Orthopedic Regeneration Research Articles

Artificial Intelligence (AI): A Potential Game Changer in Regenerative Orthopedics-A Scoping Review.

Regenerative orthopedics involves approaches like stem cell therapy, platelet-rich plasma (PRP) therapy, the use of biological scaffold implants, tissue engineering, etc. We aim to present a scoping review of the role of artificial intelligence (AI) in different treatment approaches of regenerative orthopedics. Using the PRISMA guidelines, a search for articles for the last ten years (2013-2024) on PubMed was done, using several keywords. We have discussed the state-of-the-art, strengths/benefits, and limitations of the published research, and provide a useful resource for the way ahead in future for researchers working in this area. Using the eligibility criteria out of 82 initially screened publications, we included 18 studies for this review. We noticed that the treatment responses to regenerative treatments depend on several factors; hence, to facilitate better comprehensive and patient-specific treatments, AI technology is very useful. Machine learning (ML) and deep learning (DL) are a few of the most frequently used AI techniques. They use a data-driven approach for training models to make human-like decisions. Data are fed to the ML/DL algorithm and the trained model makes classifications or predictions based on its learning. The area of regenerative orthopedics is highly sophisticated and significantly aids in providing cost-effective and non-invasive treatments to patients suffering from orthopedic ailments and injuries. Due to its promising future, the use of AI in regenerative orthopedics is an emerging and promising research field; however, its universal clinical applications are associated with some ethical considerations, which need addressing. The online version contains supplementary material available at 10.1007/s43465-024-01189-1.

Mimicking the mechanical properties of cortical bone with an additively manufactured biodegradable Zn-3Mg alloy

Additively manufactured (AM) biodegradable zinc (Zn) alloys have recently emerged as promising porous bone-substituting materials, due to their moderate degradation rates, good biocompatibility, geometrically ordered microarchitectures, and bone-mimicking mechanical properties. While AM Zn alloy porous scaffolds mimicking the mechanical properties of trabecular bone have been previously reported, mimicking the mechanical properties of cortical bone remains a formidable challenge. To overcome this challenge, we developed the AM Zn-3Mg alloy. We used laser powder bed fusion to process Zn-3Mg and compared it with pure Zn. The AM Zn-3Mg alloy exhibited significantly refined grains and a unique microstructure with interlaced α-Zn/Mg2Zn11 phases. The compressive properties of the solid Zn-3Mg specimens greatly exceeded their tensile properties, with a compressive yield strength of up to 601 MPa and an ultimate strain of >60 %. We then designed and fabricated functionally graded porous structures with a solid core and achieved cortical bone-mimicking mechanical properties, including a compressive yield strength of >120 MPa and an elastic modulus of ≈20 GPa. The biodegradation rates of the Zn-3Mg specimens were lower than those of pure Zn and could be adjusted by tuning the AM process parameters. The Zn-3Mg specimens also exhibited improved biocompatibility as compared to pure Zn, including higher metabolic activity and enhanced osteogenic behavior of MC3T3 cells cultured with the extracts from the Zn-3Mg alloy specimens. Altogether, these results marked major progress in developing AM porous biodegradable metallic bone substitutes, which paved the way toward clinical adoption of Zn-based scaffolds for the treatment of load-bearing bony defects. Statement of significanceOur study presents a significant advancement in the realm of biodegradable metallic bone substitutes through the development of an additively manufactured Zn-3Mg alloy. This novel alloy showcases refined grains and a distinctive microstructure, enabling the fabrication of functionally graded porous structures with mechanical properties resembling cortical bone. The achieved compressive yield strength and elastic modulus signify a critical leap toward mimicking the mechanical behavior of load-bearing bone. Moreover, our findings reveal tunable biodegradation rates and enhanced biocompatibility compared to pure Zn, emphasizing the potential clinical utility of Zn-based scaffolds for treating load-bearing bony defects. This breakthrough opens doors for the wider adoption of zinc-based materials in regenerative orthopedics.

Engineering Innervated Musculoskeletal Tissues for Regenerative Orthopedics and Disease Modeling.

Musculoskeletal (MSK) disorders significantly burden patients and society, resulting in high healthcare costs and productivity loss. These disorders are the leading cause of physical disability, and their prevalence is expected to increase as sedentary lifestyles become common and the global population of the elderly increases. Proper innervation is critical to maintaining MSK function, and nerve damage or dysfunction underlies various MSK disorders, underscoring the potential of restoring nerve function in MSK disorder treatment. However, most MSK tissue engineering strategies have overlooked the significance of innervation. This review first expounds upon innervation in the MSK system and its importance in maintaining MSK homeostasis and functions. This will be followed by strategies for engineering MSK tissues that induce post-implantation in situ innervation or are pre-innervated. Subsequently, research progress in modeling MSK disorders using innervated MSK organoids and organs-on-chips (OoCs) is analyzed. Finally, the future development of engineering innervated MSK tissues to treat MSK disorders and recapitulate disease mechanisms is discussed. This review provides valuable insights into the underlying principles, engineering methods, and applications of innervated MSK tissues, paving the way for the development of targeted, efficacious therapies for various MSK conditions.

From bone to nanoparticles: development of a novel generation of bone derived nanoparticles for image guided orthopedic regeneration.

Bone related diseases such as osteoporosis, osteoarthritis, metastatic bone cancer, osteogenesis imperfecta, and Paget's disease, are primarily treated with pharmacologic therapies that often exhibit limited efficacy and substantial side effects. Bone injuries or fractures are primarily repaired with biocompatible materials that produce mixed results in sufficiently regenerating healthy and homogenous bone tissue. Each of these bone conditions, both localized and systemic, use different strategies with the same goal of achieving a healthy and homeostatic bone environment. In this study, we developed a new type of bone-based nanoparticle (BPs) using the entire organic extracellular matrix (ECM) of decellularized porcine bone, additionally encapsulating indocyanine green dye (ICG) for an in vivo monitoring capability. Utilizing the regenerative capability of bone ECM and the functionality of nanoparticles, the ICG encapsulated BPs (ICG/BPs) have been demonstrated to be utilized as a therapeutic option for localized and systemic orthopedic conditions. Additionally, ICG enables an in situ monitoring capability in the Short-Wave Infrared (SWIR) spectrum, capturing the degradation or the biodistribution of the ICG/BPs after both local implantation and intravenous administration, respectively. The efficacy and safety of the ICG/BPs shown within this study lay the foundation for future investigations, which will delve into optimization for clinical translation.

Leveraging Artificial Intelligence and Machine Learning in Regenerative Orthopedics: A Paradigm Shift in Patient Care.

The integration of artificial intelligence (AI) and machine learning (ML) into regenerative orthopedics heralds a paradigm shift in clinical methodologies and patient management. This review article scrutinizes AI's role in augmenting diagnostic accuracy, refining predictive models, and customizing patient care in orthopedic medicine. Focusing on innovations such as KeyGene and CellNet, we illustrate AI's adeptness in navigating complex genomic datasets, cellular differentiation, and scaffold biodegradation, which are critical components of tissue engineering. Despite its transformative potential, AI's clinical adoption remains in its infancy, contending with challenges in validation, ethical oversight, and model training for clinical relevance. This review posits AI as a vital complement to human intelligence (HI), advocating for an interdisciplinary approach that merges AI's computational prowess with medical expertise to fulfill precision medicine's promise. By analyzing historical and contemporary developments in AI, from the foundational theories of McCullough and Pitts to sophisticated neural networks, the paper emphasizes the need for a synergistic alliance between AI and HI. This collaboration is imperative for improving surgical outcomes, streamlining therapeutic modalities, and enhancing the quality of patient care. Our article calls for robust interdisciplinary strategies to overcome current obstacles and harness AI's full potential in revolutionizing patient outcomes, thereby significantly contributing to the advancement of regenerative orthopedics and the broader field of scientific research.

Self-adaptable calcium-based bioactive phosphosilicate-infused gelatin-hyaluronic hydrogel for orthopedic regeneration

Bone regeneration is a critical and intricate process vital for healing fractures, defects, and injuries. Although conventional bone grafts are commonly used, they may fall short of optimal outcomes, thereby driving the need for alternative therapies. This research endeavors to explore synergistically designed Hyalo Glass Gel (HGG), and its explicitly for bone tissue engineering and regenerative medicine. The HGG composite comprises a modifiable calcium-based bioactive phosphosilicates-incorporated/crosslinked gelatin-hyaluronic scaffold showcasing promising functional characteristics. The study underscores the distinct attributes of each constituent (gelatin (Gel), hyaluronic acid (HA), and 45S5 calcium sodium phosphosilicates (BG)), and their cooperative influences on the scaffold's performance. Careful manipulation of crosslinking methods facilitates customization of HGG's mechanical attributes, degradation kinetics, and structural features, aligning them with the requisites of bone tissue engineering applications. Moreover, the integration of BG augments the scaffold's bioactivity, thereby expediting tissue regenerative processes. This comprehensive evaluation encompasses HGG's physicochemical aspects, mechanical traits rooted in viscoelasticity, as well as its biodegradability, in-vitro bioactivity, and interactions with stem cells. The result obtained underscores the viscoelastic nature of HGG, substantiating its capacity to foster mesenchymal stem cell viability, proliferation, and differentiation. Significantly, HGG manifests biocompatibility and adjustable attributes, exhibits pronounced drug (vancomycin) retention abilities, rendering it apt for wound healing, drug delivery, and bone regeneration. Its distinctive composition, tailored attributes, and mimicry of bone tissue's extracellular matrix (ECM) due to its bioactive nature, collectively situate its potential as a versatile biomaterial for subsequent research and development endeavors with compelling prospects in bone tissue engineering and regenerative medicine.

Infra-patellar fat pad-derived mesenchymal stem cells maintain their chondrogenic differentiation potential after arthroscopic harvest with blood-product supplementation

PurposeMesenchymal stem cells/medicinal signaling cells (MSCs) possess therapeutic potential and are used in regenerative orthopaedics. The infra-patellar fat pad (IFP) is partially resected during knee arthroscopy (KASC) and contains MSCs. Heat, irrigation, and mechanical stress during KASC may decrease MSC’s therapeutic potential. This study assessed MSCs’ regenerative potential after arthroscopic IFP harvest and potential effects of two blood products (BP) (platelet-rich plasma (PRP), hyperacute serum (HAS)) on MSCs’ viability and chondrogenic differentiation capacity.MethodsIFP was arthroscopically harvested, isolated, and counted (n = 5). Flow cytometry was used to assess cell viability via staining with annexin V/7-AAD and stemness markers via staining for CD90, CD73, and CD105. MSCs were incubated with blood products, and metabolic activity was determined via an XTT assay. Deposition of cartilage extracellular matrix was determined in histologic sections of chondrogenically differentiated 3D pellet cultures via staining with Alcian Blue. Expression of cartilage-specific genes (SOX9, MMP3/13, ACAN, COL1/2) was analyzed via quantitative PCR.ResultsMSC isolation from IFP yielded 2.66*106 ± 1.49*106 viable cells from 2.7 (0.748) g of tissue. MSC markers (CD 90/105/73) were successfully detected and annexin V staining showed 81.5% viable cells. XTT showed increased metabolic activity. Within the BP groups, this increase was significant (days 0–14, p < 0.05). PCR showed expression of cartilage-specific genes in each group. COL2 (p < 0.01) as well as ACAN (p < 0.001) expression levels were significantly higher in the HAS group. Histology showed successful differentiation.ConclusionArthroscopic harvest of IFP-MSCs yields sufficient cells with maintained regenerative potential and viability. Blood products further enhance MSCs’ viability.

Isolation and Cultivation of Adipose-Derived Mesenchymal Stem Cells Originating from the Infrapatellar Fat Pad Differentiated with Blood Products: Method and Protocol

Adipose-derived mesenchymal stem cells (ASCs) are a promising source for clinical application in regenerative orthopedics. ASCs derived from the infra-patellar fat pad (IFP)-a distinct adipose structure in the knee-show superior regenerative potential compared to subcutaneous-fat-derived cells. Furthermore, it has been shown that blood products enhance ASCs' viability. A major challenge for clinical translation of both ASCs and blood products is the low comparability of obtained data due to non-standardized harvesting, isolation and preparation methods. The aim of this method-paper is to provide reproducible protocols to help standardize basic research in the field to build a sound basis for clinical translation with an emphasize on practicability. The presented protocols include (i) ASC isolation from the IFP, (ii) blood product preparation and (iii) ASC incubation with blood products.

Comparative study between corticosteroids and platelet-rich plasma in the treatment of de Quervain’s tenosynovitis

Background: De Quervain tenosynovitis is named after the Swiss surgeon, Fritz de Quervain, who first described it in 1895. It is a condition that involves tendon entrapment affecting the first dorsal compartment of the wrist. Pain is exacerbated by thumb movement and radial and ulnar deviation of the wrist. De Quervain tendinopathy can be self-limited and may resolve without intervention. For those individuals with persistent symptoms splinting, systemic inflammatories, and corticosteroid injections are frequently used as non-surgical treatment options. Corticosteroids have both anti-inflammatory and immunosuppressive effects and have been used in the treatment of DQST. With the widespread increase in research in the field of regenerative orthopedics, PRP has become a natural, biological enhancer. Platelet-rich plasma (PRP) is safe and reduces symptoms in different tendon pathologies, such as De Quervain's disease. It has a high concentration of platelets above baseline in comparison to whole blood count to accelerate tissue healing, modulate inflammation, and provide symptomatic relief. Aim: To evaluate the effectiveness of PRP injection in comparison to corticosteroid injection in the treatment of DQST. Methods: Patients underwent randomization into groups: corticosteroids and PRP. We followed both groups at 4, 12, and 24 weeks for improvement in wrist pain, disability, and finger motion. The resolution of symptoms and improvements in the Visual Analog Scale (VAS) and Disabilities of the Arm, Shoulder, and Hand (DASH) scores were assessed to evaluate treatment success. Results: 1) Forty-four patients with suspected DQST were divided into two groups, i.e., PRP group I and corticosteroid group II in a 1:1 by lottery method. 2) Pain measured by VAS score has shown a reduction in pain in the PRP group-I with every follow-up. However, a similar pattern was not shown in the corticosteroid group II. We found in our study that a lower DASH score was found in 14(63.64%) patients of PRP group I compared to 8(36.36%) patients of corticosteroid group II. After PRP injection, pain, disability, and finger motion improve steadily and eventually get better. Conclusions: Based on results found in the present study, for De Quervain's Tenosynovitis (DQST) condition, PRP injections were superior to corticosteroid injections in terms of pain management, finger motion, and reduced disability.

Pulsed Radiofrequency Neuromodulation Contributes to Activation of Platelet-Rich Plasma in In Vitro Conditions

Recent years have brought new developments in interventional chronic pain management, namely regenerative orthopedics utilizing platelet-rich plasma (PRP) as well as further evolution of pulsed radiofrequency neuromodulation (PRF). Both methods have been used separately. Here, we investigated whether PRF may potentiate the activation of platelets in PRP samples when both these techniques are combined together in in vitro conditions. Studies were performed on concentrated PRP samples (PRPs) obtained from acid citrate dextrose-treated blood taken from 11 healthy volunteers. PRPs were divided into four groups: 1) nonactivated PRP; 2) thrombin-activated PRP as a positive control for maximal platelets activation; 3) PRF-treated PRP exposed for 20 min to PRF energy generated by neurotherm radio frequency generator at 500 kHz, with a voltage of 40 V and maximal temperature of 42°C; and 4) a combination of groups 2 and 3. PRF-induced platelet activation measured by platelet factor 4 (PF4) and ATP release from PRPs was significantly higher compared to nonactivated PRPs, and similar to PF4 and ATP release from thrombin-activated PRPs. Thrombin activation did not potentiate PF4 release in PRF samples and even reduced ATP level. Additionally, PRF neither induced any platelet membrane damage measured by lactic dehydrogenase release from PRP nor modified any platelets viability or metabolism measured by MTT. We confirmed that PRF may activate PRP without additional platelet activators. So, a combination of both methods PRF and PRP application may provide a more effective opportunity for tissue regeneration in dentistry, surgery, dermatology, or in orthopedics.

Professor Issa Navab A Life Well Spent

Professor Shaykh al-Islam Navab (1938-2018) was one of the first orthopedic surgeons in Iran. He studied general medicine, specialty and subspecialty in France and returned to Iran after completing his education. He earned a degree in regenerative orthopedics and traumatology from France and was one of the youngest physicians to become a full professor in France at the age of 32. One of his most valuable services was voluntary treatment of war Injured during the imposed war between Iran and Iraq. Also, he helped many students to continue their education in France. He can and should be a role model for upcoming generations.

Moxifloxacin-loaded in situ synthesized Bioceramic/Poly(L-lactide-co-ε-caprolactone) composite scaffolds for treatment of osteomyelitis and orthopedic regeneration

High local intraosseous levels of antimicrobial agents are required for adequate long-term treatment of chronic osteomyelitis (OM). In this study, biodegradable composite scaffolds of poly-lactide-co-ε-caprolactone/calcium phosphate (CaP) were in-situ synthesized using two different polymer grades and synthesis pathways and compared to composites prepared by pre-formed (commercially available) CaP for delivery of the antibiotic moxifloxacin hydrochloride (MOX). Phase identification and characterization by Fourier transform infra-red (FTIR) spectroscopy, X-ray powder diffraction (XRPD) and scanning electron microscope (SEM) confirmed the successful formation of different CaP phases within the biodegradable polymer matrix. The selected in-situ formed CaP scaffold showed a sustained release for MOX for six weeks and adequate porosity. Cell viability study on MG-63 osteoblast-like cells revealed that the selected composite scaffold maintained the cellular proliferation and differentiation. Moreover, it was able to diminish the bacterial load, inflammation and sequestrum formation in the bones of OM-induced animals. The results of the present work deduce that the selected in-situ formed CaP composite scaffold is a propitious candidate for OM treatment, and further clinical experiments are recommended.

Prospective Aspects of Regeneration in Orthopaedics: A Review

Musculoskeletal diseases affect millions of people worldwide and are one of the leading causes of long-term pain and physical disability. Traditional treatment methods for promoting healing and repair has always been consider gold standard, But the emergence of new therapeutic approaches aims to regenerate or repair musculoskeletal tissue. The recognition of a regenerative therapy in orthopaedics requires the demonstration of new Bone, Cartilage, ligament, tendons, healing of soft tissues injuries and Overuse conditions like plantar fasciitis or tennis elbow . Regenerative therapy boosts the body’s ability to use its repair systems to heal diseased or damaged cells after a severe injury, or other degenerative condition. A diversity of regenerative strategies have been evaluated, including distraction osteogenesis, bone grafts and bone substitute materials, bone matrix proteins, growth/differentiation factors, combined therapies and, more recently, tissue‐engineering approaches. This review aims to evaluate the current status of the therapies available and to discuss the challenges that must be faced in order to achieve predictable orthopaedic regeneration in clinical practice.

Dual Doping of Silicon and Manganese in Hydroxyapatites: Physicochemical Properties and Preliminary Biological Studies.

Silicated hydroxyapatite powders enriched with small amounts of manganese (Mn2+) cations were synthesized via two different methods: precipitation in aqueous solution and the solid-state method. The source of Mn2+ ions was manganese acetate, while silicon was incorporated using two different reagents: silicon acetate and sodium metasilicate. Powder X-ray diffraction (PXRD) analysis showed that the powders obtained via the precipitation method consisted of single-phase nanocrystalline hydroxyapatite. In contrast, samples obtained via the solid-state method were heterogenous and contaminated with other phases, (i.e., calcium oxide, calcium hydroxide, and silicocarnotite) arising during thermal treatment. The transmission electron microscope (TEM) images showed powders obtained via the precipitation method were nanosized and elongated, while solid-state synthesis produced spherical microcrystals. The phase identification was complemented by Fourier transform infrared spectroscopy (FTIR). An in-depth analysis via solid-state nuclear magnetic resonance (ssNMR) was carried out, using phosphorus 31P single-pulse Bloch decay (BD) (31P BD) and cross-polarization (CP) experiments from protons to silicon-29 nuclei (1H → 29Si CP). The elemental measurements carried out using wavelength-dispersive X-ray fluorescence (WD-XRF) showed that the efficiency of introducing manganese and silicon ions was between 45% and 95%, depending on the synthesis method and the reagents. Preliminary biological tests on the bacteria Allivibrio fisheri (Microtox®) and the protozoan Spirostomum ambiguum (Spirotox) showed no toxic effect in any of the samples. The obtained materials may find potential application in regenerative medicine, bone implantology, and orthopedics as bone substitutes or implant coatings.

Bone Tissue Engineering in a Perfusion Bioreactor Using Dexamethasone-Loaded Peptide Hydrogel.

The main goal of this study was the formation of bone tissue using dexamethasone (DEX)-loaded [COCH3]-RADARADARADARADA-[CONH2] (RADA 16-I) scaffold that has the ability to release optimal DEX concentration under perfusion force. Bone-marrow samples were collected from three patients during a hip arthroplasty. Human mesenchymal stem cells (hMSCs) were isolated and propagated in vitro in order to be seeded on scaffolds made of DEX-loaded RADA 16-I hydrogel in a perfusion bioreactor. DEX concentrations were as follows: 4 × 10−3, 4 × 10−4 and 4 × 10−5 M. After 21 days in a perfusion bioreactor, tissue was analyzed by scanning electron microscopy (SEM) and histology. Markers of osteogenic differentiation were quantified by real-time polymerase chain reaction (RT-PCR) and immunocytochemistry. Minerals were quantified and detected by the von Kossa method. In addition, DEX release from the scaffold in a perfusion bioreactor was assessed. The osteoblast differentiation was confirmed by the expression analysis of osteoblast-related genes (alkaline phosphatase (ALP), collagen I (COL1A1) and osteocalcin (OC). The hematoxylin/eosin staining confirmed the presence of cells and connective tissue, while SEM revealed morphological characteristics of cells, extracellular matrix and minerals—three main components of mature bone tissue. Immunocytochemical detection of collagen I is in concordance with given results, supporting the conclusion that scaffold with DEX concentration of 4 × 10−4 M has the optimal engineered tissue morphology. The best-engineered bone tissue is produced on scaffold loaded with 4 × 10−4 M DEX with a perfusion rate of 0.1 mL/min for 21 days. Differentiation of hMSCs on DEX-loaded RADA 16-I scaffold under perfusion force has a high potential for application in regenerative orthopedics.

Sustained and Prolonged Delivery of Protein Therapeutics from Two-Dimensional Nanosilicates

We present a nanoengineered system for sustained and prolonged delivery of protein therapeutics, which has the potential to impact current orthopedic regeneration strategies. Specifically, we introduce two-dimensional nanosilicates with a high surface area and charged characteristics for delivery of active proteins for more than 30 days. The nanosilicates show high binding efficacy without altering the protein conformation and bioactivity. The released proteins are able to maintain high activity as demonstrated by enhanced differentiation of human mesenchymal stem cells at 10-fold lower concentration compared to the exogenous control. Utilizing the nanosilicates as a delivery vehicle could minimize the negative side effects observed because of the use of supraphysiological dosages of protein therapeutics for orthopedic regeneration strategies.

Metformin Promotes Osteogenic Differentiation of Adipose-Derived Stromal Cells and Exerts Pro-Osteogenic Effect Stimulating Bone Regeneration.

Metformin, the gold standard in type 2 diabetes treatment, is a drug with multi-faceted effects. Currently, metformin has gained much attention as an agent that may find application in regenerative medicine. In this study, we considered its pro-osteogenic function in the course of in vitro osteogenesis of multipotent stromal cells derived from rat adipose tissue (rASCs). In addition, we evaluated the effect of metformin treatment on bone metabolism in a model of cranial defect in nondiabetic rats. In vitro study showed that metformin that is introduced to the culture medium at concentration equal 500 µM may promote the differentiation of rASCs into bone-forming cells, which express mRNA and secrets proteins that are related to the functional tissue (namely, alkaline phosphatase and osteocalcin). Osteogenic effect of metformin, as determined using in vitro model, was also manifested with the formation of mineralized extracellular matrix rich calcium and phosphorous deposits. We have also found, that in undifferentiated rASCs, metformin significantly activates a critical regulatory factor for osteogenic differentiation, i.e., AMPK. Moreover, using in vivo model we showed metformin administration at a dose of 250 mg/kg/day accelerated bone healing and the formation of mature tissue at a fracture site in rat cranial defect model. The obtained results shed promising light on metformin application in regenerative orthopedics, both as an agent improving functionality of ASCs for therapeutic transplantation, as well as a medication enhancing the bone healing process.

Citrate-based materials fuel human stem cells by metabonegenic regulation

A comprehensive understanding of the key microenvironmental signals regulating bone regeneration is pivotal for the effective design of bioinspired orthopedic materials. Here, we identified citrate as an osteopromotive factor and revealed its metabonegenic role in mediating citrate metabolism and its downstream effects on the osteogenic differentiation of human mesenchymal stem cells (hMSCs). Our studies show that extracellular citrate uptake through solute carrier family 13, member 5 (SLC13a5) supports osteogenic differentiation via regulation of energy-producing metabolic pathways, leading to elevated cell energy status that fuels the high metabolic demands of hMSC osteodifferentiation. We next identified citrate and phosphoserine (PSer) as a synergistic pair in polymeric design, exhibiting concerted action not only in metabonegenic potential for orthopedic regeneration but also in facile reactivity in a fluorescent system for materials tracking and imaging. We designed a citrate/phosphoserine-based photoluminescent biodegradable polymer (BPLP-PSer), which was fabricated into BPLP-PSer/hydroxyapatite composite microparticulate scaffolds that demonstrated significant improvements in bone regeneration and tissue response in rat femoral-condyle and cranial-defect models. We believe that the present study may inspire the development of new generations of biomimetic biomaterials that better recapitulate the metabolic microenvironments of stem cells to meet the dynamic needs of cellular growth, differentiation, and maturation for use in tissue engineering.

Mineralized Polysaccharide Transplantation Modules Supporting Human MSC Conversion into Osteogenic Cells and Osteoid Tissue in a Non-Union Defect.

Regenerative orthopedics needs significant devices to transplant human stem cells into damaged tissue and encourage automatic growth into replacements suitable for the human skeleton. Soft biomaterials have similarities in mechanical, structural and architectural properties to natural extracellular matrix (ECM), but often lack essential ECM molecules and signals. Here we engineer mineralized polysaccharide beads to transform MSCs into osteogenic cells and osteoid tissue for transplantation. Bone morphogenic proteins (BMP-2) and indispensable ECM proteins both directed differentiation inside alginate beads. Laminin and collagen IV basement membrane matrix proteins fixed and organized MSCs onto the alginate matrix, and BMP-2 drove differentiation, osteoid tissue self-assembly, and small-scale mineralization. Augmentation of alginate is necessary, and we showed that a few rationally selected small proteins from the basement membrane (BM) compartment of the ECM were sufficient to upregulate cell expression of Runx-2 and osteocalcin for osteoid formation, resulting in Alizarin red-positive mineral nodules. More significantly, nested BMP-2 and BM beads added to a non-union skull defect, self-generated osteoid expressing osteopontin (OPN) and osteocalcin (OCN) in a chain along the defect, at only four weeks, establishing a framework for complete regeneration expected in 6 and 12 weeks. Alginate beads are beneficial surgical devices for transplanting therapeutic cells in programmed (by the ECM components and alginate-chitosan properties) reaction environments ideal for promoting bone tissue.

Mineralized Polysaccharide Transplantation Modules Supporting Human MSC Conversion into Osteogenic Cells and Osteoid Tissue in a Non-Union Defect.

Regenerative orthopedics needs significant devices to transplant human stem cells into damaged tissue and encourage automatic growth into replacements suitable for the human skeleton. Soft biomaterials have similarities in mechanical, structural and architectural properties to natural extracellular matrix (ECM), but often lack essential ECM molecules and signals. Here we engineer mineralized polysaccharide beads to transform MSCs into osteogenic cells and osteoid tissue for transplantation. Bone morphogenic proteins (BMP-2) and indispensable ECM proteins both directed differentiation inside alginate beads. Laminin and collagen IV basement membrane matrix proteins fixed and organized MSCs onto the alginate matrix, and BMP-2 drove differentiation, osteoid tissue self-assembly, and small-scale mineralization. Augmentation of alginate is necessary, and we showed that a few rationally selected small proteins from the basement membrane (BM) compartment of the ECM were sufficient to upregulate cell expression of Runx-2 and osteocalcin for osteoid formation, resulting in Alizarin red-positive mineral nodules. More significantly, nested BMP-2 and BM beads added to a non-union skull defect, self-generated osteoid expressing osteopontin (OPN) and osteocalcin (OCN) in a chain along the defect, at only four weeks, establishing a framework for complete regeneration expected in 6 and 12 weeks. Alginate beads are beneficial surgical devices for transplanting therapeutic cells in programmed (by the ECM components and alginate-chitosan properties) reaction environments ideal for promoting bone tissue.