Background: LIGHT (Homologous to lymphotoxins, shows inducible expression, and competes with herpes simplex virus glycoprotein D for herpes virus entry mediator (HVEM)/tumor necrosis factor (TNF)-related 2, HVEM-L, TNFSF14, or CD258) is a member of TNF superfamily. It is expressed as a homotrimer on activated T cells and also on immune dendritic cells, and has three receptors such as HVEM, LT-¥â receptor (LT-¥âR) and decoy receptor 3 (DcR3). So far, three receptors with distinct cellular expression patterns are described to interact with LIGHT. Follicular DCs and stromal cells bind LIGHT through LT-¥âR. We monitored the effects of LIGHT on human bone marrow-derived mesenchymal stem cells (BM-MSCs).

Methods: At first, we checked negative and positive differentiation markers of BM-MSCs. After rhLIGHT treatment, we monitored cell count, viability, proliferation, and cell cycle distribution. Also, PDGF and TGF¥â production by rhLIGHT were examined by ELISA, and biological mechanism were checked by immunoblotting through the rhLIGHT treatment.

Results: FACS analysis result showed that LT-¥âR receptor is expressed in human BM-MSCs, but not HVEM indicating that LIGHT binds only LT-¥âR in human BM-MSCs. (Fig. 1A/B). rhLIGHT and LT-¥âR interaction increased cell numbers in BM-MSCs using an inverted microscope for cell number changes. Cell numbers by rhLIGHT enhanced dose-dependently and time-dependently (Fig. 2 A/B). Cell viability and the expression of p-AKT, Bcl-2 and Bcl-xL by rhLIGHT were significantly increased in BM-MSCs and rhLIGHT-induced IkB-¥á degradation activated NF-kB signal (Fig. 3A/B). rhLIGHT increased cell proliferation by increasing S/G2/M phase in BM-MSCs (Fig. 3C and 4D). And cell cycle regulatory proteins were enhanced by rhLIGHT in BM-MSC including cyclin B1, D1, D3, E, and cyclin dependent kinase (CDK) 1 and 2 while CDK inhibitor, p27 was decreased by rhLIGHT treatment (Fig. 3E). Moreover, rhLIGHT-induced PDGF and TGF¥â production by STAT3 and smad3 activation accelerated BM-MSCs proliferation. And we also confirmed differentiation potential of rhLIGHT on BM-MSCs by the staining for adipogenesis (Oil Red O staining), chondrogenesis (Alcian blue staining) and Osteogenesis (Alizarin red Staining).

Conclusion: LIGHT and LT-¥âR interaction increases survival and proliferation of human BM-MSCs by activation of survival proteins, anti-apoptotic proteins, CDKs and cyclins. Moreover, LIGHT-induced STAT-3 and smad-3 activation causes PDGF and TGF-¥â production, and they enhance LIGHT signals in human BM-MSCs. We proposed the pathway of LIGHT and LT-¥âR interaction in human BM-MSCs. Therefore, LIGHT may play an important role for therapy of stem cells, and contribute to modification of MSCs.

Figure 1
Figure 1.
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Figure 2
Figure 2.
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Figure 3
Figure 3.
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Disclosures

No relevant conflicts of interest to declare.

Topics:
alcian blue, antigens, differentiation, bcl-xl protein, cell cycle proteins, cyclin-dependent kinase inhibitors, cyclin-dependent kinases, cyclins, glycoprotein, i-kappa b proteins, immunoblotting

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2016 by The American Society of Hematology
2016
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