Pulmonary Toxicity, Distribution, and Clearance of Intratracheally Instilled Silicon Nanowires in Rats

Table 1

Histopathological evaluation of lung tissue.

Histopathology parameter	Time after-instillation
	Day 1	Day 3	Day 7	Day 28	Day 91
Perivascular monocyte infiltrates	Si 10 (0.50); Si 25 (0.75); Si 50 (1.00)^+; Si 100 (1.00)^+; Si 250 (1.25)^+	Si 50 (0.75); Si 100 (1.00)^∧; Si 250 (2.00)*	Si 250 (1.00)*	—	—
Perivascular & peribronchiolar eosinophil infiltrates	Si 10 (0.50); Si 25 (1.25)^∧; Si 50 (1.50)^∧; Si 100 (1.25)^∧; Si 250 (1.75)^∧	Si 25 (0.50); Si 50 (0.75); Si 100 (1.00)^∧; Si 250 (1.25)^∧	Si 50 (0.50); Si 100 (1.00)^~; Si 250 (1.00)^~	Si 100 (0.50)	—
Interstitial pneumonia	Si 10 (0.50); Si 25 (1.25)^+; Si 50 (1.50)^+; Si 100 (1.50)^+; Si 250 (2.75)*	Si 50 (0.75)^+; Si 100 (0.75)^+; Si 250 (2.25)*	—	—	—
Alveolar macrophage aggregates	Si 25 (1.00)^∧; Si 50 (1.50)^∧; Si 100 (1.25)^∧; Si 250 (2.00)^$	Si 50 (1.00)^+; Si 100 (1.00)^+; Si 250 (2.00)*	Si 100 (0.50); Si 250 (1.00)^$	Si 100 (0.50)	—
Alveolar neutrophil aggregates	Si 50 (0.75); Si 250 (0.50)	Si 100 (0.50); Si 250 (1.00)	—	—	—
Bronchiolar degeneration/; regeneration	Si 25 (0.75)^+; Si 50 (1.25)^∧; Si 100 (1.00)^∧; Si 250 (1.00)^∧	Si 50 (1.00)^$; Si 250 (1.25)^$	—	—	—
Fibrosis	—	—	—	—	—

Histopathology parameters were scored for severity on a scale of 0–5 where indices of inflammation and injury were graded as 0 (not present), 1 (minimal), 2 (mild), 3 (moderate), 4 (marked), or 5 (severe). Groups were included in a category when the parameter was observed in at least half of the animals in that group. The mean severity score is presented in parenthesis after the group (𝑛=4). *significantly greater than all groups; ^$significantly greater than DM, Si 10 and Si 25; ^~significantly greater than DM and Si 25; ^∧significantly greater than DM and Si 10; ⁺significantly greater than DM; (𝑃<0.05).