title: Ciliary Muscle Cell Changes During Guinea Pig Development.
abstract: OBJECTIVE
  Guinea pig ciliary muscle (CM) increases robustly in volume, length, and thickness with age. We wanted to characterize CM cells during development to determine the contributions of hypertrophy (cell size increase) and hyperplasia (cell number increase) during development.
  
  
  METHODS
  Six pigmented guinea pig eyes were collected at each of five ages: 1, 10, 20, 30, and 90 days. Refractive errors and axial lengths were determined. Eyes were temporally marked, enucleated, hemisected, and fixed. Nasal and temporal eye segments were embedded and 30-μm serial sections were collected; the two most central slides from each hemisection were analyzed with an epifluorescence microscope and Stereo Investigator software to determine normal morphologic parameters.
  
  
  RESULTS
  Refractive errors became less hyperopic (P = 0.0001) while axial lengths and CM lengths, cross-sectional areas, volumes, and cell sizes all increased linearly with log age (all P < 0.00001). Ciliary muscle cell numbers increased only during the first 20 days of life (P = 0.02). Nasal and temporal CM lengths (P = 0.07), cross-sectional areas (P = 0.18), and cell numbers (P = 0.70) were not different, but CM cell sizes were initially larger temporally and became larger nasally after age 30 days.
  
  
  CONCLUSIONS
  The mechanism of guinea pig CM cell growth during the first 90 days of life was characterized by early hyperplasia combined with hypertrophic cell growth throughout development that results in larger CM lengths, cross-sectional areas, and volumes. Nasal-temporal CM development was generally symmetric, but there was more CM hypertrophy nasally at older ages.
authors.affiliation: College of Optometry The Ohio State University, Columbus, Ohio, United States.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Pucker
authors.affiliation: Center for Molecular and Human Genetics, Nationwide Children's Hospital, Columbus, Ohio, United States.
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Jackson
authors.affiliation: College of Optometry The Ohio State University, Columbus, Ohio, United States.
authors.forename: Hugh J
authors.initials: HJ
authors.lastname: Morris
authors.affiliation: Department of Neuroscience, The Ohio State University, Columbus, Ohio, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Fischer
authors.affiliation: Center for Molecular and Human Genetics, Nationwide Children's Hospital, Columbus, Ohio, United States.
authors.forename: Kirk M
authors.initials: KM
authors.lastname: McHugh
authors.affiliation: College of Optometry The Ohio State University, Columbus, Ohio, United States.
authors.forename: Donald O
authors.initials: DO
authors.lastname: Mutti
mesh_terms: D000375:Aging / Q000473:pathology; D000818:Animals; D001699:Biometry; D002924:Ciliary Body / Q000033:anatomy & histology / Q000254:growth & development / Q000473:pathology*; D046169:Dermoscopy; D006168:Guinea Pigs; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000254:growth & development / Q000473:pathology*; D009216:Myopia / Q000473:pathology / Q000503:physiopathology; D009929:Organ Size; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000473:pathology* / Q000503:physiopathology