Pathological study of the levator palpebrae superioris muscle in patients with different severities of simple congenital ptosis

Objective

To observe the pathological changes of levator palpebrae superiors muscle in patients with different severities of simple congenital ptosis (SCP).

Methods

Levator palpebrae superiors muscle specimens from 102 eyes of 68 patients with SCP who received levator palpebrae superiors muscle shortening surgery at Wuhan Aier Hankou Eye Hospital from August 2018 to October 2019 were collected as the observation group.According to the severity of ptosis, the specimens were divided into three groups, coverage ≤4 mm group (n=35), coverage >4 mm to ≤6 mm group (n=30), and coverage >6 mm group (n=37). Fresh levator palpebrae superiors muscle tissues from 8 normal donors in Aier Eye Bank of Wuhan Red Cross were selected as the control group.All specimens were performed with Masson trichrome staining and immunohistochemical staining for α-smooth muscle actin (α-SMA), and ImageJ software was used to measure the collagen fiber area ratio, skeletal muscle fiber area ratio and the integrated absorbance (IA) value of α-SMA.Seventeen specimens (2 from the control group, 5 from coverage ≤4 mm group/coverage >4 mm to ≤6 mm group/coverage >6 mm group) were observed with a transmission electron microscope (TEM). This study protocol adhered to the Declaration of Helsinki and was approved by an Ethics Committee of Wuhan Aier Hankou Eye Hospital (No.HKAIER2018IRB-005-01). All patients and their legal guardians were well informed about the treatment method and the purpose of sampling and voluntarily signed informed consent.

Results

Compared with the control group, the skeletal muscle fiber was reduced in number and was in disordered arrangement, and the striation of some muscle fibers disappeared, and hyperplastic fibrous connective tissue was found in intercellular substances in the observation group.The collagen fiber area ratio of the coverage ≤4 mm group, coverage >4 mm to ≤6 mm group, coverage >6 mm group were significantly higher than that of the control group, and the skeletal muscle fiber area ratio of the three groups was significantly lower than that of the control group (all at P<0.008 3). There were more smooth muscle fibers and positive expression of α-SMA found in the specimens of the observation group.The IA value of α-SMA of the coverage ≤4 mm group, coverage >4 mm to ≤6 mm group, coverage >6 mm group was 7 195.28(5 935.69, 14 058.29), 55 584.18(33 861.88, 80 419.32), 166 507.76(119 121.95, 187 890.86), respectively, which were all higher than 5 543.03(4 867.67, 8 312.02) of the control group, among which, there were statistically significant differences between the control group and the coverage >4 mm to ≤6 mm group, coverage >6 mm group (both at P<0.008 3). Abundant organelles and some damaged mitochondria were found in smooth muscle cytoplasm in the observation group with a TEM.But no characteristic structure of smooth muscle cells such as dense patch and dense body was detected.

Conclusions

There are abnormal smooth muscle cells in the levator palpebrae superiors muscle of SCP patients, and the dysgenesis of the levator palpebrae superiors muscle may be related to this abnormal muscle cell.

Blepharoptosis, congenital; Oculomotor muscles; Pathology; Levator palpebrae superiors muscle