C. Sosio

A tissue engineered osteochondral plug : an in vitro morphological evaluation

Articular cartilage lesions have a poor intrinsic healing potential. The repair tissue is often fibrous, having insufficient biomechanical properties, which could frequently lead to the development of early osteoarthritis. In the last decade, tissue engineering approaches addressed this topic in order to restore joint function with a differentiated and functional tissue. Many biomaterials and techniques have been proposed and some of them applied in clinical practice, even though several concerns have been raised on the quality of the engineered tissue and on its integration in the host joint. In this study, we focused on engineering in vitro a biphasic composite made of cellular fibrin glue and a calcium–phosphate scaffold. Biphasic composites are the latest products of tissue engineering applied to articular cartilage and they seem to allow a more efficient integration of the engineered tissue with the host. However, a firm in vitro bonding between the two components of the composite is a necessary condition to validate this model. Our study demonstrated a gross and microscopic integration of the two components and a cartilage-like quality of the newly formed matrix. Moreover, we noticed an improvement of this integration and GAGs production during the in vitro culture.

An in vitro tissue-engineered model for osteochondral repair

One of the main topics of regenerative medicine and tissue engineering is to address the problem of lesions involving articular cartilage. In fact, these lesions do not heal spontaneously and often lead to osteoarthritis, which causes chronic pain and worsens quality of life. Moreover, the only available treatment for osteoarthritis is symptomatic therapy and prosthetic replacement, with far from satisfactory results. A more conservative approach that restores the articular surface and function with a biologic tissue is desirable. Several strategies for regenerating articular cartilage have been proposed and applied in clinical practice but a gold standard has not yet been identified. Biphasic composites are the latest products of tissue engineering applied to articular cartilage and they seem to permit a more efficient integration of the engineered neo-tissue with the host. We present an in vitro tissue engineered model for osteochondral repair based on a composite of chondrocytes-fibrin glue gel and a calciumphosphate scaffold. This composite showed a gross integration of the two components and a cartilage-like quality of the newly formed matrix. Further studies are planned to quantify the adherence between the scaffold and the cellular fibrin glue.

Motion analysis after total knee arthroplasty

The aim of this study is to evaluate the functional performance after total knee replacement (TKR). Two groups of patients, one with mobile (n=9) and one with fixed bearing (n=8) total knee prosthesis, were compared by means of motion analysis. A group of healthy subjects (n=8), matched by age, were used as controls. Kinematics, kinetics and electromyography data were collected during physiological daily activities such as walking and squatting. During walking, both groups of patients showed a speed of progression, a maximum knee extension moment (stance phase) and a maximum knee flexion (swing phase) significantly lower than the control group. Moreover, during the swing phase a co-contraction of the antagonistic muscles of the inferior limb was present. During squatting, both groups of patients showed a peak of knee flexion significantly lower than the control group. Motion pattern after TKR is unphysiological but the abnormalities seem to be independent from the differences in the implant designs.

A tissue engineered osteochondral composite for cartilage repair: an in vivo study

This work aimed to validate the efficacy of a tissue engineered osteochondral composite for the treatment of cartilage lesion produced in adult pigs. The osteochondral composite was manufactured by combining an osteo-compatible cylinder and a neocartilagineous tissue obtained by seeding swine articular chondrocytes into a collagen scaffold. Articular cartilage was harvested from the trochlea of six adult pigs and was enzymatically digested to isolate the chondrocytes [Deponti D.et al. 2005]. The cells were then expanded in monolayer culture in chondrogenic medium and seeded onto a collagen scaffold. The collagen scaffold was preintegrated in vitro, macroscopically and microscopically, to a an osteo-compatible cylinder. The seeded osteochondral scaffolds were left in standard culture condition for 3 weeks with the addition of growth factors. At the end of culture time the osteochondral scaffolds were surgically implanted in osteochondral lesion performed in the trochlea of the same pigs from which the cartilage was initially harvested. As control, some osteochondral lesions were treated with acellular scaffolds and others were left untreated. After 3 months, the repair tissue of the three experimental groups was macroscopically analyzed and processed for histological and biochemical analysis. The hystologic ICRS II scale showed a statistically significant difference between the three experimental groups only in the parameters regarding the cell morphology and the surface/superficial assessment: the lesion treated with the unseeded osteochondral scaffolds showed higher values in chondrocytes morphology and in the superficial layer recovery, with respect to the lesions treated with the seeded scaffolds or left untreated. The biochemical analysis showed a higher DNA content in the lesion repaired with cellular scaffold and a higher GAGs/DNA ratio in the lesions with a spontaneous repair. The result of this study demonstrate that an osteochondral scaffold was able to repair an osteochondral lesion in an in vivo model of adult pigs, showing a good integration with the surrounding tissue. The quality of the repair was higher when the scaffold was not seeded with chondrocytes, but filled with cells migrated from subchondral bone. This tissue engineered osteochondral composite could represent a valuable model for further in vivo studies on the repair of chondral/osteochondral lesion.

495 BONDING OF MENISCAL TISSUE WITH CELLULAR FIBRIN GLUE: A NUDE MOUSE STUDY

C. Cournil-Henrionnet Sr1, J. Goebel1, L. Galois2, C. Huselstein3, D. Mainard2, D. Bensoussan4, P. Netter1, J. Stoltz3, P. Gillet1, A. Pinzano-Watrin1. 1UMR 7561 CNRS-Nancy Universite, Vandoeuvre les Nancy, FRANCE, 2Chirurgie Orthopédique et Traumatologique, CHU Nancy, FRANCE, 3UMR 7563 CNRS-Nancy Universite, Vandoeuvre les Nancy, FRANCE, 4Unite de Therapie Cellulaire et Tisulaire, CHU Nancy Brabois, FRANCE

Calcitonin reduces steady ionic current of the growth plate

We tested the hypothesis that calcitonin regulates the electric current associated with ionic exchanges occurring at the growth plate. For this purpose, we measured the net outward current driven by the growth plate of metatarsal bones of weanling mice by means of a voltage-sensitive probe system vibrating in two dimensions. Current density was reduced by calcitonin in a dose-dependent manner. Maximal reduction (∼40%) was obtained at a calcitonin concentration of 5 IU/ml. No effect was observed for calcitonin concentrations ≤ 0.05 IU/ml. When chloride was removed from the medium, calcitonin was less effective in reducing the net current density. Neither calcitonin gene-related peptide nor clodronate was able to induce any measurable change of the current density. Our results indicate that calcitonin acts on the ionic exchanges occurring at the growth plate and suggest that endogenous electrical signals in bone might be modulated by hormones.