Link protein N-terminal peptide and fullerol promote matrix production and decrease degradation enzymes in rabbit annulus cells

Intervertebral Disc-on-a-ChipMF: A New Model for Mouse Disc Culture via Integrating Mechanical Loading and Dynamic Media Flow

This study aims to develop an ex vivo organ-on-a-chip model, intervertebral Disc-on-a-ChipMF, to investigate integrated effects of mechanical loading and nutrition on disc health. The system consists of a detachable multilayer microfluidic chip, a Computer-Arduino-based control system, and a mechanical loading unit, which were optimized for accurate axial force measurement and the maintenance of a 21-day ex vivo disc culture. To ensure accuracy of axial force, we optimized the axial mechanical loading regimen, used the Computer-Arduino-based system and low-profile force sensors (LPFS) to control the mechanical loading unit, and modeled the force distribution by using computational simulation. A 21-day ex vivo disc culture was demonstrated using the Disc-on-a-ChipMF system, with optimized mechanical loading (0.02 MPa at 1Hz, 1.5 hr/day) and flow rate (1 μL/min). The structural integrity, collagen breakdown, catabolic enzyme activities, and disc cell and collagen alignment revealed that the on-chip cultured discs exhibited a preferred disc health similar to that of native discs for up to 21 days, while discs in a static culture showed detrimental degenerative changes. The mouse Disc-on-a-ChipMF system mimics in vivo disc microenvironment and provides a valuable platform for studying the effects of various factors on disc health and degeneration and testing new therapies.

Osteoarthritis: Novel Molecular Mechanisms Increase Our Understanding of the Disease Pathology

Although osteoarthritis (OA) is the most common musculoskeletal condition that causes significant health and social problems worldwide, its exact etiology is still unclear. With an aging and increasingly obese population, OA is becoming even more prevalent than in previous decades. Up to 35% of the world’s population over 60 years of age suffers from symptomatic (painful, disabling) OA. The disease poses a tremendous economic burden on the health-care system and society for diagnosis, treatment, sick leave, rehabilitation, and early retirement. Most patients also experience sleep disturbances, reduced capability for exercising, lifting, and walking and are less capable of working, and maintaining an independent lifestyle. For patients, the major problem is disability, resulting from joint tissue destruction and pain. So far, there is no therapy available that effectively arrests structural deterioration of cartilage and bone or is able to successfully reverse any of the existing structural defects. Here, we elucidate novel concepts and hypotheses regarding disease progression and pathology, which are relevant for understanding underlying the molecular mechanisms as a prerequisite for future therapeutic approaches. Emphasis is placed on topographical modeling of the disease, the role of proteases and cytokines in OA, and the impact of the peripheral nervous system and its neuropeptides.

A multi-throughput mechanical loading system for mouse intervertebral disc

Mechanical loading plays an important role in maintaining disc health and function, and in particular, excessive mechanical loading has been identified as one of major reasons of disc degeneration. Intervertebral disc organ culture serves as a valuable tool to study disc biology/pathology. In this study, we report the development and validation of a new mouse disc organ culture system by dynamically applying compression loading in a customized micro-culture device tailored for mouse lumbar discs. Precise axial compression force was delivered by a computer-controlled system consisting of a robust micromechanical linear actuator, a force sensitive resistor, and a precision micro-stepping machinery. Customized PDMS-based loading chambers allowed simultaneous loading of six discs per regimen, which streamlined the workflow to reach sufficient statistic power. The detrimental loading regimen of mouse lumbar discs (0.5 MPa of axial compression at 1Hz for 7 days) was demonstrated through live-dead assay, histology, and fluorescence probe based collagen staining. In addition, various mechanical compression profiles were simulated using different materials and geometry designs, potentiating for more sophisticated loading protocols. In summary, we developed a new mechanical loading system for dynamic axial compression of mouse discs, which created a unique avenue to study disc pathogenesis with enriched mouse species-related resources, and complemented the existing spectrum of bioreactor systems predominately for discs of human and large animals.

Link N as a therapeutic agent for discogenic pain

Neurotrophins (NTs) are the major contributors of sensory axonal sprouting, neural survival, regulation of nociceptive sensory neurons, inflammatory hyperalgesia, and neuropathic pain. Intervertebral disc (IVD) cells constitutively express NTs. Their expression is upregulated by proinflammatory cytokines present in the IVD during degeneration, which can promote peripheral nerve ingrowth and hyperinnervation, leading to discogenic pain. Currently, there are no targeted therapies that decrease hyperinnervation in degenerative disc disease. Link N is a naturally occurring peptide with a high regenerative potential in the IVD. Therefore, the suitability of Link N as a therapeutic peptide for suppressing NTs, which are known modulators and mediators of pain, was investigated. The aim of the present study is to determine the effect of Link N on NTs expression, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and their cognate receptors TrkA and TrkB as they are directly correlated with symptomatic back pain. Furthermore, the neurotransmitter (substance P) was also evaluated in human annulus fibrosus (AF) cells stimulated with cytokines. Human AF cells isolated from normal IVDs were stimulated with interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the presence or absence of Link N. NGF release in the media was evaluated by Western blotting. Total RNA was isolated and gene expression was measured using real-time PCR. Gene expression of NGF, BDNF, TrkA, and TrkB significantly decreased in human disc cells stimulated with either IL-1β or TNF-α supplemented with Link N when compared to the cells stimulated only with IL-1β or TNF-α. NGF protein expression was also suppressed in AF cells coincubated with Link N and IL-1β when compared to the cells stimulated only with IL-1β. Link N can suppress the stimulation of NGF, BDNF, and their receptors TrkA and TrkB in AF cells in an inflammatory milieu. Thus, coupled with previous observations, this suggests that administration of Link N has the potential to not only repair the discs in early stages of the disease but also suppress pain.