title: Functional properties and connective tissue content of pediatric human detrusor muscle.
abstract: The functional properties of human pediatric detrusor smooth muscle are poorly described, in contrast to those of adult tissue. Characterization is necessary for more informed management options of bladder dysfunction in children. We therefore compared the histological, contractile, intracellular Ca2+ concentration responses and biomechanical properties of detrusor biopsy samples from pediatric (3-48 mo) and adults (40-60 yr) patients who had functionally normal bladders and were undergoing open surgery. The smooth muscle fraction of biopsies was isolated to measure proportions of smooth muscle and connective tissue (van Gieson stain); in muscle strips, isometric tension to contractile agonists or electrical field stimulation and their passive biomechanical properties; in isolated myocytes, intracellular Ca2+ concentration responses to agonists. Pediatric detrusor tissue compared with adult tissue showed several differences: a smaller smooth muscle-to-connective tissue ratio, similar contractures to carbachol or α,β-methylene ATP when corrected for smooth muscle content, and similar intracellular Ca2+ transients to carbachol, α,β-methylene ATP, raised K+ concentration or caffeine, but smaller nerve-mediated contractions and greater passive stiffness with slower stress relaxation. In particular, there were significant atropine-resistant nerve-mediated contractions in pediatric samples. Detrusor smooth muscle from functionally normal pediatric human bladders is less contractile than that from adult bladders and exhibits greater passive stiffness. Reduced bladder contractile function is not due to reduced smooth muscle contractility but to greater connective tissue deposition and to functional denervation. Significant atropine resistance in pediatric detrusor, unlike in adult tissue, demonstrates a different profile of functional neurotransmitter activation. These data have implications for the management of pediatric bladder function by therapeutic approaches.
authors.affiliation: Institute of Urology, University College London, London, United Kingdom; and Department of Pediatric Urology, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: Navroop
authors.initials: N
authors.lastname: Johal
authors.affiliation: Institute of Urology, University College London, London, United Kingdom; and.
authors.forename: Dan N
authors.initials: DN
authors.lastname: Wood
authors.affiliation: Institute of Urology, University College London, London, United Kingdom; and.
authors.forename: Adrian S
authors.initials: AS
authors.lastname: Wagg
authors.affiliation: Department of Pediatric Urology, Great Ormond Street Hospital, London, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Cuckow
authors.affiliation: Institute of Urology, University College London, London, United Kingdom; and chris.fry@bristol.ac.uk.
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Fry
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000328:Adult; D001696:Biomechanical Phenomena; D002118:Calcium / Q000032:analysis; D002217:Carbachol / Q000494:pharmacology; D002675:Child, Preschool; D003238:Connective Tissue / Q000737:chemistry / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D001743:Urinary Bladder / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*
chemical_list: D000255:Adenosine Triphosphate; D002217:Carbachol; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002118:Calcium
keywords: biomechanics; contraction; detrusor smooth muscle; intracellular calcium; pediatric bladder