Evaluation of anionic collagen membranes in the treatment of class II furcation lesions: an histometric analysis in dogs

This study aims to evaluate the effect of using anionic collagen membranes in guided tissue regeneration treatment of Class II furcation lesions in dogs. The defects were created in the buccal furcation of 16 mandibular premolars of four dogs. After 56 days without plaque control, the sites were scaled and divided into two groups according to the treatment applied: control sites, open flap debridement; and test sites, guided tissue regeneration treatment. The animals were killed after 3 months. Histological and histometrical analyses showed that the collagen membrane was better than open flap debridement in terms of newly formed cementum and epithelial migration prevention. It provided effective blockade of epithelial tissue and promoted regeneration of lost periodontal tissues, suggesting that the membrane warrants further study. (C) 1997 Elsevier B.V. Limited. All rights reserved.

Simultaneous observation of collagen and elastin in normal and pathological tissues: analysis of Sirius-red-stained sections by fluorescence microscopy

In order to observe collagen and elastic fibers simultaneously, sections of human aorta, skin, lung, liver, and bladder were stained by Sirius red and analyzed by fluorescence microscopy. In all cases, the fibers of collagen presented the characteristic fluorescent red-orange color that results from the interaction of this extracellular protein with the dye, whereas elastic fibers showed strong green fluorescence (intrinsic fluorescence). This method efficiently detects collagen and elastic fibers when these two structures are present and could have valuable applications in processes that involves both fibers.

Identification, content, and distribution of type VI collagen in bovine tendons

Tendon composition changes according to differentiation, mechanical load, and aging. In this study, we attempted to identify, localize, and quantify type VI collagen in bovine tendons. Type VI collagen was identified by the electrophoretic behavior of the alpha chains and Western blotting, and by rotary shadowing. Type VI collagen was extracted from powdered tendon with three sequential 24-h extractions with 4 M guanidine-HCl. The amount of type VI collagen was determined by enzyme-linked immunosorbent assay for purely tensional areas and for the compressive fibrocartilage regions of the deep flexor tendon of the digits, for the corresponding fetal and calf tendons, and for the extensor digital tendon. The distal fibrocartilaginous region of the adult tendon was richer in type VI collagen than the tensional area, reaching as much as 3.3 mg/g (0.33%) of the wet weight. Calf tendons showed an accumulation of type VI at the fibrocartilage site. Immunocytochemistry demonstrated that type VI collagen was evenly distributed in the tensional areas of tendons but was highly concentrated around the fibrochondrocytes in the fibrocartilages. The results demonstrate that tendons are variable with regard to the presence and distribution of type VI collagen. The early accumulation of type VI collagen in the region of calf tendon that will become fibrocartilage in the adult suggests that it is a good marker of fibrocartilage differentiation. Furthermore, the distribution of type VI collagen in tendon fibrocartilage indicates that it organizes the pericellular environment and may represent a survival factor for these cells.

Collagen-hydroxyapatite films: piezoelectric properties

In this paper we report a study of the physicochemical, dielectric and piezoelectric properties of anionic collagen and collagen-hydroxyapatite (HA) composites, considering the development of new biomaterials which have potential applications in support for cellular growth and in systems for bone regeneration. The piezoelectric strain tensor element d(14), the elastic constant s(55) and the dielectric permittivity 8(11), were measured for the anionic collagen and collagen-HA films. The thermal analysis shows that the denaturation endotherm is at 59.47 degreesC for the collagen sample. The collagen-HA composite film shows two transitions, at 48.9 and 80.65 degreesC. The X-ray diffraction pattern of the collagen film shows a broad band characteristic of an amorphous material. The main peaks associated to the crystalline HA is present in the sample of collagen-HA. In the collagen-HA composite, one can also notice the presence of other peaks with low intensities which is an indication of the formation of other crystalline phases of apatite. The scanning electron photomicrograph of anionic collagen membranes shows very thin bundles of collagen. The scanning electron photomicrography of collagen-HA film also show deposits of hydroxyapatite on the collagen fibers forming larger bundles and suggesting that a collagenous structure of reconstituted collagen fibers could act as nucleators for the formation of apatite crystal similar to those of bone. The piezoelectric strain tensor element d(14) was measured for the anionic collagen, with a value of 0.062 pC N-1, which is in good agreement compared with values reported in the literature obtained with other techniques. For the collagen-HA composite membranes, a slight decrease of the value of the piezoelectricity (0.041 pC N-1) was observed. The anionic collagen membranes present the highest density, dielectric permittivity and lowest frequency constant f.L. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Collagen type VI is a component of the extracellular matrix microfibril network of the prostatic stroma

Stroma-epithelium relationships are of great relevance in prostatic morphogenesis and physiology, However, little knowledge exists about either stromal cells or extracellular matrix composition and arrangement in this system, Ultrastructural analysis revealed the existence of a microfibrillar system which occupies large areas of the rat prostatic stroma, In this work, we have applied immunocytochemistry and an ATP treatment for the ultrastructural identification of collagen type VI microfibrils, aiming at examining its participation in the prostatic microfibrillar network. Immunocytochemistry was also extended to a human case of prostatic nodular hyperplasia, Both methods succeeded in identifying collagen type VI in the rat ventral prostate, Collagen type VI is evenly distributed throughout the stroma but mainly associated with the basal lamina, collagen fibrils, and around the stromal cells, the use of ATP treatment allowed for the discrimination between collagen type VI and elastin-associated microfibrils, and demonstrated that these two classes of microfibrils establish an extended, mixed, and open network. The same aspects of association with the basal lamina, with stromal cells (particularly with smooth muscle cells), and with fibrillar components of the stroma were observed in the human tissue, We suggest that the collagen type VI and elastin-associated microfibril system may be involved in the control of some aspects of cellular behavior and may also play a structural role, maintaining the organ integrity after the deformations occurring under smooth muscle contraction.

Implants of polyanionic collagen matrix in bone defects of ovariectomized rats

In recent years, there has been a great interest in the development of biomaterials that could be used in the repair of bone defects. Collagen matrix (CM) has the advantage that it can be modified chemically to improve its mechanical properties. The aim of the present study was to evaluate the effect of three-dimensional membranes of native or anionic (submitted to alkaline treatment for 48 or 96 h) collagen matrix on the consolidation of osteoporosis bone fractures resulting from the gonadal hormone alterations caused by ovariectomy in rats subjected to hormone replacement therapy. The animals received the implants 4 months after ovariectomy and were sacrificed 8 weeks after implantation of the membranes into 4-mm wide bone defects created in the distal third of the femur with a surgical bur. Macroscopic analysis revealed the absence of pathological alterations in the implanted areas, suggesting that the material was biocompatible. Microscopic analysis showed a lower amount of bone ingrowth in the areas receiving the native membrane compared to the bone defects filled with the anionic membranes. In ovariectomized animals receiving anionic membranes, a delay in bone regeneration was observed mainly in animals not subjected to hormone replacement therapy. We conclude that anionic membranes treated with alkaline solution for 48 and 96 h presented better results in terms of bone ingrowth.