Hippocampal collagen as a potential target for post-surgical treatment; effects of whole-body vibration and exercise
Peripheral surgery may evoke neuroinflammation, associated with neuronal damage and consequently mental health problems. However, anti-inflammatory treatment showed limited therapeutic efficacy. Preservation of neuron integrity during neuroinflammation, by targeting their protective collagen sheet, may provide an alternative strategy. Whole-body vibration (WBV) and exercise combine anti-inflammatory and collagen-increasing effects in the periphery. The present study aimed to explore the therapeutic efficacy of postoperative WBV and exercise on hippocampal neuroinflammation and collagen expression. Three months old male Wistar rats underwent abdominal surgery. Starting from one day after surgery, rats were submitted to WBV (10 min, once or twice daily, 30 Hz), running exercise (30 min, daily), or pseudo WBV/exercise, for two weeks. Rats were sacrificed and brain tissue was collected and processed for (immuno)histochemistry. Hippocampal microglia activity, total collagen content, and expression of fibrous and non-fibrous collagen subtypes were analysed. Surgery was associated with increased microglia activity in the CA1 area, which was only partly reversed by the interventions. Surgery specifically reduced total collagen expression in the CA1 area, which was restored by both WBV and exercise. Collagen I was absent in the hippocampal granular layers. The surgery-induced decrease in collagen III expression in the CA1 area was not affected by either WBV or exercise. However, surgery increased collagen III in the CA2 (ns), CA3 and DG. Exercise, and to a lower extent WBV, seemed to (partly) reverse this effect. Collagen IV expression was not altered by surgery, but increased by WBV. No significant effects were observed on collagen VI expression. WBV as well as exercise restored the surgery-induced declined collagen expression, while partly reversing microglia activation in the CA1 area. Moreover, effects on collagen appeared to be subtype- and region-specific, with overall similar effects of WBV and exercise. Nevertheless, the neuroprotective potential of postoperatively altered brain collagen needs further investigation.