FIG. 3.

Granulation tissue and capsule formation in KO matrices is delayed and impaired but can be complemented by the addition of exogenous fibrinogen. Sections of TDM matrices were stained using Masson's trichrome stain to show the deposition of collagen (blue) during capsule formation. The capsule surrounding WT (A) and Fib KO (D) matrices at 4 days is loosely organized and histologically similar. Well-developed granulation tissue surrounds 7-day-old WT matrices (B), and by 12 days (C), the capsule is composed primarily of collagen. (E) In Fib KO matrices, however, the granulation tissue response at 7 days is disorganized, edematous, and hypocellular, similar to the appearance at 4 days. (F) The addition of 500 μg/ml fibrinogen to the KO matrices allows well-organized granulation tissue to surround the matrix at 7 days. Asterisks indicate the interface between Matrigel and capsule. Original magnification, ×200.