Fine Collagen Research Articles

Platelets modulate cardiac remodeling via the collagen receptor GPVI after acute myocardial infarction.

Platelets play an important role in cardiovascular diseases. After acute myocardial infarction, platelets display enhanced activation and migrate into the infarct zone. Furthermore, platelets trigger acute inflammation and cardiac remodeling leading to alterations in scar formation and cardiac function as observed in thrombocytopenic mice. GPVI is the major collagen receptor in platelets and important for platelet activation and thrombus formation and stability. Antibody induced deletion of GPVI at the platelet surface or treatment of mice with recombinant GPVI-Fc results in reduced inflammation and decreased infarct size in a mouse model of AMI. However, the role of GPVI has not been fully clarified to date. In this study, we found that GPVI is not involved in the inflammatory response in experimental AMI using GPVI deficient mice that were analyzed in a closed-chest model. However, reduced platelet activation in response to GPVI and PAR4 receptor stimulation resulted in reduced pro-coagulant activity leading to improved cardiac remodeling. In detail, GPVI deficiency in mice led to reduced TGF-β plasma levels and decreased expression of genes involved in cardiac remodeling such as Col1a1, Col3a1, periostin and Cthrc1 7 days post AMI. Consequently, collagen quality of the scar shifted to more tight and less fine collagen leading to improved scar formation and cardiac function in GPVI deficient mice at 21d post AMI. Taken together, this study identifies GPVI as a major regulator of platelet-induced cardiac remodeling and supports the potential relevance of GPVI as therapeutic target to reduce ischemia reperfusion injury and to improve cardiac healing.

Human Dental Pulp Stem Cells Differentiate into Cementoid-Like-Secreting Cells on Decellularized Teeth Scaffolds.

Periodontitis is a common inflammatory disease that in some cases can cause tooth loss. Cementum is a mineralized tissue that forms part of the insertion periodontium and serves to fix the teeth to the alveolar bone. In addition, it acts as a reservoir of different growth and differentiation factors, which regulate the biology of the teeth. Cementogenesis is a complex process that is still under investigation and involves different factors, including dentin sialophosphoprotein (DSPP). In this work we studied the role of surface microtopography in the differentiation of human dental pulp stem cells (hDPSCs) into cementoid-like secreting cells. We cultured hDPSCs on decellularized dental scaffolds on either dentin or cementum surfaces. Cell morphology was evaluated by light and electron microscopy. We also evaluated the DSPP expression by immunohistochemistry. The hDPSCs that was cultured on surfaces with accessible dentinal tubules acquired an odontoblastic phenotype and emitted characteristic processes within the dentinal tubules. These cells synthesized the matrix components of a characteristic reticular connective tissue, with fine collagen fibers and DSPP deposits. The hDPSCs that was cultured on cementum surfaces generated a well-organized tissue consisting of layers of secretory cells and dense fibrous connective tissue with thick bundles of collagen fibers perpendicular to the scaffold surface. Intra- and intercellular deposits of DSPP were also observed. The results presented here reinforce the potential for hDPSCs to differentiate in vitro into cells that secrete a cementoid-like matrix in response to the physical stimuli related to the microtopography of contact surfaces. We also highlight the role of DSPP as a component of the newly formed matrix.

Confocal Microscopy of Filtering Blebs after Trabeculectomy.

Filtration surgery is the most effective method of lowering intraocular pressure (IOP) in patients with insufficient medical control. It consists in facilitating the drainage of the intraocular fluid (IOF) from the anterior chamber to the subconjunctival space and subsequent lowering of IOP. The formation of filtration blebs (FB) and the processes of scarring occurring in the conjunctiva are of particular importance in glaucoma surgery. In many cases, the appearance of FB does not match the IOP values, and what causes the failure after trabeculectomy often remains unclear. Often, over time, there is a change in the structure of the FB, as fibrous tissue grows, which prevents the IOF drainage. Laser scanning in vivo confocal microscopy is a non-invasive study allowing the production of layered images at the microstructural level with high resolution of both the cornea and other structures of the anterior ocular surface. To evaluate the morphological structure and function of filtering blebs after trabeculectomy using in vivo confocal microscopy taking into account the type of implant and when the surgery was performed. The study included 33 patients, 46 eyes with glaucoma. Twenty-six of the eyes had primary open-angle glaucoma (POAG), 18 eyes had pseudoexfoliative glaucoma and 2 eyes had juvenile glaucoma. All patients underwent trabeculectomy with fornix-based flap, and three of the eyes underwent retrabeculectomy. Mitomicyn C (MMC) was administered intraoperatively to all patients. The study of the filtering bleb was performed by in vivo confocal microscopy (CFM) (Heidelberg Retina Tomograph II (HRT II) /Rostock Cornea Module/ (Heidelberg Engineering GmbH, Heidelberg, Germany), the period from trabeculectomy and examination being from 1 year to 22 years. An Express implant was placed in 14 eyes, Ologen implant in 7 eyes, and 25 eyes had no implant placed. In the analysis of the morphological structure of the filtering blebs, three indicators were evaluated: the type of epithelium, the type of stroma, and blood vessels. Statistical significance was established with regard to the function and morphological structure of the filtering bleb (p=0.009). Blebs with fine collagen mesh and dense collagen mesh demonstrate good function. In the case of blebs with insufficient function, those with a dense collagen network and hyper-reflective tissue predominated and there were no blebs with a fine collagen network, and in non-functioning blebs most common were those with a pronounced collagen network and hyper-reflective tissue. With regard to vascularization, we found that the functioning blebs in the shortest postoperative period were dominated by those with one blood vessel (stage 1) and there was no stage 3, with weak tortuosity, while in non-functioning blebs in the late postoperative period, there was moderate to severe vascularization and tortuosity (p=0.037), (p=0.043), (p=0.047), (p=0.021). The type of implant affects the tortuosity of the blood vessels of the filtering bleb (p=0.026). The blebs with Express implants show a slight tortuosity, followed by the blebs with Ologen implants. The highest percentage of highly kinked blood vessels occurred in blebs without an implant. In vivo confocal microscopy is an innovative method which allows visualization of the internal structure of the filtering blebs at a cellular level, giving us a new insight into the ongoing healing processes, premising the function of the filtering blebs after glaucoma surgery.

Morphological and Histological Study of the Pineal Gland in local breed Goats (Capra hircus)

The current study was carried out to investigate both morphological and histochemical features of pineal gland in goat. Eight samples of pineal glands were used. The morphological study was involved the position, relation, weight, length and width of the glands. The tissue sections were prepared for paraffin embedding technique and stained with Hematoxyline & Eosin, Masson trichrom, Alizarin and PAS stains. The morphological result of pineal showed slightly irregular round-spherical shaped, grayish white in color. It located in the same mid-depression between the thalami body and two colliculi. The weight of gland was 0.478±0.02 mg and measured 2.10±0.06mm in length and 2.52±0.15mm in width. Histologically, the pineal gland has enveloped by a smooth thin layer of loose connective tissue capsule showed less trabiculae that carried the blood vessels into gland and the trabiculae have composed of fine collagen fibers. The glandular parenchyma showed marked lobular pattern of division with marked lighter central region which showed less cellular population. The glandular lobule consisted of three types of cells; Type I pinealocytes or dark pinealocytes, the second type was the less populated type II pinealocytes or light pinealocytes and the third type was the glial cell. The Alizarin stain was revealed multiple of variable size calcium patches within collagen fibers. The cytoplasmic contents of both pinealocytes types I & II showed no glycogen granules.

The structure and properties of natural sheep casing and artificial films prepared from natural collagen with various crosslinking treatments

The structure and properties of natural sheep casing and collagen films with various crosslinking treatments have been investigated in detail to develop satisfied artificial casings prepared from collagen. The sheep casing consists of large number of thick collagen fibers oriented at ±45° from longitudinal direction with high-density interwoven network structure. The structural feature of sheep casing gave the special mouthfeel of ‘cracking bite’ of sausages. Whereas, layered structure filled with fine collagen fibrils and large gaps in collagen film results in poor mechanical properties and higher swelling ratio in water. Furthermore, a degree of denaturation of collagen during extraction process also lead to poor mechanical properties. After glutaraldehyde (GTA) and dehydrothermal (DHT) treatments, the formation of crosslinking improved mechanical properties of collagen films significantly and the tensile strength and tensile modulus increased more than three times compared with those of untreated collagen film in wet before and after boiling. The swelling ratio of treated collagen films also decreased dramatically. No obvious effects on denaturation of collagen film after GTA treatment, but the degree of denaturation of DHT treated collagen film increased slightly.

Morphologic Characteristics of the Submandibular Salivary Gland of the Collared Peccary (Tayassu Tajacu)

Introduction Most salivary glands is located on the inside and around the oral cavity, and are divided into major and minor salivary glands. The aim of the present study was to describe the structural and ultrastructural morphological characteristics of the lingual tissue of the submandibular glands of the collared peccary (Tayassu tajacu). Materials and Methods The submandibular glands (n = 10) of adult male collared peccaries ( T. tajacu) were used for histological and ultrastructural analysis. The techniques used were light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results The submandibular salivary glands of the collared peccary (T. tajacu) showed a capsule formed by a connective tissue containing the acinus and duct cells. Histologically, the nuclei located at the basal region of the cells was observed. The light polarized microscopy clearly showed the presence of type I and type III collagen. In the SEM image, the submandibular salivary gland revealed a round aspect separated in several lobules with bundles of collagen fibers. The vibratome sections showed the groupings of acinar cells, with intermingled secretory ducts containing vessels of different diameters. The secretory granules were noted in the apical portion of the acinar and ductal cells. The thick bundles of collagen fibers formed a glandular capsule and were identified around of the acinar and ductal cells in three-dimensional SEM images. The TEM images showed a number of secretory granules, especially in the apical region of the cytoplasm of the acinar cells and in the basal portion of the nuclei. The granular endoplasmic reticulum area, the euchromatic nuclei and the cytoplasmic projections may be seen. Mucous acinar cells separated by fine collagen fibers were also observed. Conclusion The morphological characteristics of the submandibular gland of the collared peccary is similar to that of other mammals with the same eating habits and habitat.

Orthotopic Transplantation of Achilles Tendon Allograft in Rats

The biology and function of orthotopic transplantation of Achilles tendon allograft are unknown. Particularly, the revitalization of Achilles allograft is a clinical concern. Achilles allografts were harvested from donor rats and stored at −80 °C. Subcutaneous adipose tissue was harvested from the would-be allograft recipient rats for isolation of mesenchymal stem cells (MSCs). MSCs were cultured with growth differentiation factor-5 (GDF-5) and applied onto Achilles allografts on the day of transplantation. After the native Achilles tendon was resected from the left hind limb of the rats, Achilles allograft, with or without autologous MSCs, was implanted and sutured with calf muscles proximally and calcaneus distally. Animal gait was recorded presurgery and postsurgery weekly. The animals were sacrificed at week 4, and the transplanted Achilles allografts were collected for biomechanical testing and histology. The operated limbs had altered gait. By week 4, the paw print intensity, stance time, and duty cycle (percentage of the stance phase in a step cycle) of the reconstructed limbs were mostly recovered to the baselines recorded before surgery. Maximum load of failure was not different between Achilles allografts, with or without MSCs, and the native tendons. The Achilles allograft supplemented with MSCs had higher cellularity than the Achilles allograft without MSCs. Deposition of fine collagen (type III) fibers was active in Achilles allograft, with or without MSCs, but it was more evenly distributed in the allografts that were incubated with MSCs. In conclusion, orthotopically transplanted Achilles allograft healed with host tissues, regained strength, and largely restored Achilles function in 4 wk in rats. It is therefore a viable option for the reconstruction of a large Achilles tendon defect. Supplementation of MSCs improved repopulation of Achilles allograft, but large animal models, with long-term follow up and cell tracking, may be required to fully appreciate the functional benefits of MSCs.

An Experimental Study to Measure the Mechanical Properties of the Human Liver

Background: Since the liver is one of the most important organs of the body that can be injured during trauma, that is, during accidents like car crashes, understanding its mechanical properties is of great interest. Experimental data is needed to address the mechanical properties of the liver to be used for a variety of applications, such as the numerical simulations for medical purposes, including the virtual reality simulators, trauma research, diagnosis objectives, as well as injury biomechanics. However, the data on the mechanical properties of the liver capsule is limited to the animal models or confined to the tensile/compressive loading under single direction. Therefore, this study was aimed at experimentally measuring the axial and transversal mechanical properties of the human liver capsule under both the tensile and compressive loadings. Methods: To do that, 20 human cadavers were autopsied and their liver capsules were excised and histologically analyzed to extract the mean angle of a large fibers population (bundle of the fine collagen fibers). Thereafter, the samples were cut and subjected to a series of axial and transversal tensile/compressive loadings. Results: The results revealed the tensile elastic modulus of 12.16 ± 1.20 (mean ± SD) and 7.17 ± 0.85 kPa under the axial and transversal loadings respectively. Correspondingly, the compressive elastic modulus of 196.54 ± 13.15 and 112.41 ± 8.98 kPa were observed under the axial and transversal loadings respectively. The compressive axial and transversal maximum/failure stress of the capsule were 32.54 and 37.30 times higher than that of the tensile ones respectively. The capsule showed a stiffer behavior under the compressive load compared to the tensile one. In addition, the axial elastic modulus of the capsule was found to be higher than that of the transversal one. Conclusions: The findings of the current study have implications not only for understanding the mechanical properties of the human capsule tissue under tensile/compressive loading, but also for providing unprocessed data for both the doctors and engineers to be used for diagnosis and simulation purposes.

Abstract 1463: Intravital discovery of miRNA drivers of human cancer cell directional invasion

Abstract Metastatic cancer cells often use directional ECM cues such as blood vessels or collagen fibers when invading through live tissue. Oncogenic miRNAs have been implicated as key regulators of cancer progression yet the systemic discovery of miRNAs that drive directional cancer cell invasion has not been achieved. Here we describe the first in vivo quantitative whole human miRNAome screen for miRNA drivers of directional cancer cell invasion using an ex ovo avian embryo model of human cancer cell metastasis combined with high resolution intravital imaging. We identified more than twenty novel miRNAs that promote cancer cell invasion during the key rate-limiting step of cancer metastasis, the initiation and expansion of overt metastatic lesions. In silico miRNA target analysis (DIANA, Targetscan) showed significant enrichment in gene targets/pathways that control cancer cell-ECM adhesion and cancer cell contractility. These findings were further confirmed using Affymetrix gene expression analysis that showed significant changes in the expression of genes that regulate actin cytoskeleton rearrangement, cancer cell-ECM interaction and cell surface-receptor signaling. Public cancer gene expression database analysis (Oncoprint) showed that these miRNA-mRNA networks deregulated in several deadly cancers (pancreas, prostate, breast) and negatively correlate with the cancer patient survival. To elucidate potential mechanisms of these pro-metastatic miRNAs, we utilized an intravital imaging approach. In vivo 4D cancer cell tracking revealed that these pro-metastatic miRNAs are required for successful invasion into collagen-rich tissue and for attachment to the outer surface of the vascular wall. Deregulation of these miRNAs led to formation of loose contacts with the vasculature and chaotic, non-directional cancer cell invasion patterns in living tissue. Intravital second-harmonic microscopy analysis showed that inhibition of the expression of these miRNAs blocked the ability of cancer cells to rearrange the disorganized fine collagen fiber network into thicker collagen bundles that guide directional tumor cell invasion. In contrast to parental tumor cells that persistently moved along the collagen bundles, miRNA-deficient tumor cells were observed to transiently associate with multiple collagen fibers without establishing persistent collagen fiber-tumor cell protrusion contacts. Moreover, miRNA-deficient tumor cells failed to attach and protrude along preexisting perivascular collagen bundles, resulting in the complete abrogation of cancer cell/blood vessel co-option. In summary, we identified a novel panel of human miRNAs that are functionally involved in the regulation of directional invasion and metastasis. This work establishes these miRNAs as promising therapeutic targets to block the metastatic spread of lethal cancers. Citation Format: Konstantin V. Stoletov, Lian Willetts, Juan Jovel, Emma Woolner, John D. Lewis. Intravital discovery of miRNA drivers of human cancer cell directional invasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1463. doi:10.1158/1538-7445.AM2017-1463

Evaluating skin quality of some rabbit breeds under Egyptian conditions

Histological skin parameters in addition to mechanical and chemical properties of chrome tanned rabbits’ furs were determined in this study to evaluate and compare the quality of some rabbit breeds. Seventy-nine male rabbits aged 3 mo of New Zealand White (NZW, n=27), Rex (RX, n=24) and Gabaly (GB, n=28) were used. Results showed that GB skins had the highest values in skin weight (P<0.01) and area (P<0.05) followed by NZW and RX skins, respectively. Moreover, NZW skins differed in histological structure from the other 2 breeds, as total thickness and thickness of papillary and hypodermis layers in NZW were more than twice those of RX and GB (P<0.05). This structure is caused by an increase in fine collagen fibre bundles in papillary layer and a limited increase in larger collagen fibre bundles in the reticular layer. Furthermore, finished tanned furs properties clarify the superiority of GB furs in values of tensile and tearing strengths followed by NZW and RX, respectively. These results point to the possibility of using the chrome tanned furs of the 3 breeds in leather garment manufacturing.

Differences in MR signal intensity of lateral collateral ligament of knee joint on fat-suppressed proton density-weighted imaging

To investigate the relationship between the increased signal intensity (SI) of proximal lateral collateral ligament (LCL) at femoral attachment site on fat-suppressed (FS) proton density-weighted (PDW) MR imaging and the corresponding histological features on cadaveric knees. MRI was obtained from 11 cadaveric knees. Two musculoskeletal radiologists evaluated SI of LCL at femoral attachment site and the remaining caudal portion on FS PDW imaging. The SI was classified into three types; I = low, II = intermediate to slightly high, III = high SI or intraligamentous discontinuity of fibre. In addition, 100 control subjects were reviewed for normal LCL SI. All proximal LCLs at femoral attachment site showed increased SI (nine cases of Type II and two cases of Type III). The remaining caudal portion presented Type I in all cases. Histological examination of proximal LCL at femoral attachment site revealed loose distribution of fine collagen fibres, intervened with fat and vessels, whereas the remaining caudal portion was composed of parallel distribution of compact collagen bundles. There were no signs of degeneration or tear of the LCL in all our cadaveric knee samples, even for the two cases that presented as Type III. Clinical study identified increased SI of proximal LCL at femoral attachment site in 94% (94/100) of control subjects. Increased SI of proximal LCL at femoral attachment site on FS PDW imaging is due to histological characteristics, not degeneration or tear. Increased SI of proximal LCL at femoral attachment site on FS PDW MR imaging is a common, normal finding that its clinical significance can be neglected.

Changes in collagens and chondrocytes in the temporomandibular joint cartilage in growing rats fed a liquid diet

The temporomandibular joint (TMJ) of growing rats fed a soft diet is reported to be smaller in size and to have thinner condyle and glenoid fossa cartilage than rats fed a solid diet. The aim of this study was to determine the effect of a soft diet on the collagens and chondrocytes in the growing TMJ cartilage. Forty-eight male Wistar rats were divided into a control group fed a solid diet and an experimental group fed a liquid diet for 1–8 weeks. After the experimental period, the TMJs were harvested and examined histologically, immunohistochemically for collagen types I, II, and X, and with transmission electron microscopy. The condylar cartilage in the experimental rats showed weak immunoreactions for three types of collagens compared with the controls. The ultrastructure had fewer fine collagen fibrils in the experimental rats compared with that of the controls. The glenoid fossa cartilage in the experimental rats showed narrower Alcian blue-positive areas than the control staining. The immunoreactions for three types of collagen in the experimental rats were also weaker than those of the controls. The chondrocytes in the experimental rats appeared dark, had extended thin cytoplasmic processes, and had formed gap junctions, as assessed by transmission electron microscopy. Fewer fine collagen fibrils, but thick bands of collagen fibrils were observed in the glenoid fossa of the experimental cartilage. The results of the present study showed that a liquid diet had deleterious effects on the quality and quantity of collagens and chondrocytes in the TMJ cartilage in growing rats.

Scale structure in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

Scales of the Australian lungfish, Neoceratodus forsteri, are secreted within the dermis by a capsule of scleroblasts, and enclosed in a pouch made of collagen fibers, in contact with the epidermis over the posterior third of the scale. Each scale grows from a focus, which represents the first formed part of the scale. On the internal surface of the scale is elasmodin, made of collagen fiber bundles arranged in layers. Elasmodin, unmineralized in N. forsteri, contains cells in the living animal, and the number of layers increases as the scales grow. Squamulin, on the thin external part of the scale, is also laid down in layers, and based on a matrix of fine collagen fibrils, mineralized with a poorly crystalline biogenic calcium hydroxylapatite. Squamulin is divided into separate sections called squamulae, and contains long tubules with cells applied to the wall of the tubule. The anterior and lateral surfaces of the squamulin are ornamented with pediculae, and the posterior surface has longitudinal ridges, from which collagen fibers extend to anchor the scale within the pouch. Elasmodin and squamulin are linked by unmineralized collagen fibrils. The layers, formed at irregular intervals, are connected around the margin of the scale, effectively converting the whole scale into a flat structure resembling a pearl, with the first formed tissues deeply embedded inside the scale, and the youngest on the outer surface. Incremental lines in the hard tissue, and the number of layers in the elasmodin, do not reflect the chronological age of the fish.

The structural and optical properties of type III human collagen biosynthetic corneal substitutes

The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout. This arrangement differs from the predominantly biaxial alignment of collagen fibrils that exists in the human cornea. By virtue of their high water content (90%), very fine collagen filaments (2–9nm) and lack of cells, the collagen hydrogels were found to transmit almost all incident light in the visible spectrum. They also transmitted a large proportion of UV light compared to the cornea which acts as an effective UV filter. Patients implanted with these hydrogels should be cautious about UV exposure prior to regrowth of the epithelium and in-growth of corneal cells into the implants.

Microvascular vessel preparation: What are we really removing during adventitial stripping?

Although adventitial stripping has been routinely recommended and practiced during vessel preparation for microsurgical anastomoses, detailed descriptions vary regarding the adequate extent of such maneuver. We aimed to histologically clarify which components of the vessel are removed during adventitial stripping, using arterial samples harvested during microsurgical breast reconstruction. Thirteen deep inferior epigastric arteries, nine internal mammary arteries, and four thoracodorsal arteries were evaluated in each step of vessel preparation, which were (1) grossly as a vascular bundle, (2) before vessel preparation, and (3) after vessel preparation under the operative microscope. Histologic components of each sample were evaluated under light microscopy. The combined thickness of the intima and the media and the thickness of the adventitia were measured and compared. Two distinctive layers of connective tissue were observed outside the media before vessel preparation. Outer loose areolar tissue with coarse fibers was mostly removed during vessel preparation. However, the inner adventitial layer with dense, fine collagen fibers consistently remained after vessel preparation and ostensible adventitial stripping. The average thickness of this layer was comparable with that of the media. Although there was no definitive demarcation between the two differential connective tissue layers, a vasa vasorum layer was distinctly seen between the two layers. The tissue removed during standard microsurgical vessel preparation or vessel stripping is not the entire layer of the adventitia, and the inner adherent layer of adventitia with fine collagen fibers should be preserved and included in the microsuture with the intima and media during anastomosis.

Assessment of Functional Properties of Cartilage using Double Quantum Filtered MRI

ABSTRACTIt is biologically and clinically important to understand and explain the functional properties of cartilage, such as its load bearing and lubricating ability, in terms of the structure, organization, components and their interactions. Our approach tries to explain functional material properties of these tissues as arising from polymeric interactions between and among the different molecular constituents within the tissues at different hierarchical lengthscales. We treat the tissue effectively as a complex molecular composite containing highly charged polysaccharide microgels trapped within a fine collagen meshwork. We have been developing a multi-scale experimental and theoretical framework to explain key material properties of cartilage by studying those of its constituents and the interactions among them at a variety of length and time scales. We use this approach to address important biological questions. One novel application we highlight here is the use of non-invasive magnetic resonance imaging (MRI) methods to characterize different components and compartments within cartilage and the different water environments associated with each one, in an attempt to provide a comprehensive picture of the mechanical/chemical state of cartilage.

Effect of Fibrous Septa in Radiofrequency Heating of Cutaneous and Subcutaneous Tissues: Computational Study

Radiofrequency (RF) energy exposure is a popular non-invasive method for generating heat within cutaneous and subcutaneous tissues. Subcutaneous fat consists of fine collagen fibrous septa meshed with clusters of adipocytes having distinct structural, electrical and thermal properties that affect the distribution and deposition of RF energy. The objectives of this work are to (i) determine the electric and thermal effects of the fibrous septa in the RF heating; (ii) investigate the RF heating of individual fat lobules enclosed by fibrous septa; and, (iii) discuss the clinical implications. We used the finite element method to model the two-dimensional, time-dependent, electro-thermal response of a three-layer tissue (skin, subcutaneous fat, and muscle). We considered two different configurations of subcutaneous fat tissue: a homogenous layer of fat only and a honeycomb-like layer of fat with septa. Architecture of the fibrous septa was anatomically accurate, constructed from sagittal images from human micro-MRI. For a large electrode applied to the skin surface, results show that the absorbed electric power density is greater in some septa than in the surrounding fat lobules, favoring the flux of electric current density. Fibers aligned parallel to the electric field have higher electric flux and, consequently, absorb more power. Heat transfer from the septa occurs over time during and after RF energy delivery. There is a greater temperature rise in fat with fibrous septa. The presence of septa affects the local distribution of the static electric field, facilitates the flux of electric current and enhances the bulk electric power absorption of the subcutaneous fat layer. Fibrous septa aligned with the local electric field have higher absorbed power density than septa oriented perpendicular to the electric field. Individual fat lobules gain heat instantly by local power absorption and, eventually, by diffusion from the surrounding septa.

Age-related differences in microstructure, density and biomechanics of vertebral cancellous bone of Chinese males

The conventional lumbar separation was performed by removing soft tissue, subsidiary structures and leaving only the vertebral body. The vertebral body was cut into two halves along the median sagittal plane, keeping the upper and lower end plates of each half, which were subsequently used for biomechanical, morphological and density experiments. From the age of 20–29 to 30–39 years, both the horizontal trabecular thickness (Tb.Th) and vertical Tb.Th decreased; the horizontal and vertical Tb.Sp increased; the plate-like trabecular Tb.Th decreased; the apparent density and volume ratio decreased; and the elastic modulus and the ultimate stress decreased; with all changes being statistically significant (p < 0.01). Similar trends were obtained from ages 40–49 to 50–59, although the changes were not significant (p > 0.05), except for the reduction in ultimate stress (p < 0.05). With aging, the collagen cross-linking capacity declined; the thicknesses of the collagen fibrils were variable, ranging from almost the same to loose, sparse or disordered thickness; and the finer collagen fibrils between the thick filaments were disorganized. In males aged from 20 to 59 years old, the horizontal and vertical Tb.Th and the plate-like Tb.Th of the vertebral body decreased, while the horizontal and vertical Tb.Sp increased. Additionally, the density, elastic modulus and the ultimate stress of the cancellous bone decreased with age. Thus, the associated changes of bone microstructure, density and biomechanics with age may lead to an increased risk of osteoporosis and fracture.

A Special Construction of Subepidermal Capillary Loops in the Hippopotamus (Hippopotamus amphibius)

Based on LM, TEM, and histochemical methods, the study describes the specific structure of subepidemal capillary loops in the integument of the hippopotamus (Hippopotamus amphibius). At 25- 60 µm, the diameter of the capillaries was more than twenty times larger than those found in other mammals, as was the diameter of the epidermal contact area of the hairpin turn, which had enlarged up to 200-400 µm(2). At about 13,400, the number of loops per cm(2) was three times higher than in the few other mammalian species measured to date. The remarkable sheath (thickness 2- 20 µm) of the capillary loops consists of a multitude of fine collagen IV fibres, which were in direct contact with the epidermal stratum (str.) basale, emphasizing an origin from the lamina fibroreticularis of the basement membrane. Additionally, the sheath contained many regions filled with free fatty acids. All observations confirmed the view that the walls of the subepidermal capillaries in the hippopotamus are adapted to withstand high blood pressure, permitting a high rate of blood vesselbased heat transfer from the periphery of the body. Until now this function is only known as an important thermoregulatory response in highly active mammals, e.g. dolphins. However, under hot climatic conditions but without strong exercise for cooling, such ability could be an effective and energy-saving procedure in semi-aquatic mammals.

Formation and structure of scales in the Australian lungfish, neoceratodus forsteri (Osteichthyes: Dipnoi)

The large elasmoid scales of the Australian lungfish, Neoceratodus forsteri, are formed within the dermis by unpigmented scleroblasts, growing within a collagenous dermal pocket below a thick glandular epidermis. The first row of scales, on the trunk of the juvenile lungfish, appears below the lateral line of the trunk, single in this species, at around stage 53. The scales, initially circular in outline, develop anteriorly and posteriorly from the point of initiation in the mid-trunk region, and rows are added alternately below the line, and above the line, until they reach the dorsal or ventral midline, or the margins of the fins. Scales develop later on the ventral surface of the head, from a separate centre of initiation. Scales consist of three layers, all produced by scleroblasts of dermal origin. The outermost layer of interlocking plates, or squamulae, consists of a mineralised matrix of fine collagen fibrils, covered by unmineralised collagen and a single layer of cells. Squamulae of the anterior and lateral surfaces are ornamented with short spines, and the mineralised tissue of the posterior surface is linked to the pouch by collagen fibrils. The innermost layer, known as elasmodin, consists of bundles of thick collagen fibrils and cells arranged in layers. An intermediate layer, made up of collagen fibrils, links the outer and inner layers. The elasmoid scales of N. forsteri can be compared with scale types among other osteichthyan groups, although the cellsand canaliculi in the mineralised squamulae bear little resemblance to typical bone.