Biomedical subjects

Pierre-Yves Zambelli

Publications and source records attributed to Pierre-Yves Zambelli.

6 recordsLinked to original sources

PubMed2006

Bone tissue engineering using foetal cell therapy.

Different cell sources for bone tissue engineering are reviewed. In particular, adult cell source strategies have been based on the implantation of unfractionated fresh bone marrow; purified, culture expanded mesenchymal stem cells, differentiated osteoblasts, or cells that have been modified genetically to express rhBMP. Several limiting factors are mentioned for these strategies such as low number of available cells or possible immunological reaction of the host. Foetal bone cells are presented as an alternative solution and review of actual treatments using these cells is presented. Finally, foetal cells used specifically for bone tissue engineering are characterised and potentially interesting therapeutic options are proposed.

Bone Regeneration↗

PubMed2006

Local delivery of bisphosphonate from coated orthopedic implants increases implants mechanical stability in osteoporotic rats.

Patients with osteoporosis and joint disabilities represent a constant growing and challenging population to be treated in the musculoskeletal clinical field. Especially in the case of total hip arthroplasty, new solutions should be developed to compensate for the double negative factors, peri-implant osteolysis, and osteoporotic bone loss, affecting the quality of implant outcome. The goal of this study was then to establish a proof of concept for orthopedic implant used as Zoledronate delivery in osteoporotic rats, and in particular, to verify if this approach could increase the initial implant stability. Twenty-five female 6-month-old Wistar rats were ovariectomized 6 weeks before the implantation to induce osteoporosis. The animals were randomly separated in five groups representing the different Zoledronate concentrations in the HA coating: 0, 0.2, 2.1, 8.5, and 16 microg/implant. Histomorphometric measures and peri-implant bone volume fraction were assessed and mechanical stability tests were performed. Bone volume fraction and biomechanical results clearly illustrate the positive effect of Zoledronate coated implants in the osteoporotic rats. A remarkable result was to show the existence of a window of Zoledronate content (0.2 to 8.5 microg/implant) in which the mechanical fixation of the implant increased. We were able to establish the proof of concept for orthopedic implants used as a drug delivery system in osteoporotic rats. The local bisphosphonate delivery from a calcium phosphate coating allowed increase of the mechanical fixation of an orthopedic implant. This study shows that orthopedic implants containing bisphosphonates could be beneficial for osteoporotic patients in need of a total joint replacement.

Animals↗

PubMed2006

Reliable acetabular cup orientation with a new gravity-assisted guidance system.

Acetabular cup orientation is a key factor determining hip stability, and standard mechanical guides have shown little help in improving alignment. An in vitro study was carried out to compare the accuracy and precision of a new gravity-assisted guidance system with a standard mechanical guide. Three hundred ten cups were impacted by 5 surgeons, and the final cup orientation was measured. With the new guide, the average error in anteversion was 0.4 degrees , compared with 10.4 degrees with the standard guide and 0.3 degrees and -4.7 degrees , respectively, for abduction angles. The average time required for orienting the cups was similar for both guides. The accuracy and reproducibility obtained with the new guide were better (P < .0001). These good results would require a clinical validation.

Acetabulum↗

PubMed2004

Fetal bone cells for tissue engineering.

We envision the use of human fetal bone cells for engineered regeneration of adult skeletal tissue. A description of their cellular function is then necessary. To our knowledge, there is no description of human primary fetal bone cells treated with differentiation factors. The characterization of fetal bone cells is particularly important as the pattern of secreted proteins from osteoblasts has been shown to change during aging. In the first part of this work, human primary fetal bone cells were compared to adult bone cells and mesenchymal stem cells for their ability to proliferate and to differentiate into osteoblasts in vitro. Cell proliferation, gene expression of bone markers, alkaline phosphatase (ALP) activity, and mineralization were analyzed during a time-course study. In the second part of this paper, bone fetal cells behavior exposed to osteogenic factors is further detailed. The doubling time of fetal bone cells was comparable to mesenchymal stem cells but significantly shorter than for adult bone cells. Gene expression of cbfa-1, ALP, alpha1 chain of type I collagen, and osteocalcin were upregulated in fetal bone cells after 12 days of treatment, with higher inductions than for adult and mesenchymal stem cells. The increase of ALP enzymatic activity was stronger for fetal than for adult bone cells reaching a maximum at day 10, but lower than for mesenchymal stem cells. Importantly, the mineralization process of bone fetal cells started earlier than adult bone and mesenchymal stem cells. Proliferation of fetal and adult bone cells was increased by dexamethasone, whereas 1alpha,25-dihydroxyvitamin D3 did not show any proliferative effect. Mineralization studies clearly demonstrated the presence of calcium deposits in the extracellular matrix of fetal bone cells. Nodule formation and calcification were strongly increased by the differentiation treatment, especially by dexamethasone. This study shows for the first time that human primary fetal bone cells could be of great interest for bone research, due to their fast growth rate and their ability to differentiate into mature osteoblasts. They represent an interesting and promising potential for therapeutic use in bone tissue engineering.

Adult↗

PubMed2004

Optimal femoral head contour segmentation in CT images using dynamic programming.

We present a new contour segmentation method for femoral head detection in CT images. The principal idea underlying our approach is to represent the contour using active rays. Each ray has internal energy (continuity and smoothness constraints), as well as external energy (image-oriented edges and global a-priori knowledge). The causal nature of this representation allows a globally optimal, non-iterative solution to be found using dynamic programming. Moreover, even pathological bone structures can be automatically segmented. Several clinical situations on pelvis CT scan with hip degenerative change shows that this approach is more efficient than conventional methods. In this paper, we describe our method and discuss how it can be used to create graphical 3D models of the hip that are suitable for preoperative planning.

Algorithms↗

PubMedDate not supplied

Biocompatibility of bioresorbable poly(L-lactic acid) composite scaffolds obtained by supercritical gas foaming with human fetal bone cells.

The aim of this investigation was to test the biocompatibility of three-dimensional bioresorbable foams made of poly(L-lactic acid) (PLA), alone or filled with hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP), with human primary osteoblasts, using a direct contact method. Porous constructs were processed by supercritical gas foaming, after a melt-extrusion of ceramic/polymer mixture. Three neat polymer foams, with pore sizes of 170, 310, and 600 microm, and two composite foams, PLA/5 wt% HA and PLA/5 wt% beta-TCP, were examined over a 4-week culture period. The targeted application is the bone tissue-engineering field. For this purpose, human fetal and adult bone cells were chosen because of their highly osteogenic potential. The association of fetal bone cells and composite scaffold should lead to in vitro bone formation. The polymer and composite foams supported adhesion and intense proliferation of seeded cells, as revealed by scanning electron microscopy. Cell differentiation toward osteoblasts was demonstrated by alkaline phosphatase (ALP) enzymatic activity, gamma-carboxylated Gla-osteocalcin production, and the onset of mineralization. The addition of HA or beta-TCP resulted in higher ALP enzymatic activity for fetal bone cells and a stronger production of Gla-osteocalcin for adult bone cells.

Bone Substitutes↗