Abstract
Collagen-based scaffolds hold great potential for tissue engineering, since they closely mimic the extracellular matrix. We investigated tissue integration of an engineered porous collagen-elastin scaffold developed for soft tissue augmentation. After implantation in maxillary submucosal pouches in 6 canines, cell invasion (vimentin), extracellular matrix deposition (collagen type I) and scaffold degradation (cathepsin k, tartrate-resistant acid phosphatase (TRAP), CD86) were (immuno)-histochemically evaluated. Invasion of vimentin+ cells (scattered and blood vessels) and collagen type I deposition within the pores started at 7 days. At 15 and 30 days, vimentin+ cells were still numerous and collagen type I increasingly filled the pores. Scaffold degradation was characterized by collagen loss mainly occurring around 15 days, a time point when medium-sized multinucleated cells peaked at the scaffold margin with simultaneous labeling for cathepsin k, TRAP, and CD86. Elastin was more resistant to degradation and persisted up to 90 days in form of packages well-integrated in the newly formed soft connective tissue. In conclusion, this collagen-based scaffold maintained long-enough volume stability to allow an influx of blood vessels and vimentin+ fibroblasts producing collagen type I, that filled the scaffold pores before major biomaterial degradation and collapse occurred. Cathepsin k, TRAP and CD86 appear to be involved in scaffold degradation.
Highlights
Collagen is the most abundant extracellular matrix protein in the body
We previously demonstrated that this biomaterial elicits a short inflammatory phase followed by rapid cell proliferation and the fast influx of blood vessels and mesenchymal cells [9]
To evaluate the cell-mediated degradation of the scaffold, we studied the appearance of multinucleated cells using Giemsa and tartrate-resistant acid phosphatase (TRAP) histochemistry together with cathepsin K and CD86 immunostaining (Figure 7)
Summary
Collagen is the most abundant extracellular matrix protein in the body. Besides having important structural functions, collagen supports cell attachment, cell differentiation, repair, and tissue regeneration [1,2]. Biomaterials in the form of collagen-based scaffolds hold great promise for both bone and soft tissue engineering to replace damaged or lost tissues, since these biomaterials provide an environment close to the native extracellular matrix [3,4,5]. Collagen-based scaffolds should at least provide: (1) high biocompatibility, (2) a highly porous structure with interconnected pores to allow influx of progenitor cells and blood vessels, (3) mechanical properties similar to the native tissue and (4). Degradation properties and kinetics that match the characteristic speed of the tissue to be regenerated. The mechanical and degradation properties of collagen-based scaffolds can be tuned by altering the ratio between collagen and elastin on one hand, and by the type and degree of chemical cross-linking. Cross-linking, in general, enhances both structural stability and resistance against degradation
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