1,721,443 research outputs found
Innesti condrali: a che punto siamo?
No full textLe lesioni cartilaginee a tutto spessore sono una patologia di comune riscontro nella pratica ortopedica e la loro incidenza nella popolazione ha mostrato un andamento in crescita negli ultimi anni dovuto all’aumentata richiesta funzionale in particolare dei pazienti over quaranta anni. Diversi autori hanno dimostrato l’efficacia dell’impianto di condrociti autologhi a medio e lungo termine nel trattamento delle lesioni focali traumatiche e degenerative iniziali. L’evoluzione da un concetto di terapia cellulare ad uno di ingegneria tissutale, grazie all’impiego dei supporti tridimensionali o scaffold, ha fornito vantaggi non solo dal punto di vista chirurgico (minore invasività, utilizzo di tecniche artroscopiche, ridotto numero di complicazioni) ma anche dal punto di vista biologico (migliore differenziazione dei condrociti in coltura, omogenea distribuzione delle cellule nel difetto condrale, ridotta incidenza di ipertrofia dell’impianto). L’attenzione dei ricercatori si è focalizzata negli ultimi anni sul miglioramento della tecnica di base ed in particolare su tre temi fondamentali: tipo di cellule da impiantare, scaffold e fattori di crescita. A tal fine i futuri sviluppi prevedranno una migliore selezione delle cellule da impiantare ed eventualmente l’utilizzo della terapia genica per attivare la produzione di specifiche molecole della matrice extracellulare. Inoltre, l’utilizzo delle cellule staminali potrà incrementare la capacità di riparazione. Diversi studi sperimentali stanno valutando l’efficacia di scaffold biomimetici che facilitino la differenziazione di uno stesso impianto in cartilagine ed osso per la riparazione di difetti osteocondrali. L’utilizzo dei bioreattori, associato al prelievo di cellule totipotenti da sedi extraarticolari, di scaffold e di specifici fattori di crescita, consentirà in futuro di avere un tessuto cartilagineo senza dover sottoporre il paziente ad un duplice intervento chirurgico
Gene and protein expression in tendon problems.
No full textINTRODUCTION
Spontaneous tendon rupture and chronic tendon pain are common events in orthopaedic practice, although the underlying pathological processes are not well understood. Most research on tendon injuries has focused on a description of the condition and its management, rather than on the underlying cellular and molecular mechanisms. A genetic factor has been hypothesized in several tendinopathies that could explain why there is an increased risk of contralateral rupture of the Achilles tendon in subjects with a previous rupture.4 The interaction between a particular genetic pattern and the various intrinsic and extrinsic factors affecting tendon healing may develop a tendinopathy. 16 The tenocytes respond to exercise, mechanical strain and injury modifying the synthesis and degradation of the tendon extracellular matrix. 3, 25
This review will highlight the gene expression and the protein analysis of tendon and matrix-degrading enzymes implied in tendon healing and injuries.
MOLECULAR STRUCTURE AND EXTRACELLULAR MATRIX TURNOVER OF TENDON
Tendon is a poorly vascularized, highly specialized, connective tissue with a low metabolism and few cells. The extracellular matrix (ECM) consists of 70% water and 30% dry mass and it is constituted by a complex network of molecules interacting with each other, including collagen fibers, mainly represented by collagen type I (65 to 80% of dry mass), glycosaminoglycans (GAGs), proteoglycans (PGs), glycoproteins, and other noncollagenous proteins. 24 Collagen is arranged in hierarchical levels of increasing complexity, beginning with tropocollagen, a triple-helix polypeptide chain, which unites into fibrils; fibers (primary bundles); fascicles (secondary bundles); tertiary bundles; and the tendon itself. 24 Collagen molecules are surrounded by proteoglycans that are hydrophilic glycoproteins. They are involved in collagen fibrillogenesis and give resistance to compression and tensile stresses. Proteoglycans consist of a core protein with one or more covalently attached glycosaminoglycan chains. These glycosaminoglycan (GAG) chains are long, linear carbohydrate polymers made of repeated dysaccharides units that are negatively charged due to the occurrence of sulphate groups. Decorin and versican are tendon proteoglycans, while aggrecan and biglycan are specific of cartilage. Tenocytes lie in the ECM and contribute to its homeostasis. 24
The molecular structure and the metabolism of ECM is finely regulated, and involves several molecules. Matrix metalloproteases (MMPs) are involved in remodelling of the extracellular matrix of tendons, and the various MMPs can be up- or down-regulated in tendinopathy. 15 There are 23 MMPs in human subdivided into four main groups: collagenases, which cleave native collagen types I, II, and III; gelatinases, which cleave denatured collagens and type IV collagen; stromelysins, which degrade proteoglycans, fibronectin, casein, collagen types III, IV, and V; membrane type MMPs. 22 Proteoglycans are primarily degraded by enzymes of the ADAMTS family (a disintegrin and metalloproteinase with thrombospondin motifs) that consists of 19 different molecules. 10 The ADAMTS that regulate PGs turnover are known as ‘aggrecanases’, which include ADAMTS1, ADAMTS4, ADAMTS5, ADAMTS8 and ADAMTS9, although precisely which enzyme is involved in the turnover of tendon proteoglycans is currently unknown. 20 The activity of MMPs is inhibited reversibly by tissue inhibitors of metalloproteinases (TIMPs). 18 There are four types of TIMP: TIMP1, TIMP2, TIMP3, and TIMP4. 18 The balance between the activities of MMPs and TIMPs regulates tendon remodelling, and an imbalance produces collagen disturbances in tendons. 7 The mechanism of activation of MMPs is poorly understood. Their precise role in tendinopathy is still unclear, and it is conceivable that MMPs play a role in tendinopathies. 15
FROM GENE EXPRESSION TO TENDINOPATHY AND TENDON RUPTURE
Several authors have observed an high percentage of degeneration in tendon rupture. 1, 2, 11 Although the role of inflammation is still debated, there is evidence of the absence of inflammatory cells in or around the tendon. 13 It is supposed that tendinosis is the cause but not the result of rupture. The cause of tendinosis has been classically described as an overuse phenomenon in which microscopic tendon fiber damage occurs, followed by catabolic response, mechanobiological understimulation and tendon weakening. In this way a vicious circle is started which will result in tendon rupture.3 Pattern, magnitude and duration of loading influence the regulation of the tenocyte remodelling response and then the synthesis of specific metalloproteinase involved in the turnover of the tendon or others metalloproteinase leading to degeneration of the tissue. 21
Tendinopathy and tendon rupture represent two different clinical and molecular scenarios. Riley et al. 23 indicated that the amount of α1 (III) collagen in the human rotator cuff tendinosis increased as a result of degeneration and laceration and that a long-term excess of this collagen species in the human supraspinatus tendon might have unfavourable biomechanical consequences. This report suggests that production of collagen III may have an adverse effect on the tendon healing process. We have recently demonstrated that in human Achilles tendon rupture there is a significant difference in collagen I gene expression between ruptured and healthy tendon areas of the same tendon.12 The up regulation of collagen I gene testified the attempt of cells to synthesised new matrix. In normal Achilles tendon, decorin is the most highly-expressed proteoglycan while versican is higher than aggrecan. In painful tendinopathy both aggrecan and biglycan gene expression are increased compared with normal tendon samples, but levels of versican and decorin mRNA are not significantly changed. 6 This pattern resembles fibrocartilaginous regions of tendon and may reflect an altered mechanical environment at the site of the lesion. In ruptured tendons the levels of aggrecan, biglycan and versican mRNA are not changed compared with normal tendon samples, but decorin mRNA decreased markedly. 6 Main limits of these studies are the use, as control group, of tendons from other patients and the lack of analysis at protein level. It is known that an important interindividual variability can exist, related to several factors, such as use of drugs, smoke or post-mortem tissue hypoxia that can influence the tendon metabolism. 15, 21 Moreover, it is demonstrated that an apparently healthy area, also at ultrasound intraoperative examination, can be abnormal at morphological analysis. 1 A possible solution to this limit is to adopt as control group a sample harvested from the same patient in an apparently macroscopic healthy area. We found in human Achilles tendon rupture a significant increased of decorin and versican gene expression in ruptured area compared to healthy area of the same tendon. We observed presence of high amount of hyaluronan and not sulphured disaccharides in both area. 12 However, this finding is unusual for tendons. The amount of chondroitin sulfurated, testifying the presence of GAGs typical of decorin and versican, were higher in healthy areas compared to ruptured areas. The presence of big amount of hyaluronan and not sulphured disaccharides in healthy area demonstrated that this area is not normal. 6 Upregulation of decorin and versican is indicative of the repair attempt carried out by the tenocytes in the ruptured area. The low amount of GAGs in the ruptured area indicates that the catabolic processes prevail over the synthetic activity. 12
Tissue growth, remodelling, adaptation and repair depend by several proteolitic enzymes and the MMPs play a pivotal role. The MMPs differ in their activities and precisely which enzymes are implicated in the physiological and pathological turnover of tendon is still to be clarified. MMP3 plays a major role in regulation of tendon ECM degradation and tissue remodelling. An increased expression of MMP3 may be necessary for appropriate tissue remodelling and prevention of tendinopathic changes. 9 MMP3 and TIMP1, TIMP2, TIMP3 and TIMP4 are downregulated in tendinopathic tendons while TIMP1 and TIMP2 are upregulated in acute tears. 12, 15 Comparing a ruptured area to a healthy area of the same Achilles tendons we found no difference in gene expression of MMP9 while MMP2 gene expression was higher in ruptured area. However, MMP9 enzyme was more active in ruptured area compared to healthy area while no difference was observed in MMP2 activities. The activity of MMP9 and the absence of the real-time RT-PCR signal indicates that MMP9 is produced elsewhere from the tendon, and the molecule is probably secreted in the area by leucocytes. 14 MMP9 is a marker of overused tendon and it is typically observed after an intensive exercise in the circulation. 14, 17 Conversely, tenocytes produce MMP2. In fact, the high level of MMP2 expression with low MMP2 activity testifies a recent change in tenocytes activity induced by rupture. 5 These findings suggest that MMP-9, as MMP13, participates only in collagen degradation, whereas MMP-2, as MMP3 and MMP14, participates in both collagen degradation and collagen remodelling.19 In tendinopathic patellar tendons an upregulation of MMP1 gene and a suppressed expression of TIMP1 were recorded. 8 This lack of TIMP1 in tendinopathic tendon perhaps causes a shift in the delicate balance in favour of greater collagenase activity, which would suggest that tendinopathy may be a disorder in healing of tendon with abnormal cellular responses to injury or repetitive stress. The high gene expression of TIMPs, seen in acute tendon rupture, could be considered a tissue reaction to overproduction of MMPs, in an effort to reduce their catalytic activity on the tendon matrix. 5, 12 In fact, TIMP-1 is not present in normal tendons, but, after acute tears of the supraspinatus tendon, in an animal model, it is expressed at the tendon edges for 2 weeks. 5 TIMP 2 is not only involved in MMPs and in particular MMP2 inhibition, but acts as a docking element, helping MMP2 activation by the membrane type-1 matrix metalloprotease (MT1-MMP). TIMP 2 drives the pro-MMP-2 to MT1-MMP that cleaves the pro-peptide definitively activating MMP2. 26 This finding indicate that concomitant stimulation and inhibition of ECM degradation occurs during exercise suggesting that TIMPs regulate ECM degradation.
CONCLUSION
Several authors have demonstrated that ECM is not a static and inert component of tendon. The ECM is a dynamic structure constantly remodelled, with rates of turnover depending of loading forces. The balance between the activities of MMPs and TIMPs is responsible for normal tendon remodelling. Alteration of MMP and TIMP expression from basal levels leads to alteration of tendon homoeostasis with progressive degeneration and weakening. Further studies are required to clarify the complexity of the relation between the different MMPs and their inhibitors in the pathogenesis of tendinopathy and tendon rupture in order to develop specific therapeutic strategies in these patients
Medial patellofemoral ligament reconstruction for recurrent patellar dislocation. Surgical procedures review.
No full textTears of the MPFL are often considered the essential lesion of recurrent lateral patella dislocation. Cadaveric sectioning studies have demonstrated that the MPFL provides 50% to 60% of the soft tissue restraint to lateral translation, and the medial patello-meniscal ligament contributes 24%. Pathological conditions such as patella alta, trochlear dysplasia and an increased quadriceps angle from various torsional deformities of both the femur and the tibia can be associated with recurrent patello-femoral dislocation. All these conditions need to be corrected to restore the physiological biomechanics of the patello-femoral joint. Lateral retinacular release, proximal realignment and distal realignment are the most common procedures performed for this purpose. In recurrent patellar dislocation without any predisposing factor, all these non-anatomical surgical procedures have been used. They alter the pre-morbid patellar mechanics, and several studies reported inconsistent outcomes, recurrent dislocations, patello-femoral pain and arthritis in up to 40% of patients. Several reconstruction procedures of the MPFL with semitendinosus, gracilis, quadriceps tendon, adductor magnus, iliotibial band and synthetic grafts have been described. Semitendinosus tendon autografts are the most commonly used reconstruction construct. The different techniques require the fixation of the graft to the patella through bone tunnels loop, anchors, endobutton or sutured to the periosteal and fibrous tissue overlying the patella. The medial fixation to the femur is performed through bone tunnel and interference screw, endobutton, washer or through an osteoperiosteal tunnel under the adductor magnus. Most of the pre-mentioned techniques have shown acceptable medium-term results in the mean of subjective symptomatic improvement and low rate of recurrence in 85% to 93% of the involved cases. At present, there is no clear consensus as to the best method to reconstruct the MPFL. Several questions need to be resolved and in particular: the right position of graft insertion on the patella; the best fixation methods; at which degree of knee flexion the graft must be tensionated and fixed to avoid overtightening and then increased loads on the patellofemoral joint, which in the long term may result in degenerative joint disease; the right position of graft insertion on the femur since several studies have shown that the femoral attachment of the MPFL is not clearly identifiable. Biomechanical data show significant increases in medial patellofemoral contact pressures when MPFL grafts is misplaced as little as 5 mm. Incorrect graft placement accompanied by a short graft increases medial patellofemoral contact pressures by over 50%. In the future, a well controlled and standardised comparison of different surgical techniques is indicated, to assess whether a specific graft or technique is superior to the others
Tecniche chirurgiche nel trattamento delle lesioni cartilaginee articolari: stato dell’arte
No full textProspettive future nell’impianto di condrociti.
No full textLe lesioni cartilaginee a tutto spessore sono una patologia di comune riscontro nella pratica ortopedica e la loro incidenza nella popolazione ha mostrato un andamento in crescita negli ultimi anni dovuto all’aumentata richiesta funzionale in particolare dei pazienti over quaranta anni. Diversi autori hanno dimostrato l’efficacia dell’impianto di condrociti autologhi a medio e lungo termine nel trattamento delle lesioni focali traumatiche e degenerative iniziali. L’evoluzione da un concetto di terapia cellulare ad uno di ingegneria tissutale, grazie all’impiego dei supporti tridimensionali o scaffold, ha fornito vantaggi non solo dal punto di vista chirurgico (minore invasività, utilizzo di tecniche artroscopiche, ridotto numero di complicazioni) ma anche dal punto di vista biologico (migliore differenziazione dei condrociti in coltura, omogenea distribuzione delle cellule nel difetto condrale, ridotta incidenza di ipertrofia dell’impianto). L’attenzione dei ricercatori si è focalizzata negli ultimi anni sul miglioramento della tecnica di base ed in particolare su tre temi fondamentali: tipo di cellule da impiantare, scaffold e fattori d crescita. A tal fine i futuri sviluppi prevederanno una migliore selezione delle cellule da impiantare ed eventualmente l’utilizzo della terapia genica per attivare la produzione di specifiche molecole della matrice extracellulare. Inoltre, l’utilizzo delle cellule staminali potrà incrementare la capacità di riparazione. Diversi studi sperimentali stanno valutando l’efficacia di scaffold biomimetici che facilitino la differenziazione di uno stesso impianto in cartilagine ed osso per la riparazione di difetti osteocondrali. L’utilizzo dei bioreattori, associato al prelievo di cellule totipotenti da sedi extraarticolari, di scaffold e di specifici fattori di crescita, consentirà in futuro di avere un tessuto cartilagineo senza dover sottoporre il paziente ad un duplice intervento chirurgico
Bone Morphogenetic Proteins
No full textThe bone morhogenetic proteins (BMPs) are a group of dimeric proteins in the trasforming growth factor- (TGF-) based on amino acid homology. More than 20 BMPs have been identified, several of which have significant osteogenic effects.
Since these proteins govern the three key steps in the bone induction cascade (chemotaxis and mitosis of mesenchymal cells, differentiation into cartilage and then replacement by bone) BMPs are true pleiotropic morphogens.
The biological action are mediated via specific BMP receptors found on the cell surface. These are serine/threonine kinases that phosphorylate intracellular proteins called Smads. The activated Smads are then traslocated to the nucleus, where they regulate either positive or negative expression of genes involved in bone formation.
There are different BMPs sources to use in orthopaedic practice.
The available amounts of BMPs, the morbidity associated with harvesting of the graft and the variability in success rate are issues to be considered in autografting.
The osteoinductive capacity of allograft (mineralized or demineralized) is highly variable and may be inadequate for any bone-inductive effect in humans.
A recombinant production system have several advantages: its reproducibility, high concentrations, consistent purity and activity of BMP, and ability to ensure freedom from adventitious agents. However, selection of the best carrier material is difficult in order to control retention time of BMP and localize its activity.
A partial solution is derived by ultraconcentration of autologous platelets that contains multiple growth factors delivered locally in physiological way. The amount of BMPs and a possible antagonism between different growth factors are still topics of discussion
Clinical and radiographic outcomes after minimally invasive locking plating of distal tibia fractures.
No full textObjective: Assess the bone union rate, deformity, leg-length discrepancy, return to pre-injury daily and sports activities and infection rate in a selected group of 21 patients who underwent minimally invasive osteosynthesis of close distal tibia fractures with Locking plate (LP).
Material and methods: We prospectively included patients with closed distal tibia and fibula fractures, without any previous or present ipsilateral leg fracture. There were 9 women and 12 men, ranging in age from 25 to 66 yrs. Fractures were classified according to AO classification. There were 12 type A, 5 B, and 4 C fractures. Clinical, functional, and radiographic evaluations were scheduled at 6, 12, 24 weeks, 1 year, and then annually. Results were classified in accordance to criteria developed by the Association for the Study and Application of the Method of Ilizarov (ASAMI). The results were divided into bone and functional results. For bone results four criteria were evaluated: union time, infection, deformity (< 7°), and leg-length discrepancy (< 2.5 cm) at standard long-leg radiographs. The functional results were based on five criteria: limp, equinus rigidity of the ankle, soft-tissue dystrophy, pain, and inactivity (unemployment because of the leg injury or inability to return to daily activities because of the leg injury).
Results: The average follow-up was 2.8 years (range, 2 to 4). Two patients were lost to follow-up. Union was achieved in all but one patient. Four patients had angular deformity < 7°. No patient had a leg-length discrepancy ≥ 1.1 cm. Five patients had range of motion of ankle ≤ 20° compared with the contralateral side. Sixteen patients had not returned to their preinjury sporting or leisure activities. Three patients developed a delayed infection. According to the ASAMI criteria, there were 15 excellent, 3 good and 1 poor “bone results” and 11 excellent, 3 good and 5 fair “functional results”.
Conclusions: The high percentage of unions and the low rate of complications show that LP is a suitable device for treatment of distal tibia fractures. The level of physical activities appears permanently reduced in most of patients. The cost of the LP, the technically demanding procedure, and the increased exposure to radiation to perform the procedure should be considered when comparing the efficacy of this device to the normal plates. Only future prospective randomized studies may be able to clarify these issues
Tecniche chirurgiche nel trattamento delle lesioni cartilaginee articolari: stato dell’arte
No full text“Scaffold” e cartilagine
No full textAutologous chondrocyte implantation (ACI) has demonstrated a high rate of clinical success despite a considerable number of complications. The second-generation ACI techniques require three-dimensional scaffolds. Midterm studies have demonstrated comparable results to ACI, yet with a decreased rate of complications. The aim of this review is to define the requisites of a scaffold and to report clinical results and limits of these techniques
“Scaffold” e cartilagine
No full textAutologous chondrocyte implantation (ACI) has demonstrated a high rate of clinical success despite a considerable number of complications. The second-generation ACI techniques require three-dimensional scaffolds. Midterm studies have demonstrated comparable results to ACI, yet with a decreased rate of complications. The aim of this review is to define the requisites of a scaffold and to report clinical results and limits of these techniques
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