Genetic susceptibility and development of chronic non-malignant back pain

[Long-lasting low back pain and MRI changes in the intervertebral discs]

BACKGROUND

Although low back pain is usually temporary, some patients do not recover and need treatment. Therefore, it is important to uncover causal and contributing factors. Here we give an overview of recent research on MRI findings and genetic factors that may be important for development of long-lasting low back pain.

MATERIAL AND METHODS

A non-systematic search in PubMed and EMBASE was performed. The relevant research articles identified, as well as the authors' knowledge of the field formed the basis for this review.

RESULTS

It is generally accepted that low back pain often stems from intervertebral discs, facet joints and lumbar multifundi muscles. However, it is also known that many patients with pronounced disc degeneration have so-called Modic changes, i.e. MRI changes in bone marrow close to the vertebral endplates. Several recent studies have shown an association between such changes and pain. It has also been demonstrated that patients with Modic changes and low back pain often have concomitant inflammation and growth of nociceptive nerve fibers into the endplates. To which extent this occurs, may be partly based on genetics.

INTERPRETATIONS

Genetic factors may contribute to low back pain. New knowledge about genetic factors and Modic changes can create a basis for better diagnostics and more specific treatment of patients with long-lasting low back pain.

Silencing the Kir4.1 potassium channel subunit in satellite glial cells of the rat trigeminal ganglion results in pain-like behavior in the absence of nerve injury

Growing evidence suggests that changes in the ion buffering capacity of glial cells can give rise to neuropathic pain. In the CNS, potassium ion (K+) buffering is dependent on the glia-specific inward rectifying K+ channel Kir4.1. We recently reported that the satellite glial cells that surround primary sensory neurons located in sensory ganglia of the peripheral nervous system also express Kir4.1, whereas the neurons do not. In the present study, we show that, in the rat trigeminal ganglion, the location of the primary sensory neurons for face sensation, specific silencing of Kir4.1 using RNA interference leads to spontaneous and evoked facial pain-like behavior in freely moving rats. We also show that Kir4.1 in the trigeminal ganglion is reduced after chronic constriction injury of the infraorbital nerve. These findings suggests that neuropathic pain can result from a change in expression of a single K+ channel in peripheral glial cells, raising the possibility of targeting Kir4.1 to treat pain in general and particularly neuropathic pain that occurs in the absence of nerve injury.

Pain and stress in a systems perspective: reciprocal neural, endocrine, and immune interactions

This paper advances a psychophysiological systems view of pain in which physical injury, or wounding, generates a complex stress response that extends beyond the nervous system and contributes to the experience of pain. Through a common chemical language comprising neurotransmitters, peptides, endocannabinoids, cytokines, and hormones, an ensemble of interdependent nervous, endocrine, and immune processes operates in concert to cope with the injury. These processes act as a single agent and comprise a supersystem. Acute pain in its multiple dimensions, and the related symptoms that commonly occur with it, are products of the supersystem. Chronic pain can develop as a result of unusual stress. Social stressors can compound the stress resulting from a wound or act alone to dysregulate the supersystem. When the supersystem suffers dysregulation, health, function, and sense of well-being suffer. Some chronic pain conditions are the product of supersystem dysregulation. Individuals vary and are vulnerable to dysregulation and dysfunction in particular organ systems due to the unique interactions of genetic, epigenetic and environmental factors, as well as the past experiences that characterize each person.

PERSPECTIVE

Acute tissue injury activates an ensemble of interdependent nervous, endocrine, and immune processes that operate in concert and comprise a supersystem. Some chronic pain conditions result from supersystem dysregulation. Individuals vary and are vulnerable to dysregulation due to the unique interactions of genetic, epigenetic, and environmental factors and past experiences that characterize each person. This perspective can potentially assist clinicians in assessing and managing chronic pain patients.