Researchers have identified a subpopulation of mesenchymal stem cells (MSCs) that boost the healing of bone fractures and show an ability to differentiate into various cell types.

Their findings are published in the journal Bone Reports in a paper titled, “Bone marrow CD73+ mesenchymal stem cells display increased stemness in vitro and promote fracture healing in vivo,” and led by researchers from the University of Tsukuba, in collaboration with the University of Bonn, Germany.

“MSCs are multipotent and considered to be of great potential for regenerative medicine,” the researchers wrote. “We could show recently (Breitbach, Kimura, et al. 2018) that a subpopulation of MSCs, as well as sinusoidal endothelial cells (sECs) in the bone marrow (BM) of CD73-EGFP reporter mice, could be labeled in vivo. We took advantage of this model to explore the plasticity and osteogenic potential of CD73-EGFP+ MSCs in vitro and their role in the regenerative response upon bone lesion in vivo.”

“The generation of the callus is critically dependent on the recruitment of MSCs from the surrounding tissue and the bone marrow,” explained Kenichi Kimura, PhD, lead author and assistant professor at the University of Tsukuba. “Therefore, fracture healing models are helpful for exploring the cellular dynamics of MSC migration and differentiation during tissue regeneration.”

The researchers observed the CD73-positive MSCs moving towards the site of the fracture and forming new cartilage and bone cells to heal the fracture. Finally, they went on to graft CD73-positive MSCs into the area of a fracture, which markedly enhanced the healing process compared with when they grafted into CD73-negative MSCs.

The new finding of the subpopulation of MSCs paves the way for new regenerative medicine and the treatment of fractures to be made.

“Our study underscores the heterogeneity of BM-MSCs and their differential response and mobilization upon bone fracture. We found that the CD73+ subpopulation of BM- MSCs contributes to the regeneration process of bone fracture healing by promoting callus formation and that also the BM sEC fraction participates in the neovascularization process during bone repair,” concluded the researchers.