Systemically and locally administered growth hormone stimulates bone healing in combination with osteopromotive membranes: An experimental study in rats

Abstract

Growth hormone (GH) is known to be of a major importance for longitudinal bone growth, but its local effects on osteogenesis and, thus, regeneration of bone defects are less known. The aim of this investigation was to study whether GH, systemically or locally administered, has any stimulatory effects on local osteogenesis, utilizing standardized, membrane-covered, transosseous defects (5 mm diameter) in mandibles of adult albino rats. The study also addressed the question of whether GH might be a feasible option to further promote bone regeneration and neogenesis in conjunction with expanded polytetrafluoroethylene (e-PTFE) "osteopromotive" membranes (GORE-TEX). Human GH (hGH; 0.2, 2, 20, 200 micrograms/day), bovine GH (bGH; 200 micrograms/day), prolactin (200 micrograms/day) or saline was administered systemically by means of mini-osmotic pumps, implanted subcutaneously at the back of the animal. Healing was analyzed after 2, 3, and 4 weeks. Healing was also studied after local administration, just outside the defects, of hGH (0.2, 2, 20 micrograms/day) via catheters connected to mini-osmotic pumps during 4 weeks. Human GH and bGH stimulated local bone formation compared to saline and prolactin. Bone formation was significantly promoted by systemically administrated hGH, after 3 weeks and at 2 micrograms/day or higher concentrations. Enhanced bone formation was also found after 4 weeks in animals given 0.2, 2 and 20 micrograms/day of hGH locally, compared to local administration of saline. The results show that GH exerts a direct, nonliver mediated effect on bone tissue. Moreover, the study suggests that hGH may be used to stimulate bone healing and formation in conjunction with osteopromotive membranes.