ECTS2013 Poster Presentations Bone development/growth and fracture repair (40 abstracts)
Vascularisation and progenitor cells of primary and secondary ossification centres in the human growth plate
Sonja M Walzer 1 , Erdal Cetin 1 , Ruth Grübl-Barabas 1 , Irene Sulzbacher 3 , Beate Rüger 2 , Werner Girsch 4 , Reinhard Windhager 1 & Michael B Fischer 2
1Clinic of Orthopaedic Surgery, Medical University Vienna, Vienna, Austria; 2Clinic for Blood Group Serology and Transfusion Medicine, Medical University Vienna, Vienna, Austria; 3Department of Pathology, Medical University Vienna, Vienna, Austria; 4Department of Paediatric Orthopaedics, Orthopaedic Hospital Speising, Vienna, Austria.
The switch from a cartilage template to bone during endochondralossification of the growth plate requires dynamic and close interaction between the cartilage and the developing vascular structures. Vascular invasion of hypertrophic cartilage, with blood vessels coming from the bone collar, serves to bring in osteoblast- andendothelial precursor cells along with chondroclasts and their precursors into future ossification centres of the growth plate.
Potential progenitor cells in different zones of the growth plate and the surrounding encircling fibrochondrosseous structure was investigated. Vascularization of growth plate in ossification centres was studied by immunohistochemistry using markers specific for endothelial cells CD34 and CD31, smooth muscle cells α-SMA, endothelial progenitor cells CD133, CXCR4, VEGFR-2 and mesenchymal progenitor cells CD90 and CD105. Morphometric analysis was performed to quantify RUNX2+ and DLX5+ hypertrophicchondrocytes, RANK+chondro- and osteoclasts, and CD133+ progenitor cells in the different zones of the growth plate.
Vascular invasion of primary ossification centres with CD34+ endothelial cells, that did not express the mature endothelial cell marker CD31 yet led to the formation of vessels that lacked abluminal coverage with α-SMA+ smooth muscle cells. In close proximity to the seimmature vessels, single CD133+ cells were found, that seemed to be involved in the formation of the future stem-cell niche rather than in vasculogenesis because they lacked expression of VEGFR-2. Vessels in newly formed bone, in perichondrial groove of Ranvier that harboured CD90/CD105+chondro-progenitors, and in perichondrium were shown to be more developed because they were stabilized by α-SMA+ smooth muscle cells.
In conclusion, vascularisation of ossification centres of the growth plate seem to be mediated by the sprouting of newly formed capillaries coming from the bone collar or by intussusceptions rather than by de-novo vessel formation by endothelial progenitorcells.
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Bone Abstracts
ISSN 2052-1219 (online)
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