Effect of Pore Size and Void Fraction on Cellular Adhesion, Proliferation, and Matrix Deposition

TLDR

Limits of scaffold architecture, specifically void fraction and pore size, modulate in vitro cellular responses. The study aimed to determine how void fraction and pore size affect attachment, growth, and extracellular matrix deposition of several cell types. Disc‑shaped poly‑lactic acid scaffolds with 75 % or 90 % void fraction and four pore size ranges were fabricated and used to culture canine dermal fibroblasts, vascular smooth muscle cells, and microvascular epithelial cells for four weeks, with attachment, proliferation, and matrix deposition assessed by histology, metabolic activity, and ECM deposition. Micro‑CT confirmed the designed pore sizes and void fractions, and 90 % VF scaffolds supported uniform seeding of all cell types while 75 % VF scaffolds were unsuitable for tissue formation; canine dermal fibroblasts showed little pore‑size selectivity, vascular smooth muscle cells proliferated and deposited matrix similarly across the three largest pores, and microvascular epithelial cells formed sparse, disconnected tissue at 90 % VF and >38 µm pores but formed a multilayered lining on <38 µm pores.

Abstract

The aim of this study was to determine the influence of two key scaffold design parameters, void fraction (VF) and pore size, on the attachment, growth, and extracellular matrix deposition by several cell types. Disc-shaped, porous, poly(-lactic acid) (L-PLA) scaffolds were manufactured by the TheriForm solid free-form fabrication process to generate scaffolds with two VF (75% and 90%) and four pore size distributions (< 38, 38-63, 63-106, and 106-150 microm). Microcomputed tomography analysis revealed that the average pore size was generally larger than the NaCl used, while VF was at or near the designated percentage. The response of three cell types-canine dermal fibroblasts (DmFb), vascular smooth muscle cells (VSMC), or microvascular epithelial cells (MVEC)-to variations in architecture during a 4-week culture period were assessed using histology, metabolic activity, and extracellular matrix deposition as comparative metrics. DmFb, VSMC, and MVEC showed uniform seeding on scaffolds with 90% VF for each pore size, in contrast to the corresponding 75% VF scaffolds. DmFb showed the least selectivity for pore sizes. VSMC displayed equivalent cell proliferation and matrix deposition for the three largest pore sizes. MVEC formed disconnected webs of tissue with sparse extracellular matrix at 90% VF and >38 to 150 microm; however, when cultured on scaffolds with pores formed with salt particles of <38 microm, MVEC formed a multilayered lining on the scaffolds surface. Culture data from scaffolds with a 75% VF suggests that the structural features were unsuitable for tissue formation. Hence, there were limits of acceptable scaffold architecture (VF, pore size) that modulated in vitro cellular responses.