Faculty Bibliography

Bone repair and regeneration is a dynamic process that involves a complex interplay between the (1) ground substance, (2) cells, and (3) milieu. While each constituent is integral to the final product, it is often helpful to consider each component individually. Therefore, we created a two-part review to examine scaffolds and cells' roles in bone tissue engineering. In Part I, we review the myriad of materials use for in vivo bone engineering. In Part II, we discuss the variety cell types (e.g., osteocytes, osteoblasts, osteoclasts, chondrocytes, mesenchymal stem cells, and vasculogenic cells) that are seeded upon or recruited to these scaffolds. In Part III, we discuss the optimization of the microenvironment. The biochemical processes and sequence of events that guide matrix production, cellular activation, and ossification are vital to developing successful bone tissue engineering strategies and are thus succinctly reviewed herein.

Bone repair and regeneration is a dynamic process that involves a complex interplay between the (1) ground substance; (2) cells; and (3) milieu. Each constituent is integral to the final product, but it is often helpful to consider each component individually. While bone tissue engineering has capitalized on a number of breakthrough technologies, one of the most valued advancements is the incorporation of mesenchymal stem cells (SCs) into bone tissue engineering applications. With this new idea, however, came new found problems of guiding SC differentiation. Moreover, investigators are still working to understand which SCs source produces optimal bone formation in vitro and in vivo. Bone marrow-derived mesenchymal SCs and adipose-derived SCs have been researched most extensively, but other SC sources, including dental pulp, blood, umbilical cord blood, epithelial cells reprogrammed to become induced pluripotent SCs, among others, are being investigated. In Part II of this review series, we discuss the variety of cell types (e.g., osteocytes, osteoblasts, osteoclasts, chondrocytes, mesenchymal SCs, and vasculogenic cells) important in bone tissue engineering.

BACKGROUND: : Lipoaspirate centrifugation creates graded density of adipose tissue. High-density fat contains more vasculogenic cytokines and progenitor cells and has greater graft survival than low-density fat. The authors hypothesize that accelerating the bone marrow-derived progenitor cell response to injected low-density fat will improve its graft survival. METHODS: : Male 8-week-old FVB mice (n = 60) were grafted with either high-density (n = 20) or low-density (n = 40) human lipoaspirate. Half of the mice receiving low-density fat (n = 20) were treated with a stem cell mobilizer for 14 days. Grafted fat was harvested at 2 and 10 weeks for analysis. RESULTS: : Low-density fat, low-density fat plus daily AMD3100, and high-density fat had 26 +/- 3.0, 61.2 +/- 7.5, and 49.6 +/- 3.5 percent graft survival, respectively, at 2 weeks (low-density fat versus low-density fat plus daily AMD3100 and low-density fat versus high-density fat, both p < 0.01). Similar results were observed 10 weeks after grafting. Mice receiving low-density fat plus daily AMD3100 had significantly more vasculogenic progenitor cells per cubic centimeter of peripheral blood (p < 0.01) and more new blood vessels (p < 0.01). Both low-density fat plus daily AMD3100 and high-density fat contained more stromal-derived factor-1alpha and vascular endothelial growth factor mRNA/protein. CONCLUSION: : Endogenous progenitor cell mobilization enhances low-density fat neovascularization, increases vasculogenic cytokine expression, and improves graft survival to a level equal to that of high-density fat grafts.

BACKGROUND: Over the last several decades, there have been numerous advances in the fields of aesthetic, craniofacial, and microsurgery. Aesthetic units are no longer "skin deep" but are recognized as being composed of both soft and hard tissue. Indeed, hard tissue must complement the soft tissue to recreate the unit. In addition, revisionary procedures have become necessary to achieve the desired result. Here, the authors integrate seven critical concepts and provide a patient series illustrating their success. METHODS: The authors assembled a two-center, retrospective cohort review of patients who underwent free-tissue transfer of craniofacial defects at the R Adams Cowley Shock Trauma Center and the Johns Hopkins Hospital from 2003 to 2011. Patients were categorized by anatomic location, complications recorded, and illustrative cases selected. RESULTS: A total of 184 patients with craniofacial defects were identified: 79 female and 105 male patients, with a mean age of 44 years. Etiologies included cancer (51.6 percent), trauma (39.1 percent), congenital defects (6.5 percent), and infection (2.7 percent). Free-tissue transfers included 67 fibula, 42 anterolateral thigh, 41 ulnar, 18 groin, 14 iliac, three radius, and one vastus lateralis flaps. The success rate was 97.3 percent and complication rate was 10.8 percent. Secondary procedures included suction lipectomy, dermabrasion, tissue resuspension, and cutaneous flap excision followed by full-thickness skin grafting or tissue rearrangement. CONCLUSIONS: To achieve aesthetically pleasing results in free-flap facial reconstruction, the authors define seven critical concepts to guide the reconstruction: aesthetic-unit appearance, defect boundaries, tissue requirements, vascularized skeletal buttress framework, ample soft-tissue volume, early reconstruction, and local revisional procedures. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

A serious consequence of diabetes mellitus is impaired wound healing, which largely resists treatment. We previously reported that topical application of calreticulin (CRT), an endoplasmic reticulum chaperone protein, markedly enhanced the rate and quality of wound healing in an experimental porcine model of cutaneous repair. Consistent with these in vivo effects, in vitro CRT induced the migration and proliferation of normal human cells critical to the wound healing process. These functions are particularly deficient in poor healing diabetic wounds. Using a genetically engineered diabetic mouse (db/db) in a full-thickness excisional wound healing model, we now show that topical application of CRT induces a statistically significant decrease in the time to complete wound closure compared with untreated wounds by 5.6 days (17.6 vs. 23.2). Quantitative analysis of the wounds shows that CRT increases the rate of reepithelialization at days 7 and 10 and increases the amount of granulation tissue at day 7 persisting to day 14. Furthermore, CRT treatment induces the regrowth of pigmented hair follicles observed on day 28. In vitro, fibroblasts isolated from diabetic compared with wild-type mouse skin and human fibroblasts cultured under hyperglycemic compared with normal glucose conditions proliferate and strongly migrate in response to CRT compared with untreated controls. The in vitro effects of CRT on these functions are consistent with CRT's potent effects on wound healing in the diabetic mouse. These studies implicate CRT as a potential powerful topical therapeutic agent for the treatment of diabetic and other chronic wounds.

Synkinetic movements comprise abnormal involuntary contractions of one or more facial muscle groups which follow the desired contraction of another facial muscle group. They are frequently encountered in patients with long standing facial paralysis and seriously affect their psychological status due to the impairment of their facial appearance, function and emotional expressivity. PATIENTS AND METHODS: Eleven pediatric patients (2 male and 9 female) presenting with post-facial paralysis synkinesis were included in the study. Mean age was 10.3 +/- 4 years and mean denervation time 72.5 months. RESULTS: Patients underwent the following types of treatment: - Cross facial nerve grafting (CFNG) and secondary microcoaptations with botulinum toxin injection which had an improvement of 100% (3 in the 3 grade synkinesis scale) (n = 2). - Cross facial nerve grafting (CFNG) and secondary microcoaptations without botulinum toxin injection which had an improvement of 66%(2 in the 3 grade synkinesis scale) (n = 5). - CFNG and direct muscle neurotization with (n = 2) or without (n = 1) botulinum toxin injection where the improvement was 33%. - Contralateral nasalis muscle myectomy was performed in one patient along with CFNG and secondary microcoaptations which resulted in 66% synkinesis improvement. Biofeedback was invariably undertaken by all patients. Postoperative improvement in eye closure and smile was also noted in the respective cases treated for synkinesis ranging from 25 to 50%, with all patients achieving optimum functional return. CONCLUSION: CFNG with secondary microcoaptations and botulinum toxin injections was found to be a very efficient surgical modality addressing post-facial palsy synkinesis with high improvement in facial function and symmetry. Facial neuromuscular re-education contributes considerably in the treatment.

BACKGROUND: Frontal sinus cranialization is commonly indicated for posterior table fractures with significant comminution, displacement, or cerebrospinal fluid leaks. This study assessed the clinical outcomes of conservative management. METHODS: A 10-year retrospective review of all frontal sinus fractures treated at a level 1 trauma center was performed using medical records and radiographic images. RESULTS: A total of 875 patients with frontal sinus fractures were identified, and 68 had posterior table involvement. Nine died within the first 48 hours from other injuries. The remaining 59 patients constituted the study population. Average follow-up approached 1 year (342 days). The more common mechanisms of injury were blunt interpersonal violence (29 percent) and motor vehicle accidents (27 percent). Concurrent central nervous system injury was common (73 percent), and the average Glasgow Coma Scale score was 12.7. Posterior wall fracture pattern was nondisplaced and noncomminuted in 33 patients (54 percent) and comminuted and/or displaced in 27 (46 percent). Cerebrospinal fluid leak was recorded in 11 patients (19 percent). Conservative management was the more common strategy (78 percent), followed by open reduction and internal fixation with sinus preservation (12 percent), obliteration (8 percent), and cranialization (2 percent). Of the 27 patients with comminuted and/or displaced fractures, 16 (59 percent) underwent conservative management, and 11 (41 percent) underwent surgical management, but only one patient (2 percent) underwent cranialization. There was no incidence of intracranial infection, except for one patient who died from encephalitis secondary to a gunshot wound to the head. CONCLUSION: The vast majority of frontal sinus fractures involving the posterior table, including those with comminution, displacement, or cerebrospinal fluid leaks, can be safely managed without cranialization. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Repair of full thickness defects in the lower eyelid following extirpation of malignant tumors presents a challenge to the reconstructive surgeon. There are several techniques to choose from, depending on the defect's size and location.