Hemopoietic origin of certain decidual cell precursors in murine pregnancy

The possible hemopoietic origin of certain precursors of uterine decidual cells appearing during normal murine pregnancy was investigated in semiallogeneic hemopoietic chimeras with retained or regained fertility. Chimeras were produced by three different methods in two donor-host combinations: F₁ BALB/c ♀ × C3H/HeJ ♂] cells introduced into the parental strain BALB/c ♀ hosts or F₁CBA/J ♀ × C57BL/6 ♂] cells introduced into CBA/J ♀ hosts. Prenatal chimeras (PN) were made by reconstituting mouse fetuses (day 13–17) with 10⁶–10⁷ adult bone marrow or fetal liver cells through the yolk sac and they were allowed to be delivered naturally. Neonatal chimeras (NN) were made by injecting 1–2 × 10⁷ adult bone marrow cells into the anterior facial vein of neonatal mice (< 24 hr old). In both cases, experimental animals were raised to maturity. Ovary-transplanted chimeras (OT) were made by injecting 10⁷ bone marrow cells into lethally irradiated (9.5 Gy) young adult female mice, followed 6 weeks later with bilateral orthotopic transplants of syngeneic ovary grafts to restore fertility. All female chimeras produced by the three different methods were mated with syngeneic male partners to produce normal pregnancy. The extent of chimerism at the cellular level was determined in all cases by a radioautographic identification of the H-2 phenotype of splenic lymphocytes and decidual cells and macrophages in the collagenase-dispersed decidua at day 11–16 of normal pregnancy, following a sandwich labelling with monospecific anti-H-2 antibodies and ¹²⁵I– protein A. Morphological discrimination of typical decidual cells from macrophages in the collagenase-dispersed decidua was carried out on the basis of several distinctive markers: presence of surface Dec-1 and Thy-1 and absence of surface F4/80 or latex phagocytosis for decidual cells, in contrast to macrophages which were phagocytic and expressed F4/80 but not Dec-1 or Thy-1. While the degree of hemopoietic chimerism (judged by the incidence of donor-derived lymphocytes in the spleen) varied from animal to animal, in all three groups (PN, NN, and OT) comprising a total of 26 chimeras, the percentage of typical decidual cells expressing donor H-2 phenotype showed an excellent correlation with that for small lymphocytes in the spleen. These results reveal that at least a sub-population of typical decidual cells of the pregnant uterus has a hemopoietic genealogy. A possible familial relationship of these cells to granulated metrial gland cells remains unclear.