Driving mesenchymal stem cell differentiation from self-assembled monolayers

Abstract

The utilization of self-assembled monolayer (SAM) systems to direct Mesenchymal Stem Cell (MSC) differentiation has been covered in the literature for years, but finding a general consensus pertaining to its exact role over the differentiation of stem cells had been rather challenging. Although there are numerous reports on surface functional moieties activating and inducing differentiation, the results are often different between reports due to the varying surface conditions, such as topography or surface tension. Herein, in view of the complexity of the subject matter, we have sought to catalogue the recent developments around some of the more common functional groups on predominantly hard surfaces and how these chemical groups may influence the overall outcome of the mesenchymal stem cells (MSC) differentiation so as to better establish a clearer underlying relationship between stem cells and their base substratum interactions.

Scheme 1. Schematic overview of the functional groups directing the outcome of mesenchymal stem cell differentiation within the first 14 days on hard substrates.

Fig. 1. Possible surface markers and protein expression targets for the differentiated cell lineage from an MSC.

Fig. 2. (A) Attachment of cells after 3 h of culture onto the various SAMs. (B) Proliferation of cells on SAMs of different functional groups after 1, 3 and 5 days of culture. (C) MSC morphologies after 12 h cultured on different SAMs terminated with various functional groups. Better cell spreading was observed on –OH-, –NH₂-, PO₃H₂- and –COOH-terminated SAMs but not –CH₃-terminated SAMs.

Fig. 3. Osteoblastic differentiation: (A) morphology of unstained MSCs. Scale bar, 100 μm. (B) Matrix mineralization evaluated by Alizarin red staining for calcium deposits. NH₂ terminated SAMs are the most favourable for osteogenesis.

Fig. 4. Modulation of actin cytoskeleton of stem cells on fibronectin patterns. Scale bar = 25 μm. Left to right: adipocyte mimetic, modified adipocyte, square and circle patterns. Gold = F-actin, blue = nucleus.

Fig. 5. Human mesenchymal stem cell (hMSC) adhesion onto RGDSP-presenting SAMs. (A) Fluorescent photomicrographs of MSC stained with Calcein AM 24 h after seeding. (B) The attachment of hMSC per square millimetre under the RGDSP surface.

L. S. Tew

J. Y. Ching

S. H. Ngalim

Y. L. Khung