C. Zucchini

WOUND MANAGEMENT WITH N-CARBOXYBUTYL CHITOSAN

In patients undergoing plastic surgery, donor sites were treated with soft pads of freeze-dried N-carboxybutyl chitosan to promote ordered tissue regeneration. Compared to control donor sites, better histoarchitectural order, better vascularization and the absence of inflammatory cells were observed at the dermal level, whilst fewer aspects of proliferation of the malpighian layer were reported at the epidermal level. Accordingly, N-carboxybutyl chitosan leads to formation of regularly organized cutaneous tissue and reduces anomalous healing.

Osteoconductive properties of methylpyrrolidinone chitosan in an animal model

Bone defects were surgically produced in the tibiae of rabbits and medicated with freeze-dried methylpyrrolidinone chitosan. Histological observations 60 d after surgery showed a considerable presence of neoformed bone tissue, as opposed to controls, originating from the pre-existing bone as well as from the periosteum. The cationic nature and the chelating ability of the methylpyrrolidinone chitosan apparently favoured mineralization. Endosteal-periosteal and bone marrow osteoblast-like precursors, stimulated by growth factors entrapped in the coagulum-polysaccharide mixture, gave rise to intramembranous bone formation. The ultrastructural examination evidenced that bone osteoid was followed by mineralization of the tissue.

BIOMATERIALS FOR ORTHOPEDIC SURGERY IN OSTEOPOROTIC BONE : A COMPARATIVE STUDY IN OSTEOPENIC RATS

To evaluate orthopedic devices in pathological bone, an experimental study was performed by implanting Titanium (Ti) and Hydroxyapatite (HA) rods in normal and osteopenic bone. Twenty-four rats were used: 12 were left intact (Control: C) while the other 12 were ovariectomized (OVX). After 4 months all the animals were submitted to the implant of Ti or HA in the left femoral condyle (Ti-C, HA-C, Ti-OVX, HA-OVX). Two months later the animals were sacrificed for histomorphometric, ultrastructural and microanalytic studies. Our results show a significant difference between the Affinity Index (A.I.) of HA-C and Ti-C (77.0 ± 7.4 vs 61.2 ± 9.7) (p < 0.05). No significant differences were observed between the osteointegration of Ti-C and Ti-OVX (61.2 ± 9.7 vs 48.2 ± 6.7). Significant differences also exist between the osteointegration of HA-C and HA-OVX (77.0 ± 7.4 vs 57.6 ± 11.5) (p < 0.01). Microanalysis shows some modifications in Sulphur (S) concentration at the bone/biomaterial interface of the Ti-OVX group. Therefore our results confirmed the importance of biomaterials characteristics and of bone quality in osteointegration processes.

Bioactivity modulation of bioactive materials in view of their application in osteoporotic patients

The application of bioactive ceramic coatings to prostheses confers strength to a material (ceramic or biological glass) that exerts beneficial effects on bone-tissue growth but that itself lacks the toughness and stability required of an implant device. The rate of bioactivity is related to the chemical reactivity of the material and causes interface dissolution, precipitation and ion-exchange reactions. Ceramics may differ in sintering temperature and thus exhibit differences in their in vitro dissolution features and in vivo performance. To test these effects, in vitro and in vivo studies were carried out on two biocompatible biological glasses and a ceramic of proven bioactivity in view of their potential utilization as covering materials. In addition, a modified chitosan was adsorbed on the surface of a series of hydroxyapatite (HA) samples. Human fibroblasts and/or osteoblasts were used for the in vitro tests, and normal (INT) and osteoporotic (OVX) rats, normal rabbits and sheep for the in vivo studies. Similar chemical changes were observed in both glasses, suggesting that these materials underwent modifications directly dependent on their biological environment. The in vivo tests point to the possibility of improving the bioactivity of ceramic substrates with chitosan. However, the different behaviour of the materials in vitro and in vivo suggests that these tests should be conducted in parallel.

In vitro study of gingival fibroblasts from normal and inflamed tissue: Age-related responsiveness

The aim of this study was to characterize some phenotypic expressions of fibroblasts from the human oral mucosa. Gingival and lower forearm fibroblasts from young (20-30 years) and elderly (> 60 years) subjects were analyzed. Gingival fibroblasts were taken from donors with (P) and without (NP) periodontal disease, while skin biopsies were taken from healthy subjects. Cell proliferation was assessed by evaluating the cell multiplication coefficient (C.M.C.). The proliferation potential of gingival fibroblasts from elderly individuals with and without periodontopathy did not differ from that of young subjects in the same condition but differed significantly in the skin samples. Enzyme neutral endopeptidase (EC 3.4.24.11) (NEP) activity, studied as a possible marker of cell ageing, showed an age-related increase in human skin fibroblasts but not consistently in gingival fibroblasts from individuals with or without periodontal disease. Cell area and substrate adhesion were evaluated by morphometric analysis. There were no significant differences between elderly P and NP subjects, while significant differences were observed between young and elderly P subjects. In conclusion, proliferative capacity and NEP activity in gingival fibroblasts did not appear to be age-related, probably because their microenvironment is continually moistened by saliva, which continues to contain growth factors, notably EGF, even into senescence. Tissue reaction and repair are important clinical and therapeutic implications.

CERAMIC SUPPORT FOR CELL CULTURES

Research was carried out on the use of ceramics as supports to host mammalian cells. The research was part of a programme whose priority was to study the possibility of using ceramics in the non-traditional sector of the biomedical field. The aim of the study was also to verify the suitability of particular types of ceramics dealt with in the literature for these applications. Among the different samples tested the cordieritic one proved to be very interesting, at least in relation to the cellular cultures considered. The chemical composition of the material is not, however, the only important aspect, since other parameters concur to make the hosting of cells highly acceptable. Of particular importance is the rugosity and porosity of the surface and its flaking, not only externally, but also in the pores.

MITOCHONDRIAL DYSFUNCTION AND BRAIN DISORDERS

Summary According to the mitochondrial theory of aging, it is expected that in postmitotic tissues, such as nervous system, an accumulation of damage to mitochondrial DNA could lead to a progressive failure of mitochondrial function during senescence. NADH-Coenzyme Q reductase (Complex I) activity should be severely affected since 7 subunits of this enzymatic complex are encoded by mitochondrial DNA. We decided to investigate the modifications occurring to this particular complex during aging in two different neuronal populations from aged rats, using rotenone sensitivity as a functional parameter of the subunits encoded by mitochondrial DNA. In order to have an easy model to study mitochondrial modifications during senescence and in other neurodegenerative disorders, we also investigated mitochondrial membranes from platelets of young and old individuals. In all systems investigated, a decease of rotenone sensitivity in aging was observed.

Experimental Wound Dressing by Heterologous Collagen: A Morphological-Quantitative Approach

The use of heterologous collagen in skin repair processes has proved to be an efficacious approach for the reconstitution of injured tissue. A morphological and quantitative evaluation of the reactive and reparative ca pacity of injured tissue treated either with conventional medications or with heterologous collagen (Condress) in the form of sponges was carried out. We have analyzed experimental surgical lesions on an animal model and evalu ated the repair processes of the lesions, including the excision of the cutaneous and subcutaneous tissue. The heterologous collagen sponges provided biologi cal support to obtain healed skin of better quality. Tissue lesions healed more rapidly, thus reducing the risk of recurrence. This experimental study provides morphological and structural data for further investigation.

Comparative Experimental Study on the Treatment of Open Wounds

Open wounds often involve complex pathophysiological events and, consequently, difficult therapeutic problems [1]. However, our increasing understanding of tissue repair processes has permitted great progress in the treatment of open wounds. To achieve appropriate wound repair it is necessary to consider many parameters [2]. Intrinsic wound factors include: 1 Fibroblasts 2 Collagen deposition 3 Macrophages 4 Bacterial burden 5 pH 6 Angiogenic processes 7 Cellular division, migration and differentiation.