Collagen Fiber Orientation Research Articles

A multimethod approach to the differentiation of enthesis bone microstructure based on soft tissue type.

Whereas there is a wealth of research studying the nature of various soft tissues that attach to bone, comparatively little research focuses on the bone's microscopic properties in the area where these tissues attach. Using scanning electron microscopy to generate a dataset of 1600 images of soft tissue attachment sites, an image classification program with novel convolutional neural network architecture can categorize images of attachment areas by soft tissue type based on observed patterns in microstructure morphology. Using stained histological thin section and liquid crystal cross-polarized microscopy, it is determined that soft tissue type can be quantitatively determined from the microstructure. The primary diagnostic characters are the orientation of collagen fibers and heterogeneity of collagen density throughout the attachment area thickness. These determinations are made across broad taxonomic sampling and multiple skeletal elements.

Collective Cell Migration in a Fibrous Environment: A Hybrid Multiscale Modelling Approach.

The specific structure of the extracellular matrix (ECM), and in particular the density and orientation of collagen fibres, plays an important role in the evolution of solid cancers. While many experimental studies discussed the role of ECM in individual and collective cell migration, there are still unanswered questions about the impact of nonlocal cell sensing of other cells on the overall shape of tumour aggregation and its migration type. There are also unanswered questions about the migration and spread of tumour that arises at the boundary between different tissues with different collagen fibre orientations. To address these questions, in this study we develop a hybrid multi-scale model that considers the cells as individual entities and ECM as a continuous field. The numerical simulations obtained through this model match experimental observations, confirming that tumour aggregations are not moving if the ECM fibres are distributed randomly, and they only move when the ECM fibres are highly aligned. Moreover, the stationary tumour aggregations can have circular shapes or irregular shapes (with finger-like protrusions), while the moving tumour aggregations have elongate shapes (resembling to clusters, strands or files). We also show that the cell sensing radius impacts tumour shape only when there is a low ratio of fibre to non-fibre ECM components. Finally, we investigate the impact of different ECM fibre orientations corresponding to different tissues, on the overall tumour invasion of these neighbouring tissues.

Engineering collagen fiber templates with oriented nanoarchitecture and concerns on osteoblast behaviors

Nanostructure provides a closer structural support approximation to native bone architecture for cells and further regulates cell's behavior, resulting in the formation of functional tissues. In this work, three engineering collagen templates with oriented fiber architectures were fabricated via electrospinning (Es), plastic compression and tensile (PCT), and dynamic shear stress (SS) methods. Under the observation of POM, SEM, AFM and TEM, the PCT-template and SS-template are packed with well-oriented nanofibers with the native collagen architecture of 67 nm D-periodicity, and the mechanical properties conferred to the templates are better than that of the Es-template. When mentioning the cell's behavior, MC3T3-E1 adhered to grow along the alignment of collagen fiber orientation when cultured on the PCT-template and SS-template. The SS-template with nano- and micro-ordered architecture guided cells to stretch their plasma along with the orientation of collagen fiber, produce more aligned Type I collagen fibers and promote significantly higher osteogenic differentiation of MC3T3-E1 than the PCT-template and Es-template. Overall, it is strongly argued the feasibility of hierarchical collagen fiber architectures for bone tissue regeneration.

A multiscale and multiaxial model for anisotropic damage and failure of human annulus fibrosus

This article presents a multiscale model to predict deformation-induced damage and failure of human annulus fibrosus under multiaxial loading. In the modeling approach, formulated within the framework of nonlinear continuum mechanics, the hierarchical structure of the soft tissue is considered from the nano-sized collagen fibrils to the micro-sized oriented collagen fibers. At the macroscale, the multi-layered lamellar/inter-lamellar organization of the soft tissue is introduced by considering the effective interactions between adjacent layers. The stochastic process of progressive damage events operating at different scales of the solid phase is introduced for the extracellular matrix and the network of nano-sized fibrils/micro-sized fibers. The damage is made anisotropic due to lamellar oriented collagen fibers and special orientation distribution of the inter-fibrillar and inter-lamellar network of fibrils. The chemical-induced volumetric strain is also considered in our modeling approach to take into account the osmolarity effects along with the anisotropic time-dependent transversal deformations. The capacity of the model is discussed using a few available stretching datasets till failure along circumferential and radial directions. Model predictions under tilted stretching, biaxial stretching and shearing are also presented to illustrate further the efficiencies of our modeling approach. This work shows for the first time the directional effects on annulus mechanics and failure in relation to external loading mode, structure features, damage events and hydration.

Chondrocyte morphology as an indicator of collagen network integrity

ABSTRACT Osteochondral allograft (OCA) transplantation offers an attractive treatment option as it can be used to repair large cartilage defects that otherwise would not heal. The currently accepted criterion for OCA selection for joint reconstruction is the percentage of viable chondrocytes, but this criterion alone may not be sufficient to ensure structural integrity and functional performance of allografts following transplantation. We sought to determine an additional parameter that indicates matrix integrity. We used multi-photon microscopy to quantitatively assess chondrocyte viability, chondrocyte shape, and collagen structure of articular cartilage of OCAs. Chondrocyte shape varied considerably in otherwise macroscopically healthy-looking OCAs with good (>90%) cell viability. Shape varied from the expected ellipsoidal form found in healthy cartilage, to excessively elongated and flattened cells that often contained multiple cytoplasmic processes reminiscent of those observed in fibroblasts. Chondrocytes with abnormal morphology were associated with degradation of their pericellular matrix and disruption of the collagen fiber orientation, reflected by an increase in heterogeneity of second harmonic signal intensity. Cell shape may be an important marker for collagen network integrity in articular cartilage in general and OCAs specifically. We propose that, aside from cell viability, cell shape may be used as an additional criterion measure for the selection of OCAs. OCAs selected for transplantation based on these criteria showed good graft-host integration post-operation. In view of the rapid and nondestructive nature of the current approach, it may be suitable for clinical application in the future.

Decrease in Longitudinal Wave Velocity in Glycated Collagen.

Diabetic patients have a higher risk of bone fracture than those without diabetes, despite a normal bone mineral density. This higher riskmay result fromthe deterioration of collagen because of glycation. The objective of this study was to investigate the elastic properties of glycated collagen using the micro-Brillouin scattering technique. Using single-layer uniaxial collagen films with a thickness of approximately [Formula: see text], the longitudinal wave velocities, propagating in the parallel andperpendiculardirectionswith respect to the collagen fiber orientation, were measured in dry and wet film specimens. The wave velocities in the glycated collagen specimens decreased as a function of glycation time. This decrease depended on the direction of collagen fiber alignment and wave propagation. The lowest velocity due to glycation in thewet filmswas foundwhen the ultrasound propagated perpendicular to the fiber direction. These results indicate that the glycation of collagen in the bone may also reduce bone elasticity and suggest that the effects of glycation on collagen films may be anisotropic.

Influence of collagen fibre orientation on the frictional properties of articular cartilage

AbstractArticular cartilage has a unique collagen fibre network structure that exhibits both anisotropy and depth dependency. Collagen fibre orientation in a cross‐section parallel to the articular cartilage surface may affect the lubrication properties of articular cartilage. The effect of collagen fibre orientation on the frictional properties of articular cartilage was examined through finite element analysis of the friction. Specifically, a three‐dimensional fibre‐reinforced poroelastic biphasic model was used to determine the influence of collagen fibril orientation on the frictional properties of articular cartilage. The simulations reveal that collagen fibre orientation has a significant influence on the deformation behaviour of articular cartilage in front of and behind the contact area. The coefficient of dynamic friction was lower in the direction parallel to the collagen fibre orientation than in the direction perpendicular to the collagen fibre orientation, regardless of the indenter speed.

The intervertebral disc from embryonic development to disc degeneration: insights into spatial cellular organization

Background contextLow back pain is commonly attributed to intervertebral disc (IVD) degeneration. IVD resembles articular cartilage in its biochemical and cellular composition in many ways. For articular cartilage, degeneration stage-specific characteristic spatial chondrocyte patterns have recently been described. PurposeThis study addresses how spatial chondrocyte organization in the IVD changes from early embryonic development to end stage degeneration. Study designEx vivo immunohistochemical analysis. MethodsWe immunohistochemically investigated bovine IVD-tissue (n=72) from early embryonic development to early disc degeneration and human adult IVD-tissue (n=25) operated for trauma or degeneration for cellular density and chondrocyte spatial organization. IVD samples were sectioned along the main collagen fiber orientation. Nuclei were stained with DAPI and their number and spatial patterns were analyzed in an area of 250,000 µm² for each tissue category. ResultsThe initially very high cellular density in the early embryonic bovine disc (11,431 cells/mm²) steadily decreases during gestation, growth and maturation to about 71 cell/mm² in the fully grown cattle. Interestingly, in human degenerative discs, a new increase in this figure could be noted (184 cells/mm). The IVD chondrocytes appear to be predominantly present as single cells. Especially in the time after birth, string-formations represent up to 32% of all cells in the anulus fibrosus, although single cells are the predominant spatial pattern (>50%) over the entire time. With increasing degeneration, the relative proportion of single cells in human IVDs continuously decreases (12%). At the same time, the share of cells organized in clusters increases (70%). ConclusionSimilar to articular cartilage, spatial chondrocyte organization appears to be a strong indicator for local tissue degeneration in the IVD. Clinical SignificanceIn the future these findings may be important for the detection and therapy of IVD degeneration in early stages.

Bio-composites reinforced with unique coral collagen fibers: Towards biomimetic-based small diameter vascular grafts

Cardiovascular Diseases (CVDs) are the leading cause of death worldwide. Approximately 31% of all global deaths are caused by CVDs, of which 42% are attributable to coronary artery disease (CAD). CAD is characterized by a narrowing of arteries that restricts the normal blood flow. Over time, surgical intervention is required in severe cases of occlusions and includes implantation of autologous vessels. Today synthetic grafts are used successfully as replacements for blood vessels with a diameter larger than 6 mm. However, they often fail as small-diameter blood vessel replacements.This study introduces a new biocomposite material system consisting of unique and long (cm-scale) collagen fibers derived from soft corals embedded within an alginate hydrogel matrix. The new biocomposite layers were used to fabricate grafts, towards developing a new class of tissue-engineered small-diameter blood vessels. These constructs consisted of both circumferentially and longitudinally oriented collagen fibers. The mechanical properties of the grafts were investigated via a new experimental setup constructed in our lab for this purpose, which applied internal pressure levels of 0–300 mmHg. Similar to native coronary arteries, the biocomposite tubes demonstrated a compliance of 4.88 ± 0.99%/100 mmHg for a physiologic pressure range of 80–120 mmHg. Furthermore, a numerical finite element simulation model is proposed to generate the overall mechanical response of the construct. It is composed of axial and circumferential fibers embedded within the continuum alginate elements. Good prediction is demonstrated when compared with the measured pressure-strain response. Moreover, we examined biocompatibility and cell growth on the collagen fibers. Fibroblast cells proliferated during the experiment that lasted for 32 days and showed aligned configuration with the collagen fiber orientation.The novelty of this study is manifested in the use of naturally derived coral-based long collagen fibers for the development of a new class of tissue-engineered grafts. The proposed novel biocomposite graft demonstrated both mechanical and biological compatibility and can be further developed for small-diameter blood-vessel replacement.

Mechanical lengthening of porcine small intestine with decreased forces

Introductionshort bowel syndrome is marked by inadequate intestinal surface area to absorb nutrients. Current treatments are focused on medical management and surgical reconfiguration of the dilated intestine. We propose the use of spring-mediated distraction enterogenesis as a novel intervention to increase intestinal length. Given our previous success lengthening intestinal segments using springs with spring constant ~7 N/m that exerts 0.46 N or higher, we sought to determine the minimal force needed to lengthen porcine small intestinal segments, and to explore effects on intestine over time. MethodsJuvenile Yucatan pigs underwent laparotomy with enterotomy to introduce nitinol springs intraluminally (n = 21 springs). Bowel segments (control, spring-distracted) were retrieved on post-operative day (POD) 7 and 14, and lengths measured. Thickness of cross-sectional intestinal layers were measured using H&E, and submucosal collagen fiber orientation measured using trichrome stained sections. Resultsall pigs survived to POD7 and 14. Spring constants of at least 2 N/m exerting a minimum force of 0.10 N significantly lengthened intestinal segments (p <0.0001). The stronger the spring force, the greater the induced thickness of various intestinal layers at POD7 and 14. Collagen fiber orientation was also more disordered because of stronger springs. Conclusiona spring constant of approximately 2 N/m exerting 0.10 N and greater significantly lengthens intestinal segments and stimulates intestinal structural changes at POD7 and 14. This suggests a decreased force is capable of inducing spring-mediated distraction enterogenesis.

Decellularization of caprine esophagus using fruit pericarp extract of Sapindus mukorossi.

Biological detergents like sodium deoxycholate, sodium dodecyl sulphate and Triton X-100 impairs the collagenous and non-collagenous proteins, glycosaminoglycans and growth factors. Further, certain chemical and enzymes are responsible for residual cytotoxicity in the decellularized extracellular matrix. The main focus of this study was to explore the decellularization property of soap nut pericarp extract (SPE) for development of decellularized tubular esophageal scaffold. For this 2.5, 5.0 and 10% concentrations of SPE were used for decellularization of caprine esophageal tissues. Histological analysis of hematoxylin and eosin and Masson's trichrome stained tissue samples confirmed decellularization with preservation of extracellular matrix microarchitecture. Scanning electron microscopic images of luminal surface of decellularized esophageal matrix showed randomly oriented collagen fibres with large interconnected pores and cells were absent. However, the external surface was more textured with fibrous structures and collagen fibres were well preserved. DAPI stained decellularized tissues revealed complete removal of nuclear components, verified by DNA content measurement and SDS-PAGE. The FTIR spectra of decellularized esophagus shows absorption peaks of amide A, B, I, II and III. Elastic modulus of the decellularized esophagus scaffolds increased (P > 0.05) as compared to native tissues. Histological and scanning electron microscopic evaluation of in vitro seeded scaffolds showed attachment and growth of primary chicken embryo fibroblasts over and within the decellularized scaffolds. It was concluded that 5% SPE is ideal for preparation of cytocompatible decellularized caprine esophageal scaffold with well-preserved extracellular matrix architecture and, may be used as an alternative to biological detergents and other chemicals.

Collagen fibres determine the crack morphology in articular cartilage

Cracks in articular cartilage compromise tissue integrity and mechanical properties and lead to chondral lesions if untreated. An understanding of the mechanics of cracked cartilage may help in the prevention of cartilage deterioration and the development of tissue-engineered substitutes. The degeneration of cartilage in the presence of cracks may depend on the ultrastructure and composition of the tissue, which changes with aging, disease and habitual loading. It is unknown if the structural and compositional differences between immature and mature cartilage affect the mechanics of cartilage cracks, possibly predisposing one to a greater risk of degeneration than the other. We used a fibre-reinforced poro-viscoelastic swelling material model that accounts for large deformations and tension-compression non-linearity, and the finite element method to investigate the role of cartilage structure and composition on crack morphology and tissue mechanics. We demonstrate that the crack morphology predicted by our theoretical model agrees well with the histo-morphometric images of young and mature cracked cartilages under indentation loading. We also determined that the crack morphology was primarily dependent on collagen fibre orientation which differs as a function of cartilage depth and tissue maturity. The arcade-like collagen fibre orientation, first discussed by Benninghoff in his classical 1925 paper, appears to be beneficial for slowing the progression of tissue cracks by ‘sealing’ the crack and partially preserving fluid pressure during loading. Preservation of the natural load distribution between solid and fluid constituents of cartilage may be a key factor in slowing or preventing the propagation of tissue cracks and associated tissue matrix damage. Statement of significanceCracks in articular cartilage can be detrimental to joint health if not treated, but it is not clear how they propagate and lead to tissue degradation. We used an advanced numerical model to determine the role of cartilage structure and composition on crack morphology under loading. Based on the structure and composition found in immature and mature cartilages, our model successfully predicts the crack morphology in these cartilages and determines that collagen fibre as the major determinant of crack morphology. The arcade-like Benninghoff collagen fibre orientation appears to be crucial in ‘sealing’ the tissue crack and preserves normal fluid-solid load distribution in cartilage. Inclusion of the arcade-like fibre orientation in tissue-engineered construct may help improve its integration within the host tissue.

The effect of the platelet-rich plasma and ozone therapy on tendon-to-bone healing in the rabbit rotator cuff repair model

BackgroundThe aim of this study is to histologically and biomechanically investigate the effects of local PRP and ozone therapy (O2O3) on tendon-to-bone healing in a rabbit model of the supraspinatus tendon tear.MethodsFour groups were formed to have seven rabbits in each group: repair, R; repair + PRP, RP; repair + ozone, RO; and repair + PRP + ozone, RPO. The supraspinatus tendon was detached by sharp dissection from the footprint and an acute tear pattern was created. Thereafter, tendon repair was performed with the transosseous technique. In the RP group, PRP, and in the RPO group, PRP + O2O3 mixture was injected to the tendon repair site. In the RO group, O2O3 gas mixture was injected into subacromial space three times a week for a total of 4 weeks. The study was ended at postoperative 6th week.ResultsWhen compared with the R group, a statistically significant increase was observed in the biomechanical strength of the RP and RPO groups. The highest increase in biomechanical strength was detected in the RPO group. The histology of the RO and RPO groups showed better collagen fiber continuity and orientation than the R and RP groups.ConclusionsThe results obtained from this study show that the ozonized PRP can be used as biological support to increase tendon-to-bone healing. However, these results need to be supported by clinical studies.

Establishment of a long-term hypertrophic scar model by injection of anhydrous alcohol: A rabbit model.

The processes of hypertrophic scar formation are extremely complex, and current animal models have limitations in terms of the complete characterization of lesions. An ideal animal model is indispensable for exploring the complex progression of scar formation to elucidate its pathophysiology and to perform therapeutic testing. This study aimed to establish a long-term, consistent and easily testable animal model by injecting anhydrous alcohol into the dorsal trunk dermis of rabbits. The rabbits were injected with different amounts of anhydrous alcohol. Anhydrous alcohol was infiltrated into the subcutaneous and superficial fascia. The optimal amount of anhydrous alcohol was determined by measuring the area and thickness of the scar. The typical model was established by determining the optimum dosage, and then we analysed the histological characteristics and fibrosis-associated protein expression. The dermal scar was generated by treating with 2ml/kg anhydrous alcohol and displayed histopathologic features that characterize human hypertrophic scarring, including a parallel collagen fibre orientation, dermal and epidermal thickening, broad collagen deposition and the loss of dermal adnexal structures. The expression of fibrotic pan-markers was also enhanced. Moreover, the scar features and duration were compared between the anhydrous alcohol model and the rabbit ear model. Our results show that injecting anhydrous alcohol in the rabbit model thickened the dermal tissue, stimulated dermal fibroproliferation and resulted in hypertrophic scars with protein and histologic features similar to those seen in humans. Taken together, the findings from this study show that our model could be a feasible and useful tool for further research on the pathogenesis of hypertrophic scars.

Microengineered 3D Collagen Gels with Independently Tunable Fiber Anisotropy and Directionality.

Cellular processes, including differentiation, proliferation, and migration, have been linked to the alignment (anisotropy) and orientation (directionality) of collagen fibers in the native extracellular matrix (ECM). Given the critical role that biophysical cell-matrix interactions play in regulating biological functions, several microfluidic-based methods have been used to establish 3D collagen gels with defined fiber properties; these gels have helped to establish quantitative relationships between structural ECM cues and observed cell responses. Although existing microfluidic fabrication methods provide excellent definition over collagen fiber anisotropy, they have not demonstrated the independent control over fiber anisotropy and directionality necessary to replicate in vivo collagen architecture. Therefore, to advance collagen microengineering capabilities, we present a user-friendly technology platform that uses controlled fluid flows within a non-uniform microfluidic channel network to create collagen landscapes that can be tuned as a function of extensional strain rate. Herein, we demonstrate capabilities to i) control the degree of fiber anisotropy, ii) create spatial gradients in fiber anisotropy, iii) independently define fiber directionality, and iv) generate multi-material interfaces within a 3D environment. We then address the practical issue of integrating cells into microfluidic systems by using a peel-off template technique to provide direct access to microengineered collagen gels, and demonstrate that cells respond to the defined properties of the landscape. Finally, the platform's modular capability is highlighted by integrating a sub-micrometer thick porous parylene membrane onto the microengineered collagen as a method to define cell-substrate interactions.

Osteoarthritic meniscal entheses exhibit altered collagen fiber orientation

ABSTRACT Purpose/Aim The knee menisci are vital for maintaining the stability of the joint, allowing for force distribution, and protecting the underlying articular cartilage during loading. Each meniscus is attached to the underlying bone via two ligamentous entheses composed of collagen fibers that are continuous throughout all four zones of the attachment: ligament, uncalcified fibrocartilage, calcified fibrocartilage, and subchondral bone. The collagen fibers of the meniscal entheses are important for proper functionality of the entheses, particularly in preventing meniscal extrusion which is a common hallmark of osteoarthritis. The goal of this work was to assess changes in collagen fiber orientation present in osteoarthritic knee joints. Materials and Methods Entheses were harvested from patients undergoing total knee arthroplasties and prepared histological sections were stained with picrosirius red to identify collagen fiber angle and fiber deviation. Results In the calcified fibrocartilage the collagen fibers of the lateral anterior enthesis inserted at significantly (p < 0.1) shallower angles, and the fiber deviation was significantly (p < 0.1) less compared to the lateral posterior enthesis. These differences in the calcified fibrocartilage may occur as an adaptation to loading regimes of the osteoarthritic joint. When compared to the collagen fiber orientation of healthy entheses, collagen fibers in osteoarthritic tissue inserted at shallower insertion angles and demonstrated higher levels of deviation. Conclusions Changes to meniscal enthesis collagen fiber orientation with end stage osteoarthritis could offer an explanation for the change in functionality of diseased tissue and may contribute to meniscal extrusion and ultimately the degeneration of articular cartilage.

20184 A Hypothesis-Driven Parametric Study of a Computational Dermal Replacement Model

ABSTRACT IMPACT: This work will be used to improve the design of engineered dermal replacements that can be used to treat difficult-to-heal wounds such as burns or ulcers. OBJECTIVES/GOALS: Wounds of the skin are among the most common and costly medical problems experienced. Engineered dermal replacements have been developed to improve outcomes, but the optimal design features are unknown. Here we describe a hypothesis-driven study of scaffold parameters using a computational model of wound healing to simulate a variety of treatments. METHODS/STUDY POPULATION: The computational model, which was informed by animal data, was used to simulate cell, cytokine, and collagen density fields. There are reciprocal mechanobiological interactions between the cells and collagen that guide the wound healing process. We analyzed initial wound properties such as scaffold stiffness, microstructure, degradation, and wound geometry by running a one-at-a-time order-of-magnitude parameter change. We then conducted a derivative-based local sensitivity analysis for simulated experimental conditions and constructed a surrogate model of wound contraction using Gaussian process regression. RESULTS/ANTICIPATED RESULTS: We conducted finite element model simulations of scaffolds that varied in physical properties. A sensitivity analysis demonstrated that wound contraction was highly sensitive to collagen fiber stiffness and density. Wound contraction rate was also dependent on initial wound size and surface area. Collagen fiber orientation in the scaffolds affected contraction directionality and the orientation of the final wound area. A Gaussian process regression model was fit to the simulation results for use in rapid prototyping of scaffolds for design optimization. The Gaussian process model was able to reproduce the wound contracture for training and test cases. DISCUSSION/SIGNIFICANCE OF FINDINGS: This work further analyzes a computational model of wounds treated with collagen scaffold dermal replacements. The hypothesis driven analysis of the model suggested several key design features of scaffolds. The model surrogate will further be used for the purposes of prediction and optimization of tissue regeneration outcomes.

Variation of Passive Biomechanical Properties of the Small Intestine along Its Length: Microstructure-Based Characterization.

Multiaxial testing of the small intestinal wall is critical for understanding its biomechanical properties and defining material models, but limited data and material models are available. The aim of the present study was to develop a microstructure-based material model for the small intestine and test whether there was a significant variation in the passive biomechanical properties along the length of the organ. Rat tissue was cut into eight segments that underwent inflation/extension testing, and their nonlinearly hyper-elastic and anisotropic response was characterized by a fiber-reinforced model. Extensive parametric analysis showed a non-significant contribution to the model of the isotropic matrix and circumferential-fiber family, leading also to severe over-parameterization. Such issues were not apparent with the reduced neo-Hookean and (axial and diagonal)-fiber family model, that provided equally accurate fitting results. Absence from the model of either the axial or diagonal-fiber families led to ill representations of the force- and pressure-diameter data, respectively. The primary direction of anisotropy, designated by the estimated orientation angle of diagonal-fiber families, was about 35° to the axial direction, corroborating prior microscopic observations of submucosal collagen-fiber orientation. The estimated model parameters varied across and within the duodenum, jejunum, and ileum, corroborating histologically assessed segmental differences in layer thicknesses.

Synergistic effect of platelet-rich plasma in combination with fractional carbon dioxide laser versus its combination with pulsed dye laser in striae distensae: A comparative study.

Striae distensae (SD) are very common atrophic cutaneous scarring that are therapeutically challenging. Various kinds of laser had been suggested as effective treatment modalities for SD. In addition, platelet-rich plasma (PRP) was recently recommended for its therapy. To evaluate the synergistic role of PRP injection as a combined modality to fractional CO2 laser (Fr CO2 ) versus its combination with pulsed dye laser (PDL) in SD. Thirty SD patients were included in this study and treated by intradermal injection of autologous PRP on both sides, followed by laser therapy (Fr CO2 laser on right side and PDL on left side). They received 3 treatment sessions at 6weeks interval. Both treatment sides reported significant clinical improvements of SD lesions, evidenced by significant reduction of width of striae lesions and significant improvement of skin texture. Furthermore, significantly higher degree of clinical improvements were observed in response to treatment sessions by combined PRP with Fr CO2 laser rather than combined PRP with PDL. Generally, post-inflammatory hyperpigmentation (PIH) were mild in all patients. Histopathologically, SD lesions showed improvement of epidermal thickness, and more homogenization and regular orientation of dermal collagen fibers in both treatment sides, with more significant improvement on the side treated by combined PRP with Fr CO2 laser sessions rather than the other side. PRP injection in combination with Fr CO2 laser or PDL is considered safe and effective therapeutic regimens for SD. However, its combination with Fr CO2 laser is more promising with better outcome and fewer side effects.

Characterizing the transient response of knee cartilage to running: Decreases in cartilage T2 of female recreational runners.

Cartilage transmits and redistributes biomechanical loads in the knee joint during exercise. Exercise-induced loading alters cartilage hydration and is detectable using quantitative magnetic resonance imaging (MRI), where T2 relaxation time (T2 ) is influenced by cartilage collagen composition, fiber orientation, and changes in the extracellular matrix. This study characterized short-term transient responses of healthy knee cartilage to running-induced loading using bilateral scans and image registration. Eleven healthy female recreational runners (33.73 ± 4.22 years) and four healthy female controls (27.25 ± 1.38 years) were scanned on a 3T GE MRI scanner with quantitative 3D double-echo in steady-state before running over-ground (runner group) or resting (control group) for 40 min. Subjects were scanned immediately post-activity at 5-minintervals for 60 min. T2 times were calculated for femoral, tibial, and patellar cartilage at each time point and analyzed using a mixed-effects model and Bonferroni post hoc. There were immediate decreases inT2 (mean ± SEM) post-run in superficial femoral cartilage of at least 3.3% ± 0.3% (p = .002) between baseline and Time 0 that remained for 25 min, a decrease in superficial tibial cartilage T2 of 2.9% ± 0.4% (p = .041) between baseline and Time 0, and a decrease in superficial patellar cartilage T2 of 3.6% ± 0.3% (p = .020) 15 min post-run. There were decreases in the medial posterior region of superficial femoral cartilage T2 of at least 5.3 ± 0.2% (p = .022) within 5 minpost-run that remained at 60 min post-run.These results increase understanding of transient responses of healthy cartilage to repetitive, exercise-induced loading and establish preliminary recommendations for future definitive studies of cartilage response to running.