Friday, May 20, 2011

Interesting research re the MOM hip issues: Chromium 3 vs Chromium 6?

I have blogged extensively on the confusion surrounding Chromium 6 (the toxic form of Chromium) and Chromium 3, purportedly the non toxic form of Chromium found in the Depuy hip.  As mentioned previously, Chromium seems to have the ability to oxidize from 3 to 6 and vice versa. Thus far,  reported cases of this  oxidation  have occurred  only under specific industrial conditions.

 I noted two really interesting studies published with one investigator in common; Professor Mary Grant in Glasgow Scotland  She resides in the biomedical engineering department and specializes in Cell & Tissue Engineering,and Xenobiotic Metabolism and Toxicity.

My question is why are they studying the effects of Chromium 6 in metal implants when the metal in these implants is suppose to be chromium 3 (the non toxic type?)

In 2009 she published a study Response to chronic exposure to hexavalent chromium in human monocytes. 

 The question she reviewed was depletion of lymphocytes has been reported in vivo in patients with metallic prostheses, and correlated with elevated chromium and cobalt concentrations in blood. However, the implications for immune function were unclear. [Important because lymphocytes fight infection.  Prolonged inflammation from infection can result in long term  issues. ]

She assessed the in vitro responses of human monocytes to chronic exposure (4 weeks) to Cr (VI) ions at concentrations which have been measured in patients with metal artificial hip implants (0.05-0.5 microM).  She found that chronic exposure to these low clinically relevant concentrations of Cr (VI) induced a potent adaptive response on a cellular level and concluded that such direct toxicity of Cr ions may contribute to the effects of metal implants on lymphocyte populations in vivo.

In May of 2011, she was a co author of another journal article; Effect of chromium and cobalt ions on primary human lymphocytes in vitro.

The exposure of resting lymphocytes to 100 ┬ÁM Co(2+) resulted in significant decrease in  cell viability accompanied by a significant increase in apoptosis (cell death.)  The results indicate that exposure to high concentrations of metal ions initiate apoptosis that results in decreased lymphocyte proliferation (can’t fight infection/compromised immune system.)

 Her conclusion: metal ion concentrations not directly cytotoxic to lymphocytes may affect events at a molecular level, thereby impeding lymphocyte proliferation. Hence, this may contribute to altered immune system function in patients with Co-Cr implants.

You would think that studying Cr 6 is a non issue for orthopedic implants.  Guess not!

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