The impact of biomolecular medicine and tissue engineering on plastic surgery in the 21st century

Nanotechnology development in surgical applications: recent trends and developments

This paper gives a detailed analysis of nanotechnology's rising involvement in numerous surgical fields. We investigate the use of nanotechnology in orthopedic surgery, neurosurgery, plastic surgery, surgical oncology, heart surgery, vascular surgery, ophthalmic surgery, thoracic surgery, and minimally invasive surgery. The paper details how nanotechnology helps with arthroplasty, chondrogenesis, tissue regeneration, wound healing, and more. It also discusses the employment of nanomaterials in implant surfaces, bone grafting, and breast implants, among other things. The article also explores various nanotechnology uses, including stem cell-incorporated nano scaffolds, nano-surgery, hemostasis, nerve healing, nanorobots, and diagnostic applications. The ethical and safety implications of using nanotechnology in surgery are also addressed. The future possibilities of nanotechnology are investigated, pointing to a possible route for improved patient outcomes. The essay finishes with a comment on nanotechnology's transformational influence in surgical applications and its promise for future breakthroughs.

Comparative Analysis of Human Adipose-Derived Stromal/Stem Cells and Dermal Fibroblasts

Dermal fibroblasts (DFs) share several qualities with mesenchymal stem cell/multipotent stromal cells (MSCs) derived from various tissues, including adipose-derived stromal/stem cells (ASCs). ASCs and DFs are morphologically comparable and both cell types can be culture expanded through the utilization of their plastic-adherence properties. Despite these similar characteristics, numerous studies indicate that ASC and DF display distinct therapeutic benefits in clinical applications. To more accurately distinguish between these cell types, human DFs and ASCs isolated from three individual donors were analyzed for multipotency and cell surface marker expressions. The detection of cell surface markers, CD29, CD34, CD44, CD73, CD90, and CD105, were used for phenotypic characterization of the DFs and ASCs. Furthermore, both cell types underwent lineage differentiation based on histochemical staining and the expression of adipogenic related genes, CCAAT/Enhancer-Binding Protein alpha (CEBPα), Peroxisome proliferator-activated receptor gamma (PPARγ), UCP1, Leptin (LEP), and Adiponectin (ADIPOQ); and osteogenic related genes, Runt related transcription factor 2 (Runx2), Alkaline phosphatase (ALPL), Osteocalcin (OCN), and Osteopontin (OPN). Evidence provided by this study demonstrates similarities between donor-matched ASC and DF with respect to morphology, surface marker expression, differentiation potential, and gene expression, although appearance of enhanced adipogenesis in the ASC based solely on spectrophotometric analyses with no significant difference in real-time polymerase chain reaction detection of adipogenic biomarkers. Thus, there is substantial overlap between the ASC and DF phenotypes based on biochemical and differentiation metrics.

Photoaging Skin Therapy with PRP and ADSC: A Comparative Study

BACKGROUND

Stem cells from adipose tissue (ADSCs) and platelet-rich plasma (PRP) are innovative modalities that arise due to their regenerative potential.

OBJECTIVE

The aim of this study was to characterize possible histological changes induced by PRP and ADSC therapies in photoaged skin.

METHODS

A prospective randomized study involving 20 healthy individuals, showing skin aging. They underwent two therapeutic protocols (protocol 1: PRP; protocol 2: ADSCs). Biopsies were obtained before and after treatment (4 months).

RESULTS

PRP protocol showed unwanted changes in the reticular dermis, mainly due to the deposition of a horizontal layer of collagen (fibrosis) and elastic fibers tightly linked. Structural analyses revealed infiltration of mononuclear cells and depot of fibrotic material in the reticular dermis. The ADSC protocol leads to neoelastogenesis with increase of tropoelastin and fibrillin. There was an improvement of solar elastosis inducing an increment of macrophage polarization and matrix proteinases. These last effects are probably related to the increase of elastinolysis and the remodeling of the dermis.

CONCLUSIONS

The PRP promoted an inflammatory process with an increase of reticular dermis thickness with a fibrotic aspect. On the other hand, ADSC therapy is a promising modality with an important antiaging effect on photoaged human skin.

Generation of Gellan Gum-Based Adipose-Like Microtissues

Adipose tissue is involved in many physiological processes. Therefore, the need for adipose tissue-like analogues either for soft tissue reconstruction or as in vitro testing platforms is undeniable. In this work, we explored the natural features of gellan gum (GG) to recreate injectable stable adipose-like microtissues. GG hydrogel particles with different percentages of polymer (0.5%, 0.75%, 1.25%) were developed and the effect of obtained mechanical properties over the ability of hASCs to differentiate towards the adipogenic lineage was evaluated based on the expression of the early (PPARγ) and late (FABP4) adipogenic markers, and on lipids formation and accumulation. Constructs were cultured in adipogenic induction medium up to 21 days or for six days in induction plus nine days in maintenance media. Overall, no significant differences were observed in terms of hASCs adipogenic differentiation within the range of Young’s moduli between 2.7 and 12.9 kPa. The long-term (up to six weeks) stability of the developed constructs supported its application in soft tissue reconstruction. Moreover, their ability to function as adipose-like microtissue models for drug screening was demonstrated by confirming its sensitivity to TNFα and ROCK inhibitor, respectively involved in the repression and induction of the adipogenic differentiation.

Antiaging treatment of the facial skin by fat graft and adipose-derived stem cells

BACKGROUND

The regenerative property of fat grafting has been described. However, it is not clear whether the clinical results are attributable to the stem cells or are linked to other components of the adipose tissue. This work is aimed at analysis of the histologic and ultrastructural changes of aged facial skin after injection of fat graft in addition to its stromal vascular fraction, obtained by centrifugation, and to compare the results with those obtained by the injection of expanded adipose-derived mesenchymal stem cells.

METHODS

This study was performed in six consecutive patients who were candidates for face lift and whose ages ranged between 45 and 65 years. The patients underwent sampling of fat by liposuction from the abdominal region. The injection of fat and its stromal vascular fraction or expanded mesenchymal stem cells was performed in the preauricular areas. Fragments of skin were removed before and 3 months after each treatment and analyzed by optical and electron microscopy.

RESULTS

After treatment with the autologous lipidic component and stromal vascular fraction, the skin showed a decrease in elastic fiber network (elastosis) and the appearance of new oxytalan elastic fibers in papillary dermis. The ultrastructural examination showed a modified tridimensional architecture of the reticular dermis and the presence of a richer microvascular bed. Similar results following treatment with expanded mesenchymal stem cells were observed.

CONCLUSION

This study demonstrates that treatment with either fat and stromal vascular fraction or expanded mesenchymal stem cells modifies the pattern of the dermis, representing a skin rejuvenation effect.

Influence of negative pressure on the viability of adipocytes and mesenchymal stem cell, considering the device method used to harvest fat tissue

BACKGROUND

Transplanted adipose tissue has many applications in regenerative medicine. However, fat grafting yields unpredictable results because the fat that is transferred can suffer variable degrees of fat reabsorption. It is necessary to identify methods and maneuvers to minimize reabsorption rates and provide predictable long-term results.

OBJECTIVES

Our study aimed to identify the optimal method of harvesting, as well as the optimal pressure regime for fat aspiration. The primary objective was to assess the degree of adipocyte and mesenchymal stem cell death that occurred with the various devices and pressure levels used to harvest fat.

METHODS

This study was a prospective, randomized, comparative study in 15 healthy male and female subjects aged 25 to 60 who were undergoing abdominal cosmetic surgery. Various apparatuses and pressure regimens were used to harvest 8 samples of fat tissue. These samples (R1 = R8) underwent histological analysis in order to verify the integrity and functionality of the adipocytes and mesenchymal stem cells that had been harvested.

RESULTS

A total of 14 females and 1 male underwent abdominal cosmetic surgery. Quantitative analysis revealed that the adipocytes in all 8 samples had homogeneous quantitative profiles. The adipose mesenchymal stem cell (AMSC) analysis, according to Friedman ANOVA, revealed no significant variation in the percentage of mesenchymal stem cells (P = .045) between the various samples.

CONCLUSIONS

The type of device, nozzle diameter tip, and pressure regimen used in this study for harvesting fat tissue did not significantly affect the number of the adipocytes or viable AMSC harvested.

LEVEL OF EVIDENCE

3 Therapeutic.

Stem cell and research in plastic surgery

Regenerative medicine using stem cells has progressed significantly over the last decade. Plastic surgeons historically have used tissues of human being to restore various defect sites and utilized a single cell lines for the tissue regeneration. The cell sources (autologous or allogeneic), cell types (embryonic stem cell or adult stem cell), and source of tissues (bone marrow, muscle, adipose, cartilage, or blood) are very important for stem cell-based tissue coverage. Embryonic stem cells are pluripotent precursors obtained from the inner cell mass of the blastocyst and reported to be used for preventing muscle atrophy after peripheral nerve injury. Multipotent adult stem cells are easily accessed for plastic surgeons during many routine procedures. This article briefly review the current state of overall stem cell research and clinical applications in the plastic surgical field.

Assessments of injectable alginate particle-embedded fibrin hydrogels for soft tissue reconstruction

Soft tissue reconstruction is often needed after massive traumatic damage or cancer removal. In this study, we developed a novel hybrid hydrogel system consisting of alginate particles and a fibrin matrix that could maintain tissue volume long term. Alginate particles were fabricated by mixing 5% alginate with a 20 mM calcium solution. Cells and these alginate particles were then embedded in fibrin (alginate-fibrin) hydrogels using a dual syringe mixer. Cell-hydrogel constructs were evaluated in terms of cell survival and proliferation in the constructs in vitro. The results indicated that cellular viability, spreading and proliferation in the alginate-fibrin hydrogels were significantly higher compared to constructs fabricated with fibrin or alginate only. In vivo explants showed that cells contained within fibrin-only hydrogels did not contribute to neo-tissue formation, and the fibrin was fully degraded within a 12 week period. In the alginate-fibrin system, higher cellularity and vascular ingrowth were observed in vivo. This resulted in neo-tissue formation in the alginate-fibrin hydrogels. These results demonstrate that fibrin may enhance cell proliferation and accelerate the formation of extracellular matrix proteins in the alginate-fibrin system, while the alginate particles could contribute to volume retention. This injectable hybrid system composed of degradable and non-degradable hydrogels may be a preferable approach to the repair of soft tissue defects.

Comparing scaffold-free and fibrin-based adipose-derived stromal cell constructs for adipose tissue engineering: an in vitro and in vivo study

Success of adipose tissue engineering for soft tissue repair has been limited by insufficient adipogenic differentiation, an unfavorable host response, and insufficient vascularization. In this study, we examined how scaffold-free spheroid and fibrin-based environments impact these parameters in human adipose-derived stromal cell (ASC)-based adipose constructs. ASCs were differentiated in spheroids or fibrin-based constructs. After 7 days, conditioned medium was collected and spheroids/fibrin-based constructs were either harvested or implanted subcutaneously in athymic mice. Following 7 days of implantation, the number of blood vessels in fibrin-based constructs was significantly higher than in spheroids (93±45 vs. 23±11 vessels/mm(2)), and the inflammatory response to fibrin-based constructs was less severe. The reasons for these results were investigated further in vitro. We found that ASCs in fibrin-based constructs secreted significantly higher levels of the angiogenic factors VEGF and HGF and lower levels of the inflammatory cytokine IL-8. Furthermore, ASCs in fibrin-based constructs secreted significantly higher levels of leptin and showed a 2.5-fold upregulation of the adipogenic transcription factor PPARG and a fourfold to fivefold upregulation of the adipocyte-specific markers FABP4, perilipin, and leptin. These results indicate that fibrin-based ASC constructs are potentially more suitable for ASC-based adipose tissue reconstruction than scaffold-free spheroids.

Prevascular structures promote vascularization in engineered human adipose tissue constructs upon implantation

Vascularization is still one of the most important limitations for the survival of engineered tissues after implantation. In this study, we aim to improve the in vivo vascularization of engineered adipose tissue by preforming vascular structures within in vitro-engineered adipose tissue constructs that can integrate with the host vascular system upon implantation. Different cell culture media were tested and different amounts of human adipose tissue-derived mesenchymal stromal cells (ASC) and human umbilical vein endothelial cells (HUVEC) were combined in spheroid cocultures to obtain optimal conditions for the generation of prevascularized adipose tissue constructs. Immunohistochemistry revealed that prevascular structures were formed in the constructs only when 20% ASC and 80% HUVEC were combined and cultured in a 1:1 mixture of endothelial cell medium and adipogenic medium. Moreover, the ASC in these constructs accumulated lipid and expressed the adipocyte-specific gene fatty acid binding protein-4. Implantation of prevascularized ASC/HUVEC constructs in nude mice resulted in a significantly higher amount of vessels (37 ± 17 vessels/mm(2)) within the constructs compared to non-prevascularized constructs composed only of ASC (3 ± 4 vessels/mm(2)). Moreover, a subset of the preformed human vascular structures (3.6 ± 4.2 structures/mm(2)) anastomosed with the mouse vasculature as indicated by the presence of intravascular red blood cells. Our results indicate that preformed vascular structures within in vitro-engineered adipose tissue constructs can integrate with the host vascular system and improve the vascularization upon implantation.

Bioengineering strategies to generate vascularized soft tissue grafts with sustained shape

Tissue engineering offers the possibility for soft tissue reconstruction and augmentation without autologous grafting or conventional synthetic materials. Two critical challenges have been addressed in a number of recent studies: a biology challenge of angiogenesis and an engineering challenge of shape maintenance. These two challenges are inter-related and are effectively addressed by integrated bioengineering strategies. Recently, several integrated bioengineering strategies have been applied to improve bioengineered adipose tissue grafts, including internalized microchannels, delivery of angiogenic growth factors, tailored biomaterials and transplantation of precursor cells with continuing differentiation potential. Bioengineered soft tissue grafts are only clinically meaningful if they are vascularized, maintain shape and dimensions, and remodel with the host. Ongoing studies have begun to demonstrate the feasibility towards an ultimate goal to generate vascularized soft tissue grafts that maintain anatomically desirable shape and dimensions.

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.

Allogreffe de main chez le nouveau-né agénésique: étude de faisabilité

Would a newborn with a single hand benefit from hand allograft? Transantebrachial aplasia is the chosen clinical form of agenesia in our interrogation. The feasibility study presents several aspects: 1) ethical and psychological aspects. Is this a desired surgery for agenesic population? Which are the functional, psychological and social situations of agenesic patient? Is the hand transplantation in newborn ethically acceptable? What is the parents' attitude toward agenesia? Can we envisage organ donation in neonatal period? 2) immunological aspects. The non-vital character of this condition and its' good functional tolerance cannot make accepting the risk of adverse effects of hand allotransplantation. Hence, one may consider this surgery only without immunosuppression. Can the peculiarities of the neonate "immature" immune system represent an opportunity of easier tolerance obtaining, avoiding immunosuppression? 3) anatomical and technical aspects. The proximal tissues at the level of amputation are all hypoplastic in agenesic patients. Can we efficaciously suture those structures with donor eutrophic tissues? 4) cognitive aspects. Is a neonate born with only one hand is able to use two? A feasibility study on such a subject needs to take into account all these aspects. This research is useful because, even if hand allograft in agenesic newborn will never be done, the provided information will allow to progress in the vaster domain of composite tissue allotransplantation in perinatology.

Human Shaped Thumb Bone Tissue Engineered by Hydrogel-β-Tricalciumphosphate/Poly-ε-Caprolactone Scaffolds and Magnetically Sorted Stem Cells

Traumatic amputation of a thumb with bone loss leaves a patient in severe disability. Reconstructive procedures are restricted by limited shape and have the disadvantage of severe donor-site morbidity. To overcome these limitations, we used a tissue engineering approach to create a distal thumb bone phalanx, combining magnetically sorted 133+ human mesenchymal stem cells (hMSCs) suspended in successful tested hydrogels for bone formation and porous 3-dimensionally printed scaffolds (3DP) in the shape of a distal thumb bone phalanx. Collagen I and fibrin glue hydrogels with suspended hMSCs were first histologically evaluated in vitro for bone formation after 6 weeks. Then 3DP scaffolds, made from a mix of osteoinductive and -conductive beta-tricalciumphosphate (beta-TCP) and poly-epsilon-caprolactone (PCL), with hydrogels and suspended hMSCs, were implanted into nude mice subcutaneously for 15 weeks. Histologic evaluation, high-resolution volumetric CT (VCT) scanning, and biomechanical testing confirmed formation of bonelike tissue. Both hydrogels with CD 133+ hMSCs on 3DP scaffolds supported bone formation. Collagen I resulted in radiologically better bone formation. Bone tissue can be successfully tissue engineered with CD 133+ hMSCs, collagen I hydrogels, and porous 3DP beta-TCP/PCL scaffolds.

Adipose tissue engineering from human adult stem cells: clinical implications in plastic and reconstructive surgery

BACKGROUND

Despite certain levels of clinical efficacy, current autografts and synthetic materials for soft-tissue reconstruction and/or augmentation suffer from donor-site morbidity, rupture, dislocation, and volume reduction. Human adult stem cells can self-replicate and differentiate into adipogenic cells in response to appropriate signaling cues. This study investigated the shape and dimension maintenance of engineered adipose tissue from adult human mesenchymal stem cells.

METHODS

Human mesenchymal stem cells were isolated from bone marrow of a healthy donor and differentiated into adipogenic cells. Adipocytes derived from these cells were encapsulated in a poly(ethylene glycol)-based hydrogel shaped into a generic cylinder (n = 6 implants), with hydrogel encapsulating human mesenchymal stem cells (n = 6) and cell-free hydrogel (n = 6) as controls. Porous collagen sponges were also used to seed human mesenchymal stem cell-derived adipocytes (n = 6), human mesenchymal stem cells (n = 4), or without cells (n = 4). All poly(ethylene glycol) and collagen constructs were implanted subcutaneously in athymic mice for 4 weeks.

RESULTS

In vivo grafts demonstrated the formation of substantial adipose tissue encapsulating human mesenchymal stem cell-derived adipogenic cells in either poly(ethylene glycol)-based hydrogel or collagen sponge and a lack of adipose tissue formation in cell-free or human mesenchymal stem cell-derived grafts. Engineered adipose tissue in poly(ethylene glycol)-based hydrogel maintained approximately 100 percent of the original dimensions after 4-week in vivo implantation, significantly higher than the approximately 35 to 65 percent volume retention by collagen sponge.

CONCLUSIONS

These findings demonstrate that the predefined shape and dimensions of adipose tissue engineered from human mesenchymal stem cells can be maintained after in vivo implantation. These data further indicate the potential for autologous applications in reconstructive and plastic surgery procedures.

Stem cells and distraction osteogenesis: endothelial progenitor cells home to the ischemic generate in activation and consolidation

BACKGROUND

Ischemia is a limiting factor during distraction osteogenesis. The authors sought to determine the extent of ischemia in the distraction zone and whether endothelial progenitor cells home to the distraction zone and participate in local vasculogenesis.

METHODS

Laser Doppler imaging was used to assess the extent of blood flow in the distraction zone in gradually distracted, immediately distracted, and osteotomized rat mandibles during activation and consolidation. Animals (n = 50; 25 rats with unilateral gradual distraction and contralateral osteotomy as an internal control, and 25 rats with unilateral immediate distraction) were examined on postoperative days 4, 6, and 8 of activation, and after 1 and 2 weeks of consolidation. Endothelial progenitor cells isolated from human peripheral blood were labeled with fluorescent DiI dye, and 0.5 x 10 cells were injected intra-arterially under direct vision into each carotid artery at the start of activation in nude rats (n = 18) that then underwent the distraction protocol outlined above.

RESULTS

Doppler flow analysis demonstrated relative ischemia during the activation period in the distraction osteogenesis group and increased blood flow in the osteotomized control group as compared with flow in a normal hemimandible [normal, 1 (standardized); distraction osteogenesis, 0.58 +/- 0.05; control, 2.58 +/- 0.21; p < 0.05 for both results]. We observed a significantly increased endothelial progenitor cell population at the generate site versus controls at midactivation and at 1 and 2 weeks of consolidation [25 +/- 1.9 versus 1 +/- 0.3 DiI-positive cells per high-power field (p < 0.05), 124 +/- 21 versus 8 +/- 4 DiI-positive cells per high-power field (p < 0.05), and 106 +/- 18 versus 9 +/- 3 DiI-positive cells per high-power field (p < 0.05), respectively].

CONCLUSIONS

These data suggest that the distraction zone becomes relatively ischemic during activation and that endothelial progenitor cells home to the ischemic generate site during the activation phase and remain during the consolidation phase. Selective expansion of these stem cells may be useful in overcoming ischemic limitations of distraction osteogenesis. Moreover, their homing capability may be used to effect site-specific transgene delivery to the generate.

Engineered adipose tissue from human mesenchymal stem cells maintains predefined shape and dimension: implications in soft tissue augmentation and reconstruction

Soft tissue augmentation is a widespread practice in plastic and reconstructive surgery. The objective of the present study was to engineer adipose tissue constructs with predefined shape and dimensions, potentially utilizable in soft tissue augmentation and reconstruction, by encapsulating adult stem cell-derived adipogenic cells in a biocompatible hydrogel system. Bone marrow-derived adult human mesenchymal stem cells (hMSCs) were preconditioned by 1 week of exposure to adipogenic- inducing supplement followed by photoencapsulation in poly(ethylene glycol) diacrylate (PEGDA) hydrogel in predefined shape and dimensions. In two parallel experiments, the resulting hMSC-derived adipogenic cell-polymer constructs were either incubated in vitro in adipogenic medium or implanted in vivo in the dorsum of immunodeficient mice for 4 weeks. Tissue-engineered adipogenic constructs demonstrated positive reaction to oil red O staining both in vitro and in vivo, and expressed PPAR-gamma2 adipogenic gene marker in vivo. By contrast, control PEGDA hydrogel constructs encapsulating undifferentiated hMSCs failed to demonstrate the adipogenic gene marker and were negative for oil red O staining. Recovered in vitro and in vivo constructs maintained their predefined physical shape and dimensions. These data demonstrate that adipose tissue engineered from human mesenchymal stem cells can retain predefined shape and dimensions for soft tissue augmentation and reconstruction.

Tissue engineering and regenerative medicine

Regenerative medicine is evolving toward a powerful new paradigm of functional restoration. With the ethical use of gene therapy or through the manipulation of autologous tissues, improved tissue replacements may soon be available. The promise of engineered whole organs, although fraught with technical hurdles, remains on the horizon. As these advances occur, physicians and surgeons of the twenty-first century will possess ever more powerful tools to restore form and function.

Bioengineered human bone tissue using autogenous osteoblasts cultured on different biomatrices

Surgical treatment of critical-size posttraumatic bone defects is still a challenging problem, even in modern bone and joint surgery. Progress in cellular and molecular biology during the last decade now permits novel approaches in bone engineering. Recent conceptual and technical advances have enabled the use of mitotically expanded, bone-derived cells as a therapeutic approach for tissue repair. Using three different tissue carrier systems, we successfully cultivated human osteoblasts in a newly developed perfusion chamber. We studied cell proliferation and the expression of osteocalcin, osteopontin, bone morphogenetic protein-2A, alkaline phosphatase, and vascular endothelial growth factor as parameters for osteoblast function and viability. Adherence of highly enriched human osteoblasts had already started after 1 h and resulted in completely overgrown human bone pieces after 10 days. Expression analysis of bone-specific alkaline phosphatase indicated differentiating osteoblasts, whereas the high mRNA expression of osteocalcin and osteopontin revealed terminally differentiated osteoblasts and the process of mineralization. Additionally, gene expression was significantly higher when demineralized bone was used as biomatrix, compared to autoclaved bone and hydroxyapatite ceramics. We conclude that with our newly developed perfusion culture system, vital autogenous bone implants of clinically applicable size can be generated within 17 days in order to manage critical-size bone defects.