T lymphocyte-deficient mice lose trabecular bone mass with ovariectomy.
We examined OVX-induced bone loss in three TLD mouse models. In TLD mice, OVX caused trabecular bone loss equivalent to that of WT. In contrast, cortical bone loss with OVX was variable. We conclude that T lymphocytes do not influence OVX-induced trabecular bone loss.


BACKGROUND
We examined ovariectomy (OVX)-induced bone loss in three T lymphocyte-deficient (TLD) mouse models: nude mice, recombination activating gene 2-deficient (RAG2 KO) mice, and T cell receptor alpha chain-deficient (TCRalpha KO) mice.


METHODS
Bone mass was examined by DXA, microCT, and histomorphometry. We also examined the effect of OVX on T lymphocytes in the bone marrow and spleens of wildtype (WT) mice and on in vitro osteoclastogenesis and colony forming unit-granulocyte macrophage (CFU-GM) activity in the bone marrow of WT and nude mice.


RESULTS
In WT mice, OVX did not alter T lymphocyte number in the bone marrow but did increase T lymphocytes in the spleen. Comparison of bone mass in nude, RAG2 KO, and TCRalpha KO mice with WT as measured by DXA showed decreased femoral bone mass in nude mice and increased vertebral bone mass in RAG2 KO mice. In TCRalpha KO mice, femoral, tibial, and vertebral bone mass were decreased. In vertebrae and long bones, bone loss with OVX was consistently present in WT mice but variably present in TLD mice as measured by DXA. In contrast, microCT and histomorphometry showed similar trabecular bone loss after OVX in all mice. However, femoral cortical bone loss occurred only in WT and RAG2 KO mice. OVX produced similar trabecular bone loss in WT and TCRalpha KO mice and also induced cortical bone loss in both. Histomorphometry showed that TRACP(+) area in bones was increased by OVX in femurs from both WT and nude mice as was in vitro osteoclast-like cell formation and CFU-GM activity.


CONCLUSIONS
These results show that OVX caused similar trabecular bone loss in both WT and TLD mice. The ability of DXA and measurement of cortical bone loss to show OVX-induced effects on bone mass was variable. It seems that T lymphocytes are not critical for OVX-induced trabecular bone loss in these mouse models.
Lee
Sun-Kyeong
SK
Division of Endocrinology, Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut 06030-5456, USA. slee@neuron.uchc.edu
Kadono
Yuho
Y
Okada
Fumihiko
F
Jacquin
Claire
C
Koczon-Jaremko
Boguslawa
B
Gronowicz
Gloria
G
Adams
Douglas J
DJ
Aguila
Hector L
HL
Choi
Yongwon
Y
Lorenzo
Joseph A
JA
D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism / Q000502:physiology*; D005260:Female; D008214:Lymphocytes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008819:Mice, Nude; D010010:Osteoclasts / Q000378:metabolism; D010052:Ovariectomy / Q000379:methods*; D011995:Recombination, Genetic; D013234:Stem Cells / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism / Q000502:physiology*