Nerve, muscle and connective changes in the bladder of neurogenic detrusor overactive affected patients no longer responsive to botulinum toxin.

Introduction and aim of the study: It is well known that a complete supra‐sacral spinal cord lesion compromises the functional integrity of the bladder, leading to the Neurogenic Detrusor Overactivity (NDO) and/or vesico‐sphincter dyssynergia, whose main symptoms are reduced bladder capacity, frequency, urgency, residual urine and incontinence. This voiding disorder is treated with anti‐muscarinic drugs, as first choice and with intradetrusor injection of the botulinum toxin, as second treatment option. For still not clear at all reasons, with time the available therapies loss their efficacy leading some of the patients to bladder augmentation as effective long term solution (1). To date, two main hypotheses have been proposed to explain the pathogenesis of NDO: one proposes a hyperactivity of the efferent signalling the other a lowering of the afferent threshold for the voiding reflex (2). Indeed, a complex integrated sensory system entrusted to the urothelium and to some components of the lamina propria (LP), namely nerve endings, telocytes and myofibroblats has been described in the bladder and its importance in regulating the organ function is gaining continuous favors. Up to date, no investigation has been conducted in patients no longer responsive to all pharmacological treatment and extended to the entire thickness of the organ wall. Given these premises, the present work was finalized to get deeper in both NDO and drug efficacy lack pathogenesis, by investigating the innervation, muscular and connective changes in NDO bladders specimens after surgery and correlated these findings with the presurgery urodynamic outcomes. To reach these goals morphological and quantitative methodologies were applied. Materials and methods: Full‐thickness specimens of the bladder were collected from 8 NDO patients (4 females, 4 males; mean age: 40.6±2.9 years; mean years of treatment 14 ± 1.5) underwent to partial/total cystectomy. The patients were homogenous for aetiology, length of the disease and clinical course. The choice of the surgery was based on botulinum toxin and antimuscarinic treatment inefficacy, urodynamic parameters and personal motivations. The control group was represented by full‐thickness bladder specimens of 6 patients (1 female, 5 males; mean age: 72 ± 3 years) affected by bladder cancer. Attention was payed to collect the specimens far from the cancer lesions. The local Ethical Committee approved the study protocol. The specimens were processed for ultrastructural, histological and immune‐histological studies. The protein gene product 9.5 (PGP9.5), S100β and alpha smooth muscle actin (αSMA) antibodies wereused to studies neurons, glial and the smooth muscle cells, respectively. Results: The urodynamic data (Table 1) agree with the presence of NDO, variably coupled to incontinence and/or vesico‐ureteral reflux and/or kidney dilatation. The morphological studies highlight the presence of inflammation. In the lamina propria (LP) it is very intense, showing oedema, hyperaemia and a cell infiltrate rich in plasma cells and lymphocytes, all indexes of chronic inflammatory picture. In the detrusor, the inflammation mainly consists of eosinophilic granulocytes particularly numerous in the patients displaying kidney dilatation. PGP9.5 and S100β immunohistochemistry shows important differences amongst the layers (Figure 1). In the Upper part of the LP (ULP) of NDO patients, the varicose nerve fibres have an untidy distribution compared to controls and the quantitation of the two markers demonstrates a significant increase of these varicosities. In the Deep LP (DLP), no differences are observed between NDO and control patients. In the detrusor and adventitia, a significantly decreased of PGP9.5 and S100β labelling is detected in NDO patients compared to controls. Still in the detrusor, the αSMA labelling shows an abnormal clustering and distribution of the protein in the cytoplasm of smooth muscle cell (SMC); whereas the histochemical results point out a glycogen accumulation in these cells, and a marked fibrosis of the connective. The TEM images confirm the chaotic distribution of the contractilecomponents, the presence of numerous glycogen particles and a thicker SMC basal lamina.Interpretation of results: The increase of the varicose nerve fibres in the ULP, is suggestive for a sprouting of afferent nerve endings, likely excitatory ones, which could amplify the perception and reduce the voiding threshold. In the detrusor, the partial denervation might be responsible of the SMC anomalies, which, in turn, severely affect the contractile activity and compromise the proper intracellular traffic and the appearance of fibrosis. Finally, the chronic inflammation,likely neurogenic in origin, might condition and hasten the disease progression. Conclusions: Present findings confirm the main role played by the sensory system located in the ULP in conditioning the events responsible for NDO evolution and drug efficacy loss. Our findings show a correlation between low compliance urodynamic result and SMC anomalies in the bladder wall. Further, they suggest that, from a clinical point of view, a careful evaluation of any signs of urinary inflammation and its prompt treatment could positively influence the disease fate.References: 1. Hoen L et al. Long‐term effectiveness and complication rates of bladder augmentation in patients with neurogenic bladder dysfunction: A systematic review. Neurourol Urodyn. 2017 Sep;36(7):1685‐1702. Review. 2. Chapple C. Chapter 2: Pathophysiology of neurogenic detrusor overactivity and the symptom complex of "overactive bladder". Neurourol Urodyn. 2014.