Growth factor release by vesicular phospholipid gels: in-vitro results and application for rotator cuff repair in a rat model

Abstract

BackgroundBiological augmentation of rotator cuff repair is of growing interest to improve biomechanical properties and prevent re-tearing. But intraoperative single shot growth factor application appears not sufficient to provide healing support in the physiologic growth factor expression peaks. The purpose of this study was to establish a sustained release of granulocyte-colony stimulating factor (G-CSF) from injectable vesicular phospholipid gels (VPGs) in vitro and to examine biocompatibility and influence on histology and biomechanical behavior of G-CSF loaded VPGs in a chronic supraspinatus tear rat model.MethodsG-CSF loaded VPGs were produced by dual asymmetric centrifugation. In vitro the integrity, stability and release rate were analyzed. In vivo supraspinatus tendons of 60 rats were detached and after 3 weeks a transosseous refixation with G-CSF loaded VPGs augmentation (n = 15; control, placebo, 1 and 10 μg G-CSF/d) was performed. 6 weeks postoperatively the healing site was analyzed histologically (n = 9; H&E by modified MOVIN score/Collagen I/III) and biomechanically (n = 6).ResultsIn vitro testing revealed stable proteins after centrifugation and a continuous G-CSF release of up to 4 weeks. Placebo VPGs showed histologically no negative side effects on the healing process. Histologically in vivo testing demonstrated significant advantages for G-CSF 1 μg/d but not for G-CSF 10 μg/d in Collagen III content (p = 0.035) and a higher Collagen I/III ratio compared to the other groups. Biomechanically G-CSF 1 μg/d revealed a significant higher load to failure ratio (p = 0.020) compared to control but no significant differences in stiffness.ConclusionsBy use of VPGs a continuous growth factor release could be obtained in vitro. The in vivo results demonstrate an improvement of immunohistology and biomechanical properties with a low dose G-CSF application via VPG. The VPG itself was well tolerated and had no negative influence on the healing behavior. Due to the favorable properties (highly adhesive, injectable, biocompatible) VPGs are a very interesting option for biologic augmentation. The study may serve as basis for further research in growth factor application models.

Advances in biologic augmentation for rotator cuff repair

“…Low concentrations of G‐CSF–containing VPGs demonstrated a superior load‐to‐failure ratio when compared with the control group (but no improvement in stiffness), as well as lowered levels of collagen III content and improved collagen I/III ratio. In addition, placebo‐loaded VPGs did not negatively affect the healing process in any way when compared to the control, demonstrating that this delivery method is well tolerated in vivo …”

Dual Centrifugation - A Novel “in-vial” Liposome Processing Technique

“…In addition, since the ZY-beads are heavier and available in very small diameters, the number of beads can be increased to gain the aimed bead-bead interactions needed for efficient size reduction, whereas keeping the bead volume constant. However, successful preparation of liposomes by DC was also demonstrated without any mixing aid present [13,33,34].…”

“…The gentleness of the DC method opens new applications for VPGs and liposomes, namely, to incorporate highly sensitive drugs such as proteins, i.e., References [13,28,34]. As regards to the lack of a cooling unit, the short-run cycles are a common way to control the temperature rise, and Tian et al [13] made 1.5 minutes of centrifugation steps interrupted by a cooling at 2-8°C every 6-8 runs, which gave a successful incorporation of model protein erythropoietin (EPO) into the VPGs.…”

“…Moreover, the majority of the publications concern the entrapment of heat labile peptides and proteins. These proteins and peptides have been entrapped into VPGs and liposomes for different routes of administration: oral [21,30,31], nasal [33], and iv injection [17,20,28,29], or as VPG-depot formulations [13,34,48]. Various organs were targeted as therapeutic sites: cancerous tissue [10,26,35], the central nervous system (CNS) and brain [28,32,33], liver [31], and skin [18,19].…”

Effectiveness of Biologic Factors in Shoulder Disorders

“…Administration of GDF-5 in muscle-derived stem cell implantation in an in vitro tendon healing appeared to improve the outcome of tendon repair [116]. Furthermore, sustained release of granulocyte-colony stimulating factor (G-CSF) ensured via the use of vesicular phospholipid gels (VPGs) showed some promising findings in vitro [117]. More recent data, identified gene expression as a new potential direction, as demonstrated by an in vitro study that identified sry-type homeobox protein-9 (SOX-9) and regulator of G-protein signaling-10 (RGS-10) as targets for gene therapy [118].…”