Enhanced biologic activity in human induced membranes may occur for longer than reported
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Results presented at the Limb Lengthening and Reconstruction Society Annual Scientific Meeting showed enhanced biologic activity in human induced membranes for bone defects persists for longer than previously suggested from results in animal models.
“Our study demonstrates a very broad range of many osteogenic and chondrogenic growth factors have increased activity, and induced membranes continue to exhibit significantly increased levels for 16 to 20 weeks, and perhaps longer,” Kevin Tetsworth, MD, FRACS, co-author of the study, told Healio.com/Orthopedics. “The good news is that surgeons do not need to rush back in at 3 to 4 weeks to realize the biological benefits associated with the induced membrane and can instead wait until the soft tissues have fully recovered from the initial injury or first-stage surgery for infection.”
Response of human induced membranes
Tetsworth, Vadia Glatt, PhD, and colleagues harvested membranes from over 50 clinical cases of bone defects managed using the Masquelet technique with the second stage performed between 4 and 20 weeks. Glatt led the research team in conducting the preliminary comparison of biopsies of human induced membranes (n=16) and control samples (n=16) from femoral and tibial defects. Researchers used quantitative reverse transcription polymerase chain reaction to perform gene expression analysis of relevant growth factors for bone repair. Researchers used different samples for histology and stained with haematoxylin and eosin, while proteins with osteogenic and angiogenic potential were localized using immunohistochemistry.
Haematoxylin and eosin staining revealed bone-like tissue formed on the outer layer of the induced membranes, according to results. Although CD68 was homogenously expressed within the membranes, researchers found it was mostly absent in the fascia controls, while both fascia and membrane had vascular endothelial growth factor consistently expressed in blood vessels. Compared to fascia, quantitative analysis showed induced membranes had almost triple the number of active cell nuclei and double the average cell density. Membranes also had significantly upregulated growth factors relevant to bone repair vs. fascia, according to the gene expression analyses.
Results showed femurs had significantly upregulated cell proliferation, cell-cell and cell-matrix adhesion, chemokines, interleukins and platelet activation genes vs. tibias, which had more down-regulated genes. However, both groups had similar growth factors specific to bone mineral metabolism and skeletal development, according to researchers. Glatt and colleagues also found femoral membranes were more cellular and vascular at earlier time points, but tibial biologic activity later equaled that seen in femoral specimens.
“The response differed in femurs and tibias, with an even more delayed response noted in tibial specimens, as might be expected,” Glatt told Healio.com/Orthopedics. “For femoral defects, the membranes were most active between 8 to 12 weeks, with the peak at 10 weeks. For tibial defects, the membranes were most active between 12 to 16 weeks, with the peak at 14 weeks.”
Future research
While gene expression studies may indicate which genes are more active and may identify potentially important candidates in the bone healing response, Tetsworth noted it still needs to be determined if “the observed increase in RNA actually results in an increase in the production of the relevant growth factors associated.”
“Further analysis of the remaining biopsies will be adequate to allow us to compare not only femoral specimens to tibial specimens, but also compare men to women, smokers to non-smokers, young patients to older patients and more,” Tetsworth said. “This should be extremely useful in optimizing the indications for the procedure, for further refining the surgical technique and for maximizing the benefits of the induced membrane response clinically.” – by Casey Tingle
Reference:
Tetsworth K, et al. Biological activity of human-induced membranes: Temporal differences between femoral and tibial sites. Presented at: Limb Lengthening and Reconstruction Society Annual Scientific Meeting; July 19-20, 2019; Boston.
Disclosure: Tetsworth reports he is a paid presenter or speaker for 4Web Medical, Smith & Nephew and Stryker; is a board or committee member for the Australasian Limb Lengthening and Reconstruction Society; has stock or stock options with BioConsultancy Pty Ltd.; is on the editorial or governing board for the Journal of Limb Lengthening and Reconstruction; and is a paid consultant for Smith & Nephew and Stryker. Glatt reports no relevant financial disclosures.