal ligament (PDL) stem cells possess such functions. We recently developed a multipotent clonal human PDL cell line, termed cell line 1-17. Here, we investigated the effects of this cell line on neurocytic differentiation, migration, and survival. This cell line expressed the neural crest cell marker genes Slug, SOX10, Nestin, p75NTR, and CD49d and mesenchymal stem cell-related markers CD13, CD29, CD44, CD71, CD90, CD105, and CD166. Rat adrenal pheochromocytoma cells (PC12 cells) underwent neurocytic differentiation when co-cultured with cell line 1-17 or in conditioned medium from cell line 1-17 (1-17CM). ELISA analysis revealed that 1-17CM contained approximately 50 pg/ml nerve growth factor (NGF). Cell line 1-17-induced migration of PC12 cells, which was inhibited by a neutralizing antibody against NGF. Furthermore, 1-17CM exerted antiapoptotic effects on differentiated PC12 cells as evidenced by inhibition of neurite retraction, reduction in annexin V and caspase-3/7 staining, and induction of Bcl-2 and Bcl-xL mRNA expression. Thus, cell line 1-17 promoted neurocytic differentiation, migration, and survival through secretion of NGF and possibly synergistic factors. PDL stem cells may play a role in peripheral nerve reinnervation during PDL regeneration.

Compression therapy promotes proliferative repair during rat Achilles tendon immobilization

Achilles tendon ruptures are treated with an initial period of immobilization, which obstructs the healing process partly by a reduction of blood circulation. Intermittent pneumatic compression (IPC) has been proposed to enhance tendon repair by stimulation of blood flow. We hypothesized that daily IPC treatment can counteract the deficits caused by 2 weeks of immobilization post tendon rupture. Forty-eight Sprague-Dawley SD) rats, all subjected to blunt Achilles tendon transection, were divided in three equal groups. Group A was allowed free cage activity, whereas groups B-C were immobilized at the operated hindleg. Group C received daily IPC treatment. Two weeks postrupture the rats were euthanatized and the tendons analyzed with tensile testing and histological assessments of collagen organization and collagen III-LI occurrence. Immobilization significantly reduced maximum force, energy uptake, stiffness, tendon length, transverse area, stress, organized collagen diameter and collagen III-LI occurrence by respectively 80, 75, 77, 22, 47, 65, 49, and 83% compared to free mobilization. IPC treatment improved maximum force 65%, energy 168%, organized collagen diameter 50%, tendon length 25%, and collagen III-LI occurrence 150% compared to immobilization only. The results confirm that immobilization impairs healing after tendon rupture and furthermore demonstrate that IPC-treatment can enhance proliferative tendon repair by counteracting biomechanical and morphological deficits caused by immobilization.

Nerve-sparing dorsal and volar approaches to the radiocarpal joint

Surgical approaches to the wrist joint have traditionally been focused on providing wide exposure to allow adequate access to the carpus. In light of recent investigations on the innervation and proprioception of the wrist joint, one should also take into consideration not to denervate the wrist capsule and ligaments. In this manuscript, we propose 2 surgical approaches to the dorsal and volar radiocarpal joint, intended to minimize damage to the innervation of the capsule while providing ample access to the wrist.

Neural stimulation does not mediate attenuated vascular response in ACL-deficient knees: potential role of local inflammatory mediators

Chronic inflammation associated with osteoarthritis (OA) alters normal responses and modifies the functionality of the articular vasculature. Altered responsiveness of the vasculature may be due to excessive neural activity associated with chronic pain and inflammation, or from the production of inflammatory mediators which induce vasodilation. Using laser speckle perfusion imaging (LSPI), blood flow to the medial collateral ligament (MCL) of adult rabbits was measured in denervated ACL transected knees (n = 6) and compared to unoperated control (n = 6) and 6-week anterial cruciate ligament (ACL)-transected knees (n = 6). Phenylephrine and neuropeptide Y were applied to the MCL vasculature in topical boluses of 100 microL (dose range 10(-14) to 10(-8) mol and 10(-14) to 10(-9) mol, respectively). Denervation diminished vasoconstrictive responsiveness to phenylephrine compared to both control and ACL-transected knees. Denervation minimally enhanced vascular responses to neuropeptide Y (NPY) compared to ACL deficiency alone, which nevertheless remained significantly diminished from control responses. To evaluate the potential role of inflammatory dilators in the diminished contractile responses, phenylephrine was coadministered with histamine, substance P, and prostaglandin E(2). High-dose histamine, and low-dose substance P and PGE(2) were able to inhibit contractile responses in the MCL of control knees. Excessive neural input does not mediate diminished vasoconstrictive responses in the ACL transected knee; inflammatory mediators may play a role in the deficient vascular responsiveness of the ACL transected knee.

Neuromuscular recovery pattern after medial collateral ligament disruption in rats

The medial collateral ligament (MCL) is one of the most injured ligaments during sport activities. The resulting joint damage effects on neuromuscular system remain unclear. Thus this study was designed to assess the changes in neuromuscular properties of vastus medialis muscle after MCL transection. Complete rupture of MCL was performed on rats, and dynamic functional assessment during locomotion was achieved before and once a week from 1-5 wk postlesion. Twitch properties and metabo- and mechanosensitive afferent fiber responses to specific stimuli were measured 1, 3, and 5 wk after MCL transection. Results indicated that maximum knee angle measured during the stance phase of the gait cycle was decreased during 3 wk after MCL injury and then recovered. Minimum knee angle measured during the stance phase was decreased during 2 wk and showed compensatory effects at week 5. A stepwise decrease in maximum relaxation rate-to-amplitude ratio concomitant with a stepwise increase in half-relaxation time were observed following MCL injury. Variations in metabosensitive afferent response to chemical (KCl and lactic acid) injections were decreased at week 1 and recovered progressively from week 3 to week 5 postlesion. Recovery of the mechanosensitive afferent response to vibrations was not totally complete after 5 wk. Our data indicate that alteration of the sensory pathways from the vastus medialis muscle could be considered as a source of neuromuscular deficits following MCL transection. Our results should be helpful in clinical purpose to improve the knowledge of the influence exerted by ligament rupture on the motor system and permit development of rehabilitation protocols and exercises more appropriate for recovery of functional stability.

Novel approaches to tendinopathy

PURPOSE

The last decade has seen an evolution in the thinking of tendinopathy from inflammatory to degenerative and hence a change in approaches to treatment.

METHOD

We review the literature in this field to highlight the possibility of neural and neural-induced inflammation in this field.

RESULTS

Neuropathy is a possible source of pain in tendinopathy.

CONCLUSION

Further work is required to develop the neuropathic model of tendinopathy, and to determine whether these neuropathic factors are responsible. The concept of neoneurovascularization being the issue in tendinopathy is established. The underlying mechanisms for the process require further evaluation.

Joint immobilization reduces the expression of sensory neuropeptide receptors and impairs healing after tendon rupture in a rat model

Healing after mobilization versus immobilization was assessed in a model of rat Achilles tendon rupture, by RT-PCR at 8 and 17 days and by histological analyses at 14 and 28 days postrupture. The expression of mRNA for extracellular matrix (ECM) molecules (collagen type I and type III, versican, decorin, and biglycan), and the subjective histological maturation of the healing area were analyzed. Effects of immobilization on healing were related to changes in the peripheral expression of substance P (NK(1))- and calcitonin gene-related peptide (CRLR and RAMP-1)- receptors. At 8 days postinjury, mRNA levels for ECM molecules were equal in both groups. However, by day 17, the ECM mRNA expression in the mobilized group had increased up to approximately 14x that of the immobilized group, which were comparable to intact tendon values. Histological analysis confirmed a higher regenerating activity in the mobilized group, with an increased amount of blood vessels, fibroblasts, and new collagen. The expression of sensory neuropeptide receptors in the mobilized group exhibited a significant increase from 8 to 17 days postinjury similar to the increased ECM mRNA expression, whereas the immobilized group at 17 days exhibited levels comparable to the intact tendon values. Therefore, immobilization postrupture appears to hamper tendon healing, a process which may prove to be directly linked to a downregulated peripheral sensitivity to sensory neuropeptide stimulation.

Nerve growth factor improves ligament healing

Previous work has shown that innervation participates in normal ligament healing. The present study was performed to determine if exogenous nerve growth factor (NGF) would improve the healing of injured ligament by promoting reinnervation, blood flow, and angiogenesis. Two groups of 30 Sprague-Dawley rats underwent unilateral medial collateral ligament transection (MCL). One group was given 10 microg NGF and the other was given PBS via osmotic pump over 7 days after injury. After 7, 14, and 42 days, in vivo blood flow was measured using laser speckle perfusion imaging (LSPI). Morphologic assessments of nerve density, vascularity, and angiogenesis inhibitor production were done in three animals at each time point by immunohistochemical staining for the pan-neuronal marker PGP9.5, the endothelial marker vWF, and the angiogenesis inhibitor thrombospondin-2 (TSP-2). Ligament scar material and structural mechanical properties were assessed in seven rats at each time point. Increased nerve density was promoted by NGF at both 14 and 42 days. Exposure to NGF also led to increased ligament vascularity, as measured by histologic assessment of vWF immunohistochemistry, although LSPI-measured blood flow was not significantly different from controls. NGF treatment also led to decreased expression of TSP-2 at 14 days. Mechanical testing revealed that exposure to NGF increased failure load by 40%, ultimate tensile strength by 55%, and stiffness by 30% at 42 days. There were no detectable differences between groups in creep properties. The results suggest that local application of NGF can improve ligament healing by promoting both reinnervation and angiogenesis, and results in scars with enhanced mechanical properties.

Acceleration of Sensory Neural Regeneration and Wound Healing with Human Mesenchymal Stem Cells in Immunodeficient Rats

The sensory nerve is highly involved in lower extremity wound healing. In diabetic and vascular diseases, impaired nerve function and blood flow delay wound healing. Tissue regeneration using adult stem cells is a targeted therapeutic modality in disorders of nerve and blood supply. Effective delivery using an autologous vascularized fascial flap as a vehicle of stem cells leads to severed sensory nerve recovery, local tissue blood flow, and wound healing. Human MSCs (hMSCs) were transfected with green fluorescent protein (GFP) cDNA and tested for efficiency and proliferation in vitro. The nude rat model with femoral vessel and saphenous nerve severance and ligation was wrapped with a vascularized epigastric flap for GFP-hMSC, fibroblast growth factor-2 (FGF-2), or a combination of both after 2 weeks. Maximum nerve conduction velocity recovered to 70% of the presurgical level in the GFP-hMSC- and FGF-2-treated group at 2 weeks. Blood flow and nerve conduction velocity were positively correlated at 1 week. Wound healing in the ipsilateral paw had significantly improved by 1 week. Histologically, blood vessels and nerves are very organized, and regenerated neuron immunoreactivity of GAP-43 and a nerve regrowth marker of S-100 were remarkable in the human GFP (hGFP)-hMSC and FGF-2-treated group at 2 weeks; therefore, sensory nerve regeneration, blood flow, and wound healing were improved by the administration of stem cells and FGF-2 via a vascularized flap. This may be implicated in clinical denervated and reduced circulation tissue wound healing.

Neuropeptides regulate expression of matrix molecule, growth factor and inflammatory mediator mRNA in explants of normal and healing medial collateral ligament

Denervation degrades normal ligament properties and impairs ligament healing. This suggests that secreted neuromediators, such as neuropeptides, could be modulating cell metabolism in ligament and scar tissue. To test this hypothesis we investigated the effect of exogenous substance P (SP), neuropeptide Y (NPY) or calcitonin gene-related peptide (CGRP) on the mRNA levels for proteins associated with inflammation, angiogenesis, and matrix production in tissue-cultured specimens of normal and injured medial collateral ligament. SP and NPY induced increased mRNA levels for several inflammatory mediators in the 2-week post-injury specimens. All three neuropeptides induced decreases in mRNA levels for healing-associated growth factors and matrix molecules, including basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and collagen types I and III. The results indicate that neuropeptides strongly influence the metabolic activity of cells in healing ligament, particularly at early time points after injury.

Adjuvant neuropeptides can improve neuropathic ligament healing in a rat model

Diminished healing in neuropathic tissues suggests an important regulatory role for peripheral neurogenic factors in connective tissue healing. Although neurogenic factors, including neuropeptides, can induce cell proliferation and influence inflammatory cell chemotaxis in vitro, there is little appreciation of the potential of neuropeptides to affect connective tissue healing in vivo. We created both efferent and afferent peripheral neuropathies in 55 female Wistar rats. First, we showed that neuropathy led to impaired healing of ruptured ligaments. We then showed that local delivery of specific neuropeptides could reverse the functional deficits of these neuropathic ligaments in only 2 weeks. In substance P and vasoactive intestinal peptide-treated medial collateral ligaments (MCLs), the mechanical properties of these healing neuropathic tissues returned to values at or above normally innervated, intact ligaments. In addition, neuropeptide Y stimulated MCL healing in this model. These findings suggest a new paradigm to improve neuropathic soft connective tissue healing.

Physical activity modulates nerve plasticity and stimulates repair after Achilles tendon rupture

In a rat model of tendon rupture using semiquantitative methodology, healing was assessed according to the diameter of newly organized collagen and the occurrence of the sensory neuropeptides (SP, CGRP) in relation to different levels of physical activity. Normally, innervation of the Achilles tendon is confined to the paratenon. After rupture new nerve fibers grow into the tendon proper, but disappear after healing. In a first experiment to establish peak tissue and nerve regeneration after rupture, tendon tissues from freely moving rats were collected consecutively over 16 weeks. A peak increase in organized collagen and nerve ingrowth was observed between week 2 to 4 post rupture. Therefore, in a second experiment week 4 was chosen to assess the effect of physical activity on tendon healing in three groups of rats, that is, wheel running, plaster treated, and freely moving (controls). In the wheel-running group, the diameter of newly organized collagen was 94% ( p = 0.001) greater than that in the plaster-treated group and 48% ( p = 0.02) greater than that in the controls. Inversely, the neuronal occurrence of CGRP in the tendon proper was 57% ( p = 0.02) lower in the wheel-running group than that in the plaster-treated group and 53% ( p = 0.02) lower than that in the controls, suggesting an earlier neuronal in-growth and disappearance in the more active group. Physical activity speeds up tendon healing, which may prove to be linked to accelerated neuronal plasticity.

Immunohistochemical analysis of wrist ligament innervation in relation to their structural composition

PURPOSE

To analyze ligament innervation and the structural composition of wrist ligaments to investigate the potential differences in sensory and biomechanical functions.

METHODS

The ligaments analyzed were the dorsal radiocarpal, dorsal intercarpal, scaphotriquetral, dorsal scapholunate interosseous, scaphotrapeziotrapezoid, radioscaphoid, scaphocapitate, radioscaphocapitate, long radiolunate, short radiolunate, ulnolunate, palmar lunotriquetral interosseous, triquetrocapitate, and triquetrohamate ligaments. The ligaments were harvested from 5 cadaveric, fresh-frozen specimens. By using the immunohistochemical markers p75, Protein Gene Product 9.5, and S-100 protein, the mechanoreceptors and nerve fibers could be identified.

RESULTS

The innervation pattern in the ligaments was found to vary distinctly, with a pronounced innervation in the dorsal wrist ligaments (dorsal radiocarpal, dorsal intercarpal, scaphotriquetral, dorsal scapholunate interosseous), an intermediate innervation in the volar triquetral ligaments (palmar lunotriquetral interosseous, triquetrocapitate, triquetrohamate), and only limited/occasional innervation in the remaining volar wrist ligaments. The innervation pattern also was reflected in the structural differences between the ligaments. When present, mechanoreceptors and nerve fibers were consistently found in the loose connective tissue in the outer region (epifascicular region) of the ligament. Hence, ligaments with abundant innervation had a large epifascicular region, as compared with the ligaments with limited innervation, which consisted mostly of densely packed collagen fibers.

CONCLUSIONS

The results of our study suggest that wrist ligaments vary with regard to sensory and biomechanical functions. Rather, based on the differences found in structural composition and innervation, wrist ligaments are regarded as either mechanically important ligaments or sensory important ligaments. The mechanically important ligaments are ligaments with densely packed collagen bundles and limited innervation. They are located primarily in the radial, force-bearing column of the wrist. The sensory important ligaments, by contrast, are richly innervated although less dense in connective tissue composition and are related to the triquetrum. The triquetrum and its ligamentous attachments are regarded as key elements in the generation of the proprioceptive information necessary for adequate neuromuscular wrist stabilization.

Denervation alters mRNA levels of repair-associated genes in a rabbit medial collateral ligament injury model

Previous experiments revealed that denervation impairs healing of the MCL. This suggested the hypothesis that denervation would decrease repair-associated mRNA levels in the injured MCL when compared with normally innervated injured MCL. Adult, skeletally mature female rabbits were assigned to one of four groups: unoperated control, femoral nerve transection alone (denervated controls), MCL partial tear or denervated MCL partial tear. At three days, two weeks, six weeks or sixteen weeks post-surgery, cohorts of 6 rabbits from each experimental group were killed. Ligaments were harvested, RNA extracted and RT-PCR was performed using rabbitspecific primers. In the denervated injury group, mRNA levels for the angiogenesis-associated gene MMP-13, matrix components Collagen I and III, growth factor TGF-beta and angiogenesis inhibitors TIMP-3, and TSP-1 had all increased by two-weeks post-injury, in comparison to the non-denervated injury group (p < or = 0.01). An increased level of TSP-1 mRNA was also detected in the denervated injured group at sixteen weeks post injury (p < or = 0.01). Contrary to the initial hypothesis, denervation led to increased mRNA levels for many relevant molecules during the early stages of MCL healing. Thus, inappropriate timing of over-expression of some molecules may potentially contribute to the decreased quality of the scar tissue, particularly molecules such as TSP-1. Neuronal derived factors strongly influence the in vivo metabolic activity of ligament and scar fibroblasts in the initial phases of healing.

The healing rabbit medial collateral ligament of the knee responds to systemically administered glucocorticoids differently than the uninjured tissues of the same joint or the uninjured MCL: a paradoxical shift in impact on specific mRNA levels and MMP-13 protein expression in injured tissues

The impact and molecular mechanism of action of glucocorticoids in connective tissues is largely unclear, even though widely used, and whether factors such as injury and inflammation modulate this response has not been elucidated. This study describes the role of glucocorticoids in the regulation of mRNA levels for collagens I and III, MMP-13, biglycan, decorin, COX-2 and the glucocorticoid receptor in connective tissues of normal and injured joints in an established rabbit in vivo MCL scar model, and examines the potential mechanism(s) involved. In vitro promoter studies were performed using an MMP-13 promoter-luciferase expression construct in transient transfection assays with a rabbit synovial cell line (HIG-82) to identify sites of glucocorticoid-mediated transcriptional regulation and the promoter elements involved. The in vivo results indicate that scar tissue from different phases of healing (early inflammatory, granulation tissue and neovascular, and later remodelling phases, respectively) displays a different pattern of responsiveness to glucocorticoid treatment than uninjured tissue and that this responsiveness is gene dependent. The most significant impact was seen for genes such as collagen I, collagen III and MMP-13, all of which are involved in connective tissue structure and remodelling. The in vitro studies confirmed the apparent in vivo glucocorticoid-mediated response of MMP-13 mRNA and implicated the AP-1 site of the MMP-13 promoter in this regulation. Immunohistochemistry studies showed increased MMP-13 protein expression, consistent with the mRNA findings, following glucocorticoid treatment in injured tissue but not normal tissues. In conclusion, connective tissue responsiveness to glucocorticoid treatment varies depending on injury and the stage of healing of the tissue, and consequently, glucocorticoid-responsiveness may be modulated differently in states of injury and inflammation.

Unilateral Severe Chronic Periodontitis Associated With Ipsilateral Surgical Resection of Cranial Nerves V, VI, and VII

BACKGROUND

The central and peripheral nervous systems participate in several local physiological and pathological processes. There is experimental evidence that the inflammatory, local immune, and wound healing responses of a tissue can be modulated by its innervation. The aim of this clinical report is to present a case of unilateral severe periodontitis associated with ipsilateral surgical resection of the fifth, sixth, and seventh cranial nerves and to discuss the possible contribution of the nervous system to periodontal pathogenesis.

METHODS

A 39-year-old female patient with a history of a cerebrovascular accident caused by a right pontine arteriovenous malformation and destruction of the right fifth, sixth, and seventh cranial nerves was diagnosed with severe chronic periodontitis affecting only the right maxillary and mandibular quadrants. The patient's oral hygiene was similar for right and left sides of the mouth. Percentages of tooth surfaces carrying dental plaque were 41% and 36% for right and left sides, respectively. Non-surgical and surgical periodontal therapy was performed, and the patient was placed on a regular periodontal maintenance schedule.

RESULTS

Healing following initial periodontal therapy and osseous periodontal surgery occurred without complications. Follow-up clinical findings at 1 year revealed stable periodontal health.

CONCLUSIONS

This case report suggests that periodontal innervation may contribute to the regulation of local processes involved in periodontitis pathogenesis. It also suggests that periodontal therapy can be performed successfully at sites and in patients affected by paralysis.

What do we mean by the term "inflammation"? A contemporary basic science update for sports medicine

Most practicing sports medicine clinicians refer to the concept of "inflammation" many times a day when diagnosing and treating acute and overuse injuries. What is meant by this term? Is it a "good" or a "bad" process? The major advances in the understanding of inflammation in recent years are summarised, and some clinical implications of the contemporary model of inflammation are highlighted.

A laser speckle imaging technique for measuring tissue perfusion

Laser Doppler imaging (LDI) has become a standard method for optical measurement of tissue perfusion, but is limited by low resolution and long measurement times. We have developed an analysis technique based on a laser speckle imaging method that generates rapid, high-resolution perfusion images. We have called it laser speckle perfusion imaging (LSPI). This paper investigates LSPI output and compares it to LDI using blood flow models designed to simulate human skin at various levels of pigmentation. Results show that LSPI parameters can be chosen such that the instrumentation exhibits a similar response to changes in red blood cell concentration (0.1%-5%, 200 microL/min) and velocity (0-800 microL/min, 1% concentration) and, given its higher resolution and quicker response time, could provide a significant advantage over LDI for some applications. Differences were observed in the LDI and LSPI response to tissue optical properties. LDI perfusion values increased with increasing tissue absorption, while LSPI perfusion values showed a slight decrease. This dependence is predictable, owing to the perfusion algorithms specific to each instrument, and, if properly compensated for, should not influence each instrument's ability to measure relative changes in tissue perfusion.

Gene intervention in ligament and tendon: current status, challenges, future directions

Ligament and tendon injuries are common clinical problems. Healing of these tissues occurs, but their properties do not return to normal. This predisposes to recurrent injuries, instability and arthritis, loss of motion and weakness. Gene therapy offers a novel approach to the repair of ligaments and tendons. Introduction of genes into ligaments and tendons using vectors has been successful. Marker genes and therapeutic genes have been introduced into both tissues with evidence of corresponding functional alterations. In addition, gene transfer has been used to manipulate the healing environment, opening the possibility of gene transfer to investigate ligament and tendon development and homeostasis, in addition to using this technology therapeutically. Several factors modulate the 'success' of gene transfer in these tissues.

Blockade of the sympathetic nervous system degrades ligament in a rat MCL model

We hypothesize that blockade of the sympathetic nervous system degrades ligament. We tested this hypothesis in a rat medial collateral ligament (MCL) model. Fifteen animals were treated for 10 days with the sympathetic chemotoxin guanethidine using osmotic pumps, whereas 15 control rats received pumps containing saline. A reduction in plasma concentrations of norepinephrine in the guanethidine rats indicated a significant decrease in sympathetic nerve activity. Vasoactive intestinal peptide and neuropeptide Y were decreased in MCLs from guanethidine animals, as quantified by radioimmunoassays. Tissue vascularity was substantially increased in guanethidine MCLs, whereas mechanical properties were significantly decreased. Proteases, such as matrix metalloproteinases (MMP) and cysteine proteases, play a major role in ligament degradation. The proteases MMP-13, cathepsin K, and tartrate-resistant acid phosphatase (TRAP) have collagenolytic activity and have been shown in rat ligament tissues. To determine whether the degradation seen in this study was due to protease activity, we determined the expression of these enzymes in control and treated MCLs. Real-time quantitative PCR revealed that guanethidine treatment increased expression of MMP-13 and cathepsin K mRNAs, although overall expression levels of MMP-13 and TRAP were relatively low. Histology also identified increases in TRAP and cathepsin K, but not MMP-13, in guanethidine-treated tissues. Results support our hypothesis that blockade of the sympathetic nervous system substantially degrades ligament.

Indirect injury stimulates scar formation-adaptation or pathology?

In several animal models of osteoarthritis induced by cruciate ligament transection, a dense, scar-like tissue mass forms rapidly on the medial side of the knee joint. This mass mimics clinical fibrosis that sometimes occurs after joint surgery. It is unknown exactly why this medial tissue mass forms and what cells are involved in its formation. This study characterizes this medial mass by histology, biochemistry, and the expression of types I and III collagen mRNA. The medial mass is compared with the medial collateral ligament (MCL) and the MCL epiligament in anterior cruciate-transected and unoperated joints, and to normal skin and skin scar. The morphology of the medial mass resembled the epiligament and skin scar more than the MCL. The concentration of DNA and RNA and the RNA-DNA ratio were elevated dramatically in the medial mass compared with all other tissues including skin scar. However, the mRNA copy number and ratio of collagen types I and III mRNAs did not differ significantly among the medial mass, MCL, epiligament, and skin in either the control or the operated joints. The response of the medial mass, MCL, and MCL epiligament to cruciate transaction involves both hyperplasia and hypertrophy, but without a dramatic shift in cell phenotype. The medial mass may be a useful mimic or model of intraarticular adhesions, hypertrophic scars, ligament sprains, and arthrofibrosis.