Presence of heavy chain-hyaluronan/pentraxin 3 (HC-HA/PTX3) complex in human umbilical cord

The heavy chain (HC)-hyaluronan (HA)/pentraxin 3 (HC-HA/PTX3) complex is formed by tumor necrosis factor-stimulated gene-6 (TSG-6) catalyzing the covalent (ester bond) transfer of HC1 from inter-α-trypsin inhibitor (IαI) to HA followed by tight binding of PTX3. The presence of such a complex has been found in human amniotic membrane (AM) and is considered to be a major matrix component responsible for its anti‑inflammatory and anti‑scarring properties to promote regenerative healing. Because the therapeutic potentials of AM and umbilical cord (UC) are similar, we herein evaluated whether human UC also contains HC-HA/PTX3. Immunostaining of UC cross-sections showed abundant PTX3, HC1, HA, TSG-6, and bikunin. Western blot analysis suggested the presence of HC1 complex bound via a NaOH-sensitive bond and tightly bound to PTX3 multimer in UC and AM extracts but not in chorion and placenta extracts. HC-HA/PTX3 was purified from UC extract by successive runs of density gradient ultracentrifugation and verified the presence of HC1 but not HC2 or HC3 based on western blot analysis. These results suggest the presence of HC-HA/PTX3 complex in UC is similar to AM.