Naslov
Characterization of a Periosteal Mesenchymal Progenitor Cell Population Involved in Fracture Healing

Autori
Matthews, Brya ; Grčević, Danka ; Wang, L ; Rowe, David ; Adams, Douglas ; Kalajzić, Ivo

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Journal of bone and mineral reasearch / ASBMR - , 2012

Skup
ASBMR Annual Meeting 2012

Mjesto i datum
Minneapolis (MN), Sjedinjene Američke Države, 14.10.2012. - 18.10.2012

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
bone regeneration; osteoblast; progenitor cells

Sažetak
Fracture healing is a complex process that involves many cell lineages. Studies of gene expression in whole fracture callus do not distinguish contributions from different cell lineages. Previously we showed that α-smooth muscle actin (SMA) is a marker of progenitor cells that expand rapidly following fracture. We aimed to characterize this population during its commitment to callus formation. To identify and trace cells in periosteum and bone marrow (BM) we used SMA promoter-driven inducible Cre expression (SMA-CreERT2) combined with a Cre-activated TdTomato reporter Ai9 to generate SMA9 mice. Tibias were fractured in 3-4 month old SMA9 mice pretreated with tamoxifen. Periosteum/soft callus and BM were collected 2 days after treatment (unfractured), and 2 and 6 days after fracture. The majority of SMA9+ cells in unfractured periosteum are CD45-, 10% express Sca1, and 30% express CD51, a marker of committed osteoprogenitors. SMA9+ BM cells show quite different surface marker profiles, with 80% CD45+. In addition, microarray analysis revealed over 3000 genes differentially regulated between these two cell populations. Histology indicated that SMA9+ cells form chondrocytes and osteoblasts in a fracture callus, indicated by concomitant expression of Col2.3GFP and Col2A1GFP. FACS analysis showed that SMA9+ cells comprised 0.8% of cells in unfractured periosteum, and 1.2% and 3.5% 2 and 6 days after fracture, respectively, and 0.09%, 0.3% then 1.6% in BM. These SMA9+ cells were selectively isolated by FACS sorting and microarray analysis was performed. Two days after fracture many upregulated genes in periosteum were associated with mitosis or immune response (e.g. chemokines Cxcl2 and Ccl9). By day 6, upregulated genes were associated with bone and cartilage, with >50-fold increase in Acan and Col2a1, and elevated Ibsp and osterix. Numerous downregulated genes were associated with vascular and muscle development, including an expected decrease in SMA. Notch signaling components were decreased in SMA9+ cells following fracture, including Notch1, 3, 4, Hes1 and Hey1. These changes were confirmed by real time PCR. In summary, this is the first study to characterize gene expression in a defined subset of cells involved in fracture healing. After fracture, proliferation is stimulated in SMA9+ periosteal progenitor cells followed by differentiation into chondrocytes and osteoblasts. Downregulation of Notch signaling may be important in this process.

Izvorni jezik
Engleski

Znanstvena područja
Temeljne medicinske znanosti

POVEZANOST RADA