الملخص الإنجليزي
Background: Human midkine (MK) is a 13 kDa heparin-binding growth factor, MK family
has two members; the founding member MK and the other member is pleiotrophin (PTN).
PTN is 18 kDa heparin-binding cytokine. These molecules share 50% sequence identity.
They both play fundamental roles in physiological and pathological process. MK production
by innate antigen presenting cells (APCs) except myeloid dendritic cells (mDCs) was
detected from a previous study conducted in the Department of Microbiology and
Immunology, College of Medicine and Health Science, Sultan Qaboos University (SQU).
Objectives: This study aimed to investigate the production of MK by stimulated mDCs
when isolated by direct labeling method, to optimize the transfection of innate APCs with
anti-MK siRNA. In addition, the production of PTN by the stimulated innate APCs was
assessed.
Methods: MDCs were obtained from peripheral blood mononuclear cells (PBMCs) of
healthy individuals (n=3). MDCs were stimulated with Lipopolysaccharides (LPS) to assess
the expression of co-stimulatory molecules (CD80 & CD86) by flowcytometry. The MK
expression by mDCs stimulated with LPS, poly I:C, RES, and ODN was evaluated by
ELISA. Monocytes, macrophages (MΦs), monocyte-derived dendritic cells (MDDCs),
mDCs and plasmacytoid dendritic cells (pDCs) were obtained from PBMCs of healthy
volunteers (n=3 for each) and then stimulated with LPS, poly I:C, resiquimod, ODN and a
combination of all ligands to assess the production of PTN induced by the TLRs signaling
pathway. Finally, MDDCs & MΦs were transfected with control Fam-siRNA and MKsiRNA by electroporation and lepofectamine 2000 and then stimulated by LPS.
Results: MK was not produced by stimulated mDCs isolated by direct labeling method. MK
expression is inhibited in MK-siRNA transfected cells stimulated by LPS. All innate APCs
expressed PTN once stimulated with different TLRs ligands.
Conclusion: MK is not produced by stimulated mDCs. Therefore, they may not influence
the other cells with same manner like other APCs which are able to produce MK. MK
production is inhibited in cells transfected with MK-specific-siRNA. Supernatants of these
cells will be tested for their biological activities. PTN is expressed by all innate APCs, which
suggests a role for PTN in regulating the immune system and some biological activities.
