3D-printed nano-hydroxyapatite/poly(lactic-co-glycolic acid) scaffolds with adipose-derived mesenchymal stem cells enhance bone regeneration in rat model of bone defects

Three-dimensional (3D) printing has huge potential in the medical field, including bone tissue engineering scaffolds. In our study, the 3D-printed poly (lactic-co-glycolic acid) (PLGA)/nano-hydroxyapatite (HA) scaffolds carrying adipose-derived mesenchymal stem cells (ADMSCs) were constructed, and whether such scaffolds have therapeutic potential in bone defects was investigated. For <i>in vitro</i> assays, rat ADMSCs were implanted into blank cell wells (Blank) and PLGA/nHA and ADMSCs/PLGA/nHA scaffolds. The vitality and proliferation of ADMSCs were detected through calcein-AM/PI staining and CCK-8 assay to assess the biocompatibility of the scaffolds. ADMSCs in three groups were incubated in osteogenic induction medium, and ALP and ARS staining were performed after 7 days and 21 days, respectively. Runx2, Osterix, OCN, and OPN mRNA expression in ADMSCs was detected through RT-qPCR. For <i>in vivo</i> assays, rat models of radius defects were implanted by PLGA/nHA scaffolds or ADMSCs/PLGA/nHA scaffolds, and micro-CT scan analysis was conducted at week 12 after implantation. Bone marrow cell formation and Runx2 expression in rat radius tissues were evaluated through H&E and immunohistochemical staining, respectively. The results showed that ADMSCs/PLGA/nHA scaffolds provided transplanted cells with a stable carrier as well as maintained their activity and facilitated their proliferation. ADMSCs/PLGA/nHA promoted ADMSC osteogenic differentiation <i>in vitro</i>. Besides, the implantation of ADMSCs/PLGA/nHA scaffolds improved bone regeneration, enhanced bone marrow cell formation, and increased Runx2 expression in rat models of radius defects. Collectively, the 3D-printed ADMSCs/PLGA/nHA scaffolds effectively promote ADMSC osteogenic differentiation and exhibit significant bone repair effects, suggesting its therapeutical potential for bone defects.