New developments in pediatric plastic surgery research

Craniofacial surgery, from past pioneers to future promise

OBJECTIVES

As a surgical subspecialty devoted to restoration of normal facial and calvarial anatomy, craniofacial surgeons must navigate the balance between pathologic states of bone excess and bone deficit. While current techniques employed take root in lessons learned from the success and failure of early pioneers, craniofacial surgery continues to evolve, and novel modalities will undoubtedly arise integrating past and present experiences with future promise to effectively treat craniofacial disorders.

METHODS

This review provides an overview of current approaches in craniofacial surgery for treating states of bone excess and deficit, recent advances in our understanding of the molecular and cellular processes underlying craniosynostosis, a pathological state of bone excess, and current research efforts in cellular-based therapies for bone regeneration.

RESULTS

The surgical treatment of bone excess and deficit has evolved to improve both the functional and morphological outcomes of affected patients. Recent progress in elucidating the molecular and cellular mechanisms governing bone formation will be instrumental for developing improved therapies for the treatment of pathological states of bone excess and deficit.

CONCLUSIONS

While significant advances have been achieved in craniofacial surgery, improved strategies for addressing states of bone excess and bone deficit in the craniofacial region are needed. Investigations on the biomolecular events involved in craniosynostosis and cellular-based bone tissue engineering may soon be added to the armamentarium of surgeons treating craniofacial dysmorphologies.

Tissue engineering solutions for cleft palates

PURPOSE

Clefts of the lip and palate are the most prevalent congenital craniofacial birth defect in humans. The developing field of tissue engineering is considered for the management of clefts of the lip and palate.

MATERIALS AND METHODS

A review of the literature was carried out by using electronic databases (such as PubMed and ISI Web of Science) to search topics including "cleft palate," "tissue engineering," "bone engineering," "palate engineering," and "alveolar bone grafting." To reflect current practice and research, these searches were limited primarily to articles published after the year 2000.

RESULTS

Current approaches for the treatment of clefts of the lip and palate include surgery and bone grafts; however, there are limitations associated with these therapies. Tissue engineering strategies, particularly alveolar bone engineering and soft tissue engineering, may provide clinicians with new alternatives. The application of these emerging technologies to a pediatric population must be well considered.

CONCLUSIONS

A tissue engineering approach may be a useful alternative for the treatment of cleft palates as it mitigates the concerns of donor site morbidity as well as provides additional options including scaffold implantation and growth factor delivery.

Uniaxial mechanical strain: an in vitro correlate to distraction osteogenesis

BACKGROUND

Distraction osteogenesis is a valuable clinical tool; however the molecular mechanisms governing successful distraction remain unknown. We have used a uniaxial in vitro strain device to simulate the uniaxial mechanical environment of the interfragmentary distraction gap.

MATERIALS AND METHODS

Using the Flexcell system, normal human osteoblasts were subjected to different levels of cyclical uniaxial mechanical strain. Cellular morphology, proliferation, migration, and the expression of angiogenic (vascular endothelial growth factor [VEGF] and fibroblast growth factor-2 [FGF-2]) and osteogenic (osteonectin, osteopontin, and osteocalcin) proteins and extracellular matrix molecules (collagen IalphaII) were analyzed in response to uniaxial cyclic strain.

RESULTS

Osteoblasts exposed to strain assumed a fusiform spindle-shaped morphology aligning parallel to the axis of uniaxial strain and osteoblasts exposed to strain or conditioned media had a 3-fold increase in proliferation. Osteoblast migration was maximal (5-fold) in response to 9% strain. Angiogenic cytokine, VEGF, and FGF-2, increased 32-fold and 2.6-fold (P < 0.05), respectively. Osteoblasts expressed greater amounts of osteonectin, osteopontin, and osteocalcin (2.1-fold, 1.8-fold, 1.5-fold respectively, P < 0.01) at lower levels of strain (3%). Bone morphogenic protein-2 production increased maximally at 9% strain (1.6-fold, P < 0.01). Collagen I expression increased 13-, 66-, and 153-fold in response to 3, 6, and 9% strain, respectively.

CONCLUSIONS

Uniaxial cyclic strain using the Flexcell device under appropriate strain parameters provides a novel in vitro model that induces osteoblast cellular and molecular expression patterns that simulate patterns observed in the in vivo distraction gap.

Recent developments in tissue engineering and regenerative medicine

PURPOSE OF REVIEW

Currently, patients suffering from diseased and injured organs are treated with transplanted organs or cells. There is, however, a severe shortage of donor tissues and organs that is worsening yearly given the aging population. This paper reviews recent advances that have occurred in regenerative medicine and describes applications of new technologies to treat diseased or damaged organs and tissues.

RECENT FINDINGS

Most current strategies for tissue engineering depend upon a sample of autologous cells from the diseased organ of the patient. Biopsies from patients with extensive end-stage organ failure, however, may not yield enough normal cells. In these situations, stem cells are envisioned as being an alternative source. Stem cells can be derived from discarded human embryos (human embryonic stem cells), from fetal tissue or from adult sources (bone marrow, fat, skin). Therapeutic cloning offers a potentially limitless source of cells for tissue engineering applications.

SUMMARY

Increasingly, scientists in the fields of regenerative medicine and tissue engineering have applied the principles of cell transplantation, material science and bioengineering to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues.