Gastrectomy has no effect on bone regeneration in rats despite a decrease in bone mass

Background: Gastrectomy, specifically the removal of the acid-producing part of the stomach (fundectomy), is known to cause osteopenia. This effect has been ascribed to the elimination of a hypothetical osteotropic peptide hormone, presumably produced in the oxyntic mucosa. Since osteopenia is due to a disturbed balance between bone formation and resorption, we assessed the effect of gastrectomy on osteogenesis, more specifically mandibular orthotopic bone regeneration. Methods: Adult rats were either gastrectomized or sham-operated. Two weeks later, unilateral 5-mm transosseous defects were made in the mandibles and covered with microporous barrier membranes (GORE-TEX(R) Membrane). After 6 weeks of healing, bone-bridging of the defects was analyzed by computerized light microscopic image analysis. Furthermore, bone mass was analyzed in the contralateral untreated mandibular side, in calvaria l bone, and in femora by morphometry and dry/ash weights. Results: While gastrectomy resulted in a clearly decreased bone mass, manifested as increased marrow spaces in all bones and as decreased dry and ash weights in femora, no difference in mandibular bone healing rate was found between the groups. Conclusions: Since secluding of the defect space by membrane barriers implies that osteogenic cells have to be recruited primarily from intra-osseous stem cells by their proliferation and differentiation into actively bone-forming osteoblasts, the results indicate that gastrectomy has no effect on these processes. The findings thus imply that the disturbed balance in bone remodeling caused by gastrectomy, resulting in osteopenia, may be due to stimulated bone resorption rather than to reduced bone formation