Emerging strategies of bone and joint repair

Regeneration of bone using nanoplex delivery of FGF-2 and BMP-2 genes in diaphyseal long bone radial defects in a diabetic rabbit model

Bone fracture healing impairment related to systemic diseases such as diabetes can be addressed by growth factor augmentation. We previously reported that growth factors such as fibroblast growth factor-2 (FGF-2) and bone morphogenetic protein-2 (BMP-2) work synergistically to encourage osteogenesis in vitro. In this report, we investigated if BMP-2 and FGF-2 together can synergistically promote bone repair in a leporine model of diabetes mellitus, a condition that is known to be detrimental to union. We utilized two kinds of plasmid DNA encoding either BMP-2 or FGF-2 formulated into polyethylenimine (PEI) complexes. The fabricated nanoplexes were assessed for their size, charge, in vitro cytotoxicity, and capacity to transfect human bone marrow stromal cells (BMSCs). Using diaphyseal long bone radial defects in a diabetic rabbit model it was demonstrated that co-delivery of PEI-(pBMP-2+pFGF-2) embedded in collagen scaffolds resulted in a significant improvement in bone regeneration compared to PEI-pBMP-2 embedded in collagen scaffolds alone. This study demonstrated that scaffolds loaded with PEI-(pBMP-2+pFGF-2) could be an effective way of promoting bone regeneration in patients with diabetes.

Bone-forming capacity of mesenchymal stromal cells when cultured in the presence of human platelet lysate as substitute for fetal bovine serum

In tissue engineering, strategies are being developed to repair large bone defects by combining biomaterials and bone marrow-derived multipotent mesenchymal stromal cells (MSCs). For expansion of MSCs under good manufacturing practice conditions, human platelet lysate (PL) can serve as substitute for fetal bovine serum (FBS) in culture media. We compared the in vivo bone-forming capacity of passage 3 MSCs cultured with either PL or FBS for nine different human donors. We also tested the growth kinetics, antigen expression profile, and the multilineage differentiation capacity in vitro of these MSCs. The in vivo bone-forming capacity was determined by seeding culture-expanded MSCs onto biphasic calcium phosphate scaffolds. Hybrid constructs were implanted subcutaneously in nude mice, retrieved after 6 weeks, and analyzed using histomorphometry. PL-supplemented cultures resulted in significantly larger colonies, shorter culture time period, and higher population doublings between P1 and P3 compared to FBS-containing cultures. No differences were observed in antigen expression profiles or differentiation capacities into the osteoblastic, chondrogenic, and adipogenic lineages, qualitatively. In vivo bone formation with PL-supplemented cultures of MSCs was demonstrated in 9/9 donors versus 6/9 for FBS-supplemented cultures. These results warrant the use of PL for ex vivo expansion of human MSCs for bone tissue engineering applications.

Progenitor and stem cells for bone and cartilage regeneration

Research in regenerative medicine is developing at a significantly quick pace. Cell-based bone and cartilage replacement is an evolving therapy aiming at the treatment of patients who suffer from limb amputation, damaged tissues and various bone and cartilage-related disorders. Stem cells are undifferentiated cells with the capability to regenerate into one or more committed cell lineages. Stem cells isolated from multiple sources have been finding widespread use to advance the field of tissue repair. The present review gives a comprehensive overview of the developments in stem cells originating from different tissues and suggests future prospects for functional bone and cartilage tissue regeneration.

Seeding Osteoblastic Cells into a Macroporous Biodegradable CaP/PLGA Scaffold by a Centrifugal Force

This study aims to construct a hybrid biomaterial by seeding osteoblastic cells into a CaP/PLGA scaffold by a centrifugal force. Constructs are evaluated with respect to potential application in bone tissue engineering. Cells adher, spread, and form a layer of tissue lining the scaffold and are capable of migrating, proliferating, and producing mineralized matrix. We have demonstrated that the centrifugal force is highly efficient for constructing a hybrid biomaterial, which acts similarly to bone explants in a cell culture environment. In this way, these constructs could mimic an autogenous bone graft in clinical circumstances. Such a strategy may be useful for bone tissue engineering.

Vascular endothelial growth factor expression in cultured periosteal-derived cells

The purpose of this study was to examine the expression of vascular endothelial growth factor (VEGF) during osteoblastic differentiation of cultured human periosteal-derived cells. Periosteal tissues were obtained from mandible during surgical extraction of lower impacted third molars. Periosteal-derived cells were introduced into cell culture. After passage 3, the periosteal-derived cells were further cultured for 42 days in an osteogenic-inductive culture medium containing dexamethasone, ascorbic acid, and beta-glycerophosphate. The alkaline phosphatase activity in the cultured periosteal-derived cells increased rapidly up to day 14, followed by decrease in activity. The Runx2 protein was expressed at day 7 and day 14, and its expression was not observed thereafter. Both VEGF(165) and VEGF(121) were expressed strongly at days 35 and 42 of culture, particularly during the later stages of differentiation. Alizarin red S-positive nodules were first observed on day 14 and then increased in number during the entire culture period. Osteocalcin and VEGF were first detected in the culture medium on day 14, and their levels increased thereafter in a time-dependent manner. These results suggest that VEGF secretion from cultured human periosteal-derived cells increases along with the mineralization process of the extracellular matrix.

Bespoke human hypertrophic chondrocytic cell lines provide the osteoinductive signals required for vascularized bone formation

Hypertrophic cartilage provides the morphological and biochemical template for orchestrating bone growth. To produce a bone-inductive material such as hypertrophic cartilage for clinical use, we have conditionally immortalized hypertrophic chondrocytic cells from human femur and expanded them in vitro through more than 145 divisions. The clonal cell lines generated by this process consistently express signals that induce both rat and human marrow cells to differentiate in vitro into osteoblastic cells. Further, implantation of the cell-free extracellular matrix from the immortalized chondrocytic cells causes vascularized bone to form in vivo in bony defects, but not in ectopic sites such as skeletal muscle. This study shows that molecular techniques can be used to generate bespoke human cell lines for bone tissue engineering. It also demonstrates that matrix material generated from human immortalized hypertrophic chondrocytic cells may provide an abundant, efficacious, and safer alternative to bone autograft--the currently preferred material for fracture repair.

Osteogenic phenotypes and mineralization of cultured human periosteal-derived cells

Stem cells or osteogenic precursor cells isolated from bone marrow, trabecular tissues in bone, cartilage, muscle, and fat are the most suitable source for bone tissue engineering. In this study, we investigated the osteogenic phenotypes and mineralization of cultured human periosteal-derived cells obtained from mandibular periosteums. These periosteal-derived cells were positive for CD44, CD90, and CD166 antigens. They are successfully differentiated into osteoblasts in the medium containing dexamethasone, ascorbic acid, and beta-glycerophosphate. We observed that alkaline phosphatase (ALP) was largely expressed in the earlier stage of osteoblastic differentiation according to histochemical staining and RT-PCR analysis, whereas osteocalcin was dominantly expressed and secreted into the medium at the later stage. In addition, mineralized nodule formation has been observed by von Kossa staining in a time-dependent manner. These results suggest that periosteal-derived cell has the potential osteogenic activity and could be a good candidate for tissue engineering to restore the bony defects of the maxillofacial region.

Human bone marrow stromal cells: In vitro expansion and differentiation for bone engineering

Stromal cells from marrow hold a great promise for bone regeneration. Even if they are already being exploited in many clinical settings, the biological basis for the source and maintenance of their proliferation/differentiation potential after in vitro isolation and expansion needs further investigation. Most studies on osteogenic differentiation of marrow stromal cells (MSC) have been performed using bone marrow from the iliac crest. In this study, MSC were derived from spare femoral bone marrow obtained during hip replacement surgery from 20 adult donors. After in vitro isolation the cells were grown in osteogenic medium, and their proliferation and differentiation analysed during in vitro expansion. We found that MSC isolated from the femur of adult patients consistently maintain an osteogenic potential. Using biochemical signals, these cells turn to fully differentiated osteoblasts with a predictable set of molecular and phenotypic events of in vitro bone deposition. When seeded on polycaprolactone-based scaffold or surfaces, the proliferation and mineralization of femur-derived MSC were modulated by the surface chemistry/topography. Despite remarkable differences between individual colony-forming ability, alkaline phosphatase production, and mineralization ability, these cells are a potential source for bone engineering, either by direct autologous reimplantation or by ex vivo expansion and reimplantation combined to a proper scaffold.

Mesenchymal stem cells for bone, cartilage, tendon and skeletal muscle repair

Literature data concerning the biology and differentiation potential of mesenchymal stem cells (MSCs) have become huge in less than 10 years, although some of these data still remain contradictory. MSCs seem to be a very promising tool for cell therapy because of their peculiar characteristics, which mimic partially those of embryonic stem cells, but with some advantages in terms of availability, expandability, transplantability, and ethical implications. We discuss here the potential use of MSCs in degenerative or inflammatory diseases involving bone, cartilage, tendon and muscle tissues, on the basis of the experimental evidence.

The future of bone healing

With more than 5.5 million fractures and 1 million bone repair surgeries annually, bone graft plays a significant role in aiding fracture repair. In the United States alone, surgeons perform an estimated 500,000 to 600,000 bone grafting procedures annually. With the advent of possibilities from bone substitutes, growth factors, and stem cell research, the potential for enhancing bone healing is vast. This article attempts to survey current trends and to highlight upcoming techniques in the future of bone healing.

The development and identification of constructing tissue engineered bone by seeding osteoblasts from differentiated rat marrow stromal stem cells onto three-dimensional porous nano-hydroxylapatite bone matrix in vitro

The purposes of this study were to develop a new cultural method for the rat bone marrow stromal cells (MSCs) to differentiate into osteoblasts well in vitro, and to investigate the feasibility of using MSCs as seed cells and three-dimensional porous nano-hydroxylapatite as scaffolds for constructing tissue-engineered bone. MSCs of rats were isolated, cultured, induced to differentiate into osteoblasts, and then observed with inverted microscopy. Histochemical staining and radio-immunological analysis were applied for identifying MSCs. Whereafter MSCs were seeded onto three-dimensional porous nano-hydroxylapatite scaffolds, and scanning electron microscopy was applied to evaluate their growth on scaffolds. Results showed that MSCs were typical fibroblast-like and possessed a better proliferating capability; the activity of alkaline phosphatase (ALP) and the secretion of osteocalcin of MSCs were produced gradually and increased continuously; the cells seeded on three-dimensional porous nano-hydroxylapatite scaffolds adhered, proliferated and differentiated well. These results demonstrated that the new improved culture method had the advantages of short isolating time, less risk of contamination and higher efficiency and accordingly was conducive to MSCs proliferating and differentiating into osteoblasts, and that it was advantageous to constructing tissue-engineered bone using MSCs as seed cells and three-dimensional porous nano-hydroxylapatite as scaffolds.

Skeletal tissue engineering: opportunities and challenges

Tissue engineering is a field of biomedicine that is growing rapidly and is critically driven by scientific advances in the areas of developmental and cell biology and biomaterial sciences. Regeneration of skeletal tissues is among the most promising areas of biological tissue repair and is providing a broad spectrum of potential clinical applications, including joint resurfacing. The availability of novel tools such as pluripotent stem cells, morphogens, smart biomaterials and gene transfer technologies, makes us dream of many exciting novel therapeutic approaches. Despite these opportunities in regenerative medicine, good clinical practice requires the clinician to question the consistency, reproducibility, validation and appropriate regulation of these new biological treatments.