Ascorbic acid reduces Ropivacaine-induced myotoxicity in cultured human osteoporotic skeletal muscle cells.

BACKGROUND: Osteoporosis is a worldwide health issue. Loss of bone mass is a potential risk factor for fragility fractures, and osteoporotic fractures place a considerable burden on society. Bone and muscle represent a functional unit in which the two tissues are intimately interconnected. Ropivacaine is a potent local anesthetic used in clinical practice for intraoperative anesthesia and postoperative pain management, in particular for hip surgery. When injected, Ropivacaine can diffuse locally through, in particular in surrounding skeletal muscle tissue, causing dose-dependent cytotoxicity, oxidative stress and myogenesis impairment. Based on those evidences, we focused our attention on Ropivacaine-induced cytotoxicity on cultured human myoblasts. METHODS: Primary human myoblasts and myotubes from healthy subjects, osteoarthritic and osteoporotic patients (OP) were cultured in the presence of Ropivacaine. In some experiments, ascorbic acid (AsA) was added as a potent antioxidant agent. Cell viability and ROS levels were evaluated to investigate the myotoxic activity and Real-Time PCR and Western blot analysis carried out to investigate the expression of proliferation and myogenic markers. RESULTS: A dose-dependent decrease of cell viability was observed after Ropivacaine exposure in both OP myoblasts and myotubes cultures, whereas those effects were not observed in the presence of Propofol, a general anesthetic. The adding of AsA reduced Ropivacaine negative effects in OP myoblast cultures. In addition, Ropivacaine exposure also increased ROS levels and upregulated Nox4 expression, an enzyme primarily implicated in skeletal muscle ROS generation. AsA treatment counteracted the oxidant activity of Ropivacaine and partially restored the basal condition in cultures. Positive myogenic markers, such as MyoD and Myf5, were downregulated by Ropivacaine exposure, whereas myostatin, a negative regulator of muscle growth and differentiation, was upregulated. The phenotypic deregulation of myogenic controllers in the presence of Ropivacaine was counteracted by AsA treatment. CONCLUSIONS: Our findings highlight the oxidative stress-mediated myotoxic effect of Ropivacaine on human skeletal muscle tissue cell cultures, and suggest treatment with AsA as valid strategy to mitigate its negative effects and allowing an ameliorated functional skeletal muscle recovery in patients undergoing hip replacement surgery for osteoporotic bone fracture.

Gaps and alternative surgical and non-surgical approaches in the bone fragility management: an updated review.

Osteoporotic fractures are one of the major problems facing healthcare systems worldwide. Undoubtedly, fragility fractures of the hip represent a far greater burden in terms of morbidity, mortality, and healthcare costs than other fracture sites. However, despite the significant impact on the health and quality of life of older adults, there is a general lack of awareness of osteoporosis, which results in suboptimal care. In fact, most high-risk individuals are never identified and do not receive adequate treatment, leading to further fragility fractures and worsening health status. Furthermore, considering the substantial treatment gap and the proven cost-effectiveness of fracture prevention programs such as Fracture Liaison Services, urgent action is needed to ensure that all individuals at high risk of fragility fracture are adequately assessed and treated. Based on this evidence, the aim of our review was to (i) provide an overview and comparison of the burden and management of fragility fractures, highlighting the main gaps, and (ii) highlight the importance of using alternative approaches, both surgical and non-surgical, with the aim of implementing early prevention of osteoporotic fractures and improving the management of osteoporotic patients at imminent and/or very high risk of fracture.

PTX3 Effects on Osteogenic Differentiation in Osteoporosis: An In Vitro Study.

Pentraxin 3 (PTX3) is a glycoprotein belonging to the humoral arm of innate immunity that participates in the body's defence mechanisms against infectious diseases. It has recently been defined as a multifunctional protein, given its involvement in numerous physiological and pathological processes, as well as in the pathogenesis of age-related diseases such as osteoporosis. Based on this evidence, the aim of our study was to investigate the possible role of PTX3 in both the osteoblastic differentiation and calcification process: to this end, primary osteoblast cultures from control and osteoporotic patients were incubated with human recombinant PTX3 (hrPTX3) for 72 h. Standard osteinduction treatment, consisting of ß-glycerophosphate, dexamethasone and ascorbic acid, was used as control. Our results showed that treatment with hrPTX3, as well as with the osteogenic cocktail, induced cell differentiation towards the osteoblastic lineage. We also observed that the treatment not only promoted an increase in cell proliferation, but also the formation of calcification-like structures, especially in primary cultures from osteoporotic patients. In conclusion, the results reported here suggest the involvement of PTX3 in osteogenic differentiation, highlighting its osteoinductive capacity, like the standard osteoinduction treatment. Therefore, this study opens new and exciting perspectives about the possible role of PTX3 as biomarker and therapeutic agent for osteoporosis.

DNA Methylation Signatures of Bone Metabolism in Osteoporosis and Osteoarthritis Aging-Related Diseases: An Updated Review.

DNA methylation is one of the most studied epigenetic mechanisms that play a pivotal role in regulating gene expression. The epigenetic component is strongly involved in aging-bone diseases, such as osteoporosis and osteoarthritis. Both are complex multi-factorial late-onset disorders that represent a globally widespread health problem, highlighting a crucial point of investigations in many scientific studies. In recent years, new findings on the role of DNA methylation in the pathogenesis of aging-bone diseases have emerged. The aim of this systematic review is to update knowledge in the field of DNA methylation associated with osteoporosis and osteoarthritis, focusing on the specific tissues involved in both pathological conditions.

Reviewing Bone Marrow Edema in Athletes: A Difficult Diagnostic and Clinical Approach.

Bone marrow edema (BME) is defined as an area of low signal intensity on T1-weighted (T1W) MRI images and associated with intermediate or high signal intensity findings on T2-weighted (T2W) MRI images. BME represents a typical imaging finding that characterizes common stress-related bone injuries of professional and amateur athletes. The etiology of stress-related injuries is influenced by numerous factors, including the initiation of a new sports activity or changes in an existing training protocol. The clinical significance of BME remains unclear. However, a correlation between the imaging pattern of BME, the clinical history of the patient and the type of sports activity practiced is essential for correct diagnosis and adequate therapeutic treatment. It is also important to clarify whether there is a specific threshold beyond which exercise can adversely affect the bone remodeling process, as the clinical picture may degenerate into the presence of BME, pain and, in the most severe cases, bone loss. In our review, we summarize the current knowledge on the etiopathogenesis and treatment options for BME and highlight the main aspects that make it difficult to formulate a correct diagnosis and establish an adequate therapeutic treatment.

Effects of Simulated Microgravity on Muscle Stem Cells Activity.

BACKGROUND/AIMS: The study of the effects of simulated microgravity on primary cultures of human satellite cells represents a reliable model for identifying the biomolecular processes involved in mechanic load-related muscle mass loss. Therefore, this study aims to investigate the role of myostatin and Bone Morphogenetic Protein-2 in human satellite cells response to simulated microgravity condition. METHODS: In order to identify the main molecules involved in the phenomena of degeneration/regeneration of muscle tissue related to the alteration of mechanic load, we performed a morphological and immunohistochemical study on 27 muscle biopsies taken from control, osteoporotic and osteoarthritic patients, underwent hip arthroplasty. For each patient, we set up primary satellite cell cultures subjected to normogravity and simulated microgravity (110h) regimens. Cellular functionality has been studied through a morphological evaluation performed by optical microscopy, and an ultrastructural evaluation carried out by transmission electron microscopy. Furthermore, we evaluated the expression of Bone Morphogenetic Protein-2 and myostatin through immunocytochemical reactions. RESULTS: Our results showed that in the very early phases of simulated microgravity condition the satellite cells are more active than those subjected to the normogravity regime, as demonstrated by both the increase in the number of myotubes and the significant increase in the expression of Bone Morphogenetic Protein-2 in all experimental groups. However, with prolongated exposure to simulated microgravity regime (>72h), satellite cells and new formed myotubes underwent to cell death. It is important to note that, in early phases, simulated microgravity can stimulate the formation of new myotubes from satellite cells derived by osteoporotic patients. Furthermore, we observed that simulated microgravity can induce changes in myostatin expression levels by group-dependent variations. CONCLUSION: The results obtained allowed us to hypothesize a possible molecular mechanism of response to simulated microgravity, confirming the importance of Bone Morphogenetic Protein-2 and myostatin in the physio-pathogenesis of muscle tissue. In addition, these data can lay the foundation for new therapeutic approached in the prevention/cure of osteoporosis and sarcopenia.

Differences between muscle from osteoporotic and osteoarthritic subjects: in vitro study by diffusion-tensor MRI and histological findings.

BACKGROUND: Osteoarthritis and osteoporosis are strongly coupled with alterations of muscles quality and fats metabolism. However, there are no studies for investigating possible differences between osteoporotic and osteoarthritic muscles. Understanding muscle-bone and muscle-cartilage interactions would be of high clinical value. AIM: Investigate potential microstructural and physiological differences between osteoporotic and osteoarthritic muscles by diffusion Nuclear Magnetic Resonance (NMR) imaging (diffusion MRI) and histological findings. METHODS: Vastus-lateralis muscles excised from osteoporotic (n = 26, T Score < - 2.5, Kellgren-Lawrence ≤ 2) and osteoarthritic (n = 26, T Score > - 2.5, Kellgren--Lawrence 3 and 4) age-matched women were investigated by NMR relaxometry, diffusion-tensor imaging (DTI) at 9.4 T, and histological techniques. Intramyocellular (IMCL) and extramyocellular (EMCL) lipid were quantified. The percentage and mean diameters of fibers I and II were evaluated. Relationship between mean diffusivity (MD), fractional anisotropy (FA), the DTI eigenvalues (λ1, λ2, λ3), histological findings in muscles and clinical data (Kellgren-Lawrence and T score, age, menopausal age, body mass index) were studied. Pairwise comparisons between groups were made using one-way analysis of variance and correlation between variables was assessed with linear correlation analysis (Pearson's r coefficient). RESULTS: Osteoporotic muscles showed higher MD, λ1, λ2, λ3 compared to osteoarthritis ones. This is explainable with a significant higher density of IMCL droplets found inside the osteoarthritic muscles and a large amount of fibrotic tissue and IMCL infiltration between fibers, i.e. in endomysium and perimysium that lead to a more hindered diffusion. Furthermore, histological analysis suggests mitochondrial degeneration as the origin of the greatest amount of IMCL droplets in osteoarthritic muscles. CONCLUSION: This work highlights differences between muscles of osteoporotic and osteoarthritic subjects that can be quantified by NMR DTI investigations.

Densitometric evaluation of bone remodelling around Trabecular Metal Primary stem: a 24-month follow-up.

BACKGROUND: Today, an increasing number of total hip arthroplasty (THA) procedures are being performed. Osseointegration is a physiological phenomenon that leads to the direct anchorage of an implant by the formation of bony tissue around the implant without the growth of fibrous tissue at the bone-implant interface. Several factors may affect this phenomenon: some of these depend on the patient and others may depend on implant design and materials. Variations in periprosthetic bone mineral density (BMD) can be studied through several scans by dual energy X-ray absorptiometry (DEXA) around the femoral stem. AIMS: The purpose of this study is to investigate correlations between periprosthetic BMD and the factors affecting osseointegration. METHODS: We retrospectively analysed patients who underwent primary THA. In all the patients, Trabecular Metal Primary (TMP), a standard uncemented tapered stem with a proximal porous tantalum coating, was implanted. Preoperatively, postoperatively, 3 and 6 months, 1 year and 2 years after implantation, DEXA scans were performed around the femoral stem. The patients were matched for diagnosis, sex, BMD of the lumbar spine and contralateral femur, Body Mass Index and age. RESULTS: One hundred and eight patients (51 males and 57 females) with a mean age of 73 years were studied. Different BMD changing patterns were observed and a greater bone resorption was noted in all the conditions associated with poor bone quality. DISCUSSION: The proximal coating of Trabecular Metal Primary (TMP) seemed to be effective in promoting new bone formation in the proximal femur also in the conditions associated with poor bone quality. CONCLUSIONS: At the present time, DEXA is considered the most reliable tool for evaluating bone remodelling after THA.

Augmentation of tibial plateau fractures with an injectable bone substitute: CERAMENT™. Three year follow-up from a prospective study.

BACKGROUND: Reduction of tibial plateau fractures and maintain a level of well aligned congruent joint is key to a satisfactory clinical outcome and is important for the return to pre-trauma level of activity. Stable internal fixation support early mobility and weight bearing. The augmentation with bone graft substitute is often required to support the fixation to mantain reduction. For these reasons there has been development of novel bone graft substitutes for trauma applications and in particular synthetic materials based on calcium phosphates and/or apatite combined with calcium sulfates. Injectable bone substitutes can optimize the filling of irregular bone defects. The purpose of this study was to assess the potential of a novel injectable bone substitute CERAMENT™|BONE VOID FILLER in supporting the initial reduction and preserving alignment of the joint surface until fracture healing. METHODS: From June 2010 through May 2011 adult patients presenting with acute, closed and unstable tibial plateau fractures which required both grafting and internal fixation, were included in a prospective study with percutaneous or open reduction and internal fixation (ORIF) augmented with an injectable ceramic biphasic bone substitute CERAMENT™|BONE VOID FILLER (BONESUPPORT™, Lund, Sweden) to fill residual voids. Clinical follow up was performed at 1, 3, 9 and 12 months and any subsequent year; including radiographic analysis and Rasmussen system for knee functional grading. RESULTS: Twenty four patients, balanced male-to-female, with a mean age of 47 years, were included and followed with an average of 44 months (range 41-52 months). Both Schatzker and Müller classifications were used and was type II or 41-B3 in 7 patients, type III or 41-B2 in 12 patients, type IV or 41-C1 in 2 patients and type VI or 41-C3 in 3 patients, respectively. The joint alignement was satisfactory and manteined within a range of 2 mm, with an average of 1.18 mm. The mean Rasmussen knee function score was 26.5, with 14 patients having an excellent result and the remaining 10 with a good result. CONCLUSION: It can be concluded that radiological and clinical outcome was satisfactory and obtained in all cases without complications. This injectable novel biphasic hydroxyapatite and calcium sulfate ceramic material is a valuable armamentarium in the treatment of trauma where bone graft is required.

Thoraco-lumbar traumatic vertebral fractures augmentation by osteo-conductive and osteo-inductive bone substitute containing strontium-hydroxyapatite: our experience.

INTRODUCTION: The aim of our study was to evaluate the effectiveness of osteointegrable strontium-hydroxyapatite (Sr-HA) bone cement in the treatment of thoracolumbar traumatic vertebral fractures by percutaneous vertebroplasty (VTP). METHODS: We treated 35 patients [29 (82.85 %) men, 6 (17.14 %) women, mean age 34.05 ± 8.36 years (range 21-54 years)] with single type A1.1 and A1.2 thoracolumbar traumatic vertebral fracture without endospecal bone fragments. Pain intensity was evaluated before and at 1 day; 1 week; and 1, 6, and 12 months after VTP by a 10-point visual analog scale (VAS) score (0 = no pain, 10 = unbearable pain). Physical status and quality of life were evaluated by Oswestry Disability Index (ODI) questionnaire before and 1, 6, and 12 months after VTP. RESULTS: Procedural technical success was achieved in all patients with no deaths observed during follow-up. In three patients (8.57 %), postprocedural CT showed cement leakages: one intradiscal and two in venous plexus. No adjacent vertebral body fractures nor intrasomatic recollapse was detected. The VAS and ODI scores showed a statistically significant reduction 1 week after procedure (P value <0.0001) with a progressive statistically significant reduction during follow-up (P value <0.0001). Twenty-three patients (65.71 %) assigned a value of 0 to the VAS scale at 1 year after treatment. CONCLUSIONS: Strontium-hydroxyapatite bone cement is an effective and safe bone filler in percutaneous vertebroplasty with low leakage rate and absence of major complications when performed by a skilled equipe. It allows an immediate and long-lasting stabilization with a significant pain reduction and quality of life improvement.

Osseointegration of Fitmore stem in total hip arthroplasty.

Currently, an increasing number of younger patients undergo total hip arthroplasty surgery. This has led to a minimal invasive approach and the use of short, bone preserving, femoral stems. In this study, we sought to evaluate osseointegration of the Fitmore stem (Zimmer, Inc; Warsaw, IN) during the first 12 mo after surgery, which reflects the biological phenomenon of osseointegration with radiographic evaluation and bone densitometry (dual-energy X-ray absorptiometry). We evaluated 33 patients (mean age 62.3) using dual-energy X-ray absorptiometry scan around the stem and X-ray. Moreover, we studied functional recovery using the Harris Hip Score, timed up and go test, and a quality of life form (SF-36), during the follow-up period. At 12 mo, we observed an increased periprosthetic bone mineral density in region of interest 1 (1.7%) and region of interest 7 (8.3%), where there is usually a greater amount of bone resorption. Also Harris Hip Score, timed up and go test, and SF-36 showed an improvement of clinical conditions of all patients. We also used a control group with a standard stem implanted. Because this is the first study correlating osseointegration and clinical outcome of the Fitmore stem, further clinical studies will be necessary to confirm good/positive results and a long stable fixation.

Stress fractures in the elderly: different pathogenetic features compared with young patients.

Stress fractures mainly occur in the lower limb as a result of cyclic submaximal stresses. Most commonly affected by this specific type of fractures are young athletes, military or elderly subjects with metabolic bone diseases like osteoporosis. In consideration of the heterogeneity of affected patients is presumable that there are different pathogenic mechanisms. In young person bone tissue, although metabolically intact, is not able to withstand the stresses to which it is chronically subjected, also because of muscle fatigue. This leads to a macrostructural failure and to the development of "fatigue" fractures. Instead, in elderly patients, there are numerous physiological conditions that determine a bone metabolism alteration. This is the main reason for the structural changes in trabecular and cortical bone, which is reflected in reduced biomechanical strength. In addition, muscular situation, such as muscle fiber atrophy, is unable to correctly support bone tissue, leading to the development of insufficiency fractures.

Osteoporosis and sarcopenia: the connections.

Osteoporosis and sarcopenia are the most frequent musculoskeletal disorders affecting older people. Osteoporosis is a widespread disorder affecting millions of individuals of all ethnic backgrounds worldwide, particularly among older women. It is characterized by reduced bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in the risk of fracture. Sarcopenia is considered to be one of the major factors responsible for functional limitations and motor dependency in elderly persons. In age-related muscle atrophy, a decrease in muscle fiber size and number, and a preferential loss of type II fibers have been reported. A decrease in the circulating levels of specific hormones (e.g., estrogen, testosterone, growth hormone, and insulin-like growth factor-1) has been shown to be associated with sarcopenia and this appears to play an important role in its pathogenesis.

Lumbar spine MRI in upright position for diagnosing acute and chronic low back pain: statistical analysis of morphological changes.

BACKGROUND: Patients with low back pain frequently demonstrate recumbent magnetic resonance imaging (MRI) alterations not always related to homogeneous clinical symptoms. The purpose of this study was to evaluate and quantify the statistical significance of variations of some anatomical parameters of the lumbosacral spine and reveal occult disc pathologies from recumbent to upright position in patients with acute and chronic low back pain. MATERIALS AND METHODS: Fifty-seven patients complaining of low back pain (27 women, 30 men) underwent dynamic lumbosacral MRI with a 0.25-T tilting system (G-scan Esaote). We settled five parameters for which variations have been evaluated: lumbosacral angle, lordosis angle, L3-L4 intersomatic disc height, L3-L4 interspinous processes distance, and widest anteroposterior dural sac diameter. Images were obtained in both recumbent and upright positions. RESULTS: Statistically significant differences [one-way analysis of variance (ANOVA), p = 0.0043] were found between each pair of values of parameters sampled in recumbent and upright positions. In 70 % of patients, on visual qualitative analysis only, an increment of disc protrusions and/or spondylolisthesis was found in the upright position; in three cases, in the upright position only, an interarticular pseudocyst was found. CONCLUSIONS: Dynamic MRI with an open-configuration, low-field tilting MRI system is a feasible and promising tool to study degenerative pathology of the spine. Moreover, in cases of low back pain with negative MRI in the recumbent position or in patients with pain in the upright position only, tilting MRI permits visualization of occult spine and disc pathologies in patients with acute or chronic low back pain.

Osteosarcopenia and Pain: Do We Have a Way Out?

Osteosarcopenia (OSP) is a geriatric syndrome characterized by the coexistence of osteoporosis and sarcopenia and associated with an increased risk of fragility fractures, disability, and mortality. For patients with this syndrome, musculoskeletal pain represents the most significant challenge since, in addition to limiting the individual's functionality and promoting disability, it has a huge psychological burden involving anxiety, depression, and social withdrawal. Unfortunately, the molecular mechanisms involved in the development and persistence of pain in OSP have not yet been fully elucidated, although immune cells are known to play a key role in these processes. Indeed, they release several molecules that promote persistent inflammation and nociceptive stimulation, resulting in the gating of ion channels responsible for the generation and propagation of the noxious stimulus. The adoption of countermeasures to counteract the OSP progression and reduce the algic component appears to be necessary, providing patients with a better quality of life and greater adherence to treatment. In addition, the development of multimodal therapies, based on an interdisciplinary approach, appears to be crucial, combining the use of anti-osteoporotic drugs with an educational programme, regular physical activity, and proper nutrition to eliminate risk factors. Based on this evidence, we conducted a narrative review using the PubMed and Google Scholar search engines to summarize the current knowledge on the molecular mechanisms involved in the pain development in OSP and the potential countermeasures to be taken. The lack of studies addressing this topic highlights the need to conduct new research into the resolution of an ever-expanding social problem.

Role of the Vitamin D Receptor (VDR) in the Pathogenesis of Osteoporosis: A Genetic, Epigenetic and Molecular Pilot Study.

The vitamin D receptor (VDR) regulates bone development and calcium homeostasis, suggesting a central role in musculoskeletal diseases such as osteoporosis (OP). Several studies have examined the contribution of VDR polymorphisms and epigenetic signatures in bone metabolism and OP risk, with sometimes inconclusive results. Our study aimed to explore the association between genetic variability, expression and the methylation pattern of VDR with the risk of OP in a cohort of Caucasian patients. Genomic DNA from 139 OP, 54 osteopenic (Ope) and 73 healthy (CTR) subjects were used for genotyping the rs731236 (TaqI), rs2228570 (FokI) and rs11568820 (Cdx2) polymorphisms of the VDR gene by an allelic discrimination assay. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis of VDR expression levels and pyrosequencing analysis of a VDR promoter CpG island were carried out in a subcohort (25 OP and 25 CTR) of subjects. Data obtained showed a significantly higher OP risk for rs11568820 G/A and A/A genotypes (p = 0.05). qRT-PCR revealed lower VDR gene expression levels in the OP group compared to CTR subjects (p = 0.0009), also associated with both the rs11568820 A/A genotype (p = 0.03) and femoral fragility fractures (p = 0.05). No association was found between the methylation pattern of the region analyzed of the VDR promoter and its expression levels. Our results identify a significative association between Cdx2 rs11568820 polymorphism and OP risk. In addition, the VDR transcriptomic profile suggests a putative interconnection with OP progression, providing a useful tool to stratify OP phenotype and fragility fracture risk.

Recombinant irisin prevents cell death and mineralization defects induced by random positioning machine exposure in primary cultures of human osteoblasts: A promising strategy for the osteoporosis treatment.

Spaceflight exposure, like prolonged skeletal unloading, is known to result in significant bone loss, but the molecular mechanisms responsible are still partly unknown. This impairment, characterizing both conditions, suggests the possibility of identifying common signalling pathways and developing innovative treatment strategies to counteract the bone loss typical of astronauts and osteoporotic patients. In this context, primary cell cultures of human osteoblasts derived from healthy subjects and osteoporotic patients were exposed to random positioning machine (RPM) to reproduce the absence of gravity and to exacerbate the pathological condition, respectively. The duration of exposure to RPM was 3 or 6 days, with the aim of determining whether a single administration of recombinant irisin (r-irisin) could prevent cell death and mineralizing capacity loss. In detail, cellular responses were assessed both in terms of death/survival, by MTS assay, analysis of oxidative stress and caspase activity, as well as the expression of survival and cell death proteins, and in terms of mineralizing capacity, by investigating the pentraxin 3 (PTX3) expression. Our results suggest that the effects of a single dose of r-irisin are maintained for a limited time, as demonstrated by complete protection after 3 days of RPM exposure and only partial protection when RPM exposure was for a longer time. Therefore, the use of r-irisin could be a valid strategy to counteract the bone mass loss induced by weightlessness and osteoporosis. Further studies are needed to determine an optimal treatment strategy based on the use of r-irisin that is fully protective even over very long periods of exposure and/or to identify further approaches to be used in a complementary manner.

The collagenolytic action of MMP-1 is regulated by the interaction between the catalytic domain and the hinge region.

The role of the hinge region in the unwinding and cleavage of type I collagen by interstitial collagenase (MMP-1) has been studied at 37 °C and pH 7.3. The collagenolytic processing by MMP-1 displays a very similar overall rate for both chains of collagen I, even though the affinity is higher for the α-1 chain and the cleavage rate is faster for the α-2 chain. MMP-1 binding to collagen I brings about a significant unwinding of the triple-helical arrangement only after the first cleavage step of the α-1 and α-2 chains. The proteolytic processing by wild-type MMP-1 on a synthetic substrate and collagen I has been compared with that observed for site-directed mutants obtained either by truncating the hinge region (∆255-272) or by individually replacing the conserved amino acids Val268, Gly272, and Lys277 of the hinge region with residues observed for the corresponding position in stromelysin-1 (MMP-3), a noncollagenolytic metalloproteinase. The ∆256-272 mutant has no collagenolytic activity, clearly demonstrating the crucial role of this region for the enzymatic processing of collagen I. However, among various mutants investigated, only Gly272Asp shows a dramatically reduced enzymatic activity both on the synthetic substrate and on collagen I. This effect, however, is clearly related to the substituting residue, since substitution of Ala or Asn for Gly272 does not have any effect on the kinetic properties of MMP-1. These data suggest that the substrate specificity of MMP-1 is dictated by the reciprocal structural relationships between the catalytic domain and the carboxy-terminal domain through the conformational arrangement of the hinge region.

Chronic Pain in Musculoskeletal Diseases: Do You Know Your Enemy?

Musculoskeletal pain is a condition that characterises several diseases and represents a constantly growing issue with enormous socio-economic burdens, highlighting the importance of developing treatment algorithms appropriate to the patient's needs and effective management strategies. Indeed, the algic condition must be assessed and treated independently of the underlying pathological process since it has an extremely negative impact on the emotional and psychic aspects of the individual, leading to isolation and depression. A full understanding of the pathophysiological mechanisms involved in nociceptive stimulation and central sensitization is an important step in improving approaches to musculoskeletal pain. In this context, the bidirectional relationship between immune cells and neurons involved in nociception could represent a key point in the understanding of these mechanisms. Therefore, we provide an updated overview of the magnitude of the musculoskeletal pain problem, in terms of prevalence and costs, and summarise the role of the most important molecular players involved in the development and maintenance of pain. Finally, based on the pathophysiological mechanisms, we propose a model, called the "musculoskeletal pain cycle", which could be a useful tool to counteract resignation to the algic condition and provide a starting point for developing a treatment algorithm for the patient with musculoskeletal pain.

Hip replacement in femoral neck fractures: the role of cementation and its technical difficulties.

Hip fractures in elderly patients are an arising problem due to aging of population and still represent a controversial challenge for orthopedic surgeon who should help achieve the best functional recovery in the shortest time. Cementation in hip replacement plays an important role, but it should be carefully planned considering the possible risks. According to the literature, there are still no certainties regarding the superiority of an uncemented implant compared to a cemented one. The purpose of this work is to conduct an overview of the scientific literature that can clarify the advantages and disadvantages of cemented and non-cemented implants from a biological and biomechanical point of view.