GP130/OSMR is the only LIF/IL-6 family receptor complex to promote osteoblast differentiation of calvaria progenitors.

Leukemia inhibitory factor (LIF) and its receptor (LIFR) are "twins" of Oncostatin M (OSM) and OSMR, respectively, likely having arisen through gene duplications. We compared their effects in a bone nodule-forming model of in vitro osteogenesis, rat calvaria (RC) cell cultures. Using a dominant-negative LIF mutant (hLIF-05), we showed that in RC cell cultures mouse OSM (mOSM) activates exclusively glycoprotein 130 (gp130)/OSMR.

Global amplification polymerase chain reaction reveals novel transitional stages during osteoprogenitor differentiation.

Mesenchymal stem cells give rise to osteoprogenitors that proliferate and differentiate into identifiable preosteoblasts, osteoblasts, bone lining cells and osteocytes. To identify and establish a molecular profile for the more primitive and uncharacterized cells in the lineage, relatively rare (<1%) osteoprogenitors present in primary cultures of fetal rat calvaria cell populations were identified by a replica plating technique. Since the cell number was limited in each colony sampled, we used global amplification PCR to analyze the repertoire of genes expressed in osteoprogenitors.

Expression and distribution of SPARC in early Xenopus laevis embryos.

SPARC (Secreted Protein, Acidic, Rich in Cysteine) is a highly conserved, calcium-binding, extracellular matrix protein. To investigate its role in early embryogenesis, we examined its tissue distribution in early Xenopus embryos. SPARC mRNA transcripts were detectable by Northern blot analysis beginning at the early neurula stage.