ABSTRACT
With the development of nanotechnology, a better understanding of the role of feature size (nano, micro, and macro) on cell and tissue behavior, and a focused effort of regenerative medicine and tissue engineering (TE) research on mimicking native tissue dimension and composition, staunch advancements have been made in the areas of tissue and organ regeneration. Through the course of this chapter, we will discuss and explore technological advancements at the nanoscale with emphasis in osteochondral (bone-cartilage) tissue regeneration. We will begin with a brief overview of the anatomy and physiology of osteochondral tissue then explore regenerative approaches for the disparate tissues (bone and cartilage) which comprise the osteochondral tissue unit. Next we will delve in to current strategies and techniques for the manufacture of gradient and stratified scaffolds for regeneration
of the entire tissue unit with emphasis on synthetic and natural nanocomposite materials. 18.1 IntroductionAcute and chronic osteochondral defects caused by degenerative joint disease (such as osteoarthritis (OA)) and trauma present a common and serious clinical problem. Currently, 48 million Americans are afflicted with this condition and 67 million Americans are projected to suffer from OA by 2030 [8,42] leading to a pressing need for new treatment options to address these defects. Clinically, OA is defined as the progressive degeneration of hyaline cartilage leading to structural and functional failure at the bonecartilage interface [5]. In severe cases, the cartilage may be missing completely and the subchondral bone is exposed. Not surprisingly, bone-on-bone contact leads to inhibited joint motion and increased pain. Currently, there is no cure for OA and the course of treatment is determined by the severity, type, size, and location of the defect.Several traditional surgical treatment options are available for focal defects, (>5mm) which include autografts, autologous chondrocyte implantation, allografts, debridement [1], microfracture [11], and mosaicplasty [51]. Even though they are clinically viable options, they are still not perfect. The “gold standard” for osteochondral repair (autograft) largely involves the harvest and transplantation of autologous tissue. In this procedure, cylindrical osteochondral “plugs,” which include cartilage and subchondral bone tissue, are harvested from sites within the patient’s body that do not experience much mechanical stress and transplanted to defect site(s) wherein greater mechanical stress is experienced [51]. This procedure is considerably limited due to insufficient donor tissue and donor site morbidity. For patients with severe and advanced OA, total joint arthroplasty (TJA) is a common treatment option [57]. Total joint arthroplasty is an invasive procedure wherein the articulating surfaces of the joint are replaced by complex systems comprised of metallic, ceramic, and polymeric components. While generally minor in prevalence, complications such as infection, particulate induced bone loss (osteolysis), and reaction to metal ions can affect the longevity of TJA. Since all mechanical and implanted devices have the potential for failure, treatment of
a diseased or damaged joint with an implantable biodegradable single-unit scaffold is appealing. In particular, TE approaches may one day offer the possibility of treating and potentially curing the progression of degenerative joint disease in younger patients thus minimizing the need for TJA. With an increasingly active lifestyle, TE approaches to osteochondral repair may also offer a favorable alternative that enables patients to return to high-impact activities like skiing and running or competitive sports, which are not recommended for patients with TJA.
