Concentrated growth factor in combination with insulin for improving type 2 diabetes mellitus alveolar bone regeneration: a pilot study

To compare the cumulative release concentrations of transforming growth factor-β1 (TGF-β1), bone morphogenetic protein-2 (BMP-2), insulin-like growth factor-1 (IGF-1) and insulin in concentrated growth factor (CGF) biomaterials derived from healthy and type 2 diabetes mellitus (T2DM) Sprague–Dawley (SD) rats, and to evaluate the feasibility of CGF in combination with insulin for improving alveolar bone regeneration in T2DM rats. 54 SD rats were included in the present study. 20 were fed a normal diet; 34 received a high-fat/high-sugar diet and intraperitoneal STZ (30 mg/kg) to induce T2DM. Blood from 8 healthy rats (inferior vena cava) was used to prepare SD-CGF. Blood from 16 T2DM rats was used to prepare T2DM-CGF; for 8 of the latter, insulin was added before centrifugation to prepare T2DM-In-CGF. From each group, 6 gel samples were analyzed by ELISA for cumulative release of TGF-β1, BMP-2, IGF-1, and insulin at 0, 1, 7, 14, 21, and 28 days. The remaining gels were implanted. The remaining rats (healthy and T2DM) were randomly divided into five groups (n = 6): T2DM-In-CGF (CGF with insulin in T2DM), T2DM-CGF (CGF alone in T2DM), SD-CGF (CGF in healthy), T2DM-BC (T2DM blank), and SD-BC (healthy blank). After bilateral maxillary first molar extraction, the corresponding implants were placed while blank control with blood clot filling. Six weeks later, rats were sacrificed and alveolar bone specimens were HE-stained. Bone regeneration was observed and the mean new bone area percentage was calculated and compared. Over 28 days, TGF‑β1 release did not differ among groups. BMP‑2 showed higher early release in the diabetic groups at days 1 and 7, while IGF‑1 was significantly higher in SD‑CGF at days 0, 14, and 28; at day 21, SD‑CGF was higher than T2DM‑In‑CGF but not T2DM‑CGF. Insulin release was overall highest in T2DM‑In‑CGF and lowest in T2DM‑CGF, with SD‑CGF intermediate; at day 7, SD‑CGF was slightly but not significantly higher than T2DM‑In‑CGF (p = 1.000). After 6 weeks, all gel‑implanted groups exhibited superior bone regeneration compared with their respective blank controls. New bone area was greatest in SD‑CGF and T2DM‑In‑CGF, which did not differ significantly (p = 1.000). Both groups had significantly greater new bone formation than T2DM‑CGF (p = 0.003 and p = 0.038, respectively) and than both blank controls (all p < 0.001). T2DM‑CGF was significantly higher than T2DM‑BC (p < 0.001) but not significantly different from SD‑BC (p = 0.100). No significant difference was found between the two blank controls (p = 0.436). CGF derived from T2DM rats exhibits altered growth factor release kinetics, most notably mean IGF‑1 levels persistently lower, with significant pairwise reductions mainly at days 0, 14, and 28. Exogenous insulin can be effectively incorporated into the CGF matrix and released in a sustained manner. In vivo, insulin‑supplemented diabetic CGF achieves alveolar bone regeneration comparable to that of healthy CGF and significantly outperforms unsupplemented diabetic CGF. These findings indicate that insulin supplementation may restore the impaired regenerative capacity of diabetic CGF and represents a promising strategy for enhancing bone healing in T2DM, although further studies are warranted to elucidate the underlying mechanisms and optimize the supplementation protocol.