Investigation into the release of bioactive recombinant human growth hormone from normal and low-viscosity poly(methylmethacrylate) bone cements
✍ Scribed by Goodwin, C. J. ;Braden, M. ;Downes, S. ;Marshall, N.J.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 264 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0021-9304
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✦ Synopsis
Previous studies showed that recombinant human growth of their cytotoxicity. The major fraction of the bioactivity was hormone (hGH) released from hormone-loaded poly(methyl-released from both of the PMMA cements during the first methacrylate) (PMMA) cement stimulated osteoid formation 24 h, but the hormone remained detectable in eluates colin a rabbit model. Local delivery of hGH from cemented hip lected after 36 days of elution. Comparison of the bio-and arthroplasties may thereby provide a means of reducing the immunoactivity of the hGH released showed that the ratio problem of aseptic loosening. We have investigated two dif-of these two activities (i.e., the B:I ratio) was constant over this ferent formulations of PMMA as delivery systems for bioac-time period. However in parallel studies in which hormonetive hGH. The bioactivity of the hormone release in vitro was loaded discs were stored under dry conditions prior to elumonitored with an eluted stain assay (ESTA). The hGH was tion, we found that the B:I ratio then declined markedly. also measured by an immunoassay, which provides an alter-This suggests that fully hydrated conditions, such as when native assessment of structural integrity of the hormone re-the discs are bathed in assay medium, are necessary to mainleased. In addition, we adapted the ESTA bioassay to assess tain the bioactivity of the hGH. Both cements released only the in vitro cytotoxicity of the cements. Using unloaded ce-ȁ1% of the hormone originally incorporated, but the hGH ments, the undiluted eluates from both types of PMMA concentration which accumulated in the eluates were high proved cytotoxic. This cytotoxicity could be diluted out, and in physiologic terms (ȁ1000 mU/L). ᮊ 1997 John Wiley & the procedure allowed us to measure the bioactivity of hGH Sons, Inc.
in the eluates from hormone-loaded cements independent