The intervertebral disc (IVD) is a highly hydrated and hyperosmotic tissue, water and salt content fluctuate daily due to mechanical loading. Resident IVD cells must adapt to this ever-changing osmotic environment, to maintain normal behaviour. However, during IVD degeneration the disc becomes permanently dehydrated and cells can no longer perform their correct function. Here, we investigated how human nucleus pulposus (NP) cells respond to altered osmolality with regards to cell size and the rate of water permeability, along with the potential involvement of aquaporins (AQPs) and transient receptor potential vanilloid (TRPV) membrane channels. Water permeability of NP cells exposed to altered osmolality (225–525mOsm/kg) in the presence or absence of AQP and TRPV channel inhibitors was investigated with the cell-permeable calcein-AM fluorescent dye, and cell size determined using microscopy and flow cytometry.Introduction
Methods
Within the intervertebral disc (IVD), nucleus pulposus (NP) cells reside within a unique microenvironment. Factors such as hypoxia, osmolality, pH and the presence of cytokines all dictate the function of NP cells and as such the cells must adapt to their environment to survive. Previously we have identified the expression of aquaporins (AQP) within human IVD tissue. AQPs allow the movement of water across the cell membrane and are important in cellular homeostasis. Here we investigated how AQP gene expression was regulated by the microenvironment of the IVD. Human NP cells were cultured in alginate beads prior to cytokine, osmolality, pH and hypoxia treatments and subsequent RT-qPCR to assess regulation of AQP gene expression.Introduction
Methods
To evaluate the efficacy of Vacuum Assisted Closure (VAC) in the management of post surgical spinal sepsis. A retrospective analysis was performed of patients with severe post operative spinal wound infections treated using a combination surgical debridement, antibiotics and VAC therapy. Full records were available for a total of twenty adult all of whom had had prior thoracic or lumbar instrumentation. Comorbidities included disseminated carcinomatosis (25 % of patients), Ankylosing spondylitis (5 %), rheumatoid arthritis (5%) and Polio (5%). In one patient there had been a prior history of irradiation of the surgical field. Most infections treated by this regime were identified within two weeks following surgery. At surgery infection deep to the dorso-lumbar fascia was found in 87 % of cases. It was possible to retain instrumentation in 60 % of cases. An average of three trips to theatre were required prior to wound closure, which was possible in 95 % of cases. The VAC device was left in situ for an average of 11 days. Complications included recurrence of infection necessitating further treatment in 20 % of cases, wound dehiscence necessitating healing by secondary intention in 5%, the need for free flap wound cover in 5 % and death from unrelated causes in 5%. VAC therapy may facilitate the management of wound sepsis following spinal surgery in susceptible patients allowing the maintenance of instrumentation and surgical correction.
