Thymosin β4 administration enhances fracture healing in mice

Thymosin β₄ (Tβ₄) is a regenerative peptide that we hypothesized would promote healing of fractured bone. Mice received a bilateral fibular osteotomy and were given i.p. injections of either Tβ₄ (6 mg/kg) or saline. Calluses from saline‐ and Tβ₄‐treated mice were analyzed for: (1) biomechanical properties and (2) composition using micro‐computed tomography (µCT) and histomorphometry. Biomechanical analysis showed that Tβ₄‐treated calluses had a 41% increase in peak force to failure (p < 0.01) and were approximately 25% stiffer (p < 0.05) than saline‐treated controls. µCT analysis at 21 days post‐fracture showed that the fractional volume of new mineralized tissue and new highly mineralized tissue were respectively 18% and 26% greater in calluses from Tβ₄‐treated mice compared to controls (p < 0.01; p < 0.05, respectively). Histomorphometry complemented the µCT data; at 21 days post‐fracture, Tβ₄‐treated calluses were almost 23% smaller (p < 0.05), had nearly 47% less old cortical bone (p < 0.05) and had a 31% increase in new trabecular bone area/total callus area fraction compared with controls (p < 0.05). Our finding of enhanced biomechanical properties of fractures in mice treated with Tβ₄ provides novel evidence of the therapeutic potential of this peptide for treating bone fractures. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1277–1282, 2014.