Decreasing inflammatory response of injured patellar tendons results in increased collagen fibril diameters

Saturated fatty acids negatively affect musculoskeletal tissues in vitro and in vivo

Fish oils rank among the world's most popular nutritional supplements and are purported to have numerous health benefits. Previous work suggested that fish oils increase collagen production; however, the effect of fish oils on musculoskeletal health is poorly understood. Further, the divergent effects of omega-3 (Ω3FA) and saturated fatty acids (SFA) remains poorly understood. We tested the effects of Ω3FA and SFAs on in vitro-engineered human ligament (EHL) function. EHLs were treated with bovine serum albumin (BSA)-conjugated eicosapentaenoic acid (EPA, 20:5(n-3)), palmitic acid (PA, 16:0), or a BSA control for 6 days. EPA did not significantly alter, whereas PA significantly decreased EHL function and collagen content. To determine whether this was an in vitro artifact, mice were fed a control or high-lard diet for 14 weeks and musculoskeletal mass, insulin sensitivity, and the collagen content, and mechanics of tendon and bone were determined. Body weight was 40 % higher on a HFD, but muscle, tendon, and bone mass did not keep up with body weight resulting in relative losses in muscle mass, tendon, and bone collagen, as well as mechanical properties. Importantly, we show that PA acutely decreases collagen synthesis in vitro to a similar extent as the decrease in collagen content with chronic treatment. These data suggest that Ω3FAs have a limited effect on EHLs, whereas SFA exert a negative effect on collagen synthesis resulting in smaller and weaker musculoskeletal tissues both in vitro and in vivo.

Tendon healing is adversely affected by low-grade inflammation

BACKGROUND

Tendinopathy is common, presents with pain and activity limitation, and is associated with a high risk of recurrence of the injury. Tendinopathy usually occurs as a results of a disrupted healing response to a primary injury where cellular and molecular pathways lead to low grade chronic inflammation.

MAIN FINDINGS

There has been a renewed interest in investigating the role of Inflammation in the pathogenesis of tendinopathy, in particular during the initial phases of the condition where it may not be clinically evident. Understanding the early and late stages of tendon injury pathogenesis would help develop new and effective treatments addressed at targeting the inflammatory pathways.

CONCLUSION

This review outlines the role of low-grade Inflammation in the pathogenesis of tendinopathy, stressing the role of proinflammatory cytokines, proteolytic enzymes and growth factors, and explores how Inflammation exerts a negative influence on the process of tendon healing.

Tenogenic effects of silymarin following experimental Achilles tendon transection in rats

Tendon healing is prolonged due to the small number of cells, poor circulation, and low metabolism. The optimal tendon healing and its complete functional recovery have always been a challenge for researchers. Silymarin possesses anti-inflammatory, anti-oxidant, analgesic, and regenerative properties. The present study aimed to investigate the effects of silymarin on healing the Achilles tendon in rats. Twenty-four male Wistar rats were divided into two groups of control and treatment. After surgical preparation, a complete transverse incision was made in the middle part of the Achilles tendon, and then a modified Kessler suture was placed. The control group received 1.00 mL normal saline for five consecutive days, and the treatment group received 50.00 mg kg^-1 of silymarin suspended in 1.00 mL normal saline for five days, orally. During the experimental period, Achilles functional index (AFI) was recorded. Six weeks after surgery, sampling was done. Histopathologically, a significant increase in the density of collagen fibers and reduction in neovascularization and inflammatory cells infiltration were observed in the treatment group. The biomechanical evaluation showed a significant increase in tensile strength of the tendon in the treatment group compared to the control group. The AFI results were concomitant with the results stated above, indicating an improvement in the AFI of rats in the treatment group. The present study results showed that oral administration of silymarin improved tissue healing indices, biomechanical properties, and functional index, leading to optimal healing of experimental Achilles tendon injury in the rat.

The role of the macrophage in tendinopathy and tendon healing

The role of the macrophage is an area of emerging interest in tendinopathy and tendon healing. The macrophage has been found to play a key role in regulating the healing process of the healing tendon. The specific function of the macrophage depends on its functional phenotype. While the M1 macrophage phenotype exhibits a phagocytic and proinflammatory function, the M2 macrophage phenotype is associated with the resolution of inflammation and tissue deposition. Several studies have been conducted on animal models looking at enhancing or suppressing macrophage function, targeting specific phenotypes. These studies include the use of exogenous biological and pharmacological substances and more recently the use of transgenic and genetically modified animals. The outcomes of these studies have been promising. In particular, enhancement of M2 macrophage activity in the healing tendon of animal models have shown decreased scar formation, accelerated healing, decreased inflammation and even enhanced biomechanical strength. Currently our understanding of the role of the macrophage in tendinopathy and tendon healing is limited. Furthermore, the roles of therapies targeting macrophages to enhance tendon healing is unclear. Clinical Significance: An increased understanding of the significance of the macrophage and its functional phenotypes in the healing tendon may be the key to enhancing tendon healing. This review will present the current literature on the function of macrophages in tendinopathy and tendon healing and the potential of therapies targeting macrophages to enhance tendon healing.

The role of the immune system in tendon healing: a systematic review

INTRODUCTION

The role of the immune system in tendon healing relies on polymorphonucleocytes, mast cells, macrophages and lymphocytes, the 'immune cells' and their cytokine production. This systematic review reports how the immune system affects tendon healing.

SOURCES OF DATA

We registered our protocol (registration number: CRD42019141838). After searching PubMed, Embase and Cochrane Library databases, we included studies of any level of evidence published in peer-reviewed journals reporting clinical or preclinical results. The PRISMA guidelines were applied, and risk of bias and the methodological quality of the included studies were assessed. We excluded all the articles with high risk of bias and/or low quality after the assessment. We included 62 articles assessed as medium or high quality.

AREAS OF AGREEMENT

Macrophages are major actors in the promotion of proper wound healing as well as the resolution of inflammation in response to pathogenic challenge or tissue damage. The immune cells secrete cytokines involving both pro-inflammatory and anti-inflammatory factors which could affect both healing and macrophage polarization.

AREAS OF CONTROVERSY

The role of lymphocytes, mast cells and polymorphonucleocytes is still inconclusive.

GROWING POINTS

The immune system is a major actor in the complex mechanism behind the healing response occurring in tendons after an injury. A dysregulation of the immune response can ultimately lead to a failed healing response.

AREAS TIMELY FOR DEVELOPING RESEARCH

Further studies are needed to shed light on therapeutic targets to improve tendon healing and in managing new way to balance immune response.

Boosting the Biogenesis and Secretion of Mesenchymal Stem Cell-Derived Exosomes

A limitation of using exosomes to their fullest potential is their limited secretion from cells, a major bottleneck to efficient exosome production and application. This is especially true for mesenchymal stem cells (MSCs), which can self-renew but have a limited expansion capacity, undergoing senescence after only a few passages, with exosomes derived from senescent stem cells showing impaired regenerative capacity compared to young cells. Here, we examined the effects of small molecule modulators capable of enhancing exosome secretion from MSCs. The treatment of MSCs with a combination of N-methyldopamine and norepinephrine robustly increased exosome production by three-fold without altering the ability of the MSC exosomes to induce angiogenesis, polarize macrophages to an anti-inflammatory phenotype, or downregulate collagen expression. These small molecule modulators provide a promising means to increase exosome production by MSCs.

Effect of norbixin-based poly(hydroxybutyrate) membranes on the tendon repair process after tenotomy in rats

Purpose:

To determine the efficacy of norbixin-based poly(hydroxybutyrate) (PHB) membranes for Achilles tendon repair.

Methods:

Thirty rats were submitted to total tenotomy surgery of the right Achilles tendon and divided into two groups (control and membrane; n = 15 each), which were further subdivided into three subgroups (days 7, 14, and 21; n = 5 each). Samples were analyzed histologically.

Results:

Histological analysis showed a significant reduction in inflammatory infiltrates on days 7, 14 (p < 0.0001 for both), and 21 (p = 0.0004) in the membrane group compared to that in the control group. There was also a significant decrease in the number of fibroblasts in the control group on days 7, 14 (p < 0.0001), and 21 (p = 0.0032). Further, an increase in type I collagen deposition was observed in the membrane group compared to that in the control group on days 7 (p = 0.0133) and 14 (p = 0.0107).

Conclusion:

Treatment with norbixin-based PHB membranes reduces the inflammatory response, increases fibroblast proliferation, and improves collagen production in the tendon repair region, especially between days 7 and 14.

Tendon healing in presence of chronic low-level inflammation: a systematic review

BACKGROUND

Tendinopathy is a common musculoskeletal condition affecting subjects regardless of their activity level. Multiple inflammatory molecules found in ex vivo samples of human tendons are related to the initiation or progression of tendinopathy. Their role in tendon healing is the subject of this review.

SOURCES OF DATA

An extensive review of current literature was conducted using PubMed, Embase and Cochrane Library using the term 'tendon', as well as some common terms of tendon conditions such as 'tendon injury OR (tendon damage) OR tendonitis OR tendinopathy OR (chronic tendonitis) OR tendinosis OR (chronic tendinopathy) OR enthesitis' AND 'healing' AND '(inflammation OR immune response)' as either key words or MeSH terms.

AREAS OF AGREEMENT

An environment characterized by a low level of chronic inflammation, together with increased expression of inflammatory cytokines and growth factors, may influence the physiological tendon healing response after treatment.

AREAS OF CONTROVERSY

Most studies on this topic exhibited limited scientific translational value because of their heterogeneity. The evidence associated with preclinical studies is limited.

GROWING POINTS

The role of inflammation in tendon healing is still unclear, though it seems to affect the overall outcome. A thorough understanding of the biochemical mediators of healing and their pathway of pain could be used to target tendinopathy and possibly guide its management.

AREAS TIMELY FOR DEVELOPING RESEARCH

We require further studies with improved designs to effectively evaluate the pathogenesis and progression of tendinopathy to identify cellular and molecular targets to improve outcomes.

Effect of curcumin on bone healing: An experimental study in a rat model of femur fracture

OBJECTIVE

To determine the radiologic, histologic and biomechanical effects of curcumin on bone healing using a total rat femur fracture injury model.

MATERIALS AND METHODS

Sixty four male Wistar-Albino rats weighing 170-210 g were used in this study. The animals were randomly divided into eight groups and 5 or 6 animals were placed in each cage. A transverse femur shaft fracture model used. The animals in study groups received oral curcumin at a dose of 200 mg/kg for 14 days or 28 days. Remaining animals received only saline solution by oral gavage for a period of 14 days and 28 days as control groups. After sacrification the left femurs used for radiological, histological and biomechanical evaluation.

RESULTS

The groups treated with curcumin showed no significant difference in terms of radiological, histological and biomechanical evaluations in 14 days groups. Also there was no significant difference between curcumin and control groups for 28 days according to radiological, histological and biomechanical tests.

CONCLUSIONS

According to our results, curcumin has no positive effect on fracture healing not only histologically but also radiologically and biomechanically. Curcumin's antioxidant effect may be more noticeable with long term follow up investigation as it may have a positive effect in remodelling phase. Long term follow up designed studies may be planned to investigate its effect on remodelling phase of fracture healing.

Effect of curcumin on tendon healing: an experimental study in a rat model of Achilles tendon injury

PURPOSE

This in vivo study aims to investigate the effects of curcumin which is recently developed for tendon healing using a rat Achilles tendon injury model.

MATERIALS AND METHODS

Eighteen male Wistar albino rats weighing 300-400 g were used in this study. Under anesthesia, Achilles tendon injuries were created and repaired surgically. Nine rats of the study group received curcumin (suspended in saline at a dose of 200 mg/kg orally) and eight rats of the control group received only saline solution by oral gavage for a period of 28 days. Animals were euthanized on the 28th post-operative day, and all the Achilles tendons were removed and transferred immediately for biomechanic and histological analysis.

RESULTS

Macroscopically, all the tendons were fully healed. Total mean Bonar score was higher in the control group. When the parameters of Bonar score were analysed separately, tenocyte morphology, collogen, and ground substance scores were statistically lower than the control group (p = 0.03, 0.041, 0.049, respectively). Vascularity parameter did not show any statistical difference (p > 0.05). Of the nine biomechanical parameters, five of them (failure load, cross-sectional area, length, ultimate stress, strain) showed better results which were also statistically significant (p = 0.046, 0.027, 0.011, 0.021, 0.002, respectively). When the remaining four parameters were examined, the study group also had better results, but this difference was not statistically significant.

CONCLUSION

Curcumin had better results for total tendon healing not only histologically but also biomechanically. Curcumin could be an additional agent in the management of surgically repaired tendon injuries.

Piperine ameliorates collagenase-induced Achilles tendon injury in the rat

Tendinopathy is a common clinical pathology found in athletes and workers with mixed treatment results. Piperine, a major alkaloid found in the black and long pepper, has been demonstrated to have variety of pharmacological properties such as analgesic and anti-inflammatory effects. The present study was designed to investigate the effects of piperine on collagenase-induced Achilles tendon injury. Rats were intratendineously injected with collagenase in the right Achilles tendon, followed by intragastrical administration of piperine (100 mg/kg). Morphological structure and biochemical analysis of glycosaminoglycans, hydroxyproline, collagen III, and the activity of matrix metallopeptidases in the tendon tissues were performed. Our results showed that collagenase injection resulted in clear degenerative changes in the tendon. Administration of piperine improved the morphological structure of tendon, increased glycosaminoglycans and hydroxyproline levels, and inhibited the expression and activities of MMP-2 and MMP-9. Furthermore, piperine inhibited the activation of ERK and p38 signaling pathways in injured tendon. These results indicate a beneficial role of piperine against collagenase-induced tendon injury.

Amniotic membrane as an option for treatment of acute Achilles tendon injury in rats

PURPOSE

To evaluate the effect of human amniotic membrane (hAM) fragment on inflammatory response, proliferation of fibroblast and organization of collagen fibers in injured tendon.

METHODS

Sixty rats were divided into 3 groups: C - surgical procedures without tendon lesion and with simulation of hAM application; I - surgical procedures, tendon injury and simulation of hAM application; T - surgical procedures, tendon injury and hAM application. These groups were subdivided into four experimental times (3, 7, 14 and 28 days). The samples underwent histological analysis and ATR-FTIR spectroscopy.

RESULTS

Histological analysis at 14 days, the T group showed collagen fibers with better alignment. At 28 days, the I group presented the characteristics described for the T group at 14 days, while this group presented aspects of a mature connective tissue. FT-IR analysis showed a clear distinction among the three groups at all experimental times and groups T and I presented more similarities to each other than to group C.

CONCLUSION

Acute injury of tendon treated with human amniotic membrane fragment showed a faster healing process, reduction in inflammatory response, intense proliferation of fibroblasts and organization of collagen fibers.

Synthetic sutures: Clinical evaluation and future developments

Today's sutures are the result of a 4000-year innovation process with regard to their materials and manufacturing techniques, yet little has been done to enhance the therapeutic value of the suture itself. In this review, we explore the historical development, regulatory database and clinical literature of sutures to gain a fuller picture of suture advances to date. First, we examine historical shifts in suture manufacturing companies and review suture regulatory databases to understand the forces driving suture development. Second, we gather the existing clinical evidence of suture efficacy from reviewing the clinical literature and the Food and Drug Administration database in order to identify to what extent sutures have been clinically evaluated and the key clinical areas that would benefit from improved suture materials. Finally, we apply tissue engineering and regenerative medicine design hypotheses to suture materials to identify routes by which bioactive sutures can be designed and passed through regulatory hurdles, to improve surgical outcomes. Our review of the clinical literature revealed that many of the sutures currently in use have been available for decades, yet have never been clinically evaluated. Since suture design and development is industry driven, incremental modifications have allowed for a steady outflow of products while maintaining a safe regulatory position and limiting costs. Until recently, there has been little academic interest in suture development, however the rise of regenerative medicine strategies is shifting the suture paradigm from an inert material, which mechanically approximates tissue, to a bioactive material, which also actively promotes cell-directed repair and a positive healing response. These materials hold significant therapeutic potential, but could be associated with an increased regulatory burden, cost, and clinical evaluation compared with current devices.

A possible link between loading, inflammation and healing: Immune cell populations during tendon healing in the rat

Loading influences tendon healing, and so does inflammation. We hypothesized that the two are connected. 48 rats underwent Achilles tendon transection. Half of the rats received Botox injections into calf muscles to reduce mechanical loading. Cells from the regenerating tissue were analyzed by flow cytometry. In the loaded group, the regenerating tissue contained 83% leukocytes (CD45⁺) day 1, and 23% day 10. The M1/M2 macrophage ratio (CCR7/CD206) peaked at day 3, while T helper (CD3⁺CD4⁺) and T_reg cells (CD25⁺ Foxp3⁺) increased over time. With Botox, markers associated with down-regulation of inflammation were more common day 5 (CD163, CD206, CD25, Foxp3), and M1 or M2 macrophages and T_reg cells were virtually absent day 10, while still present with full loading. The primary variable, CCR7/CD206 ratio day 5, was higher with full loading (p = 0.001) and the T_reg cell fraction was lower (p < 0.001). Free cage activity loading is known to increase size and strength of the tendon in this model compared to Botox. Loading now appeared to delay the switch to an M2 type of inflammation with more T_reg cells. It seems a prolonged M1 phase due to loading might make the tendon regenerate bigger.

Curcumin improves tendon healing in rats: a histological, biochemical, and functional evaluation

Curcumin, a compound extracted from the roots of Zingiberaceae, has been proposed as a treatment for tissue injury but studies are yet to be done on its effect on tendon healing. Therefore, we performed a series of experiments to test our hypothesis that curcumin has positive effects on tendon repair. Patellar tendon window defect was created in Sprague-Dawley rats and these were divided into two groups: (i) control and (ii) curcumin-treated. Curcumin (100 mg/kg body weight) was applied by oral gavage. Its potential for promoting tendon healing was assessed by histological evaluation, mRNA expression of tenocyte-related genes, malondialdehyde (MDA) levels, manganese-dependent superoxide dismutase (MnSOD) activity, quantification of hydroxyproline (HOPro), and biomechanical testing. In this tendon injury model, curcumin significantly improved the healing properties as evidenced by extensive deposition of well-organized collagen fibers, decreased MDA levels, and increase in the biomechanical properties and MnSOD activity of the regenerated tendon tissues. The current study showed that curcumin can improve the quality of tendon rupture healing, and thus represents a promising strategy in the management of injured tendon tissue.

Acupuncture Increases the Diameter and Reorganisation of Collagen Fibrils during Rat Tendon Healing

Background

Our previous study showed that electroacupuncture (EA) increases the concentration and reorganisation of collagen in a rat model of tendon healing. However, the ultrastructure of collagen fibrils after acupuncture is unknown.

Objectives

To assess the effect of acupuncture protocols on the ultrastructure of collagen fibrils during tendon healing.

Methods

Sixty-four rats were divided into the following groups: non-tenotomised (normal group), tenotomised (teno group), tenotomised and subjected to manual acupuncture at ST36 (ST36 group), BL57 (BL57 group) and ST36+BL57 (SB group) and EA at ST36+BL57 (EA group). The mass-average diameter (MAD) and the reorganisation of collagen fibril diameters were determined during the three phases of tendon healing (at 7, 14 and 21 days).

Results

The MAD increased during the three phases of healing in the SB group. In the EA group, MAD increased initially but was reduced at day 21. The reorganisation of collagen fibrils was improved in the EA and SB groups at days 14 and 21, respectively. EA at day 21 appeared to reduce the reorganisation.

Conclusions

These results indicate that the use of EA up to day 14 and manual acupuncture at ST36+BL57 up to day 21 improve the ultrastructure of collagen fibrils, indicating strengthening of the tendon structure. These data suggest a potential role for acupuncture in rehabilitation protocols.

Mid-long term effect of non-ablative high radiofrequency therapy on the rabbit dermal extracellular matrix

This study quantitatively investigated the postoperative effects of radiofrequency (RF) application on the normal dermal extracellular matrix (ECM) of in vivo rabbits. Postoperative effects were evaluated by histology and atomic force microscopy analysis of dermal tissues treated using three RF energy levels (10 ~ 30 W) and either a single- or multiple-pass procedure. Progressive changes in the morphology of rabbit dermal ECMs were investigated over a 30-day postoperartive period. All RF-treated groups, except for the low energy group (10 W), displayed more prominent inflammatory responses compared to the control. This inflammatory reaction was more prominent a day after application. Dermal tissues 30 days after RF application exhibited prominent myofibroblast activity associated with ECM contractile activity during wound healing in addition to chronic inflammation. A decrease in the morphology of dermal ECMs after RF application continued until seven days postoperatively. The ECM diameter increased to near baseline at 30 days postoperatively. Low energy and multi-pass applications resulted in greater collagen fibril contraction and recovery at the ultra-structural level at 30 days postoperatively than did a single high energy application.

Scaffold fiber diameter regulates human tendon fibroblast growth and differentiation

The diameter of collagen fibrils in connective tissues, such as tendons and ligaments is known to decrease upon injury or with age, leading to inferior biomechanical properties and poor healing capacity. This study tests the hypotheses that scaffold fiber diameter modulates the response of human tendon fibroblasts, and that diameter-dependent cell responses are analogous to those seen in healthy versus healing tissues. Particularly, the effect of the fiber diameter (320 nm, 680 nm, and 1.80 μm) on scaffold properties and the response of human tendon fibroblasts were determined over 4 weeks of culture. It was observed that scaffold mechanical properties, cell proliferation, matrix production, and differentiation were regulated by changes in the fiber diameter. More specifically, a higher cell number, total collagen, and proteoglycan production were found on the nanofiber scaffolds, while microfibers promoted the expression of phenotypic markers of tendon fibroblasts, such as collagen I, III, V, and tenomodulin. It is possible that the nanofiber scaffolds of this study resemble the matrix in a state of injury, stimulating the cells for matrix deposition as part of the repair process, while microfibers represent the healthy matrix with micron-sized collagen bundles, thereby inducing cells to maintain the fibroblastic phenotype. The results of this study demonstrate that controlling the scaffold fiber diameter is critical in the design of scaffolds for functional and guided connective tissue repair, and provide new insights into the role of matrix parameters in guiding soft tissue healing.

Postoperative effect of radiofrequency treatments on the rabbit dermal collagen fibrillary matrix

This study quantitatively examined the short and mid-long term effects of radiofrequency (RF) treatment on the normal dermal collagen fibrils of live rabbits. Effects were evaluated by histology and scanning probe microscopy analysis of dermal tissues treated using three RF energy levels (10, 20, and 30 W) and either a single- or multiple-pass procedure. Progressive changes in the morphology of rabbit dermal collagen fibrils were investigated over a 30-day post-treatment period. All RF-treated groups, except for the low-energy group (10 W), displayed more prominent inflammatory responses compared to the control. This inflammatory response was more prominent a day after treatment. Dermal tissues 30-days after RF treatment exhibited prominent myofibroblast activity associated with collagen contractile activity during wound healing in addition to chronic inflammation. A decrease in the morphology of dermal collagen fibrils after RF treatment continued until seven days postoperatively. The collagen fibril diameter increased to near baseline at 30 days postoperatively. Low-energy and multi-pass treatments resulted in greater collagen fibril contraction and recovery at the nanostructural level at 30 days postoperatively than did a single high-energy treatment.

Effects of extracorporeal shockwave therapy on nanostructural and biomechanical responses in the collagenase-induced Achilles tendinitis animal model

The aim of this study was to quantitatively investigate the effects of extracorporeal shockwave therapy (ESWT) on the nanostructure and adhesion force of collagen fibrils in a rat model of collagenase-induced Achilles tendinitis (CIAT) using histology and atomic force microscopy. A total of 45 rats were divided into experimental groups of three rats each: a control group, 27 CIAT rats with nine time points, and 15 ESWT rats with five time points. Progressive changes in nanostructure including the fibrillary diameter and D-periodicity, and biomechanical properties including the fibrillary adhesion forces in each healing phase were investigated over a 5-week period after collagenase injection. On postoperative day 3, CIAT rats showed granulomatous tissue associated with subacute inflammation, and a deterioration in nanostructure and mechanical properties compared to controls. On postoperative day 12, the ESWT group showed increased vascularity, fibroblastic activity, lymphocyte and plasma cell infiltration, dense histocytes, and disorganization of the fibers compared to the CIAT group. The ESWT group showed and improvement in nanostructure and mechanical properties compared to controls, while the CIAT group showed a deterioration in nanostructure and mechanical properties compared to controls. On postoperative day 26, the ESWT group showed 30% inflamed tissue and 70% fibrotic tissue, while the CIAT group showed chronic inflammation. By the end of the experiments, in both groups the changes had reversed and the tissues were similar in appearance to those in the control group. Following ESWT the deformed and irregular collagen network returned to a well-aligned normal collagen network nanostructure. These results suggest that ESWT may promote the healing response in Achilles tendinitis.

Short-term nanostructural effects of high radiofrequency treatment on the skin tissues of rabbits

The aim of this study is to quantitatively investigate the short-term effects of RF tissue-tightening treatment in in vivo rabbit dermal collagen fibrils. These effects were measured at different energy levels and at varying pass procedures on the nanostructural response level using histology and AFM analysis. Each rabbit was divided into one of seven experimental groups, which included the following: control group, and six RF group according to RF energy (20 W and 40 W) and three RF pass procedures. The progressive changes in the diameter and D-periodicity of rabbit dermal collagen fibrils were investigated in detail over a 7-day post-treatment period. The dermal tissues treated with the RF tissue-tightening device showed more prominent inflammatory responses with inflammatory cell ingrowth compared to the control. This effect showed more prominent with the passage of day after treatment. Although an increase in the diameter and D-periodicity of dermal collagen fibrils was identified immediately after the RF treatment, a decrease in the morphology of dermal collagen fibrils continued until post-operative day 7. Furthermore, RF treatment led to the loss of distinct borders. Increases in RF energy with the same pass procedure, as well as an increase in the number of RF passes, increased the occurrence of irreversible collagen fibril injury. A multiple-pass treatment at low energy rather than a single-pass treatment at high energy showed a large amount of collagen fibrils contraction at the nanostructural level.

Effects of phosphate-buffered saline concentration and incubation time on the mechanical and structural properties of electrochemically aligned collagen threads

A key step during the synthesis of collagen constructs is the incubation of monomeric collagen in phosphate buffer saline (PBS) to promote fibrillogenesis in the collagen network. Optimal PBS-treatment conditions for monomeric collagen solutions to induce gelation are well established in the literature. Recently, a report in the literature (Cheng et al 2008 Biomaterials 29 3278-88) showed a novel method to fabricate highly oriented electrochemically aligned collagen (ELAC) threads which have orders of magnitude greater packing density than collagen gels. The optimal PBS-treatment conditions for induction of D-banding pattern in such a dense and anisotropic collagen network are unknown. This study aimed to optimize PBS treatment of ELAC threads by investigating the effect of phosphate ion concentration (0.5×, 1×, 5× and 10×) and incubation time (3, 12 and 96 h) on the mechanical strength and ultrastructural organization by monotonic mechanical testing, small angle x-ray scattering and transmission electron microscopy (TEM). ELAC threads incubated in water (no PBS) served as the control. ELAC threads incubated in 1× PBS showed significantly higher extensibility compared to those in 0.5× or 10× PBS along with the presence of D-banded patterns with a periodicity of 63.83 nm. Incubation of ELAC threads in 1× PBS for 96 h resulted in significantly higher ultimate stress compared to 3 or 12 h. However, these threads lacked the D-banding pattern. TEM observations showed no significant differences in the microfibril diameter distribution of ELAC threads treated with or without PBS. This indicates that microfibrils lacked D-banding following electrochemical alignment and the subsequent PBS-treatment-induced D-banding by reorganization within microfibrils. It was concluded that incubation of aligned collagen in 1× PBS for 12 h results in mechanically competent, D-banded ELAC threads which can be used for the regeneration of load bearing tissues such as tendons and ligaments.

The cellular biology of flexor tendon adhesion formation: an old problem in a new paradigm

Intrasynovial flexor tendon injuries of the hand can frequently be complicated by tendon adhesions to the surrounding sheath, limiting finger function. We have developed a new tendon injury model in the mouse to investigate the three-dimensional cellular biology of intrasynovial flexor tendon healing and adhesion formation. We investigated the cell biology using markers for inflammation, proliferation, collagen synthesis, apoptosis, and vascularization/myofibroblasts. Quantitative immunohistochemical image analysis and three-dimensional reconstruction with cell mapping was performed on labeled serial sections. Flexor tendon adhesions were also assessed 21 days after wounding using transmission electron microscopy to examine the cell phenotypes in the wound. When the tendon has been immobilized, the mouse can form tendon adhesions in the flexor tendon sheath. The cell biology of tendon healing follows the classic wound healing response of inflammation, proliferation, synthesis, and apoptosis, but the greater activity occurs in the surrounding tissue. Cells that have multiple "fibripositors" and cells with cytoplasmic protrusions that contain multiple large and small diameter fibrils can be found in the wound during collagen synthesis. In conclusion, adhesion formation occurs due to scarring between two damaged surfaces. The mouse model for flexor tendon injury represents a new platform to study adhesion formation that is genetically tractable.