Effects of electrospun submicron fibers in calcium phosphate cement scaffold on mechanical properties and osteogenic differentiation of umbilical cord stem cells.

Fibrous scaffolds are promising for tissue engineering because of the high surface area and fibrous features mimicking the extracellular matrix in vivo. Calcium phosphate cements (CPCs) can be injected and self-set in the bone defect. A literature search revealed that there have been no reports on stem cell seeding on CPC containing electrospun submicron fibers. The objective of this study was to investigate for the first time the effects of electrospun fibers in CPC on mechanical properties and human umbilical cord mesenchymal stem cell (hUCMSC) proliferation, osteogenic differentiation and mineralization. Poly(D,L-lactide-co-glycolide) fibers were made via an electrospinning technique to yield an average fiber diameter of 650 nm. The fibers were incorporated into CPC consisting of tetracalcium phosphate, dicalcium phosphate anhydrous and chitosan lactate. Fiber volume fractions were 0%, 2.5%, 5% and 10%. CPC with 10% fibers had a flexural strength that was twice that of CPC without fibers, and a work-of-fracture (toughness) that was an order of magnitude larger than that of CPC without fibers. hUCMSCs proliferated rapidly and synthesized bone minerals when attached to the electrospun fiber-CPC scaffolds. Alkaline phosphatase, osteocalcin and collagen I expressions of hUCMSCs were doubled, while mineralization was increased by 40%, when fiber volume fraction in CPC was increased from 0% to 10%. The enhanced cell function was attributed to the high surface area and biomimetic features of the fiber-CPC scaffold. In conclusion, incorporating submicron fibers into CPC greatly improved the strength and toughness of the CPC. Creating submicron fibrous features in CPC was a useful method for enhancing the osteogenic differentiation and mineralization of stem cells. The novel electrospun fiber-CPC-hUCMSC construct is promising for stem cell delivery and bone tissue engineering.