The present study analysed the clinical outcome and the histological characteristics of membrane-seeded autolo-gous chondrocytes implantation at 24 month after surgery for chondral defects.

A prospectic study was performed on fifteen patients (8 males and 7 females, mean age 38 years) suffering from cartilage lesions of the knee (12 cases) and the ankle (3 case). The patients underwent matrix-induced autologous chondrocyte implantation (MACI). Clinical outcomes were assessed by revised IKDC form and Knee Osteoarthritis and Injury Outcome Score (KOOS). At 12 months after implantation biopsy samples were obtained from 7 patients. The specimens were analysed by histochemistry, immunohistochemistry (ICRS visual histological assessment scale) and histomorphometry (Quantimet 500+).

Improvement 12 months after operation was found subjectively (39.7 to 57.9) and in articular function levels. IKDC scores showed marked improvement at 12 months (88% A/B). 90% of biopsies showed: smooth articular surface, hyaline-like matrix, columnar cell distribution, viable cells, normal subchondral bone, tide-mark. All sections were clearly stained with safranin-O, alcian blue, and revealed immunoreaction for S-100 protein, chondroitin-S and type II collagen.

Clinical improvement and hyaline-like appearance of the repair tissue indicate that MACI implantation is an effective technique for the treatment of cartilage lesions.

The search for bone substitutes has stimulated the study of growth factors with osteoinductive properties. Bone morphogenetic proteins (BMPs) have been shown to have a central role in endochondral and intramembranous bone formation and are thought to promote normal bone healing. Recent studies demonstrated that platelet-rich plasma (PRP) can provide several growth factors and stimulate osteogenesis. The aim of the present study was to analyse the in vitro effects of rhBMP-7 and PRP on phenotype and proliferation of cells from the site of non-union and from non-affected bone.

During the surgical treatment of seven cases of non-union, normal cancellous bone and tissue from the non-union site were harvested. Osteoblast-like cells and fibroblast-like cells were isolated and characterised. Mesenchymal cells were obtained from bone marrow of the same patients. Each cell type was incubated with rhBMP-7 and PRP at different concentrations. Proliferation rate and alkaline phosphatase activity were assessed at 3, 7, 15 and 30 days. Histochemical and immunohistochemical analyses were performed at 15 and 30 days.

The proliferation rate of osteoblast-like cells and mesenchymal cells wasalways higher than that of fibroblast-like cells from the non-union site. Growth factors induced mesenchymal cells to express osteoblast phenotype markers.

The results suggest that fibroblast-like cells from the site of non-union are poorly responsive to growth factors, even at highest stimulation. In surgical practice these data strongly suggest adding osteoblast-like cells and mesenchymal cells from non-affected sites at the non-union site to enhance the osteogenic response to growth factors.

Autogenous cancellous bone is the most effective material in stimulating osteogenic response and the standard graft augmentation for patients with nonunions or bone defects. However it may not be available in sufficient quantity and bone harvesting may give rise to morbidity. Allograft does not have the osteogenic potential of autogenous bone and may be complicated by immunological reaction and transmission of infections.

The search of bone substitutes has led to study several growth factors capable of inducing bone formation. Bone morphogenetic proteins (BMPs) have been shown to have a central role in endochondral and intramembranous bone formation and are thought to promote normal bone healing process. Recent studies demonstrated that platelet-rich plasma (PRP) provides several growth factors and stimulates osteogenesis.

The aim of the study was the evaluation of rhBMP-7 (rhOP-1) and PRP effects on the different cells detected at the site of nonunion, such as osteoblast-like cells, fibroblast-like cells and mesenchymal cells.

During the surgical treatment of seven nonunion cases, cancellous bone and nonunion tissue were harvested. Osteoblast-like cells and fibroblast-like cells were isolated and characterized. Mesenchymal cells were obtained from bone marrow samples of the same patients. Each cell type was incubated with rhBMP-7 and PRP at different concentrations. Proliferation rate and alkaline phosphatase (ALP) activity were assessed at 3, 7, 15, and 30 days. cytochemical and immunocytochemical analysis were performed at 15 and 30 days.

Proliferation rate was higher in osteoblast-like cells and mesenchymal cells than in fibroblast-like cells. Growth factors induced mesenchymal cells to express osteoblast phenotype markers.

The results show that fibroblast-like cells at the site of nonunion are responsive to growth factors stimulation, though their low osteoblastic differentiation rate, even at highest concentration of growth factors. These data suggest that the use of growth factors in nonunion treatment should be combined with autologous cancellous bone and/or bone marrow graft, sources of target cells, in order to enhance osteogenic response.

Bone marrow would represent a useful source of cells for skeletal tissue engineering. Marrow mesenchymal stem cells (MSC) can generate cartilage, bone and fat. The differentiation of this multipotent population into fibroblast, chondrocytes or osteoblasts can be inducted in vitro by the addiction of growth factor like bFGF, TGFA7, BMP-2.

In order to evaluate the possibility of inducing cell differentiation by cell-matrix interaction, we studied the in vitro behaviour of human MSC cultured on various scaffolds.

Bone marrow was obtained during surgery for pelvic fractures or hip arthroplasty. MSC were isolated by cell sorting (CD45/glycophorin A micromagnetic beads), expanded and characterised by FACSCalibur flow cytometry system (CD3, CD34, CD14, CD45, CD90 and CD105). Then cells were grown for 30 days on different scaffolds: type I and type II collagen, type I collagen + hydroxyapatite. Histochemical (alcian blue, safranin O, ALP and von Kossa stains), immunohistochemical (type I e II collagen, chondroitin sulphate, osteonectin), histomorphometric (area %) and spectrophotometric (cell proliferation, PG synthesis, ALP activity) analyses were performed after 15 and 30 days of culture.

Among the scaffolds tested in the present study, we observed a great variability in terms of MSC adhesion and proliferation. MSC grown on type II collagen differentiated into cells expressing chondrocytes markers (S100, collagen II, chondroitin-S). MSC grown on type I collagen + hydroxyapatite differentiated into osteoblast-like cells.

These data evidenced that MSC-matrix interaction can influence phenotype expression, cell adhesion and growth rate.