| Research Abstract |
Megakaryocytes (Mgk) derived from CFU-Meg cultureed in vitro are able to generate cytoplasmic processes (CP) with proplatelets.
Scanning microscopic analysis of bone marrow sinusoid revealed that CP penetrated endothelial cells (EC) and released the platelets into circulation. Adhesion between CP and EC may be important for releasing platelets. During experimental period, thrombopoietin (Tpo, Mpl-ligand) was purified and added to experimental design. Following subjects were investigated during 1993-94.
1) What kinds of adhesion molecules are expressed on Mgk with CP ?
2) What kinds of adhesion mechanism are exsited between Mgk with CP and EC ?
3) What kinds of stimulants are required to release platelets from CP ?
Adhesion molecules expressed on the platelets (CDw49b, CDw49e, CDw49f, CD54, CD31, CD62, CD42b) were also expressed on the Mgk with CP as well as Mgk. Among adhesion molecules, CD31 (PECAM-1) was accumulated on the tip of CP.This may give an important role to extend CP on the EC.
When Mgk were stimulated by IL-6, IL-11 and m-Tpo, CP forming rate were 12.5<plus-minus>3.3%, 10.5<plus-minus>3,8%, 13.5<plus-minus>2.6%, respectively, indicating of no significance, comparing with non-stimulated Mgk. However, stimulated Mgk were cultured on the EC,CP forming rate were increased to 18.3<plus-minus>4,6%, 17.0<plus-minus>5.7%, 32.1<plus-minus>12.6%, respectively.Tpo shows most striking effects in the cytokines examine
Terminal maturation of Mgk may required cell-cell interaction in addition to cytokine stimulation.
|
