Lipid co-factor essential for cell density signaling

1. An isolated tissue-specific lipid co-factor having a formula C63H123N2O11P and a mass of about 1114.89 MW, said lipid cofactor binds to a polypeptide factor that comprises the amino acid sequence set forth in SEQ ID NO: 3 or SEQ ID NO: 5 to form a protein/lipid cell density signaling complex, said cell density signally complex controlling cell proliferation, differentiation or apoptosis in bone and cartilage tissue, and said lipid co-factor comprising a ceramide phosphate, a glycerol lipid with a single fatty acid, and a linker.

2. An isolated tissue-specific lipid co-factor having a formula C30H74NO5P and a mass of about 696.65 MW, said lipid cofactor binds to a polypeptide factor that comprises the amino acid sequence set forth in SEQ ID NO: 3 or SEQ ID NO: 5 to form a protein/lipid cell density signaling complex; said cell density signally complex controlling cell proliferation, differentiation or apoptosis in tendon tissue and said lipid co-factor comprising two fatty acid chains connected directly to a phosphate molecule.

3. A method of isolating the lipid co-factor of claim 1 or 2 comprising:

a. filtering conditioned medium containing said protein lipid complex through a 0.2 micron filter;

b. adding 5M NaCl in an amount equivalent to 1/10 th the resulting conditioned medium volume;

c. using an ultrafilter in a stirred cell under pressurized nitrogen to concentrate the high salt conditioned medium to 1 ml of retentate;

d. diluting the retentate to 10 ml with water and reconcentrating to 0.5 ml;

e. capturing the free protein factor in the retentate; and,

f. capturing the free lipid cofactor in the filtrate.

4. A cell density signaling complex comprising a tissue-specific lipid cofactor of claim 1 or 2 , which is tightly bound to a polypeptide factor that comprises the amino acid sequence set forth in SEQ ID NO: 3 or SEQ ID NO: 5.