L. Mangiavini

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.

Allogeneic Umbilical Cord-Derived Mesenchymal Stem Cells as a Potential Source for Cartilage and Bone Regeneration: An In Vitro Study

Umbilical cord (UC) may represent an attractive cell source for allogeneic mesenchymal stem cell (MSC) therapy. The aim of this in vitro study is to investigate the chondrogenic and osteogenic potential of UC-MSCs grown onto tridimensional scaffolds, to identify a possible clinical relevance for an allogeneic use in cartilage and bone reconstructive surgery. Chondrogenic differentiation on scaffolds was confirmed at 4 weeks by the expression of sox-9 and type II collagen; low oxygen tension improved the expression of these chondrogenic markers. A similar trend was observed in pellet culture in terms of matrix (proteoglycan) production. Osteogenic differentiation on bone-graft-substitute was also confirmed after 30 days of culture by the expression of osteocalcin and RunX-2. Cells grown in the hypertrophic medium showed at 5 weeks safranin o-positive stain and an increased CbFa1 expression, confirming the ability of these cells to undergo hypertrophy. These results suggest that the UC-MSCs isolated from minced umbilical cords may represent a valuable allogeneic cell population, which might have a potential for orthopaedic tissue engineering such as the on-demand cell delivery using chondrogenic, osteogenic, and endochondral scaffold. This study may have a clinical relevance as a future hypothetical option for allogeneic single-stage cartilage repair and bone regeneration.

Pulsed Electromagnetic Fields Improve Tenogenic Commitment of Umbilical Cord-Derived Mesenchymal Stem Cells: A Potential Strategy for Tendon Repair—An In Vitro Study

Tendon repair is a challenging procedure in orthopaedics. The use of mesenchymal stem cells (MSCs) and pulsed electromagnetic fields (PEMF) in tendon regeneration is still investigational. In this perspective, MSCs isolated from the human umbilical cord (UC) may represent a possible candidate for tendon tissue engineering. The aim of the study is to evaluate the effect of low-frequency PEMF on tenogenic differentiation of MSCs isolated from the human umbilical cord (UC-MSCs) in vitro. 15 fresh UC samples from women with healthy pregnancies were retrieved at the end of caesarean deliveries. UC samples were manually minced into small fragments (less than 4 mm length) and cultured in MSC expansion medium. Part of the UC-MSCs was subsequently cultured with PEMF and tenogenic growth factors. UC-MSCs were subjected to pulsed electromagnetic fields for 2 h/day, 4 h/day, or 8 h/day. UC-MSCs cultured with FGF-2 and stimulated with PEMF showed a greater production of collagen type I and scleraxis. The prolonged exposure to PEMF was also related to the greatest expression of tenogenic markers. Thus, the exposure to PEMF provides a positive preconditioning biophysical stimulus, which may enhance UC-MSC tenogenic potential.

Recent advances in cartilage repair (ICL 3)

Articular cartilage possesses low intrinsic healing property due to its lack of vascularity and progenitor cells. Thus, damage to the hyaline cartilage may lead to a progressive degeneration of the joint and eventually to osteoarthritis (OA). In the last years, different surgical techniques have been introduced in the clinical practice to overcome this issue. Bone marrow stimulation, for example, is a widely known method to allow cell invasion from the bloodstream to the site of damage. However, the reparative tissue has different morphological and biomechanical properties when compared to the native cartilage. In particular, the newly formed fibrocartilage has a low amount of proteoglycans and a higher concentration of type I collagen. This different matrix composition leads to a decrease in the mechanical strength and to a poor integration of the reparative tissue with the native cartilage.

Pathophysiology of Cartilage Injuries

Articular cartilage lesions represent one of the major unsolved problems in orthopedic surgery due to the limited capacity of articular cartilage for self-repair following trauma. The biological response of cartilage to injury varies depending on the extent of the traumatic event. When a lesion is confined to the superficial layer, the repair process is not initiated, as the inflammatory stimulus is too weak to stimulate the resident chondrocytes surrounding the lesion; consequently, the defect persists. However, when a full-thickness lesion occurs, reaching the vessels of the subchondral bone, the inflammatory stimulus is more important. Bleeding from the bone marrow occurs, allowing the access of growth factors and reparative cells to the lesion site. These cells are mainly fibroblasts in addition to a low percentage of mesenchymal stem cells. As a result, the newly formed reparative tissue differs from the normal hyaline cartilage in term of morphology, biochemical composition, and biomechanical properties. For these reasons it is called fibrocartilage. The aim of this chapter is to review the morphology, composition, and biomechanical function of normal cartilage and to present an analysis of the response of the cartilage tissue to the different traumas.

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