Stem cell-based scaffolds for orthopedic applications

Abstract

In the proposed work, we fabricated bioactive scaffolds in combination with stem cells and growth factors. Towards this goal, we made use tunable polyethylene glycol diacrylate (PEGDA)-based scaffolds. Mesenchymal stem cells (MSCs) as well as embryonic stem cells (ESCs) were encapsulated in PEGDA-based scaffolds in separate studies. Initially, bone marrow-derived MSCs were encapsulated in PEGDA-polydimethylsiloxane (PDMS) scaffolds along with bone morphogenetic protein-2 (BMP-2) for specific osteoblastic differentiation. Low dosage levels of BMP-2 appeared to significantly enhance PEG-PDMS osteoinductivity. Subsequently, in the following study, transforming growth factor-beta1 (TGF-β1) was incorporated in PEGDA-chondroitin sulfate (CSC) scaffolds for driving chondrocytic differentiation of synovium-derived MSCs (SMSCs). In addition, intermediate levels of TGF-β1, PDMS and BMP-2 appeared to induce mix ‘cartilage/bone’ cell behavior in SMSCs. Overall, SMSCs appeared to be spatially guided for layer-specific differentiation depending on the initial biochemical composition of PEGDA scaffolds. In addition, the second study also established SMSCs as a viable MSC alternative for osteochondral repair.

As a whole, the current work adds to the existing knowledge of stem cell—based therapies that are emerging as potential strategies for treating musculoskeletal conditions. The understanding from this work will take us one step forward in the rational development of promising scaffolds to treat the affected patients.

Human ESCs (hESCs) were investigated for directed osteoblastic differentiation using step-wise differentiation involving an intermediate mesodermal lineage. Enhancement of FOXD3 expression in transfected hESCs using doxycycline (DOX) treatment followed by 3D osteogenic culture appeared to downregulate pluripotency levels and increase mesodermal commitment. Moreover, 48h of initial DOX treatment in 2D culture appeared to significantly upregulate osteoblastic marker expression suggesting directed differentiation.

Musculoskeletal diseases are becoming one of the major concerns in the US due the aging population, increasing cases of congenital defects, and trauma-related incidents. Drug therapies and exercise could provide temporary relief but do not heal the injured tissue. Surgical treatments and autologous grafts are common strategies used to treat these defects; however, they are inefficient at restoring full tissue function. The current study aims at providing potential stem cell-based tissue engineering strategies that could be used for osteochondral and skeletal repair.