Elastic Cartilage Research Articles

Long-term, Time-course Evaluation of Ligamentum Flavum Hypertrophy Induced by Mechanical Stress: An Experimental Animal Study.

Experimental animal study. The aim of this study was to clarify chronological effects of mechanical stress on ligamentum flavum (LF) using a long-term fusion rabbit model. LF hypertrophy is a major pathology of lumbar spinal stenosis (LSS), but its mechanism remains unclear. We previously demonstrated mechanical-stress-induced LF hypertrophy with a rabbit model. However, we only investigated LFs at a single time point in the short-term; the effects of long-term mechanical stress have not been elucidated. Eighteen-week-old male New Zealand White rabbits were randomly divided into two groups: the mechanical stress group underwent L2-3 and L4-5 posterolateral fusion and resection of the L3-4 supraspinal muscle, whereas the control group underwent only surgical exposure. Rabbits were sacrificed 16 and 52 weeks after the procedure. Axial specimens of LFs at L3-4 were evaluated histologically. Immunohistochemistry for alpha-smooth muscle actin (α-SMA) was performed to assess the numbers of vessels and myofibroblasts. In the mechanical stress group, LFs at the L3-4 level exhibited hypertrophy with elastic fiber disruption and cartilage matrix production at 16 and 52 weeks. A trend test indicated that mechanical stress induced LF hypertrophy, elastic fiber disruption, and cartilage matrix production in a time-dependent manner, with the lowest levels before treatment and the highest at 52 weeks. Immunostaining for α-SMA showed similar numbers of vessels in both groups, whereas the percentage of myofibroblasts was significantly larger at 16 and 52 weeks in the mechanical stress group than in the control group. We demonstrated that long-term mechanical stress caused LF hypertrophy with progressive elastic fiber disruption and cartilage matrix production accompanied by enhanced myofibroblasts. In addition, the reported rabbit model could be extended to elucidate the mechanism of LF hypertrophy and to develop new therapeutic strategies for LSS by preventing LF hypertrophy.Level of Evidence: SSSSS.

Unilateral cervical chondrocutaneous branchial remnant in Korean: A case report

Background: Compared to the frequency of occurrence of pre-auricular skin tag, cervical chondrocutaneous branchial remnants is one of congenital, benign neck masses that is very rare all over the world. Most of these rare anomalies are reported in case reports and especially, rare cases of unilateral cervical chondrocutaneous branchial remnants have been reported in Korean. Materials & Methods: A 9-year-old male patient visited the hospital on September 2017 for a rod-shaped mass. As a simultaneous diagnosis and treatment method, complete surgical excision was executed. Results: Excised mass was 0.5cm in diameter, 1.2cm in. Histologically, a hyaline and elastic cartilage was found in the core. As a family history, the same remnant was found in the right Anterior neck area of his mother. Conclusion: In this case, it is possible to diagnose and treat simply at the same time and even an optimal aesthetic result can be obtained. Key Words: Cervical Chondrocutaneous Branchial Remnant, Skin tag, Choristoma

12 Degrees of Freedom Muscle Force Driven Fibril-Reinforced Poroviscoelastic Finite Element Model of the Knee Joint.

Accurate knowledge of the joint kinematics, kinetics, and soft tissue mechanical responses is essential in the evaluation of musculoskeletal (MS) disorders. Since in vivo measurement of these quantities requires invasive methods, musculoskeletal finite element (MSFE) models are widely used for simulations. There are, however, limitations in the current approaches. Sequentially linked MSFE models benefit from complex MS and FE models; however, MS model's outputs are independent of the FE model calculations. On the other hand, due to the computational burden, embedded (concurrent) MSFE models are limited to simple material models and cannot estimate detailed responses of the soft tissue. Thus, first we developed a MSFE model of the knee with a subject-specific MS model utilizing an embedded 12 degrees of freedom (DoFs) knee joint with elastic cartilages in which included both secondary kinematic and soft tissue deformations in the muscle force estimation (inverse dynamics). Then, a muscle-force-driven FE model with fibril-reinforced poroviscoelastic cartilages and fibril-reinforced poroelastic menisci was used in series to calculate detailed tissue mechanical responses (forward dynamics). Second, to demonstrate that our workflow improves the simulation results, outputs were compared to results from the same FE models which were driven by conventional MS models with a 1 DoF knee, with and without electromyography (EMG) assistance. The FE model driven by both the embedded and the EMG-assisted MS models estimated similar results and consistent with experiments from literature, compared to the results estimated by the FE model driven by the MS model with 1 DoF knee without EMG assistance.

Development of a Method for Scaffold-Free Elastic Cartilage Creation.

Microtia is a congenital aplasia of the auricular cartilage. Conventionally, autologous costal cartilage grafts are collected and shaped for transplantation. However, in this method, excessive invasion occurs due to limitations in the costal cartilage collection. Due to deformation over time after transplantation of the shaped graft, problems with long-term morphological maintenance exist. Additionally, the lack of elasticity with costal cartilage grafts is worth mentioning, as costal cartilage is a type of hyaline cartilage. Medical plastic materials have been transplanted as alternatives to costal cartilage, but transplant rejection and deformation over time are inevitable. It is imperative to create tissues for transplantation using cells of biological origin. Hence, cartilage tissues were developed using a biodegradable scaffold material. However, such materials suffer from transplant rejection and biodegradation, causing the transplanted cartilage tissue to deform due to a lack of elasticity. To address this problem, we established a method for creating elastic cartilage tissue for transplantation with autologous cells without using scaffold materials. Chondrocyte progenitor cells were collected from perichondrial tissue of the ear cartilage. By using a multilayer culture and a three-dimensional rotating suspension culture vessel system, we succeeded in creating scaffold-free elastic cartilage from cartilage progenitor cells.

Use of collagen and auricular cartilage in bioengineering: scaffolds for tissue regeneration.

The aim of this study was the development of collagen and collagen/auricular cartilage scaffolds for application in dermal regeneration. Collagen was obtained from bovine tendon by a 72h-long treatment, while bovine auricular cartilage was treated for 24h and divided into two parts, external (perichondrium, E) and internal (elastic cartilage, I). The scaffolds were prepared by mixing collagen (C) with the internal part (CI) or the external part (CE) in a 3:1 ratio. Differential scanning calorimetry, scanning electron microscopy (SEM) analysis, microcomputed tomography imaging (micro-CT) and swelling degree were used to characterize the scaffolds. Cytotoxicity, cell adhesion, and cell proliferation assays were performed using the cell line NIH/3T3. All samples presented a similar denaturation temperature (Td) around 48°C, while CE presented a second Td at 51.2°C. SEM micrographs showed superficial pores in all scaffolds and micro-CT exhibited interconnected pore spaces with porosity above 60% (sizes between 47 and 149µm). The order of swelling was CE < CI < C and the scaffolds did not present cytotoxicity, showing attachment rates above 75%-all samples showed a similar pattern of proliferation until 168h, whereas CI tended to decrease after this time. The scaffolds were easily obtained, biocompatible and had adequate morphology for cell growth. All samples showed high adhesion, whereas collagen-only and collagen/external part scaffolds presented a better cell proliferation rate and would be indicated for possible use in dermal regeneration.

Cervical chondrocutaneous branchial remnants: A report of 29 cases and review of the literature

ObjectiveCervical chondrocutaneous branchial remnants (CCBRs) are rare masses located in the anterior region of the neck. Though the basic characteristics of these rare masses were first described by Atlan in 1997, a critical amount of information about these masses remains unknown. This study aimed to further clarify the characteristics of these rare masses. MethodsWe retrospectively reviewed the clinical records of patients with CCBRs in our facility during a 32-year period ranging from 1988 to 2019. We then compared our clinical records with other case reports. ResultsThere were 29 patients with CCBRs in our facility, including 19 males and ten females, Three patients were involved bilaterally (among patients involved unilaterally, the right side included 11 patients, and the left side was 15 patients), eight patients also had associated abnormalities. We submitted CCBRs from 18 patients to pathology, and all of them contained elastic cartilages. Among all the surgical data could be confirmed, cartilages did not reach beyond the musculature of the neck.We could confirm a similar tendency with Atlan regarding sex, the location of CCBRs (involvement side, localization in the neck), and the depth of CCBRs. Among the cases contained in this study, there was a disparity in the rate of associated abnormalities and pathology of contained cartilages. ConclusionSome critical characteristics of CCBRs included, a male predominance, scarcity of bilateral cases and common left side involvement among unilateral involved cases, a common location of CCBRs in the inferior third of the neck and anterior to the sternocleidomastoid muscle, and an involvement of cartilage in CCBRs which has no connections to deep underlying structure of the neck. Further investigations are required to determine the origin of CCBRs and the precise incidence of the associated abnormalities. Systemic examination in patients with CCBRs is recommended because many associated abnormalities have been reported.

Accessory Tragus: A Rare Congenital Anomaly in a Dog

Accessory tragus is a congenital malformation of part of the external ear, commonly reported in humans. Clinically, it is a benign, cutaneous mass located anywhere between the tragus of the ear and the angle of the mouth, along the migratory path of the first branchial arch. An accessory tragus was diagnosed in an otherwise healthy six-month-old male castrated American pit bull terrier that had a haired, pedunculated cutaneous mass on the left maxillary region from birth. Histologically, the mass was a polypoid extension of histologically normal haired skin with a central core of subcutaneous adipose tissue and well-differentiated elastic cartilage. To the authors' knowledge, this is the first report of this lesion in a non-human species. Retrospective examination of records from 2008 to 2018 at the Washington Animal Disease Diagnostic Laboratory failed to identify any other case. As accessory tragus in humans is commonly linked with other congenital anomalies and syndromes, recognition of this lesion in animals may aid in early discovery of other congenital defects and inform adequate excision of the lesion to prevent chondrodermatitis.

Protein profile of ear auricle cartilage and the important role of ITGB1/PTK2 in microtia

BackgroundMicrotia is a congenital malformation of the external ear that involves anything from a small reduction in size to a complete absence. The external ear is composed of elastic cartilage which is also the important skeleton of the outer ear. However no previous study explored the difference between abnormal elastic cartilage and normal cartilage in the molecular level. MethodsMicrotia cartilage and normal cartilage tissue samples from patients subjected to autologous costal cartilage reconstruction were obtained in surgery. Total proteins were extracted and purified, and then proteomic analyzed via LC-MS/MS using DDA/DIA data collection methods. Proteins were also isolated with lysis beads and then analyzed via antibody chip. Differentially expressed proteins were identified in both experiments and further analyzed with functional enrichment analysis and KEGG pathway analysis. Valuable regulatory gene expression level was verified by RT-PCR. ResultsA total of 4178 protein types were identified in the DDA experiment. A total of 2154 proteins were quantified, 172 of which were significantly upregulated and 82 downregulated in the microtia group (P < 0.05). Antibody chip detection allowed identification of 584 protein phosphorylation sites with 102 upregulation sites and 9 downregulation sites (P < 0.05). Differentially altered proteins were annotated to 143 KEGG pathways, while differentiated phosphate site-associated genes were annotated into 21 KEGG pathways. Two intersecting pathways, the PI3K/AKT/mTOR pathway and the focal adhesion pathway, may paly important role on ear auricle cartilage development. One item is significant in both differential protein expression and phosphorylation. Integrin beta-1, that is downregulated in protein quantification of the microtia group. The mean ITGB1 mRNA level of the microtia patient group was significantly lower than in the healthy control group (P = 0.0007 < 0.05). And the gene expression of downstream gene PTK2 was also decreased. (P = 0.0288 < 0.05). ConclusionThe research locates the key protein Integrin Beta-1, and verified it at the mRNA level. The increasing level of ITGB1 and decreasing of PTK2 may play an important role in congenital ear deformity. This research will inspire more otolaryngologists and orthopedics doctors to pay attention to the etiology and mechanism of microtia.

Regeneration of elastic cartilage with accurate human-ear shape based on PCL strengthened biodegradable scaffold and expanded microtia chondrocytes

Tissue engineering provides a promising approach for auricle reconstruction of microtia. Although the first clinical trial of tissue-engineered ear reconstruction has been performed using in vitro engineered human-ear-shaped cartilage, this approach is not regarded as the clinically available treatment yet, due to individual differences in clinical efficacy. In the present study, the feasibility and in vivo long-term fate of elastic cartilage regenerated with an accurate human-ear shape were explored using polycaprolactone (PCL) inner support strengthened biodegradable scaffold and expanded microtia chondrocytes (MCs) to identify factors that may result in discrepant clinical outcomes. Polyglycolic acid/polylactic acid (PGA/PLA) scaffolds with or without PCL inner support were prepared into different shapes by three-dimensional (3D) printing, hot-compressing, and pre-molding technologies. The expanded MCs were seeded into the scaffolds to evaluate biocompatibility of PCL inner support and its influence on cartilage regeneration, tissue integration, mechanical strength, and shape maintenance. The results testified that all the cartilages generated by different patients’ cells were highly consistent in both qualitative and quantitative data, indicating high repeatability and stability of cartilage construction technology. PCL inner support manifested a satisfactory biocompatibility and it had no inhibitory effect on cartilage formation, maturation, and tissue integration. After in vivo implantation, the regenerated cartilage without PCL inner support showed the same level of mechanical strength and shape maintenance ability as the PCL strengthened cartilage. Mature and continuous elastic cartilage with an accurate ear shape could be successfully regenerated in vivo with a long-term shape maintenance. All the cells of regenerated cartilage were derived from the implanted MCs, which could survive and maintain their phenotype for a long time. The current study provides reliable evidence, key techniques, and optimized strategies for further clinical applications of in vitro regenerated cartilage with special shapes such as ear, nose, and trachea.

Regeneration of human-ear-shaped cartilage with acellular cartilage matrix-based biomimetic scaffolds

Tissue engineering technology provides a promising approach for external ear reconstruction. Although the first clinical breakthrough of tissue engineered auricular reconstruction has been achieved based on polymer scaffold, the discrepant clinical efficacy among different patients triggered by residual scaffold mediated aseptic inflammatory reaction seriously hinders its further clinical application. A proper natural scaffold with low inflammatory reaction is urgently required to address this problem. Among all the natural materials, acellular cartilage matrix (ACM) is considered to be the ideal cartilage-specific microenvironmental biomimetic scaffold. However, no breakthroughs have been achieved for the regeneration of human-ear-shaped cartilage based on ACM so far. The main challenge is how to prepare ACM into a three-dimensional (3D) porous scaffold with precise human-ear shape and proper mechanical strength. In this study, ACM powder, prepared by freezing pulverization and decellularization, was successfully prepared into 3D porous scaffolds using gelatin as an auxiliary crosslinker. By optimizing proportion and concentration of ACM and gelatin, the scaffolds presented proper pore structure and degradation rate as well as good mechanical strength and biocompatibility. Furthermore, ACM/Gelatin could be fabricated into porous scaffolds with precise human-ear shape and proper mechanical strength by integrating 3D printing, polycaprolactone (PCL) inner core designing, cast molding, and freeze-drying technologies. Finally, human-ear-shaped cartilage with good elasticity and cartilage-specific extracellular matrices was successfully regenerated using the ACM/Gelatin-PCL scaffolds and auricular chondrocytes (elastic cartilage). All of these results provide important support for the application and clinical translation of human-ear-shaped cartilage.

Coating Medpor® Implant with Tissue-Engineered Elastic Cartilage.

Inert biomaterials used for auricular reconstruction, which is one of the most challenging and diverse tasks in craniofacial or head and neck surgery, often cause problems such as capsule formation, infection, and skin extrusion. To solve these problems, scaffold consisting of inert biomaterial, high-density polyethylene (Medpor®) encapsulated with neocartilage, biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) was created using a tissue engineering strategy. PLGA scaffold without Medpor® was created to serve as the control. Scaffolds were vacuum-seeded with rabbit chondrocytes, freshly isolated from the ear by enzymatic digestion. Then, cell-seeded scaffolds were implanted subcutaneously in the dorsal pockets of nude mice. After 12 weeks, explants were analyzed by histological, biochemical, and mechanical evaluations. Although the PLGA group resulted in neocartilage formation, the PLGA–Medpor® group demonstrated improved outcome with the formation of well-surrounded cartilage around the implants with higher mechanical strength than the PLGA group, indicating that Medpor® has an influence on the structural strength of engineered cartilage. The presence of collagen and elastin fibers was evident in the histological section in both groups. These results demonstrated a novel method of coating implant material with engineered cartilage to overcome the limitations of using biodegradable scaffold in cartilage tissue regeneration. By utilizing the patient’s own chondrocytes, our proposed method may broaden the choice of implant materials while minimizing side effects and immune reaction for the future medical application.

Histological analysis of elastic cartilages treated with alkaline solution

ABSTRACT The elastic cartilage is composed by chondroblasts and chondrocytes, extracellular matrix and surrounded by perichondrium. It has a low regeneration capacity and is a challenge in surgical repair. One of obstacles in engineering a structurally sound and long-lasting tissue is selecting the most appropriate scaffold material. One of the techniques for obtaining biomaterials from animal tissues is the decellularization that decreases antigenicity. In this work, alkaline solution was used in bovine ear elastic cartilages to evaluate the decellularization and the architecture of the extracellular matrix. The cartilages were treated in alkaline solution (pH13) for 72 hours and lyophilized to be compared with untreated cartilages by histological analysis (hematoxylin-eosin, Masson's trichrome and Verhoeff slides). Areas of interest for cell counting and elastic fiber quantification were delineated, and the distribution of collagen and elastic fibers and the presence of non-fibrous proteins were observed. The results demonstrated that the alkaline solution caused 90% decellularization in the middle and 13% in the peripheral region, and maintenance of the histological characteristics of the collagen and elastic fibers and non-fibrous protein removal. It was concluded that the alkaline solution was efficient in the decellularization and removal of non-fibrous proteins from the elastic cartilages of the bovine ear.

Comparison of the compressive mechanical properties of auricular and costal cartilage from patients with microtia

Children born with a small or absent ears undergo surgical reconstruction to restore their auricle. Currently, rib (costal) cartilage is used to carve the auricle. However as alternative, tissue engineered and synthetic materials are being developed to restore the auricle shape to overcome donor site morbidity and limited availability of rib cartilage. However, to date there is limited knowledge regarding the mechanical properties of the auricular and costal cartilage to optimise the required compressive properties of the graft. The remnant auricular and costal cartilage from 20 patients undergoing stage-1 microtia surgery was harvested. On the day of surgery, the cartilage was evaluated in compression, with each sample loaded to 300 g at 1 mm/s. ResultsThe costal cartilage was observed to have a significantly higher Young’s Elastic Modulus than auricular cartilage (average costal cartilage 11.43 MPa vs average auricular cartilage 2 MPa, p < 0.0001). The auricular cartilage showed a significantly higher relaxation rate than costal cartilage (average costal cartilage 0.72 MPa10-4 vs average auricular cartilage 1.93 MPa10-4, p < 0.05). The final absolute relaxation was significantly lower for elastic cartilage than costal cartilage (average costal cartilage 3.35 MPa vs average auricular cartilage 0.2 MPa, p < 0.0001). Alloplastic cartilage replacements used as alternatives for reconstruction were also evaluated. Silicone, Gore-Tex and Medpor were observed to have significantly higher Young’s Elastic Modulus than costal and auricular cartilage.Costal cartilage has a higher Young’s Elastic Modulus in compression compared to auricular cartilage. Current synthetic materials used to replace synthetic cartilage do not mimic costal cartilage, which should be addressed in the future.

EMG-Assisted Muscle Force Driven Finite Element Model of the Knee Joint with Fibril-Reinforced Poroelastic Cartilages and Menisci

Abnormal mechanical loading is essential in the onset and progression of knee osteoarthritis. Combined musculoskeletal (MS) and finite element (FE) modeling is a typical method to estimate load distribution and tissue responses in the knee joint. However, earlier combined models mostly utilize static-optimization based MS models and muscle force driven FE models typically use elastic materials for soft tissues or analyze specific time points of gait. Therefore, here we develop an electromyography-assisted muscle force driven FE model with fibril-reinforced poro(visco)elastic cartilages and menisci to analyze knee joint loading during the stance phase of gait. Moreover, since ligament pre-strains are one of the important uncertainties in joint modeling, we conducted a sensitivity analysis on the pre-strains of anterior and posterior cruciate ligaments (ACL and PCL) as well as medial and lateral collateral ligaments (MCL and LCL). The model produced kinematics and kinetics consistent with previous experimental data. Joint contact forces and contact areas were highly sensitive to ACL and PCL pre-strains, while those changed less cartilage stresses, fibril strains, and fluid pressures. The presented workflow could be used in a wide range of applications related to the aetiology of cartilage degeneration, optimization of rehabilitation exercises, and simulation of knee surgeries.

First evidence of a functional spiracle in stem chondrichthyan acanthodians, with the oldest known elastic cartilage.

Spiracles are a general character of gnathostomes (jawed fishes), being present in antiarch placoderms, commonly regarded as the most basal gnathostome group. The presence of spiracular tubes in acanthodians has been deduced from grooves on the neurocranium of the derived acanthodiform Acanthodes bronni from the Permian of Germany, but until now these tubes were presumed to lack an external opening, rendering them non-functional. Here we describe the external spiracular elements in specimens of the Middle Devonian acanthodiforms Cheiracanthus murchisoni, Cheiracanthus latus and Mesacanthus pusillus from northern Scotland, and the internal structure of these elements in C.murchisoni, demonstrating that the spiracle in acanthodiforms differed from all known extant and extinct fishes in having paired cartilage-pseudobranch structures. This arrangement represents a transitional state between the presumed basal gnathostome condition with an unconstricted first gill slit (as yet not identified in any fossil) and the derived condition with a spiracle and a single pseudobranch derived from the posterior hemibranch of the mandibular arch. We identify the main tissue forming the pseudobranch as elastic cartilage, a tissue previously unrecorded in fossils.

Morphological study of larynx, trachea, and lungs of Didelphis marsupialis (LINNAEUS, 1758)

Background and Aim:From a biomedical point of view, the value of marsupials as a model of primitive mammals is indisputable. Among its species, the possum is a model that allows the study of the ontogeny of different organic systems, as well as their physiological aspects. The relevance of anatomical, functional, evolutionary, and phylogenetic study of marsupials for the development of comparative morphology is extensively documented in the literature. However, there are still many aspects to be further evaluated, as the anatomy and histology of the respiratory tract of this species. The aim of this study was to describe the morphology of the larynx, trachea, and lungs of Didelphis marsupialis.Materials and Methods:Five adult male animals were donated to the Comparative Animal Anatomy Laboratory – LAAC/CCAA-UFMA, for morphological studies. Specimens were washed in running water to perform biometrics. Then, they were fixed with 10% formaldehyde solution. After the fixation period, the specimens were positioned in dorsal decubitus position, for dissection of the respiratory system organs, by opening the ventral region of the neck and thoracic cavity, with subsequent removal of the pectoral muscles, ribs, and sternum. For histological analysis, fragments of 1 cm2 of the larynx (epiglottis and thyroid cartilages), trachea, and lungs were collected and fixed in 10% formaldehyde solution. Right after fixation, the fragments were dehydrated in increasing concentrations of ethyl alcohol (70, 80, 95, and 100%), diaphanized in xylene, embedded in paraffin, and sectioned into thin slices of 5 μm using a microtome. Sections were stained using the hematoxylin and eosin technique.Results:Anatomically, the larynx starts right after the pharynx. It consisted of four cartilages: Epiglottis, cricoid, thyroid, and arytenoid. The trachea was made of dorsally incomplete cartilaginous rings. At the entrance of the thoracic cavity, it bifurcated into the left and right main bronchus. The left lung was smaller than the right lung, with two lobes (cranial and caudal). The right lung presents the cranial, middle, caudal, and accessory lobes. Histologically, the epiglottis consisted of elastic cartilage and is covered by a non-keratinized stratified squamous epithelium. Thyroid cartilage is made of hyaline cartilage covered by smooth muscle. The trachea presents hyaline cartilage, with ciliated pseudo-stratified epithelium, serous glands, isogenic groups of chondrocytes, and perichondrium. The lung consisted of bronchi, bronchioles, and alveoli, also presenting blood vessels and arteries.Conclusion:Morphologically, the larynx, trachea, and lungs of D. marsupialis were similar to those of the other Didelphids described in the literature.

Study of Some Histological Properties of Skeletal Muscles in a Fish Gymnura micrura

The present study showed some histological properties of skeletal muscles in Gymnura micrura belong to the family Dasyatidae, specimens of fish collected from the AL-Fao area in Iraqi territorial waters with assistance from a fisherman. The results declare two types of cartilage that can be distinguished: hyaline cartilage, which constitutes a large percentage of the cartilage mass, in addition to the presence of another type, the elastic cartilage. The results showed that the diameter of red muscle fibers alternated between (22.30 - 37.17 microns), while it alternated between (44.61 – 104.09 microns) of the white muscle fibers diameter in studied fish, this difference possibly attributed to the functional role of white and red muscle fibers and their effect in the mechanics of movement.

Regenerative medicine of tissue engineering： auricular cartilage regeneration and functional reconstruction

Summary Deformity of the auricle can result from congenital defects, oncologic resection, or traumatic injury. Current clinical strategy is to utilize autologous costal cartilage for reconstructing auricular scaffolds with long-term stability. However, this method is limited by donor-site morbidity, a complex surgical sculpting process, and differing mechanical properties compared to elastic auricular cartilage. Alternatively, alloplastic implants can offer precise shape and avoid donor-site surgery, but suffer from poor biocompatibility and high rates of infection and extrusion. A tissue engineering approach to auricular reconstructions would overcome the limitations of both autologous and alloplastic transplants. In this review we focus on tissue engineering auricular cartilage reconstruction, including auricular seed cells culture and their differentiated control strategy, scaffolds choices and design technique. Many studies found that auricular chondrocytes were the most suitable seed cells to fabricate elastic cartilage; progenitor cells from auricular cartilage could differentiate into elastic chondrocytes, and other types of chondrocytes had its limitation because of the final ossification. Many types of growth factors had the differing potential ability for accelerating chondrocytes growth, differentiation, or maintaining chondrocytes phenotype. Recent advances in tissue engineering auricular cartilage, including several clinic applications, implied that tissue engineering auricules would become a hopefully potential soulution for the future of auricular reconstruction.

Age estimation based on different molecular clocks in several tissues and a multivariate approach: an explorative study.

Several molecular modifications accumulate in the human organism with increasing age. Some of these "molecular clocks" in DNA and in proteins open up promising approaches for the development of methods for forensic age estimation. A natural limitation of these methods arises from the fact that the chronological age is determined only indirectly by analyzing defined molecular changes that occur during aging. These changes are not linked exclusively to the expired life span but may be influenced significantly by intrinsic and extrinsic factors in the complex process of individual aging. We tested the hypothesis that a combined use of different molecular clocks in different tissues results in more precise age estimates because this approach addresses the complex aging processes in a more comprehensive way. Two molecular clocks (accumulation of D-aspartic acid (D-Asp), accumulation of pentosidine (PEN)) in two different tissues (annulus fibrosus of intervertebral discs and elastic cartilage of the epiglottis) were analyzed in 95 cases, and uni- and multivariate models for age estimation were generated. The more parameters were included in the models for age estimation, the smaller the mean absolute errors (MAE) became. While the MAEs were 7.5-11.0years in univariate models, a multivariate model based on the two protein clocks in the two tissues resulted in a MAE of 4.0years. These results support our hypothesis. The tested approach of a combined analysis of different molecular clocks analyzed in different tissues opens up new possibilities in postmortem age estimation. In a next step, we will add the epigenetic clock (DNA methylation) to our protein clocks (PEN, D-Asp) and expand our set of tissues.

Computational evaluation of altered biomechanics related to articular cartilage lesions observed in vivo.

Chondral lesions provide a potential risk factor for development of osteoarthritis. Despite the variety of in vitro studies on lesion degeneration, in vivo studies that evaluate relation between lesion characteristics and the risk for the possible progression of OA are lacking. Here, we aimed to characterize different lesions and quantify biomechanical responses experienced by surrounding cartilage tissue. We generated computational knee joint models with nine chondral injuries based on clinical in vivo arthrographic computed tomography images. Finite element models with fibril-reinforced poro(visco)elastic cartilage and menisci were constructed to simulate physiological loading. Systematically, the lesions experienced increased peak values of maximum principal strain, maximum shear strain, and minimum principal strain in the surrounding chondral tissue (p < 0.01) compared with intact tissue. Depth, volume, and area of the lesion correlated with the maximum shear strain (p < 0.05, Spearman rank correlation coefficient ρ = 0.733-0.917). Depth and volume of the lesion correlated also with the maximum principal strain (p < 0.05, ρ = 0.767, and ρ = 0.717, respectively). However, the lesion area had non-significant correlation with this strain parameter (p = 0.06, ρ = 0.65). Potentially, the introduced approach could be developed for clinical evaluation of biomechanical risks of a chondral lesion and planning an intervention. Statement of Clinical Relevance: In this study, we computationally characterized different in vivo chondral lesions and evaluated their risk of cartilage degeneration. This information is vital in decision-making for intervention in order to prevent post-traumatic osteoarthritis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.