Collagenous bone matrix-induced endochondral ossification hemopoiesis.

Abstract

Transplantation of collagenous matrix from the rat diaphyseal bone to subcutaneous sites resulted in new bone formation by an endochondral sequence. Functional bone marrow develops within the newly formed ossicle. On day 1, the implanted matrix was a discrete conglomerate with fibrin clot and polymorphonuclear leukocytes. By day 3, the leukocytes disappeared, and this event was followed by migration and close apposition of fibroblast cell surface to the collagenous matrix. This initial matrix-membrane interaction culminated in differentiation of fibroblasts to chondroblasts and osteoblasts. The calcification of the hypertrophied chondrocytes and new bone formation were correlated with increased alkaline phosphatase activity and 4sCa incorporation. The ingrowth of capillaries on day 9 resulted in chondrolysis and osteogenesis. Further remodelling of bony trabeculae by osteoclasts resulted in an ossicle of cancellous bone. This was followed by emergence of extravascular islands of hemocytoblasts and their differentiation into functional bone marrow with erythropoietic and granulopoietic elements and megakaryocytes in the ossicle. The onset and maintenance of erythropoiesis in the induced bone marrow were monitored by 5'Fe incorporation into protein-bound heme. These findings imply a role for extracellular collagenous matrix in cell differentiation.There is growing knowledge about the intracellular molecules involved in cell differentiation (8). However, information pertaining to the possible role of extracellular matrix macromolecules such as collagen and proteoglycans has lagged (20). A characteristic feature of multicellular metazoa is the presence of extracellular matrix. In skeletal and dental tissues, extracellular matrices are most prominent and may provide important clues to their role.On contact with demineralized collagenous matrices of bone and tooth, responding fibroblasts (mesenchymal cells) show an alteration of gene expression which results in emergence of new phenotypes (18,19,22,32,33). Simple techniques to study this phenomenon were developed and the temporal sequence of events were delineated (22).

Analyses of Very Early Hemopoietic Regeneration After Bone Marrow Transplantation: Comparison of Intravenous and Intrabone Marrow Routes

“…Taken together, it is obvious that IBM-BMT causes a unique process in the early period after BMT, which is not observed in sham-operated tibiae in the IV-BMT group. Considering that the timing is crucial in ontogeny [21,22] and that regeneration recapitulates ontogeny [20,[23][24][25], this early difference might explain why IBM-BMT is advantageous.…”

Calcitonin stimulates bone formation when administered prior to initiation of osteogenesis.

“…The day of implantation was designated as day 0. The present study investigated the influence of salmon calcitonin, 15 MRCU subcutaneous injections daily, (Calcimar, Armour Pharmaceuticals, Scottsdale, Ariz.) on four distinct phases of matrixinduced bone formation (11) in treated and untreated control rats: (a) proliferation of mesenchymal cells 3 d after implantation by [3H]thymidine incorporation (13) and ornithine decarboxylase (ODC) activity (14,15); (b) chondrogenesis on day 7, monitored by 35SO4 incorporation into proteoglycans (11,12); (c) osteogenesis on day 14 monitored by 45Ca incorporation (11,12); and (d) bone marrow formation was monitored by 59Fe incorporation on day 21, (11,12). The tissue activities of alkaline and acid phosphatases (11) were determined because of their close association with bone formation and resorption, respectively.…”

“…Some investigators have found that pharmacologic doses of CT are without effect on bone formation (6), while others have found it is stimulatory (7-9) or inhibitory (10). To determine the influence of CT on developing cartilage, bone and bone marrow, a demineralized collagenous bone matrix-induced endochondral bone-forming system was used (11,12). This permitted the temporal segregation of the various stages of bone formation and allowed us to examine the influence of CT on each of the phases.…”

Lack of repair of rat skull critical size defect treated with bovine morphometric protein bound to microgranular bioabsorbable hydroxyapatite

“…Subsequent studies have demonstrated that this inductive capacity was due to water-insoluble protein factors present in the organic bone matrix (2).…”