Lung Morphometry, Collagen and Elastin Content: Changes after Hyperoxic Exposure in Preterm Rabbits

Abstract

INTRODUCTIONElastic and collagen fiber deposition increases throughout normal lung development, and this fiber network significantly changes when development of the lung is disturbed. In preterm rats and lambs, prolonged hyperoxic exposure is associated with impaired alveolization and causes significant changes in the deposition and structure of elastic fibers.OBJECTIVESTo evaluate the effects of hyperoxic exposure on elastic and collagen fiber deposition in the lung interstitial matrix and in alveolarization in preterm rabbits.METHODSAfter c-section, 28-day preterm New-Zealand-White rabbits were randomized into 2 study groups, according to the oxygen exposure, namely: Room air (oxygen = 21%) or Oxygen (oxygen ≥ 95%). The animals were killed on day 11 and their lungs were analyzed for the alveolar size (Lm), the internal surface area (ISA), the alveoli number, and the density and distribution of collagen and elastic fibers.RESULTSAn increase in the Lm and a decrease in the alveoli number were observed among rabbits that were exposed to hyperoxia with no differences regarding the ISA. No difference in the density of elastic fibers was observed after oxygen exposure, however there were fewer collagen fibers and an evident disorganization of fiber deposition.DISCUSSIONThis model reproduces anatomo-pathological injuries representing the arrest of normal alveolar development and lung architecture disorganization by just a prolonged exposition to oxygen.CONCLUSIONSIn the preterm rabbit, prolonged oxygen exposure impaired alveolization and also lowered the proportion of collagen fibers, with an evident fiber network disorganization.

Functional assessment of hyperoxia-induced lung injury after preterm birth in the rabbit

“…The feeding consisted of a mixture of soybean oil (Intralipid 30%, 270 kcal/100 ml; Fresenius Kabi), pure casein (100% Casein, 360 kcal/100 mg; Optimum Nutrition), pediatric milk formula (Nutrilon HA nr 2, 453 kcal/100 mg; Nutricia), and water. This mixture gives a nutritional value of 16 g lipids, 5.3 g proteins, 2.7 g carbohydrates (176 kcal in total)/100 ml and was chosen in accordance to prior studies using a preterm rabbit model (21,22). The amount of feeding steadily increased from 80 to 100 to 150 to finally 200 mg·kg Ϫ1 ·day Ϫ1 on days 0, 1, 2, and 3 (until 7), respectively.…”

“…The amount of feeding steadily increased from 80 to 100 to 150 to finally 200 mg·kg Ϫ1 ·day Ϫ1 on days 0, 1, 2, and 3 (until 7), respectively. On day 2, vitamin K was administered intramuscularly (0.002 mg/kg, Konakion pediatrique; Roche, Basel, Switzerland), and from that point pups were given a daily intramuscular injection of benzylpenicillin (20,000 E·kg Ϫ1 ·day Ϫ1 , Penicilline; Kela, Sint-Niklaas, Belgium) and amikacin (20 mg·kg Ϫ1 ·day Ϫ1 , Amukin; Bristol-Myers-Squibb) (21,22). The pups remained in the incubator except for the feeding moments for which they were removed from the incubator for a maximum of 10 min/feed.…”

“…Even more important, rabbits start alveolizing before birth, as do humans (26). Our own experience (8,28,30) combined with the findings from published data like the preterm rabbit model described by Mascaretti et al (21) and Mataloun et al (21,22) led us to select rabbits as the best candidate model to study the effects of hyperoxia after preterm birth. Our aim was to create a model with a full methodological description, including histological and immunohistochemical outcomes, as well as functional lung tests.…”

Avaliação dos artigos de pneumologia publicados em periódicos Brasileiros além do Jornal Brasileiro de Pneumologia

“…(2) The presence of associated diseases, such as rhinitis (symptoms are present in 90% of cases), gastroesophageal Sleep 5 [16][17][18][19][20] Physiology, exercise, and rehabilitation 12 [21][22][23][24][25][26][27][28][29][30][31][32] COPD 8 [33][34][35][36][37][38][39][40] Pathology 3 [41][42][43] CT 2 [44][45] Occupational medicine 1 46 Pulmonary thromboembolism 2 [47][48] Pulmonary hypertension 3 [49][50][51] Lung cancer 3 [52][53][54] Smoking 2 [55][56] Evaluation of articles on pulmonology published in Brazilian In their study involving patients with severe OSAS, Neves et al found that the use of sildenafil worsens OSAS, as well as causing deleterious cardiovascular effects because of the increased parasympathetic tone and affecting the HR variability. (19) Pires et al, in a study of drivers engaged in night shift work, contradicted the notion that the sleep pattern of older individuals is more negatively affected than that of younger individuals.…”

“…Mascaretti et al concluded that rabbits exposed to hyperoxia develop fiber network disorganization in the lung parenchyma. (41) In their article, Capelozzi et al demonstrated that the major changes identified in the histopathological analysis of material obtained by lung biopsy from patients with severe acute respiratory distress syndrome secondary to confirmed infection with the influenza A (H1N1) virus were necrotizing bronchiolitis and diffuse alveolar damage. (42) Oliveira et al analyzed histomorphometric and respiratory changes in a rat model of sepsis-induced lung injury in which one study group was treated with pentoxifylline and found that the drug, in combination with mechanical ventilation with low tidal volumes, restored oxygenation and reduced the deleterious effects of the septic process.…”