The vertebral endplate: disc degeneration, disc regeneration

Abstract

The vertebral endplates are critical for maintaining disc function yet like other components of the disc are vulnerable to degeneration. This paper provides an overview of the development and normal function of the endplates as well as an impression of what happens when they undergo progressive degeneration. Recent research suggests that the degenerative process can be retarded or reversed.Keywords Disc AE Endplate AE Degeneration AE Regeneration ManuscriptDespite all that is known from decades of research the intervertebral disc remains an enigma. It is a unique and remarkable entity and perhaps the one aspect that is responsible for much of its mystery is that such a large structure is able to survive and function under the most difficult physiological conditions. The discs of the human spine are the largest non-vascularised structures in the body, and in the largest of them (in the lumbar spine) some cells can be 20 mm from the nearest direct blood supply. Despite their apparent resilience however, the resident cells are not immortal. It is not unusual for discs to show signs of deterioration by the age of 25 years and it is in this regard that the vertebral endplate plays an important role.Discs are roughly cylindrical structures that vary in size and shape progressively from the cervical to the lumbar region. They all comprise a well-hydrated central nucleus pulposus that is surrounded by the firm but flexible collagenous lamellae of the annulus fibrosus [40]. At the cranial and caudal ends of each disc are the endplates that separate the vertebral bone from the disc itself and prevent the highly hydrated nucleus from bulging into the adjacent vertebrae. The endplates also absorb the considerable hydrostatic pressure that results from mechanical loading of the spine [10]. The endplates are typically less than 1 mm thick, and while this varies considerably across the width of any single disc, they tend to be thinnest in the central region adjacent to the nucleus [16,44].The endplates are identifiable from an early embryological stage and have an osseous as well as a hyaline cartilage component [50]. The cartilaginous component appears to generate great interest since it persists throughout normal maturation while the adjacent vertebrae undergo ossification. It comprises a gel of hydrated proteoglycan molecules reinforced by a network of collagen fibrils. Unlike the articular cartilage of the synovial joints the collagen fibrils do not connect the endplate directly to the vertebral bone [22], although the endplate does have intimate contact with the disc through the lamellae of the inner annulus [21]. A network of microscopic blood vessels penetrates the endplates during development of the growing spine, principally to provide nutrition for the disc, before disappearing around the time of skeletal maturity [50]. Apart from a sparse vascular supply in the outer

A morphological study of lumbar vertebral endplates: radiographic, visual and digital measurements

“…The endplate is important in maintaining the integrity and functions of the intervertebral disc [3], and its morphology, which is less well known, could have practical relevance, such as for disc arthroplasty. It has been suggested that endplate morphometrics, especially the degree of concavity and concordance between the two endplates adjacent to a disc, may be important to artificial disc design [4][5][6].…”

A survey of the “surgical and research” articles in the European Spine Journal, 2006

“…For anyone involved in the basic science of the disc this supplement brings many strands of basic science together, genetics [11], degeneration imaging [4] tissue repair [22], senescence [43], regeneration [36] and much other work on the basic science of the disc, and its elucidation.…”

Injection of a polymerized hyaluronic acid/collagen hydrogel matrix in an in vivo porcine disc degeneration model

“…However, at present such approaches to humans are still rare and limited due to remaining concerns about safety and biological potency. Although tremendous efforts have been made to improve disc cell therapy, today's results are rather disappointing with early loss of implanted cells caused by annular damage at the injection site and cell death due to the harsh intradiscal environment characterized by insufficient nutrition, accumulation of waste products and high intradiscal pressures [3][4][5][6][7]. Additionally, cell-based strategies are expensive, time demanding, and invasive with potentially more complications, since autologous cells have to be collected in a first operation, with the need for processing and cultivation, and then application to the disc in a second operative procedure.…”