Histogenesis of antlerogenic tissues cultivated in diffusion chambers in vivo in red deer (Cervus elaphus).

In a previous study we showed that formation of deer pedicle and first antler proceeded through four ossification pattern change stages: intramembranous, transition, pedicle endochondral, and antler endochondral. In the present study antlerogenic tissues (antlerogenic periosteum, apical periosteum/perichondrium, and apical perichondrial of pedicle and antler) taken from four developmental stages were cultivated in diffusion chambers in vivo as autografts for 42-68 days. The results showed that all the cultivated tissues without exception formed trabecular bone de novo, irrespective of whether they were forming osseous, osseocartilaginous, or cartilaginous tissue at the time of initial implant surgery; in two cases in the apical perichondria from antler group, avascularized cartilage also formed. Therefore, the antlerogenic cells, like the progenitor cells of somatic secondary type cartilage, have a tendency to differentiate into osteoblasts and then form trabecular bone. Consequently, the differentiation pathway whereby antlerogenic cells change from forming osteoblasts to forming chondroblasts during pedicle formation is caused by extrinsic factors. Both oxygen tension and mechanical pressure are postulated to be the factors that cause this alteration of the differentiation pathway.