Research Article: Chemical group-dependent plasma polymerisation preferentially directs adipose stem cell differentiation towards osteogenic or chondrogenic lineages

Date Published: March 01, 2017

Publisher: Elsevier

Author(s): M.F. Griffin, A. Ibrahim, A.M. Seifalian, P.E.M. Butler, D.M. Kalaskar, P. Ferretti.


Human adipose derived stem cells (ADSCs) are being explored for the repair of craniofacial defects due to their multi-differentiation potential and ease of isolation and expansion. Crucial to using ADSCs for craniofacial repair is the availability of materials with appropriate biomechanical properties that can support their differentiation into bone and cartilage. We tested the hypothesis that different modifications of chemical groups on the surface of a nanocomposite polymer could increase human ADSC adhesion and selectively enhance their osteogenic and chondrogenic differentiation. We show that the COOH modification significantly promoted initial cell adhesion and proliferation over 14 days compared to NH2 surfaces. Expression of focal adhesion kinase and vinculin was enhanced after plasma surface polymerisation at 24 h. The COOH modification significantly enhanced chondrogenic differentiation as indicated by up-regulation of aggrecan and collagen II transcripts. In contrast, NH2 group functionalised scaffolds promoted osteogenic differentiation with significantly enhanced expression of collagen I, alkaline phosphatase and osteocalcin both at the gene and protein level. Finally, chorioallantoic membrane grafting demonstrated that both NH2 and COOH functionalised scaffolds seeded with ADSCs were biocompatible and supported vessel ingrowth apparently to a greater degree than unmodified scaffolds. In summary, our study shows the ability to direct ADSC chondrogenic and osteogenic differentiation by deposition of different chemical groups through plasma surface polymerisation. Hence this approach could be used to selectively enhance bone or cartilage formation before implantation in vivo to repair skeletal defects.

Human adipose derived stem cells (hADSCs) are an exciting stem cell source for regenerative medicine due to their plentiful supply and ease of isolation. However, the optimal environmental cues to direct stem cells towards certain lineages change have to has not been identified. We have shown that by modifying the surface of the scaffold with specific chemical groups using plasma surface polymerisation techniques we can control ADSCs differentiation. This study shows that ADSCs can be differentiated towards osteogenic and chondrogenic lineages on amine (NH2) and carboxyl (COOH) modified scaffolds respectively. Plasma polymerisation can be easily applied to other biomaterial surfaces to direct stem cell differentiation for the regeneration of bone and cartilage.

Partial Text

Craniofacial defects caused by congenital deformities, cancer, trauma or burns remain one of the greatest challenges for plastic and reconstructive surgeons [1]. Currently, surgical options to restore bone and cartilage defects includes autologous grafts, causing donor site morbidity and are limited by the availability of suitable tissue [1]. Synthetic options available include inert materials such as porous polyethylene Medpor, which acts as a mechanical support for tissue ingrowth but does not allow for bone or cartilage regeneration [1]. Therefore, there is a clinical demand to create advanced materials, which can promote bone and cartilage formation [1].

All reagents and tissue culture plastic were from Sigma Alrich (UK) unless otherwise specified.

This study shows for the first time, that plasma polymerisation of POSS-PCU nanocomposite scaffolds with NH2 and COOH groups selectively enhance differentiation of human ADSC along the osteogenic and chondrogenic lineages, respectively. Furthermore, these modifications increase ADSC adhesion to the nanoscaffold and their proliferation, as well as supporting angiogenesis, as suggested by the in vivo CAM-grafting model.

In conclusion, this study has important implications for skeletal tissue engineering using ADSCs, having established that NH2 modified scaffolds preferentially promote osteogenesis and COOH surfaces chondrogenesis of these cells. Previous evidence of no changes in the mechanical properties of POSS-PCU scaffolds following plasma functionalisation [8] together with the ability of these modified scaffolds to selectively enhance differentiation of ADSCs towards the desired phenotypes, and their biocompatibility supported by the short term in ovo studies, provide a strong basis for future testing in larger animal studies. Clinical application of plasma polymerisation for the generation of bone and cartilage constructs appears promising.

This study was funded by the Medical Research Council (MRC) and Action Medical Research (AMR), Grant No. GN2239.




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