Acceptability and feasibility of insect consumption among pregnant women in Liberia.

Maternity waiting homes (MWHs) in Liberia promote facility-based delivery to reduce maternal mortality. However, women often must bring their own food and supplies to MWHs, which makes food insecurity a barrier to the utilisation of MWHs. Consumption of edible indigenous insects is a common practice and has notable nutritional benefits but has not been studied in Liberia as a potential solution to food insecurity at MWHs. The purpose of this study is to (a) examine the acceptability of insect consumption in the context of Liberian beliefs, (b) identify species commonly consumed by pregnant women in Liberia, and (c) examine the feasibility of harvesting insects as food and income generation for women staying at MWHs. Focus groups were conducted at 18 healthcare facilities in Liberia. Participants included chiefs, community leaders, women of reproductive age, traditional birth attendants, women staying at MWHs, and male partners. Focus group participants identified many different species of insects consumed by pregnant women in the community as well as the perceived health impacts of insect consumption. They also described their own experiences with insect hunting and consumption and the perceived marketability of insects, particularly palm weevil larvae. The results of these discussions demonstrate that insect consumption is an acceptable practice for pregnant women in rural Liberia. These findings suggest that it is feasible to further explore the use of palm weevil larvae as dietary supplementation and income generation for women staying at MWHs in Liberia.

Nonvascularized Bone Graft Reconstruction of the Irradiated Murine Mandible: An Analogue of Clinical Head and Neck Cancer Treatment.

Nonvascularized bone grafts (NBGs) represent a practical method of mandibular reconstruction that is precluded in head and neck cancer patients by the destructive effects of radiotherapy. Advances in tissue-engineering may restore NBGs as a viable surgical technique, but expeditious translation demands a small-animal model that approximates clinical practice. This study establishes a murine model of irradiated mandibular reconstruction using a segmental iliac crest NBG for the investigation of imperative bone healing strategies. Twenty-seven male isogenic Lewis rats were divided into 2 groups; control bone graft and irradiated bone graft (XBG). Additional Lewis rats served as graft donors. The XBG group was administered a fractionated dose of 35Gy. All rats underwent reconstruction of a segmental, critical-sized defect of the left hemi-mandible with a 5 mm NBG from the iliac crest, secured by a custom radiolucent plate. Following a 60-day recovery period, hemi-mandibles were evaluated for bony union, bone mineralization, and biomechanical strength (P < 0.05). Bony union rates were significantly reduced in the XBG group (42%) compared with controls (80%). Mandibles in the XBG group further demonstrated substantial radiation injury through significant reductions in all metrics of bone mineralization and biomechanical strength. These observations are consistent with the clinical sequelae of radiotherapy that limit NBGs to nonirradiated patients. This investigation provides a clinically relevant, quantitative model in which innovations in tissue engineering may be evaluated in the setting of radiotherapy to ultimately provide the advantages of NBGs to head and neck cancer patients and reconstructive surgeons.

Abnormal type I collagen post-translational modification and crosslinking in a cyclophilin B KO mouse model of recessive osteogenesis imperfecta.

Cyclophilin B (CyPB), encoded by PPIB, is an ER-resident peptidyl-prolyl cis-trans isomerase (PPIase) that functions independently and as a component of the collagen prolyl 3-hydroxylation complex. CyPB is proposed to be the major PPIase catalyzing the rate-limiting step in collagen folding. Mutations in PPIB cause recessively inherited osteogenesis imperfecta type IX, a moderately severe to lethal bone dysplasia. To investigate the role of CyPB in collagen folding and post-translational modifications, we generated Ppib-/- mice that recapitulate the OI phenotype. Knock-out (KO) mice are small, with reduced femoral areal bone mineral density (aBMD), bone volume per total volume (BV/TV) and mechanical properties, as well as increased femoral brittleness. Ppib transcripts are absent in skin, fibroblasts, femora and calvarial osteoblasts, and CyPB is absent from KO osteoblasts and fibroblasts on western blots. Only residual (2-11%) collagen prolyl 3-hydroxylation is detectable in KO cells and tissues. Collagen folds more slowly in the absence of CyPB, supporting its rate-limiting role in folding. However, treatment of KO cells with cyclosporine A causes further delay in folding, indicating the potential existence of another collagen PPIase. We confirmed and extended the reported role of CyPB in supporting collagen lysyl hydroxylase (LH1) activity. Ppib-/- fibroblast and osteoblast collagen has normal total lysyl hydroxylation, while increased collagen diglycosylation is observed. Liquid chromatography/mass spectrometry (LC/MS) analysis of bone and osteoblast type I collagen revealed site-specific alterations of helical lysine hydroxylation, in particular, significantly reduced hydroxylation of helical crosslinking residue K87. Consequently, underhydroxylated forms of di- and trivalent crosslinks are strikingly increased in KO bone, leading to increased total crosslinks and decreased helical hydroxylysine- to lysine-derived crosslink ratios. The altered crosslink pattern was associated with decreased collagen deposition into matrix in culture, altered fibril structure in tissue, and reduced bone strength. These studies demonstrate novel consequences of the indirect regulatory effect of CyPB on collagen hydroxylation, impacting collagen glycosylation, crosslinking and fibrillogenesis, which contribute to maintaining bone mechanical properties.

A novel loss-of-function mutation in Npr2 clarifies primary role in female reproduction and reveals a potential therapy for acromesomelic dysplasia, Maroteaux type.

We discovered a new spontaneous mutant allele of Npr2 named peewee (pwe) that exhibits severe disproportionate dwarfism and female infertility. The pwe phenotype is caused by a four base-pair deletion in exon 3 that generates a premature stop codon at codon 313 (L313X). The Npr2(pwe/pwe) mouse is a model for the human skeletal dysplasia acromesomelic dysplasia, Maroteaux type (AMDM). We conducted a thorough analysis of the female reproductive tract and report that the primary cause of Npr2(pwe/pwe) female infertility is premature oocyte meiotic resumption, while the pituitary and uterus appear to be normal. Npr2 is expressed in chondrocytes and osteoblasts. We determined that the loss of Npr2 causes a reduction in the hypertrophic and proliferative zones of the growth plate, but mineralization of skeletal elements is normal. Mutant tibiae have increased levels of the activated form of ERK1/2, consistent with the idea that natriuretic peptide receptor type 2 (NPR2) signaling inhibits the activation of the MEK/ERK mitogen activated protein kinase pathway. Treatment of fetal tibiae explants with mitogen activated protein kinase 1 and 2 inhibitors U0126 and PD325901 rescues the Npr2(pwe/pwe) growth defect, providing a promising foundation for skeletal dysplasia therapeutics.

Characterization of bone microstructure using photoacoustic spectrum analysis.

Osteoporosis is a progressive bone disease that is characterized by a decrease in bone mass and the deterioration in bone microarchitecture. This study investigates the feasibility of characterizing bone microstructure by analyzing the frequency spectrum of the photoacoustic (PA) signal from the bone. Modeling and numerical simulation of PA signal were performed on trabecular bone simulations and CT scans with different trabecular thicknesses. The resulting quasi-linear photoacoustic spectra were fittted by linear regression, from which the spectral parameter slope was quantified. The simulation based on two different models both demonstrate that bone specimens with thinner trabecular thicknesses have higher slope. Experiment on osteoporotic rat femoral heads with different mineral content was conducted. The finding from the experiment was in good agreement with the simulation, demonstrating that the frequency-domain analysis of PA signals can provide an objective assessment of bone microstructure and deterioration. Considering that PA measurement is non-ionizing, non-invasive, and has sufficient penetration in both calcified and non-calcified tissues, this new bone evaluation method based on photoacoustic spectral analysis holds potential for clinical management of osteoporosis and other bone diseases.

Bone assessment via thermal photo-acoustic measurements.

The feasibility of an innovative biomedical diagnostic technique, thermal photo-acoustic (TPA) measurement, for non-ionizing and non-invasive assessment of bone health is investigated. Unlike conventional photo-acoustic PA methods that are mostly focused on the measurement of absolute signal intensity, TPA targets the change in PA signal intensity as a function of the sample temperature, i.e., the temperature-dependent Grueneisen parameter that is closely relevant to the chemical and molecular properties in the sample. Based on the differentiation measurement, the results from TPA technique are less susceptible to the variations associated with sample and system, and could be quantified with improved accurately. Due to the fact that the PA signal intensity from organic components such as blood changes faster than that from non-organic mineral under the same modulation of temperature, TPA measurement is able to objectively evaluate bone mineral density (BMD) and its loss as a result of osteoporosis. In an experiment on well-established rat models of bone loss and preservation, PA measurements of rat tibia bones were conducted over a temperature range from 37°C to 44°C. The slope of PA signal intensity verses temperature was quantified for each specimen. The comparison among three groups of specimens with different BMD shows that bones with lower BMD have higher slopes, demonstrating the potential of the proposed TPA technique in future clinical management of osteoporosis.

A case series study on the effect of Ebola on facility-based deliveries in rural Liberia.

BACKGROUND: As communities' fears of Ebola virus disease (EVD) in West Africa exacerbate and their trust in healthcare providers diminishes, EVD has the potential to reverse the recent progress made in promoting facility-based delivery. Using retrospective data from a study focused on maternal and newborn health, this analysis examined the influence of EVD on the use of facility-based maternity care in Bong Country, Liberia, which shares a boarder with Sierra Leone - near the epicenter of the outbreak. METHODS: Using a case series design, retrospective data from logbooks were collected at 12 study sites in one county. These data were then analyzed to determine women's use of facility-based maternity care between January 2012 and October 2014. The primary outcome was the number of facility-based deliveries over time. The first suspected case of EVD in Bong County was reported on June 30, 2014. Heat maps were generated and the number of deliveries was normalized to the average number of deliveries during the full 12 months before the EVD outbreak (March 2013 - February 2014). RESULTS: Prior to the EVD outbreak, facility-based deliveries steadily increased in Bong County reaching an all-time high of over 500 per month at study sites in the first half of 2014 - indicating Liberia was making inroads in normalizing institutional maternal healthcare. However, as reports of EVD escalated, facility-based deliveries decreased to a low of 113 in August 2014. CONCLUSION: Ebola virus disease has negatively impacted the use of facility-based maternity services, placing childbearing women at increased risk for morbidity and death.

Texting From the Bush: Data Collection Using SMS Text Messaging in Areas of Low Network Coverage From Low-Literacy Providers.

Mobile health technology, specifically Short Message Service (SMS), provides a low-cost medium to transmit data in real time. SMS has been used for data collection by highly literate and educated health care workers in low-resource countries; however, no previous studies have evaluated implementation of an SMS intervention by low-literacy providers. The Liberian Ministry of Health and Social Welfare identified a lack of accurate data on the number of pregnancies from rural areas. To capture these data from 11 rural communities in Liberia, 66 low-literate traditional midwives and 15 high-literate certified midwives were trained to report data via SMS. Data were reported via a 9-digit code sent from Java-based mobile phones. Study aims included determining the following components of SMS transmission: success rate, accuracy, predictors of successful transmission, and acceptance. Success rate of SMS transmission was significantly higher for certified midwives than for traditional midwives. The error rate was significantly higher for traditional midwives than for certified midwives. Years of education was the only predictor of successful SMS transmission. Traditional midwives and certified midwives accepted the intervention, although certified midwives found it easier to use. Certified midwives performed significantly better than did traditional midwives. SMS texting interventions should be targeted to health care workers with higher rates of literacy.

Comparison of quality, birth outcomes, and service utilization between health facilities with and without maternity waiting homes in Liberia.

OBJECTIVE: 1) To assess the quality of health facilities associated with functional Maternity Waiting Homes and health facilities without functional maternity waiting homes in Liberia. 2) To examine birth outcomes and care utilization amongst health facilities with and without functional maternity waiting homes in Liberia. DESIGN: Secondary analysis design using data from a facility capacity checklist and Liberia's Health Management Information System. SETTING: 71 health facilities associated with functional maternity waiting homes and 14 health facilities without functional maternity waiting homes across 14 counties of Liberia. PARTICIPANTS: No human participants were used in this study. METHODS: Independent t-test, Pearson chi-square test, and logistic regression were performed to assess quality, birth outcomes, and service utilization between health facilities with and without functional maternity waiting homes. FINDINGS: The overall health facility quality was not significantly different between health facilities associated with functional maternity waiting homes and those without. However, health facilities with functional maternity waiting homes had better infection control with the presence of soap and sharps boxes. Health facilities with functional maternity waiting homes were also more likely to have parenteral oxytocic drugs and were better able to perform assisted vaginal deliveries. The presence of functional maternity waiting homes were not significantly associated with health facility quality, birth outcomes, or care utilization. CONCLUSION AND IMPLICATIONS: Health facilities with functional MWHs were better prepared to prevent infection and manage complicated deliveries. This study further highlights specific areas for quality improvement amongst these health facilities, including labor complications management.

Utilization of maternity waiting homes: before, during, and after the Ebola virus disease outbreak in Bong County, Liberia.

BACKGROUND: Maternity waiting homes (MWHs) are used to increase the number of women delivering at health care facilities. The first MWHs in Liberia were opened in 2012, prior to the Ebola virus disease (EVD) outbreak. METHODS: Longitudinal data were collected from registries on MWH use, antenatal care, postnatal care and facility deliveries from 2012 to 2016 to assess MWH utilization. RESULTS: All indicators examined declined during the EVD outbreak, but within 6 months of the cessation of the outbreak they returned to pre-EVD levels. CONCLUSIONS: Findings suggest MWH utilization remained stable after international funding ceased and EV affected the region.

Maternity waiting homes in Liberia: Results of a countrywide multi-sector scale-up.

OBJECTIVE: Descriptions of maternity waiting homes (MWHs) as an intervention to increase facility delivery for women living in remote geographic areas dates back to the 1950s, yet there is limited information on the scale-up and sustainability of MWHs. The objective of this study was to describe the evolutionary scale-up of MWHs as a component of health system strengthening efforts and document the successes, challenges, and barriers to sustainability in Liberia. METHODS: Data were collected from a national sample of 119 MWHs in Liberia established between 2010-2018. The study used a mixed method design that included focus group discussions, individual interviews, logbook reviews, and geographic information systems. Qualitative data were grouped into themes using Glaser's constant comparative method. Quantitative data were analyzed using negative binomial regression to measure the differences in the counts of monthly stays at facilities with different funding sources and presence of advisory committee. Additionally, each MWH was geo-located for purposes of geo-visualization. RESULTS: In the years since the original construction of five MWHs, an additional 114 MWHs were constructed in 14 of the 15 counties in Liberia. Monthly stays at facilities funded by community were 2·5 times those funded by NGOs (IRR, 2·46, 95% CI 1·33-4·54). Attributes of sustainability included strong local leadership/active community engagement and community ownership and governance. CONCLUSION: Success factors for scale-up and sustainability included strong government support through development of public policy, local and county leadership, early and sustained engagement with communities, and self-governance. A multi-pronged approach with strong community engagement is key to the scale-up and sustainability of MWHs as an intervention to increase facility delivery for women living the farthest from a healthcare facility.

Substitution of murine type I collagen A1 3-hydroxylation site alters matrix structure but does not recapitulate osteogenesis imperfecta bone dysplasia.

Null mutations in CRTAP or P3H1, encoding cartilage-associated protein and prolyl 3-hydroxylase 1, cause the severe bone dysplasias, types VII and VIII osteogenesis imperfecta. Lack of either protein prevents formation of the ER prolyl 3-hydroxylation complex, which catalyzes 3Hyp modification of types I and II collagen and also acts as a collagen chaperone. To clarify the role of the A1 3Hyp substrate site in recessive bone dysplasia, we generated knock-in mice with an α1(I)P986A substitution that cannot be 3-hydroxylated. Mutant mice have normal survival, growth, femoral breaking strength and mean bone mineralization. However, the bone collagen HP/LP crosslink ratio is nearly doubled in mutant mice, while collagen fibril diameter and bone yield energy are decreased. Thus, 3-hydroxylation of the A1 site α1(I)P986 affects collagen crosslinking and structural organization, but its absence does not directly cause recessive bone dysplasia. Our study suggests that the functions of the modification complex as a collagen chaperone are thus distinct from its role as prolyl 3-hydroxylase.

Maternity waiting homes as an intervention to increase facility delivery in rural Zambia.

This study indicates a higher rate of facility delivery at clinics with a maternity waiting home in rural Zambia.

Single dose of bisphosphonate preserves gains in bone mass following cessation of sclerostin antibody in Brtl/+ osteogenesis imperfecta model.

Sclerostin antibody has demonstrated a bone-forming effect in pre-clinical models of osteogenesis imperfecta, where mutations in collagen or collagen-associated proteins often result in high bone fragility in pediatric patients. Cessation studies in osteoporotic patients have demonstrated that sclerostin antibody, like intermittent PTH treatment, requires sequential anti-resorptive therapy to preserve the anabolic effects in adult populations. However, the persistence of anabolic gains from either drug has not been explored clinically in OI, or in any animal model. To determine whether cessation of sclerostin antibody therapy in a growing OI skeleton requires sequential anti-resorptive treatment to preserve anabolic gains in bone mass, we treated 3week old Brtl/+ and wild type mice for 5weeks with SclAb, and then withdrew treatment for an additional 6weeks. Trabecular bone loss was evident following cessation, but was preserved in a dose-dependent manner with single administration of pamidronate at the time of cessation. In vivo longitudinal near-infrared optical imaging of cathepsin K activation in the proximal tibia suggests an anti-resorptive effect of both SclAb and pamidronate which is reversed after three weeks of cessation. Cortical bone was considerably less susceptible to cessation effects, and showed no structural or functional deficits in the absence of pamidronate during this cessation period. In conclusion, while SclAb induces a considerable anabolic gain in the rapidly growing Brtl/+ murine model of OI, a single sequential dose of antiresorptive drug is required to maintain bone mass at trabecular sites for 6weeks following cessation.

Translational treatment paradigm for managing non-unions secondary to radiation injury utilizing adipose derived stem cells and angiogenic therapy.

BACKGROUND: Bony non-unions arising in the aftermath of collateral radiation injury are commonly managed with vascularized free tissue transfers. Unfortunately, these procedures are invasive and fraught with attendant morbidities. This study investigated a novel, alternative treatment paradigm utilizing adipose-derived stem cells (ASCs) combined with angiogenic deferoxamine (DFO) in the rat mandible. METHODS: Rats were exposed to a bioequivalent dose of radiation and mandibular osteotomy. Those exhibiting non-unions were subsequently treated with surgical debridement alone or debridement plus combination therapy. Radiographic and biomechanical outcomes were assessed after healing. RESULTS: Significant increases in biomechanical strength and radiographic metrics were observed in response to combination therapy (p < .05). Importantly, combined therapy enabled a 65% reduction in persisting non-unions when compared to debridement alone. CONCLUSION: We support the continued investigation of this promising combination therapy in its potential translation for the management of radiation-induced bony pathology. © 2015 Wiley Periodicals, Inc. Head Neck 38: E837-E843, 2016.

Prevention of radiation-induced bone pathology through combined pharmacologic cytoprotection and angiogenic stimulation.

Pathologic fractures and associated non-unions arising in previously irradiated bone are severely debilitating diseases. Although radiation is known to have deleterious effects on healthy tissue cellularity and vascularity, no clinically accepted pharmacologic interventions currently exist to target these destructive mechanisms within osseous tissues. We utilized amifostine-a cellular radioprotectant-and deferoxamine-an angiogenic stimulant-to simultaneously target the cellular and vascular niches within irradiated bone in a rat model of mandibular fracture repair following irradiation. Rats treated with combined therapy were compared to those undergoing treatment with singular amifostine or deferoxamine therapy, nontreated/irradiated animals (XFx) and non-treated/non-irradiated animals (Fx). 3D angiographic modeling, histology, Bone Mineral Density Distribution and mechanical metrics were utilized to assess therapeutic efficacy. We observed diminished metrics for all outcomes when comparing XFx to Fx alone, indicating the damaging effects of radiation. Across all outcomes, only the combined treatment group improved upon XFx levels, normalized all metrics to Fx levels, and was consistently as good as, or superior to the other treatment options (p<0.05). Collectively, our data demonstrate that pharmacologically targeting the cellular and vascular environments within irradiated bone prevents bone injury and enhances fracture healing.

Thrombospondin-2 deficiency in growing mice alters bone collagen ultrastructure and leads to a brittle bone phenotype.

Thrombospondin-2 (TSP2) is a matricellular protein component of the bone extracellular matrix. Long bones of adult TSP2-deficient mice have increased endosteal bone thickness due to expansion of the osteoblast progenitor cell pool, and these cells display deficits in osteoblastic potential. Here, we investigated the effects of TSP2 deficiency on whole bone geometric and mechanical properties in growing 6-wk-old male and female wild-type and TSP2-knockout (KO) mice. Microcomputed tomography and mechanical testing were conducted on femora and L2 vertebrae to assess morphology and whole bone mechanical properties. In a second series of experiments, femoral diaphyses were harvested from wild-type and TSP2-KO mice. Detergent-soluble type I collagen content was determined by Western blot of right femora. Total collagen content was determined by hydroxyproline analysis of left femora. In a third series of experiments, cortical bone was dissected from the anterior and posterior aspects of the femoral middiaphysis and imaged by transmission electron microscopy to visualize collagen fibrils. Microcomputed tomography revealed minimal structural effects of TSP2 deficiency. TSP2 deficiency imparted a brittle phenotype on cortical bone. Femoral tissue mineral density was not affected by TSP2 deficiency. Instead, transmission electron microscopy revealed less intensely stained collagen fibrils with altered morphology in the extracellular matrix assembled by osteoblasts on the anterior surface of TSP2-KO femora. Femoral diaphyseal bone displayed comparable amounts of total collagen, but the TSP2-KO bones had higher levels of detergent-extractable type I collagen. Together, our data suggest that TSP2 is required for optimal collagen fibrillogenesis in bone and thereby contributes to normal skeletal tissue quality.

Type III collagen modulates fracture callus bone formation and early remodeling.

Type III collagen (Col3) has been proposed to play a key role in tissue repair based upon its temporospatial expression during the healing process of many tissues, including bone. Given our previous finding that Col3 regulates the quality of cutaneous repair, as well as our recent data supporting its role in regulating osteoblast differentiation and trabecular bone quantity, we hypothesized that mice with diminished Col3 expression would exhibit altered long-bone fracture healing. To determine the role of Col3 in bone repair, young adult wild-type (Col3+/+) and haploinsufficent (Col3+/-) mice underwent bilateral tibial fractures. Healing was assessed 7, 14, 21, and 28 days following fracture utilizing microcomputed tomography (microCT), immunohistochemistry, and histomorphometry. MicroCT analysis revealed a small but significant increase in bone volume fraction in Col3+/- mice at day 21. However, histological analysis revealed that Col3+/- mice have less bone within the callus at days 21 and 28, which is consistent with the established role for Col3 in osteogenesis. Finally, a reduction in fracture callus osteoclastic activity in Col3+/- mice suggests Col3 also modulates callus remodeling. Although Col3 haploinsufficiency affected biological aspects of bone repair, it did not affect the regain of mechanical function in the young mice that were evaluated in this study. These findings provide evidence for a modulatory role for Col3 in fracture repair and support further investigations into its role in impaired bone healing.

Prophylactic amifostine preserves the biomechanical properties of irradiated bone in the murine mandible.

BACKGROUND: The authors have previously demonstrated that amifostine prophylaxis mitigates the pernicious effects of radiation in settings of fracture repair and distraction osteogenesis. Expanding on these studies, the authors examined the biomechanical properties of uninjured bone exposed to both radiation and amifostine. The authors hypothesize that radiation will degrade the biomechanical properties of native bone, and further hypothesize that prophylactic amifostine will preserve biomechanical properties to levels of normal bone and protect against radiation-induced morbidities. METHODS: Rats were randomized into control, irradiated, and amifostine pretreatment plus radiation (amifostine-pretreated) groups. Irradiated animals received a fractionated dosing schedule of 35 Gy, with amifostine-pretreated animals receiving amifostine before irradiation. Hemimandibles were harvested at 8 and 18 weeks for biomechanical testing and micro-computed tomographic analysis. RESULTS: At 8 weeks, irradiated specimens displayed elevations above controls for all biomechanical properties. At 18 weeks, the biomechanical properties of irradiated specimens degraded in comparison with controls; at both time points, amifostine-pretreated specimens were maintained at levels comparable to controls. There was a significant decrease in tissue mineral density from 8- to 18-week irradiated specimens, whereas no such change existed for control and amifostine-pretreated specimens. CONCLUSIONS: The authors' findings demonstrate paradoxical and transient elevations in the initial biomechanical properties of irradiated specimens that were not sustained through the later study time point. Amifostine pretreatment, however, provided uninterrupted preservation of the biomechanical properties of normal, native bone at both time points. This supports the contention that amifostine is capable of providing continuous protection to bone against the untoward effects of radiation therapy.

Early detection of heterotopic ossification using near-infrared optical imaging reveals dynamic turnover and progression of mineralization following Achilles tenotomy and burn injury.

Heterotopic ossification (HO) is the abnormal formation of bone in soft tissue. Current diagnostics have low sensitivity or specificity to incremental progression of mineralization, especially at early time points. Without accurate and reliable early diagnosis and intervention, HO progression often results in incapacitating conditions of limited range of motion, nerve entrapment, and pain. We hypothesized that non-invasive near-infrared (NIR) optical imaging can detect HO at early time points and monitor heterotopic bone turnover longitudinally. C57BL6 mice received an Achilles tenotomy on their left hind limb in combination with a dorsal burn or sham procedure. A calcium-chelating tetracycline derivative (IRDye 680RD BoneTag) was injected bi-weekly and imaged via NIR to measure accumulative fluorescence for 11 wk and compared to in vivo microCT images. Percent retention of fluorescence was calculated longitudinally to assess temporal bone resorption. NIR detected HO as early as five days and revealed a temporal response in HO formation and turnover. MicroCT could not detect HO until 5 wk. Confocal microscopy confirmed fluorophore localization to areas of HO. These findings demonstrate the ability of a near-infrared optical imaging strategy to accurately and reliably detect and monitor HO in a murine model.