An improved freeze-dried PRP-coated biodegradable material suitable for connective tissue regenerative therapy.

We previously published an investigation indicating freeze-dried platelet-rich plasma (PRP)-coated polyglactin mesh was a promising wound-dressing material. However, one of its disadvantages was the inflammatory nature due to degradation of the polyglactin. Therefore, in this study, we investigated the use of a collagen sponge as the carrier for PRP. When implanted subcutaneously in nude mice, the PRP-coated sponge alone rapidly induced angiogenesis and infiltration of surrounding connective tissue without inducing appreciable inflammation. Moreover, addition of periosteal fibroblastic cells substantially augmented the angiogenic response. With in vitro studies, the PRP-coated sponge provided various major growth factors at high levels to stimulate the proliferation of cells cultured on plastic dishes, but did not stimulate the proliferation of cells inoculated into the PRP-coated sponge. Cells were embedded in the fibrin mesh and maintained their spherical shape without stretching. The atomic force microscopic analysis demonstrated that the fibrin gel formed on the PRP-coated sponge was much softer (approx. 22 kPa) than the cross-linked collagen that formed the sponge base (appox. 1.9 MPa). Because insoluble matrices have recently and increasingly been considered important regulatory factors of cellular behavior, as are soluble growth factors, it is suggested that this soft fibrin mesh possibly suppresses cell survival. Overall, our investigation has successfully demonstrated improved wound-healing and regenerative potential of the PRP-coated mesh by combining it with the collagen sponge. In the clinical setting, this PRP-coated collagen sponge is a promising material for connective tissue regenerative therapy, such as periodontal therapy, burn victim treatment and in cosmetic or plastic surgery.