Background: Topography at different scales plays an important role in directing mesenchymal stem cell differentiation including adipose-derived stem cells (ASCs) and the differential effect remains to be investigated. 
Purpose: This study aimed to investigate the similarity and difference between micro- and nanoscaled aligned topography for inducing tenogenic differentiation of human ASCs (hASCs). 
Methods: Parallel microgrooved PDMS membrane and a parallel aligned electrospun nanofibers of gelatin/poly-ε-caprolactone mixture were employed as the models for the study. 
Results: Aligned topographies of both microscales and nanoscales could induce an elongated cell shape with parallel alignment, as supported by quantitative cell morphology analysis (cell area, cell body aspect, and cell body major axis angle). qPCR analysis also demonstrated that the aligned topography at both scales could induce the gene expressions of various tenogenic markers at the 7th day of in vitro culture including tenomodulin , collagen I  and collagen VI , decorin , tenascin-C  and biglycan , but with upregulated expression of scleraxis  and tenascin-C  only in microscaled topography. Additionally, tenogenic differentiation at the 3rd day was confirmed only at microscale. Furthermore, microscaled topography was confirmed for its tenogenic induction at tissue level as neotendon tissue was formed with the evidence of mature type I collagen fibers only in parallel aligned polyglycolic acid (PGA) microfibers after in vitro culture with mouse ASCs. Instead, only fat tissue was formed in random patterned PGA microfibers. 
Conclusion: Both microscaled and nanoscaled aligned topographies could induce tenogenic differentiation of hASCs and micro-scaled topography seemed better able to induce elongated cell shape and stable tenogenic marker expression when compared to nanoscaled topography. The microscaled inductive effect was also confirmed at tissue level by neotendon formation in vitro.
Keywords: microscales and nanoscales, aligned topography, human adipose-derived stem cells, tenogenic differentiation, microscaled PGA fibers