Zirconia-Based Biomaterials for Hard Tissue Reconstruction

Implantable biomaterials are increasingly important in the practice of modern medicine, including fixative, replacement, and regeneration therapies, for reconstruction of hard tissues in patients with pathologic osseous and dental conditions. A number of newly developed advanced biomaterials have been introduced as promising candidates for tissue reconstruction. Among these, zirconia-based biomaterials have gained attention as a biomaterial for hard tissue reconstruction due to superior mechanical properties and good chemical and biological compatibilities. This review summarizes the types of zirconia, advantages of zirconia-based biomaterials for hard tissue reconstruction including bone and dental tissues, responses of tissue and cells to zirconia, and surface modifications for enhanced bioactivity of zirconia. Current and future applications of zirconia-based biomaterials for bone and dental reconstruction, ie, medical implanted devices, dental prostheses, and biocompatible osteogenic scaffolds, are also discussed.

Hydroxyapatite–-Past, Present, and Future in Bone Regeneration

Hydroxyapatite (HA) is an essential element required for bone regeneration. Different forms of HA have been used for a long time. The essence of bone regeneration always revolves around the healthy underlying bone or it may be the surroundings that give enough strength. HA is well known for bone regeneration through conduction or by acting as a scaffold for filling of defects from ancient times, but emerging trends of osteoinductive property of HA are much promising for new bone regeneration. Emerging technology has made the dreams of clinicians to realize the use of HA in different forms for various regenerative purposes both in vivo and in vitro. The nanostructured calcium apatite plays an important role in the construction of calcified tissues. The nanostructured material has the ability to attach biological molecules such as proteins, which can be used as functional materials in many aspects, and the capability of synthesizing controlled structures of apatite to simulate the basic structure of bone and other calcified tissues. The process of regeneration requires a biomimetic and biocompatible nanostructured novel material. The nanostructured bioceramic particles are of interest in synthetic bone grafts and bone cements both injectable and controlled setting, so that such composites will reinforce the strength of bioceramics. Extensive research is being carried out for bone regeneration using nanotechnology. Artificial bone formation is not far from now. Nanotechnology has made many dreams come true. This paper gives comprehensive insights into the history and evolution with changing trends in the use of HA for various regenerative purposes.

Carbon Nanotube Surface Regular Topography Improves Cell Response, Depending on Cell Passage

Through mediation of integrin clustering, nanoscale surface structure of carbon nanotubes (CNTs) directly affects cell binding and subsequent behavior. The influence of morphological structures on proliferation, differentiation, and organization of focal adhesions and cytoskeleton of human mesenchymal stem cells (hMSCs) was studied. The following two surface morphologies were fabricated and examined: a random network multiwalled carbon nanotubes film (RNCNT) and a vertically aligned multiwalled carbon nanotube (VACNT) film. hMSCs adhered and spread earlier on both CNT surfaces than on control. A statistically significantly increased number of attached cells were observed on VACNT surfaces. No CNT substrate enhanced differentiation, but both maintained the differentiation property of hMSCs. VACNTs recruited vinculin from the cytoplasm for the formation of focal adhesion complexes earlier in comparison to RNCNT. There is still disparity on how nanostructures regulate the progression toward an osteoblastic phenotype. It is necessary to explore various architectures in order to understand how they initiate osteoinductive or proliferating signals.

Determining the Mineral Apposition Rate of Heterotopie Ossification in Military Healthcare System Patients after Total Joint Replacement: A Case Series

Heterotopic ossification (HO) is frequently reported following total joint replacement (TJR) surgery. Symptomatic HO may limit the range of motion, cause pain, and require surgical excision. Deciding an appropriate time for ectopic bone excision is based on clinical judgment, and a more well-defined link between clinical predictors and histological analysis is needed to minimize recurrence. A case series was performed with military healthcare system patients undergoing TJR, who required removal of periarticular ectopic bone. Patients were prescribed oxytetracycline to assess the mineral apposition rate (MAR; ie, bone growth rate) of HO, and excised specimens were analyzed using scanning electron microscopy and light microscopy. Two males and one female were enrolled in this study, with height of 69.0 ± 7.8 inches, weight of 237.7 ± 28.3 pounds, and age of 61 ± 7 years at the time of HO removal. Ectopic bone occurred in two cases following total knee arthroplasty and one total hip arthroplasty. Data indicated that MAR levels were 1.7 times higher than that reported previously for nonpathological human bone (1.7 ± 0.7 µm/day; range: 1.3–2.6 µm/day), and microscopic imaging confirmed that the osseous tissues were still actively remodeling at the time of surgical intervention. Further characterization is needed to optimize HO excision timing and to better understand this pathological bone disorder.

Article Commentary: Cornea as a Model for Testing CTGF-Based Antiscarring Drugs

Scarring remains a serious complication of the wound healing process that can lead to the formation of excessive fibrous connective tissue in an organ or tissue leading to pain and loss of function. This process is mainly regulated by Transforming growth factor β1 (TGF-β1), which binds to receptors and induces its downstream mediator, Connective tissue growth factor (CTGF). The number of drugs targeting CTGF for treating scars has been on the rise in the past few years. The purpose of this article is to suggest the possibility of using cornea as a model for testing anti-CTGF therapies for scarring.

Future of Bone Repair

Bone can suffer from various conditions such as fractures and diseases such as osteoporosis, osteogenesis imperfecta and tumors. Osteoporosis globally causes >8.9 million fractures each year. Current epidemiological data relevant to this and other diseases urge us to focus critically on promising and efficacious treatments for bone injury. Because of the limitations of conventional treatments for bone fracture, such as limited quantity for autograft, there is a demand to investigate better alternatives for bone healing. The main aim of this review is to highlight repair of bone injury, particularly focusing on several new research methods studied in preclinical trials and in vitro. New research methods such as low-level laser therapy, mesenchymal stem cell-based therapy, nanomaterials, biodegradable hydrogels, extracellular matrix-mimetic materials, and controlled delivery of growth factors from polymer scaffolds look promising for bone healing, and further clinical studies are suggested that use them in routine bone repair treatment in the near future.

A Review of the Pathogenesis of Osteoarthritis and the Use of Intra-articular Platelet Therapy for Joint Disease in Animals and Humans

Osteoarthritis (OA) is the most prevalent musculoskeletal disease in humans and domestic animals. It causes significant clinical problems and substantial health care costs. In the absence of disease-modifying medical intervention, therapy is currently restricted to palliative measures prior to surgical intervention. We review the pathogenesis, as well as conservative and emerging restorative therapeutic approaches, including cytokines, stem cells, and platelets. The various methods of platelet concentrate preparations and their reported outcomes are discussed. Data collected from the use of intra-articular platelet therapy (IAPT) in dogs are reviewed, which suggest that this approach may delay or in some cases even obviate the need for surgical intervention.

Nanotechnology in the Regeneration of Complex Tissues

Modern medicine faces a growing crisis as demand for organ transplantations continues to far outstrip supply. By stimulating the body's own repair mechanisms, regenerative medicine aims to reduce demand for organs, while the closely related field of tissue engineering promises to deliver “of-the-self” organs grown from patients' own stem cells to improve supply. To deliver on these promises, we must have reliable means of generating complex tissues. Thus far, the majority of successful tissue engineering approaches have relied on macroporous scaffolds to provide cells with both mechanical support and differentiative cues. In order to engineer complex tissues, greater attention must be paid to nanoscale cues present in a cell's microenvironment. As the extracellular matrix is capable of driving complexity during development, it must be understood and reproduced in order to recapitulate complexity in engineered tissues. This review will summarize current progress in engineering complex tissue through the integration of nanocomposites and biomimetic scaffolds.

Characterization of Human Anulus Fibrosus– and Nucleus Pulposus–Derived Cells During Monolayer Expansion and in Hydrogel Cultures

In vitro-expanded intervertebral disc (IVD) cells could be a source for disc repair. However, IVD cell characterization still remains challenging and is demanded to detect phenotypical shifts. Therefore, the aim of the present study was to determine IVD cell expression profile during two- and three-dimensional culturing in direct comparison to in situ conditions. Human IVD tissue was analyzed immunohistologically and anulus fibrosus (AF) and nucleus pulposus (NP) cells were isolated and characterized for cytoskeletal architecture and expression of typical markers (type I, II, and III collagens, aggrecan, decorin, cartilage oligomeric protein, the chondrogenic transcription factor sox9, the tendon markers scleraxis and tenascin C) during 6 monolayer passages using real-time detection polymerase chain reaction and/or immunolabellings. Cells were introduced in alginate and collagen hydrogels and cell morphology and viablility was determined after 7 days. In addition to typical extracellular matrix components, IVD tissue and isolated cells revealed scleraxis expression. In early passages of cell expansion, genes of sox9, scleraxis, and the small proteoglycan decorin were expressed higher, but type I and III collagen genes were expressed lower in NP cells compared with AF cells. However, in passage 6, actin stress fibers increased and the expression levels of sox9 were nearly similar in NP and AF cells. The immunolabeling indicated that the fibroblast marker tenascin C could only be detected in vitro in both cell types but not in situ. Decorin protein expression decreased in both cell types in vitro in passage 6. IVD cells survived in both hydrogel cultures, and some cells elongated in collagen gels.