Regenerative engineering of long bones using the small molecule forskolin

Abstract

Bone grafting procedures have become increasingly common in the United States, with approximately 500,000 cases occurring each year at a societal cost exceeding $2.4 billion. Recombinant human bone morphogenetic proteins (rhBMPs) are therapeutic agents that have been widely used by orthopedic surgeons to stimulate bone tissue formation alone and when paired with biomaterials. However, significant limitations such as immunogenicity, high production cost, and ectopic bone growth from these therapies remain. Therefore, efforts have been made to discover and repurpose osteoinductive small-molecule therapeutics to promote bone regeneration. Previously, we have demonstrated that a single-dose treatment with the small-molecule forskolin for just 24 h induces osteogenic differentiation of rabbit bone marrow–derived stem cells in vitro, while mitigating adverse side effects attributed with prolonged small-molecule treatment schemes. In this study, we engineered a composite fibrin–PLGA [poly(lactide-co-glycolide)]-sintered microsphere scaffold for the localized, short-term delivery of the osteoinductive small molecule, forskolin. In vitro characterization studies showed that forskolin released out of the fibrin gel within the first 24 h and retained its bioactivity toward osteogenic differentiation of bone marrow–derived stem cells. The forskolin-loaded fibrin–PLGA scaffold was also able to guide bone formation in a 3-mo rabbit radial critical-sized defect model comparable to recombinant human bone morphogenetic protein-2 (rhBMP-2) treatment, as demonstrated through histological and mechanical evaluation, with minimal systemic off-target side effects. Together, these results demonstrate the successful application of an innovative small-molecule treatment approach within long bone critical-sized defects.

The Osteocyte with SB216763-Activated Canonical Wnt Signaling Constructs a Multifunctional 4D Intelligent Osteogenic Module

“…A highlight of this study is the identification of a safe, usable small-molecule drug for activating Wnt signaling in osteocytes. In bone tissue engineering, small-molecule drugs offer unique advantages, including precise control over drug dosage, convenient modulation of treatment time windows, and a lower risk of side effects [ 28 , 29 ]. GSK-3 inhibitors, by blocking the activity of GSK-3 and preventing β-catenin degradation, activate the Wnt/β-catenin signaling pathway [ 18 ].…”

The Use of Small-Molecule Compounds for Cell Adhesion and Migration in Regenerative Medicine

“…Various forms of natural and synthetic scaffolds (e.g., hydrogels, ceramics, fibers, composites, etc.) have been coupled with small molecules to aid in the promotion of osteogenic signaling and sustained release, while also providing a matrix for osteoblast or stem cell adherence at defects sites [ 44 ]. Commonly used polymeric scaffolding materials like PLGA, polyurethane, calcium phosphate, and HA microspheres have all exhibited success in the delivery and sustained release of small molecules in vivo.…”