Poly-L-lactic acid (PLLA) is one of the most commonly used synthetic materials for regenerative medicine, and silk fibroin (SF) is a natural protein with excellent biocompatibility. Combination of PLLA and SF in a proper proportion by electrospinning may generate composite nanofibers that could meet the requirements of scaffolding in bone tissue engineering. The application of PLLA/SF nanofibrous scaffold for osteogenesis is well established in vitro and in vivo. However, PLLA/SF nanofibrous scaffold does not have an ideal ability to promote cell adhesion, proliferation, and differentiation. Extracellular matrix (ECM) plays a critical role in modulating cellular behavior. However, the role of combination of natural ECM with nanofibrous scaffold in regulating osteogenic differentiation is unclear. In this study, we aimed to develop a novel composite PLLA/SF nanofibrous scaffold coated with osteoblastderived extracellular matrix (O-ECM/PLLA/SF) and analyze the effects of the modified scaffold on osteogenic differentiation of BMSCs. The surface structural features and compositions of the O-ECM/PLLA/SF scaffold were characterized by SEM and immunofluorescence staining. The capacities of the O-ECM/PLLA/SF scaffold to induce osteogenic differentiation of BMSCs were investigated by alkaline phosphatase (ALP) and alizarin red staining (ARS). The results showed BMSCs cultured on O-ECM/PLLA/SF scaffold significantly increased osteogenic differentiation compared with cells cultured individually on a scaffold or O-ECM. Collectively, these findings indicate that O-ECM-coated nanofibrous scaffold can be a promising strategy for osteogenic differentiation of BMSCs, opening a new possibility of utilizing composite scaffolds for bone tissue engineering.

Bone defects that arise from trauma, skeletal diseases, or tumor resections have become the commonest and most thorny problems in orthopedic clinics. Recently, biocomposite materials used as artificial bone repair materials have provided a promising approach for bone regeneration. In this study, poly (l-lactide acid) (PLLA) and silk fibroin (SF) were used to fabricate nanofiber scaffolds by electrospinning technology. In order to simulate a biomimetic osteoblast microenvironment, decellularized extracellular matrix from osteoblasts was loaded into the biocomposite scaffolds (O-ECM/PLLA/SF). It was found that the O-ECM/PLLA/SF scaffolds were nontoxic for L929 cells and had good cytocompatibility. Their effects on mesenchymal stem cells derived from human-induced pluripotent stem cell (iPSC-MSC) behavior were investigated. As a result, the scaffolds with the addition of O-ECM showed enhanced alizarin red S (ARS) activity. In addition, higher expression of osteogenic gene markers such as runt-related transcription factor 2 (Runx2), collagen type I (Col-1), and osteocalcin (OCN) as well as upregulated expression of osteogenic marker protein osteopontin (OPN) and Col-1 further substantiated the applicability of O-ECM/PLLA/SF scaffolds for osteogenesis. Furthermore, the in vivo study also indicated maximal new bone formation in the skull defect model of Sprague Dawley (SD) rats treated with the O-ECM/PLLA/SF carried by human iPSC-MSCs. Hence, this study suggests that O-ECM/PLLA/SF scaffolds have a potential application in bone tissue engineering.

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