Constructing Injectable Bone-Forming Units by Loading a Subtype of Osteoprogenitors on Decellularized Bone Matrix Powders for Bone Regeneration

Induction of osteogenic differentiation by the extracellular matrix of fetal bone tissues and adult cartilage

Decellularized cortical bone powder derived from adult animals has been shown to induce bone remodeling. Furthermore, it is increasingly evident that the extracellular matrix (ECM) within decellularized tissues differs depending on the source tissue and the age of the animal, leading to distinct effects on cells. In this study, we prepared powders from decellularized fetal and adult porcine bone tissues and conducted biological analyses to determine if the decellularized tissue could induce adipose-derived stem cell differentiation. Decellularized fetal tissues and adult cortical bone were converted into powder by cryomilling, but decellularized adult bone marrow and cartilage were not powdered through this process. In vitro assessments revealed that decellularized fetal tissues, decellularized adult cartilage extract, and decellularized fetal cartilage powder can induce osteoblast differentiation. This study suggests that decellularized fetal bone tissues and adult cartilage contain ECM components that can induce osteoblast differentiation. Additionally, it highlights the utility of decellularized fetal cartilage powder for bone reconstruction.

Three Birds, One Stone: An Osteo-Microenvironment Stage-Regulative Scaffold for Bone Defect Repair through Modulating Early Osteo-Immunomodulation, Middle Neovascularization, and Later Osteogenesis

In order to repair critical-sized bone defects, various polylactic acid-glycolic acid (PLGA)-based hybrid scaffolds are successfully developed as bone substitutes. However, the byproducts of these PLGA-based scaffolds are known to acidify the implanted site, inducing tiresome acidic inflammation. Moreover, these degradation productions cannot offer an osteo-friendly microenvironment at the implanted site, matching natural bone healing. Herein, inspired by bone microenvironment atlas of natural bone-healing process, an osteo-microenvironment stage-regulative scaffold (P80/D10/M10) is fabricated by incorporating self-developed decellularized bone matrix microparticles (DBM-MPs) and multifunctional magnesium hydroxide nanoparticles (MH-NPs) into PLGA with an optimized proportion using low-temperature rapid prototyping (LT-RP) 3D-printing technology. The cell experiments show that this P80/D10/M10 exhibits excellent properties in mechanics, biocompatibility, and biodegradability, meanwhile superior stimulations in osteo-immunomodulation, angiogenesis, and osteogenesis. Additionally, the animal experiments determined that this P80/D10/M10 can offer an osteo-friendly microenvironment in a stage-matched pattern for enhanced bone regeneration, namely, optimization of early inflammation, middle neovascularization, and later bone formation. Furthermore, transcriptomic analysis suggested that the in vivo performance of P80/D10/M10 on bone defect repair is mostly attributed to regulating artery development, bone development, and bone remodeling. Overall, this study reveals that the osteo-microenvironment stage-regulative scaffold provides a promising treatment for bone defect repair.

Periosteum-derived skeletal stem cells encapsulated in platelet-rich plasma enhance the repair of bone defect

BACKGROUND

Spontaneous restoration of large bone defects remains a challenge under infections, tumors, and crushing conditions. Current stem cell-based therapies for treating bone defects need improvement, because the used stem cells are isolated by a traditional protocol, which is based on their properties of in-vitro plastic adherence and fibroblastic colony formation. The stem cells isolated by the traditional protocol belong to a multicellular type mixture, individual cells vary in proliferative and osteogenic potential. Thus, developing a protocol capable of isolating stem cell subset with higher purity is required and urgent.

AIM

This study aimed to sort a subpopulation of stem cells from periosteum using flow cytometry (named as FC-PSCs), and evaluate the proliferative and osteogenic capacity of FC-PSCs in-vitro, and then establish a new stem cell-based therapies for treating bone defects by delivering the FC-PSCs within platelet-rich plasma (PRP).

METHODS

Mouse periosteum was used to sort FC-PSCs using flow cytometry with CD45-TER119-TIE2-ITGAV+CD90 + 6C3-CD105- markers, or isolate periosteum-derived stem cells with the traditional protocol (TP-PSCs) as control. After evaluating the FC-PSCs proliferation and osteogenic differentiation in-vitro as well as the promotive efficacy of platelet-rich plasma (PRP) on FC-PSCs proliferation and osteogenic differentiation, the FC-PSCs were delivered into the femoral epiphysis bone defect site of a mouse model by platelet-rich plasma (PRP). At postoperative 14 or 28 days, these mice were euthanized for harvest the femur specimens for micro-CT, histological evaluation.

RESULTS

In-vitro results determined that the FC-PSCs showed more capacity for proliferation and osteogenic differentiation compared with the TP-PSCs. In addition, in-vitro results showed the promotive efficacy of PRP on FC-PSCs proliferation and osteogenic differentiation. In-vivo results showed that the FC-PSCs delivered by PRP was able to facilitate the repair of bone defects by stimulating new bone formation and remodeling.

CONCLUSION

FC-PSCs delivered by PRP enhance the repair of bone defects by stimulating new bone formation and remodeling.