Herbert Wells

Effects of prostaglandins and other drugs on the cyclic AMP content of cultured bone cells.

Prostaglandins of the E-series (PGE1 and PGE2) may be involved in disease-related, localized loss of bone. E-prostaglandins increase the cyclic AMP content of many cells; and, to determine if their effects on bone are mediated by cyclic AMP, we examined the effects of E-prostaglandins and of other agents on the cyclic AMP content of cultured bone cells. PGE2 produced a rapid, marked and dose-related increase in the cyclic AMP content of confluent monolayers of bone cells isolated from newborn rat calvaria. At 2.8 X 10(-6) M, PGE1 and PGE2 had approximately the same effect, while the effect of PGF2alpha was much less pronounced. In the presence of theophylline, PGE2 had a more marked effect than parathyroid hormone (PTH) and the combination of PGE2 and PTH had a synergistic effect. The divalent, cationic, ionophore, A23187, produced an increase in cellular cyclic AMP and had an additive effect in combination with PGE2. Synthetic salmon calcitonin (CT), which inhibits the bone resorptive effect of PGE2, increased cellular cyclic AMP and had an additive effect in combination with PGE2. A prostaglandin antagonist, SC-19220, partially inhibited the resorptive effect of PGE2 and reduced its effect on cellular cyclic AMP. The calcium antagonist, D600, inhibited the bone resorptive effects of PGE2 but had no effect on increased cellular cyclic AMP produced by PGE2. The marked effect of PGE2 on bone cell cyclic AMP suggests that this action is involved in the mechanism of PGE2-related bone loss. The fact that agents with different effects on PGE2-induced increases in cellular cyclic AMP can inhibit its resorptive actions, suggests that PGE2-induced changes in cyclic AMP may be related less to its resorptive actions than to its inhibitory effect on bone formation.

Bone induction in experimental periodontal bony defects in dogs with decalcified allogeneic bone matrix grafts. A preliminary study.

Abstract Decalcified allogeneic bone matrix grafts have been studied in periodontal bony defects in twenty-seven dogs. DABM grafts were resorbed and replaced by new bone. There occurred union of new bone to the cemental (tooth) surface (ankylosis). Clinical, radiologic, fluorescent, and histologic studies revealed that such grafts could ultimately be of use in human beings, especially since these grafts are not rejected and, to our knowledge, do not cause any immunologic response.

Experimental osteogenesis in periapical areas with decalcified allogeneic bone matrix

Abstract Decalcified allogeneic bone matrix grafts were implanted in fourteen teeth after pulpotomy, in twenty root canals after pulp extirpation, and in the periapical areas of forty-eight teeth after apicoectomy. These procedures were carried out in five dogs and three monkeys. Results of the present investigation reveal that DABM grafts stimulate osteogenesis and cementogenesis. Although present data are insufficient, it can be speculated that DABM grafts would result in physiologic seal at the apical foramen of apicoectomized teeth with new bone and cementum. Thus, this increased osteogenesis and cementogenesis will prolong the survival of nonvital teeth in human beings.

Improved healing of experimental defects in the canine mandible by grafts of decalcified allogenic bone.

Abstract Standardized surgical defects were made on the buccal surface of canine mandibles. Autologous and decalcified allogenic grafts of canine bone were placed in these defects and allowed to heal for a period of from 2 to 8 weeks. Histologic study revealed that the decalcified allogenic bone grafts underwent complete resorption which was accompanied by new bone formation. The autologous grafts maintained their viability, were not resorbed, and were accepted by the host tissues. Bone regeneration appeared to be somewhat more rapid in decalcified allogenic grafts as compared to autologous grafts. These results suggest that decalcified allogenic bone grafts should be studied in more detail, for they could be of use in the treatment of bony defects in the facial bones.

Stimulation of new bone formation on intact bones by decalcified allogeneic bone matrix

Abstract The results of the present experiments indicate that grafts of allogeneic bone matrix are not rejected and that they induce formation of new bone at the site of their placement. The fact that decalcified allogeneic bone matrix induces little or no immune response suggests that it has a very weak, if any, antigenic activity, but at present there is no really clear explanation for the fact that this material does not elicit such a response.

Cyclic AMP formation and release by cultured bone cells stimulated with prostaglandin E2

PGE2 produced a marked and dose-related increase in cAMP content of cultured bone cells and in the release of cAMP into the incubation medium. The amount of cAMP released from the cells by PGE2 was proportional to the cellular concentration, and was dependent upon the time of incubation with PGE2. The cAMP levels released into the media increased slowly at a linear rate during a 60 min treatment with PGE2. This release was blocked by theophylline, probenecid, ouabain and dinitrophenol, suggesting that the release of cAMP was not a simple diffusive process and required energy. SC-19220 reduced the formation of cAMP more than the release, suggesting that the formation and the release may arise from separate events. Inability of D600 to inhibit PGE2-induced release of cAMP indicates that the release does not require calcium.

Demineralization of bone transplants in vivo.

Abstract A standard experimental model was designed by creating midfibular fracture gaps in rats, for the study of grafts of decalcified allogeneic bone matrix (DABM), fresh autologous bone, fresh allogeneic bone, and decalcified xenogeneic bone matrix (DXBM). The results reveal that DABM implants were accepted by the host in fresh and chronic fibular gaps. There was a gradual increase in calcium concentration, which reached normal levels by the eighth postoperative week at fracture gap sites. DXBM grafts demonstrated very small concentration of calcium after 4 weeks, which was mainly due to formation of callus around the grafts; and 55 per cent of these grafts were rejected, as evidenced by exudate and exfoliation. Fresh autologous and fresh allogeneic bone transplants demonstrated a fall in calcium concentration in the initial 3-week intervals, then a gradual increase in mineralization, and the attainment of normal levels by the eighth postoperative week. All autologous bone grafts were accepted, whereas 45 per cent of fresh allogeneic bone grafts were rejected from the mid-fibular implanted sites. The study with autologous bone transplants was repeated, and the implanted bone was isolated from new bone for calcium estimation at various postoperative intervals. The results revealed gradual decrease in calcium concentration up to 4 weeks, and the later intervals could not be estimated because of difficulty in separation of implanted bone from the new bone. The results of these experiments suggest that calcified bone grafts (autologous or allogeneic) undergo partial or complete decalcification in tissues after implantation. Since this decalcification of bone could be accomplished in vitro, it would appear that the DABM grafts are worthy of trials in human osseous deformities.

Experimental osteogenesis with decalcified allogeneic bone matrix in palatal defects

Abstract Decalcified allogeneic bone matrix grafts were implanted in fresh palatal defects in six monkeys and chronic palatal defects in seven dogs. The chronic palatal defects were created with an air drill and with insertion of silicone rubber in palatal defects for 4 weeks. Clinical, histologic, fluorescent, and radiologic studies reveal that DABM grafts form new bone, thus resulting in bony union of the host bone to new bone. The DABM grafts were not rejected by the host tissue; rather, they were resorbed and replaced by new bone. It is speculated at this time, from the present results, that DABM grafts may have a clinical implication for patients with cleft palate.

Maintenance of acrylic teeth with decalcified allogeneic bone implanted into fresh extraction sites in monkeys and dogs

Abstract Sixty-five acrylic resin tooth implants were placed in fresh extraction sockets in six monkeys and sevev dogs. Twenty-one of these implants were surrounded with decalcified allogeneic bone matrix. Clinical, radiologic, fluorescent, and histologic studies indicated that, with the use of DABM grafts, the plastic tooth implants were maintained firm within the experimental period of 22 weeks.

Decalcified allogeneic bone matrix implantation in joint spaces of rats.

Abstract Decalcified allogeneic bone matrix (DABM) grafts were investigated in joint spaces of rats. In the first experiment, DABM grafts were implanted after early postnatal unilateral condylectomies in 1-day-old albino rats. Similarly, in the second experiment, DABM grafts were placed after excision of the fibular heads at the fibulo-femur joints in adult albino rats. The results indicate that DABM grafts act as a center of mandibular growth, do not interfere with growth of the mandible, and form new bone and condyle (new joint) of the same size and shape without resulting in ankylosis. In the controls, in which DABM grafts were not implanted, there was no new bone formation; and joint spaces were filled with fibrous connective tissue and resulted in malgrowth of the mandible in young rats. The clinical, radiologic, and histologic evidence demonstrates the regeneration of new bone in the formation of the heads of fibulae in adult rats. The DABM grafts were resorbed and replaced by new bone and did not seem to evoke an immunologic response.