Re: Mast cell counts are not useful in the diagnosis of nonulcerative interstitial cystitis

Interstitial cystitis: a neuroimmunoendocrine disorder

Interstitial cystitis (IC) is a sterile bladder condition occurring primarily in females. It is characterized by frequency, nocturia, and suprapubic pain. IC symptoms are exacerbated during ovulation and under stress, thus implicating neurohormonal processes. The most prevalent theories to explain the pathophysiology of IC appear to be altered bladder lining and increased number of activated bladder mast cells. A defective bladder glycosaminoglycan (GAG) layer could allow penetration of allergic triggers, as well as chemicals, food preservatives, drugs, toxins, and adherent bacteria, all of which can activate bladder mast cells. Vasoactive, nociceptive, and proinflammatory molecules released can lead to immune cell infiltration and can sensitize neurons to secrete neurotransmitters or neuropeptides that can further activate mast cells. Mast cell-derived proteases can directly cause tissue damage, and it is noteworthy that urine tryptase is elevated in IC. Bladder mast cells are located close to neuronal processes, which are increased in IC, and they can be activated in situ by acetylcholine (ACh) and substance P (SP). Such activation is augmented by estradiol, which acquires significance in view of the fact that human bladder mast cells express estrogen receptors, but few progesterone receptors, which may explain the worsening of IC symptoms during ovulation. Finally, acute psychological stress in rats leads to mast cell activation that can be reduced by depletion of SP or neutralization of peripheral immune corticotropin-releasing hormone (CRH). These findings suggest that IC could be a syndrome with neural, immune, and endocrine components, in which activated mast cells play a central role.

Interstitial cystitis: a critique of current concepts with a new proposal for pathologic diagnosis and pathogenesis

Interstitial cystitis (IC) has continued to be an unresolved problem in clinical urology despite intense investigation over the past 16 or more years. Its etiology and pathogenesis are still undetermined, and its pathologic diagnosis is essentially one of exclusion, with no specific or clear criteria. In this review, current concepts of the etiology/pathogenesis and pathology are critically analyzed, new pathologic observations summarized, and a proposal of neurogenic inflammation as the primary pathogenetic factor is presented in the context of all currently available information. The popular postulate attributing IC to a deficient or defective glycosaminoglycan urothelial surface layer is not substantiated by morphologic, experimental, clinical, or therapeutic observations. Although the consensus seems to discount an infectious etiology, there is sufficient evidence that a microbial factor-short of a bona fide clinical infection-may have a role. Both autoimmunity and mast cell infiltration also appear to have a role, despite the lack of evidence that either is involved as the primary etiologic factor. Claims that the so-called feline urologic syndrome may represent a natural animal model of IC are shaky. As it now stands, there is no natural or induced animal model that duplicates IC as it occurs in humans. No specific or diagnostic light microscopic pathologic features are provided by either routine histopathology or immunohistochemistry. Increasingly, it has been recognized that detrusor mast cell count has little or no diagnostic value. On the other hand, electron microscopy has provided important new observations: (a) presence of mast cells, activated by piecemeal degranulation, in close proximity to intrinsic nerves-particularly in suburothelium: (b) distinctive pathologic changes in urothelium, suburothelium, and muscularis in biopsy samples obtained after diagnostic bladder hydrodistension; (c) constant associated changes in venules, capillaries, and neural elements in the same biopsy samples; and (d) diffuse involvement of bladder wall, with the most evident and profound pathologic changes in posthydrodistension biopsy samples obtained from cystoscopically obvious lesions (glomerulations). These features are sufficiently distinctive to allow definitive pathologic diagnosis of IC, and provide a firm basis for primary involvement of neurogenic inflammation in its pathogenesis. A proposal is presented regarding the mechanisms invoked by neurogenic inflammation. This proposal revolves around sensory nerve excitation, the release of neuropeptides, and activated differential secretion of potent mast cell mediators. This proposal can account for the heterogeneity and variability of observed pathologic features, and upholds the tacit acceptance of IC as a disease of pluricausal etiology and multifactorial pathogenesis.