Hemoglobin in Cartilage Cells

AAAS: "More than red blood cells depend on hemoglobin, surprising study of cartilage reveals." Look carefully at the photomicrograph + you can see clumps of red in this chondrocytes or cartilage cells in the growth plate of young, juvenile cartilage. There are no blood vessels in cartilage, which must scavenge oxygen from surrounding tissue or joint fluid. Think here of a knee cartilage known as a meniscus. Erythrocytes or red blood cells are red because about 95% of their content is hemoglobin, which holds + releases oxygen. Hemoglobin has now been demonstrated to support the cartilage cells in a low-oxygen environment. Chinese scientists "turned to genetically altered mice that produce fewer functional hemoglobin molecules than normal. Analyzing the animals’ cartilage, they found that large numbers of chondrocytes perished in the growth plates." Prior research has demonstrated hemoglobin in other cell types, including nerve cells, lung cells + immune cell called macrophages, but no previous evidence has shown its physiologic role in these disparate cell types. This is all new information from when I was in med school—but granted that was half a century ago.