Table 1. Major findings on the interplay between osteoclasts and hematopoiesis.

Model	Major findings	Reference
Ectopic transplantation of bone marrow plug in blood-letting mice	Increased hematopoiesis Reduced bone volume	11
Ovariectomized rats	Reduced hematopoiesis with time Increased osteoclasts	16
Osteopetrotic humans and mice	Fibrotic medullary tissue in osteoclast-rich forms	20,21
	Hematopoietic tissue in osteoclast-poor forms	22,23
RANKL-treated mice	Increased HSC mobilization Inhibition of HSC anchorage to the niche Cathepsin K-dependent cleavage of CXCL12 Increased MMP-9 Decreased endosteal osteopontin content	24
MMP-9-deficient mice	MMP-9 required for HSC mobilization	24,25,26
	MMP-9 not required for HSC mobilization	27,28
Mice treated with strontium ranelate	Inhibition of osteoclasts Delay in recovery after bone marrow transplantation	6
Mice treatment with PGE2	Increased hematopoiesis Disruption of bone trabecular microarchitecture. Stimulation of bone resorption	29
Calcium sensing receptor-deficient mice	Reduced cellularity in bone marrow Reduced HSC content in bone marrow	31
Id1−/− mice	Osteoporosis Upregulation of osteoclast-specific genes Increased myeloid differentiation and HSC proliferation	33
Crebbp−/− mice	Exacerbated myeloid differentiation Reduced bone volume Increased osteoclastogenesis Increased levels of MMP-9	37
Bone marrow transplantation in thyroparathyroidectomized rats	Delay in hematocrit recovery Restoration upon PTH treatment	42
Treatment of mice with erythropoietin and bisphosphonates	Increased erythropoiesis Increased osteoclastogenesis blocked by bisphosphonates Oncostatin M released by erythroid cells in response to erythropoietin, which stimulates osteoclast formation	43,44,45,46
Treatment of mice with bisphosphonates	Impaired bone marrow engraftment Decrease of HSC number in bone marrow	48,52
	Promotion of proliferation and differentiation of hematopoietic progenitor cells Increase of HSC mobilization	49
Genetic knock-down in mice to induce osteopetrosis or osteoporosis, treatment with anti-resorptive agents	Increased HSC mobilization into the peripheral blood in osteopetrotic mice Increased HSC mobilization into the peripheral blood in mice treated with bisphosphonates or RANKL antibody Decreased HSC mobilization in osteoporotic mice Decrease of HSC number in bone marrow	50
Treatment of mice with bisphosphonates, oc/oc osteopetrotic mice	Impaired B cells in bone marrow Decrease in expression of CXCL12 and IL-7 Retention of B cells outside the bone marrow niche	51

Abbreviations: HSC, hematopoietic stem cell; MMP-9, matrix metalloproteinase-9; PGE2, prostaglandin E2; PTH, parathyroid hormone.