Search

The effect of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) on bone healing was examined in calvarial defects in rabbits. Bicortical circular (critical size) defects were prepared in the calvarial bone of 16 rabbits. The defects were closed on the dural side and covered externally with expanded polytetrafluoroethylene membranes to prevent interference with osteogenesis within the defect by the surrounding tissue and to keep the growth factor in place. A single dose of methylcellulose gel (4.4%) with (n = 8) or without rhPDGF-BB (50 micrograms/ml) (n = 8) was applied to the defects, and the bone formation was evaluated after 8 weeks. Healing of defects in both groups was characterized by the presence of newly formed bone along the edges of the original defect and by a central area of fibrous connective tissue. The newly formed bone in the rhPDGF-BB treated defects had a trabecular structure; in contrast, a more compact structure was found in the control defects. In the rhPDGF-BB-treated defects, the bone ingrowth was 51.8 +/- 7.1% compared to 30.5 +/- 3.3% in the control defects. Furthermore, the amount of mineralized tissue was increased 112% in the rhPDGF-BB group. The amount of bone marrow was increased 75% in the rhPDGF-BB-treated defect. The porosity of cortical lamella in the newly formed bone was 84% higher in the rhPDGF-BB-treated defects compared to the control. These results show that administration of a single dose of rhPDGF-BB stimulates bone formation in critical size calvarial defects.

An enhanced formation of bone, dentin, and collagen fibers in periodontal wounds after application of polypeptide growth factors has recently been reported. However, the complex environment in vivo makes it impossible to determine the specific effects of growth factors on various cells involved in the wound-healing process. We have therefore investigated the mitogenic and morphogenic effects of recombinant epidermal growth factor (rEGF), natural platelet-derived growth factor (nPDGF), and natural fibroblast growth factor (nFGF) on periodontal ligament fibroblast-like cells. A cell line was established from rat PDL tissue. The cell line was characterized according to morphology, growth pattern, cytoskeletal proteins, and growth kinetics. The mitogenic effect of growth factors was assessed by incorporation of [3H]thymidine in the cellular DNA for 4 hours. Differences between groups of observations were assessed by the Student t-test. The morphogenic effects of growth factors were described with respect to growth pattern, cell orientation, and cell and nucleus form after a random photographic recording. The fibroblast-like cell type and the non-transformed phenotype of the cell line have been identified by the presence of parameters considered to be characteristic of a normal fibroblast-like cell line. The morphogenic analysis of both experimental and control cultures showed a monolayer of adherent cells with spindle or stellate morphology, a random alignment and round or elongated nuclei. Incorporation of [3H]-thymidine was increased in a dose-dependent manner by all growth factors. Maximal effect on the DNA synthesis was: rEGF, 131%; nPDGF, 274%; and nFGF, 182%.(ABSTRACT TRUNCATED AT 250 WORDS)

Repopulation of the detached root surface by cells from the periodontal ligament (PDL) is a prerequisite for new attachment formation. Stimulation of PDL-cell growth may therefore serve as an essential method to enhance formation of new attachment. Studies have demonstrated that insulin-like growth factor-I (IGF-I) has a mitogenic effect on fibroblasts originating from various connective tissues and cell-lines. Further, human growth hormone (hGH) is known to regulate the plasma concentration of IGF-I and to mediate cellular biological effects. In the present study we examined the effect of IGF-I and hGH on morphology, growth pattern, and DNA synthesis. The expression of IGF-I and hGH receptors on the surface of cultured PDL fibroblasts is also described. A primary fibroblastic cell line was established from rat PDL tissue, and blind, photographic recordings of morphology and growth pattern, as well as incorporation of [3H]thymidine in cellular DNA, was carried out in the presence and absence of IGF-I and hGH. The presence of specific membrane receptors was investigated by binding of [125I]IGF-I and [125I]hGH. The analysis of photographs showed that IGF-I and hGH had no effect on morphology and growth pattern. Incorporation of 3H-thymidine, however, was increased in a dose-dependent manner by IGF-I, whereas hGH alone or in combination with IGF-I produced no dose-dependent response. Maximum effect (% of control) on DNA synthesis was 176% for IGF-I and 91% for hGH.(ABSTRACT TRUNCATED AT 250 WORDS)