Immunohistochemical staining for collagen type I to label newly formed collagen within the scaffold pores. Collagen type I is stained in brown (DAB+). No collagen type I immunostaining is observed at 4 days (A,E), or at 7 days in the center of the scaffold (F). Collagen type I starts to fill the scaffold pores at 7 days starting from the periphery (B). At 15 days, compact structures positive for collagen type I fill the pores at the periphery of the scaffold (C) and start filling the central pores (G). At 30 days, newly formed collagen type I fills the scaffold pores, irrespective of their location (D,H).