Chronic pain (CP) represents a complex pathology profoundly involving both neural and glial compartments of the central nervous system. While most CP studies have also investigated the macroscopic brain vascular system, its microstructural architecture still remains largely unexplored. Further, the adaptive modifications of the vascular microstructure as consequence of diseases or pathological insults did not receive adequate attention. Here we show microtomographic signs of diffuse and conspicuous microvascular neogenesis in somatosensory cortex of CP animal models already peaking at 15 days from the model instantiation.Progressive fading of this microvessel neogenesis then ensued in the next six months yet maintaining higher vascular density with a preserved small fraction of them. Due to the important consequences on the neuronglial-vessel arrangements and on the resulting metabolic and functional disorders of the local networks, novel additional scenarios of CP are thus conceivable with profound consequences of potential future CP diagnostic and therapeutic appraisals.
Significance StatementChronic pain (CP) is an excruciating condition with various clinical presentations. Major signs are characterized by a rich repertoire of pain quality, intensity and length. While neuronal and glial anomalies have been associated to CP less attention has been granted to the micro-vessel and capillary compartments of the involved brain regions. Our research illustrates how the microvessel compartments of the somatosensory cortex in experimental animals present profound and long-lasting signs of extensive neogenesis (about fourfold) early within the first two weeks from the CP start, undergoing a slow and incomplete decline within six months. These results may change the CP clinical picture with potential novel therapeutic approaches to it.
IntroductionAt the level of the central nervous system, Chronic Pain (CP) displays a cohort of signs and symptoms, where the percept of pain dominates within a complex morpho-functional background of anomalous neuronal and glial events. These appear variously combined and causative of a global, maladaptive condition. At large scales, brain regional anomalous activations in CP patients 1-3 , as shown by functional neuroimaging, are seemingly accompanied by metabolic dysfunctions and local macrostructural signs such as cortical thickness reductions or cortical laminar misalignments 4 . At lower cell-level scales, CP-related functional disorders have been described, in the past, mostly as gangliar, spinal or central neuronal dynamic irregularities 5-8 .These mainly included spontaneous hyper-or hypo-activities, hyper-responsiveness to non-noxious and noxious stimuli, anomalous spiking patterns, often accompanied by variable signs of local neuronal degeneration and by cortical somatotopic mapping readjustments of sensory projection fields. These signs appeared complementary and ascribed to perceptual conditions such as spontaneous pain, allodynia and hyperalgesia. A step forward was then envi...