title: Osteoporosis of hematologic etiology.
abstract: OBJECTIVE
  Here we present evidence that overexertion of the hematopoietic system following chronic bleeding plays an important role in the etiology of osteoporosis.
  
  
  METHODS
  C57BL/6 mice were exposed to chronic bloodletting (0.2 mL twice per month for 10 months), total body irradiation (900 cGy), or aging (20-30 months old). Bone marrow from standard untreated donors was transplanted under the kidney capsules of all three categories of recipients to investigate the influence of each of these conditions on new bone marrow formation. Cellularity and histologic structure of developed osteohematopoietic sites and histomorphometry of lumbar vertebrae were studied, thus assessing the role of bleeding, irradiation, and old age on new bone formation and effects on existing bone.
  
  
  RESULTS
  Chronic blood loss led to augmented production of hematopoietic microenvironment, relative reduction in the amount of generated bone, and activation of the bone resorptive process in the newly forming osteohematopoietic complex. Similar results were seen in irradiated and senescent mice. Activity, stimulating expansion of hematopoietic microenvironment, was revealed in the plasma of all three categories of experimental mice. Likewise, quantification of the relative amount of bone and hematopoietic areas in skeletal sites showed a significant reduction in bone tissue of the first lumbar vertebrae of chronically bled mice.
  
  
  CONCLUSIONS
  Our experimental data, together with existing clinical observations documenting the role of hematopoietic insufficiency in the development of osteoporosis, confirm our working hypothesis that chronic blood loss may be the primary factor responsible for the rapid and consistent development of postmenopausal osteoporosis.
authors.affiliation: Department of Bone Marrow Transplantation and Cancer Immunotherapy, Hadassah University Hospital, Jerusalem, Israel.
authors.forename: Olga
authors.initials: O
authors.lastname: Gurevitch
authors.forename: Sofia
authors.initials: S
authors.lastname: Khitrin
authors.forename: Andrei
authors.initials: A
authors.lastname: Valitov
authors.forename: Shimon
authors.initials: S
authors.lastname: Slavin
mesh_terms: D000367:Age Factors; D000818:Animals; D001861:Bone Regeneration; D001862:Bone Resorption; D006410:Hematopoiesis; D006413:Hematopoietic System / Q000503:physiopathology*; D006470:Hemorrhage / Q000150:complications*; D008159:Lumbar Vertebrae / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D010024:Osteoporosis / Q000209:etiology*; D014916:Whole-Body Irradiation