Modeled gravitational unloading triggers differentiation and apoptosis in preosteoclastic cells.
Gravity acts permanently on organisms as either static or dynamic stimulation. Understanding the influence of gravitational and mechanical stimuli on biological systems is an intriguing scientific problem. More than two decades of life science studies in low g, either real or modeled by clinostats, as well as experimentation with devices simulating different types of controlled mechanical stimuli, have shown that important biological functions are altered at the single cell level. Here, we show that the human leukemic line FLG 29.1, characterized as an osteoclastic precursor model, is directly sensitive to gravitational unloading, modeled by a random positioning machine (RPM). The phenotypic expression of cytoskeletal proteins, osteoclastic markers, and factors regulating apoptosis was investigated using histochemical and immunohistochemical methods, while the expression of the corresponding genes was analyzed using RT-PCR. A quantitative bone resorption assay was performed. Autofluorescence spectroscopy and imaging were applied to gain information on cell metabolism. The results show that modeled hypogravity may trigger both differentiation and apoptosis in FLG 29.1 cells. Indeed, when comparing RPM versus 1 x g cultures, in the former we found cytoskeletal alterations and a marked increase in apoptosis, but the surviving cells showed an osteoclastic-like morphology, overexpression of osteoclastic markers and the ability to resorb bone. In particular, the overexpression of both RANK and its ligand RANKL, maintained even after return to 1 x g conditions, is consistent with the firing of a differentiation process via a paracrine/autocrine mechanism.
Monici
Monica
M
CEO--Center of Excellence in Optronics, L. Enrico Fermi 6, I-50125 Florence, Italy. monici@ino.it
Fusi
Franco
F
Paglierani
Milena
M
Marziliano
Nicola
N
Cogoli
Augusto
A
Pratesi
Riccardo
R
Bernabei
Pietro Antonio
PA
D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000737:chemistry; D001862:Bone Resorption / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D000091344:Filaggrin Proteins; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D014411:Neoplastic Stem Cells / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D010010:Osteoclasts / Q000737:chemistry / Q000378:metabolism / Q000473:pathology*; D010024:Osteoporosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D018474:Weightlessness Simulation
D014408:Biomarkers, Tumor; C000717249:FLG protein, human; D000091344:Filaggrin Proteins