Resumo

Objectives: Muscle function frequently becomes progressively more compromised in children with spastic cerebral palsy contributing to the development of contractures and weakness. Histological analyses of muscle biopsies from patients with CP have shown changes in muscle size. In the present study, the effects of maternal exposure to low doses of bacterial endotoxin (lipopolysaccharide, LPS) on soleus and tibialis anterior muscles morphology were examined in rats. LPS was also associated to perinatal asphyxia (PA) with or without subsequent sensorimotor restriction (SR). Materials and Methods: For gestational LPS treatment, timed pregnant Wistar rats were divided into 2 groups: Group 1 (n = 10), LPS injected rats (200 µg/kg diluted in 100 µL of saline) and Group 2 (n = 10), saline injected rats (100 µL). The pregnant rats were injected with LPS or saline at 12-hour intervals until the end of gestation. On the day of birth (P0) half of the pups born from both group of mothers were subjected to PA. For this procedure, rat pups were placed for 20 min into a temperature controlled chamber (37º C ± 1º C) with a flow of 9 L/min of 100% N2. At P2 half of the animals of each group were submitted to SR (16 h/day) until P28. The pup’s hind limbs were immobilized in an extended position by a support made of epoxy resin. Accordingly to these procedures, male pups were randomly assigned to eight different groups (n = 6): rats exposed to saline during the embryonic period (CT); rats exposed to LPS; PA; LPS+PA; saline and sensorimotor restriction (SR); LPS+SR; saline, anoxia and sensorimotor restriction (PA+SR); LPS+PA+SR. All procedures were approved by the Ethical Committee at the UFRGS (no 2008189). Fixed soleus and tibialis anterior muscles of 29 days old rats were prepared to electron microscopy and cut at 1µm to count fiber’s area. Data were analyzed using three-way analysis of variance (ANOVA) followed by post hoc Duncan test. Results: Soleus atrophy was confirmed in SR, LPS+SR, PA+SR and LPS+PA+SR groups (741.6 ± 59.7; 720.0 ± 70.9; 677.8 ± 37.6; 549.8 ± 97.8, respectively compared to CT (998.5 ± 71.6; P<0.001). No difference on soleus’s cross sectional area (CSA) was observed in LPS, PA and LPS+PA groups (1178.6 ± 37.6, 1097.4 ± 38.0 and 1154.5 ± 89.9, respectively) when compared between them and to CT. There was a trend to decrease LPS+PA+SR’s soleus’ CSA compared to SR (P=0.069). Atrophy of tibialis anterior was only detected in LPS+PA+SR rats (635 ± 41.4). A significantly decrease on CSA was observed in this group when compared to CT (978.0 ± 79.0), LPS (947.8 ± 53.1), PA (952.5 ± 60.2), SR (1192.2 ± 153.5), LPS+SR (1014.5 ± 104.1) and PA+SR (938.1 ± 97.2) group (P<0.05). Conclusion: Prenatal exposure to LPS, PA or SR alone or in combination had various degrees of consequences on muscle morphology. These data support the idea that early experience-dependent movements could play an important role in shaping the muscular pattern and that the lack of sensorimotor experience can contribute to the development of aberrant muscular morphology observed in CP patients. This research was supported by CNPq, CAPES (Brazil).