Functional Validation of a Complex Loading Whole Spinal Segment Bioreactor Design.

Intervertebral disk (IVD) degeneration is a prevalent health problem that is highly linked to back pain. To understand the disease and tissue response to therapies, ex vivo whole IVD organ culture systems have recently been introduced. The goal of this work was to develop and validate the design of a whole spinal segment culturing system that loads the disk in complex loading similar to the in vivo condition, while preserving the adjacent endplates and vertebral bodies. The complex loading applied to the spinal segment (flexion-extension (FE), bilateral bending, and compression) was achieved with three pneumatic cylinders rigidly attached to a triangular loading platform. A culture container housed the spinal segment and was attached to the loading mechanism, which allowed for loading of the spinal segment. The dynamic bioreactor was able to achieve physiologic loading conditions with 100 N of applied compression and approximately 2-4 N · m of applied torque. The function of the bioreactor was validated through testing of bovine caudal IVDs with intact endplates and vertebral bodies that were isolated within 2 hrs of death and cultured for 14 days. The resulting IVD cell viability following 14 days of loading was much higher than unloaded control IVDs. The loading system accurately mimicked FE, bilateral bending, and compression motions seen during daily activities. The results indicate that this complex dynamic bioreactor may be appropriate for extended preclinical testing of vertebral-mounted spinal devices and therapies.

MRI evaluation of spontaneous intervertebral disc degeneration in the alpaca cervical spine.

Animal models have historically provided an appropriate benchmark for understanding human pathology, treatment, and healing, but few animals are known to naturally develop intervertebral disc degeneration. The study of degenerative disc disease and its treatment would greatly benefit from a more comprehensive, and comparable animal model. Alpacas have recently been presented as a potential large animal model of intervertebral disc degeneration due to similarities in spinal posture, disc size, biomechanical flexibility, and natural disc pathology. This research further investigated alpacas by determining the prevalence of intervertebral disc degeneration among an aging alpaca population. Twenty healthy female alpacas comprised two age subgroups (5 young: 2-6 years; and 15 older: 10+ years) and were rated according to the Pfirrmann-grade for degeneration of the cervical intervertebral discs. Incidence rates of degeneration showed strong correlations with age and spinal level: younger alpacas were nearly immune to developing disc degeneration, and in older animals, disc degeneration had an increased incidence rate and severity at lower cervical levels. Advanced disc degeneration was present in at least one of the cervical intervertebral discs of 47% of the older alpacas, and it was most common at the two lowest cervical intervertebral discs. The prevalence of intervertebral disc degeneration encourages further investigation and application of the lower cervical spine of alpacas and similar camelids as a large animal model of intervertebral disc degeneration.