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The current study examined the influence of culture substrates modified with the functional groups –OH, –COOH, –NH2, and –CH3 using SAMs technology, in conjunction with TAAB control, on the osteogenic differentiation of rabbit BMSCs. The CCK-8 assay revealed that BMSCs exhibited substrate-dependent cell viability. The cells plated on –NH2- and –OH-modified substrates were well spread and homogeneous, but those on the –COOH- and –CH3-modified substrates showed more rounded phenotype. The mRNA expression of BMSCs revealed that –NH2-modified substrate promoted the mRNA expression and osteogenic differentiation of the BMSCs. The contribution of ERK1/2 signaling pathway to the osteogenic differentiation of BMSCs cultured on the –NH2-modified substrate was investigated in vitro. The –NH2-modified substrate promoted the expression of integrins; the activation of FAK and ERK1/2. Inhibition of ERK1/2 activation by PD98059, a specific inhibitor of the ERK signaling pathway, blocked ERK1/2 activation in a dose-dependent manner, as revealed for expression of Cbfα-1 and ALP. Blockade of ERK1/2 phosphorylation in BMSCs by PD98059 suppressed osteogenic differentiation on chemical surfaces. These findings indicate a potential role for ERK in the osteogenic differentiation of BMSCs on surfaces modified by specific chemical functional groups, indicating that the microenvironment affects the differentiation of BMSCs. This observation has important implications for bone tissue engineering.

This study investigated how human adipose stem cells (hASCs) could be influenced by surface chemistry. Self-assembled monolayers of alkanethiolates on gold were introduced as a surface chemistry model to provide a range of functional groups such as OH, COOH, NH₂, Phenyl, SH, Br, and CH₃ on surfaces. Initially, morphological changes of hASCs in response to different surface chemistries were observed with focal adhesion. Cell growth behaviour evaluated by Cell Counting Kit-8 (CCK8) assay (Dojindo Molecular Technologies Inc., Shanghai, China) and cytoskeletal F-actin Biochem Kit™ (Denver, CO, USA) staining revealed a descending order of growth rate on the following surfaces: NH₂ > SH > COOH > Phenyl > Br > OH > CH₃. The mRNA expressions of lineage specific markers including alkaline phosphatase (ALP), osteocalcin (OCN), type II collagen, aggrecan, peroxisome proliferator-activated receptor gamma (PPARγ), and fatty acid binding protein-2 (aP2), were determined using real-time reversed transcriptase-polymerase chain reaction (RT-PCR). Results revealed that NH₂ favoured hASC differentiation toward osteogenic, while phenyl and SH promoted chondrogenic differentiation of hASCs with a high level up-regulation of type II collagen and aggrecan. hASCs on Br increased in PPARγ and aP2 expression, indicating adipogenic differentiation. These results highlight the vital role of surface chemistry on the modulation of hASC differentiation and suggests chemical methods for designing biomaterials for stem cell-based tissue regeneration.

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