Cadherin-6 mediates the heterotypic interactions between the hemopoietic osteoclast cell lineage and stromal cells in a murine model of osteoclast differentiation

Osteoclasts are multinucleated cells of hemopoietic origin that are responsible for bone resorption during physiological bone remodeling and in a variety of bone diseases. Osteoclast development requires direct heterotypic cell-cell interactions of the hemopoietic osteoclast precursors with the neighboring osteoblast/stromal cells. However, the molecular mechanisms underlying these heterotypic interactions are poorly understood. We isolated cadherin-6 isoform, denoted cadherin-6/2 from a cDNA library of human osteoclast-like cells. The isolated cadherin-6/2 is 3,423 bp in size consisting of an open reading frame of 2,115 bp, which encodes 705 amino acids. This isoform lacks 85 amino acids between positions 333 and 418 and contains 9 different amino acids in the extracellular domain compared with the previously described cadherin-6. The human osteoclast-like cells also expressed another isoform denoted cadherin-6/1 together with the cadherin-6. Introduction of cadherin-6/2 into L-cells that showed no cell-cell contact caused evident morphological changes accompanied with tight cell-cell association, indicating the cadherin-6/2 we isolated here is functional. Moreover, expression of dominant-negative or antisense cadherin-6/2 construct in bone marrow-derived mouse stromal ST2 cells, which express only cadherin-6/2, markedly impaired their ability to support osteoclast formation in a mouse coculture model of osteoclastogenesis. Our results suggest that cadherin-6 may be a contributory molecule to the heterotypic interactions between the hemopoietic osteoclast cell lineage and osteoblast/bone marrow stromal cells required for the osteoclast differentiation. Since both osteoclasts and osteoblasts/bone marrow stromal cells are the primary cells controlling physiological bone remodeling, expression of cadherin-6 isoforms in these two cell types of different origin suggests a critical role of these molecules in the relationship of osteoclast precursors and cells of osteoblastic lineage within the bone microenvironment.     

Induction of tolerance to an experimental cardiac allograft through intrathymic inoculation of class II major histocompatibility complex disparate antigens

Indefinite donor-specific tolerance to a cardiac allograft can be induced through pretransplantation intrathymic injection of donor spleen cells and a single intraperitoneal injection of antilymphocyte serum. This study was designed to determine whether this phenomenon was reproducible with grafts differing in either class I major histocompatibility complex only or class II MHC only. Donors of cells and hearts in all experiments were RP rats. Class I MHC disparate grafts were performed by placing an RP heart into a Lewis recipient, and class II disparate grafts were performed with RP donors and Wistar Furth recipients. Lewis (n = 10) and Wistar Furth (n = 10) recipients underwent intraperitoneal injection of 1 ml antilympocyte serum and intrathymic injection of 5 x 10(7) RP spleen cells. Three weeks later, heterotopic cardiac transplantation was done with a heart from an RP rat. Control rats had no pretreatment or received antilympocyte serum alone. Without pretreatment, RP hearts survived 7 to 9 days (mean 8 days) in Lewis recipients (n = 5) and 9 to 14 days (mean 12 days) in Wistar Furth recipients (n = 5). Antilymphocyte serum alone produced slight prolongation of graft survival. Lewis rats pretreated with class I disparate RP splenocytes and antilympocyte serum had graft survivals of 8 to 27 days (mean 14 days), not significantly different from the results with antilympocyte serum alone. Class II disparate RP grafts placed in pretreated Wistar Furth rats had significant prolongation of graft survival, with four of five grafts surviving longer than 60 days (p < 0.01 vs antilympocyte serum alone). These results suggest that a disparity at the class II locus of the major histocompatibility complex is critical for the induction of cardiac allograft tolerance after intrathymic inoculation of allogeneic cells.     

Effects of waterlogging at different stages of development on the growth and yield of winter wheat

The response of winter wheat to waterlogging at different stages of growth outdoors was studied for 3 years using lysimeters containing undisturbed monoliths of sandy loam and clay soils. The treatments were selected as the most extreme likely to occur in field conditions in Britain, i.e. waterlogging to the soil surface for up to 16 days in October, 42 days in January and February and 6 days in May. Waterlogging in midwinter was common to all experiments. Yield losses from mid-winter waterlogging ranged from 15% when yields were heavy (10 t ha^?1), to nil when yields were light (3-4 t ha^?1) after the plants had been affected by frost damage in late winter and by take-all. Winter wheat was most sensitive to waterlogging after germination but before emergence. At this stage, 16 days waterlogging killed all seedlings and 6 days waterlogging depressed plant populations to 12% (clay) and 38% (sandy loam) of the control. However, there was vigorous compensatory growth in the remainder of the growing season and yield was only depressed to about 82% of the control. When the crop was waterlogged at any stage after emergence plant populations were not affected; however, winter waterlogging treatments usually depressed shoot numbers and, to a lesser extent, ear numbers at harvest. Shoot survival under waterlogged conditions seemed related to nitrogen availability in the soil. The amount of ‘take-all’ (Gaeumannomyces graminis var. tritici) was increased by waterlogging.