Scientific principles of regenerative medicine and their application in the female reproductive system

Regenerative medicine for the treatment of chronic low back pain: a narrative review

Low back pain (LBP) is a common and important clinical problem. In addition to pain, patients are also affected by personal, social, and economic burdens. Intervertebral disc (IVD) degeneration is a common cause of LBP, further increasing the patient's morbidity and medical costs. The limitations of current treatment strategies for long-term pain relief mean that increasing attention has been paid to regenerative medicine. We carried out a narrative review to explore the roles of four types of regenerative medicine for treating LBP: marrow-derived stem cells, growth factors, platelet-rich plasma, and prolotherapy. Marrow-derived stem cells are regarded as an ideal cell source for IVD regeneration. Growth factors may stimulate the synthesis of extracellular matrix and attenuate or reverse the degenerative process in IVD, while platelet-rich plasma, which contains multiple growth factors, is thought to be a promising alternative therapy for IVD degeneration. Prolotherapy can initiate the body's inflammatory healing response to repair injured joints and connective tissues. This review summarizes the mechanisms, in vitro and in vivo studies, and clinical applications of these four types of regenerative medicine in patients with LBP.

Stem Cells and the Microenvironment: Reciprocity with Asymmetry in Regenerative Medicine

Much of the current research in regenerative medicine concentrates on stem-cell therapy that exploits the regenerative capacities of stem cells when injected into different types of human tissues. Although new therapeutic paths have been opened up by induced pluripotent cells and human mesenchymal cells, the rate of success is still low and mainly due to the difficulties of managing cell proliferation and differentiation, giving rise to non-controlled stem cell differentiation that ultimately leads to cancer. Despite being still far from becoming a reality, these studies highlight the role of physical and biological constraints (e.g., cues and morphogenetic fields) placed by tissue microenvironment on stem cell fate. This asks for a clarification of the coupling of stem cells and microenvironmental factors in regenerative medicine. We argue that extracellular matrix and stem cells have a causal reciprocal and asymmetric relationship in that the 3D organization and composition of the extracellular matrix establish a spatial, temporal, and mechanical control over the fate of stem cells, which enable them to interact and control (as well as be controlled by) the cellular components and soluble factors of microenvironment. Such an account clarifies the notions of stemness and stem cell regeneration consistently with that of microenvironment.

Cell-based endometrial regeneration: current status and future perspectives

Endometrial-related disorders including Asherman's syndrome, thin endometrium, pelvic organ prolapse, and cesarean scar pregnancies can be accompanied by different symptoms such as amenorrhea, infertility, abnormal placental implantation and recurrent miscarriage. Different methods have been introduced to overcome these problems such as surgery and hormonal therapy but none of them has shown promising outcomes. On the other hand, the development of novel regenerative therapeutic strategies has opened new avenues for the treatment of endometrial-related deficiencies. In this regard, different types of scaffolds, acellular matrices and also cell therapy with adult or stem cells have been investigated for the treatment of endometrial-related deficiencies. In this paper, we review the current status of cell-based endometrium regeneration using scaffold dependent and scaffold-free methods and future perspectives in this field. Moreover, we discuss the endometrial diseases that can be candidates for cell-based treatments. Also, the cells with the potential for endometrial regeneration are explained.

Regenerative Medicine Approaches in Bioengineering Female Reproductive Tissues

Diseases, disorders, and dysfunctions of the female reproductive tract tissues can result in either infertility and/or hormonal imbalance. Current treatment options are limited and often do not result in tissue function restoration, requiring alternative therapeutic approaches. Regenerative medicine offers potential new therapies through the bioengineering of female reproductive tissues. This review focuses on some of the current technologies that could address the restoration of functional female reproductive tissues, including the use of stem cells, biomaterial scaffolds, bio-printing, and bio-fabrication of tissues or organoids. The use of these approaches could also be used to address issues in infertility. Strategies such as cell-based hormone replacement therapy could provide a more natural means of restoring normal ovarian physiology. Engineering of reproductive tissues and organs could serve as a powerful tool for correcting developmental anomalies. Organ-on-a-chip technologies could be used to perform drug screening for personalized medicine approaches and scientific investigations of the complex physiological interactions between the female reproductive tissues and other organ systems. While some of these technologies have already been developed, others have not been translated for clinical application. The continuous evolution of biomaterials and techniques, advances in bioprinting, along with emerging ideas for new approaches, shows a promising future for treating female reproductive tract-related disorders and dysfunctions.

Creation of a Bioengineered Ovary: Isolation of Female Germline Stem Cells for the Repopulation of a Decellularized Ovarian Bioscaffold

Ovarian failure is the most common cause of infertility and affects about 1% of young women. One innovative strategy to restore ovarian function may be represented by the development of a bioprosthetic ovary, obtained through the combination of tissue engineering and regenerative medicine.We here describe the two main steps required for bioengineering the ovary and for its ex vivo functional reassembling. The first step aims at producing a 3D bioscaffold, which mimics the natural ovarian milieu in vitro. This is obtained with a whole organ decellularization technique that allows the maintenance of microarchitecture and biological signals of the original tissue. The second step involves the use of magnetic activated cell sorting (MACS) to isolate purified female germline stem cells (FGSCs). These cells are able to differentiate in ovarian adult mature cells, when subjected to specific stimuli, and can be used them to repopulate ovarian decellularized bioscaffolds. The combination of the two techniques represents a powerful tool for in vitro recreation of a bioengineered ovary that may constitute a promising solution for hormone and fertility function restoring. In addition, the procedures here described allow for the creation of a suitable 3D platform with useful applications both in toxicological and transplantation studies.

Engineering Functional Rat Ovarian Spheroids Using Granulosa and Theca Cells

Although menopausal hormone therapy (MHT) is the most effective approach to managing the loss of ovarian activity, serious side effects have been reported. Cell-based therapy is a promising alternative for MHT. This study constructed engineered ovarian cell spheroids and investigated their endocrine function. Theca and granulosa cells were isolated from ovaries of 10-week-old rats. Two types of engineered ovarian cell spheroids were fabricated through forced aggregation in microwells, multilayered spheroids with centralized granulosa aggregates surrounded by an outer layer of theca cells and mixed ovarian spheroids lacking spatial rearrangement. The ovarian cell spheroids were encapsulated into a collagen gel. Non-aggregated ovarian cells served as controls. The endocrine function of the engineered ovarian spheroids was assessed over 30 days. The structure of the spheroids was well maintained during culture. The secretion of 17β-estradiol from both types of engineered ovarian cell spheroids was higher than in the control group and increased continuously in a time-dependent manner. Secretion of 17β-estradiol in the multi-layered ovarian cell spheroids was higher than in the non-layered constructs. Increased secretion of progesterone was detected in the multi-layered ovarian cell spheroids at day 5 of culture and was sustained during the culture period. The initial secretion level of progesterone in the non-layered ovarian cell spheroids was similar to those from the controls and increased significantly from days 21 to 30. An in vitro rat model of engineered ovarian cell spheroids was developed that was capable of secreting sex steroid hormones, indicating that the hormone secreting function of ovaries can be recapitulated ex vivo and potentially adapted for MHT.

Combating COVID-19 with tissue engineering: a review

The ongoing COVID-19 pandemic triggered by SARS-CoV-2 emerged from Wuhan, China, firstly in December 2019, as well spread to almost all around the world rapidly. The main reason why this disease spreads so many people in a short time is that the virus could be transmitted from an infected person to another by infected droplets. The new emergence of diseases usually may affect multiple organs; moreover, this disease is such an example. Numerous reported studies focus on acute or chronic organ damage caused by the virus. At this point, tissue engineering (TE) strategies can be used to treat the damages with its interdisciplinary approaches. Tissue engineers could design drug delivery systems, scaffolds, and especially biomaterials for the damaged tissue and organs. In this review, brief information about SARS-CoV-2, COVID-19, and epidemiology of the disease will be given at first. After that, the symptoms, the tissue damages in specific organs, and cytokine effect caused by COVID-19 will be described in detail. Finally, it will be attempted to summarize and suggest the appropriate treatments with suitable biomaterials for the damages via TE approaches. The aim of this review is to serve as a summary of currently available tissue damage treatments after COVID-19.

Bioengineering the ovary to preserve and reestablish female fertility

Different bioengineering strategies can be presently adopted and have been shown to have great potential in the treatment of female infertility and ovarian dysfunction deriving from chemotherapy, congenital malformations, massive adhesions as well as aging and lifestyle. One option is transplantation of fresh or cryopreserved organs/fragments into the patient. A further possibility uses tissue engineering approaches that involve a combination of cells, biomaterials and factors that stimulate local ability to regenerate/ repair the reproductive organ. Organ transplant has shown promising results in large animal models. However, the source of the organ needs to be identified and the immunogenic effects of allografts remain still to be solved before the technology may enter the clinical practice. Decellularization/ repopulation of ovary with autologous cells or follicles could represent an interesting, still very experimental alternative. Here we summarize the recent advancements in the bioengineering strategies applied to the ovary, we present the principles for these systems and discuss the advantages of these emerging opportunities to preserve or improve female fertility.

Whole-ovary decellularization generates an effective 3D bioscaffold for ovarian bioengineering

PURPOSE

To develop a new protocol for whole-ovary decellularization for the production of a 3D bioscaffold suitable for in vitro/ex vivo studies and for the reconstruction of a bioengineered ovary.

METHODS

Porcine ovaries were subjected to the decellularization process (DECELL; n = 20) that involved a freeze-thaw cycle, followed by sequential incubations in 0.5% SDS for 3 h, 1% Triton X-100 for 9 h, and 2% deoxycholate for 12 h. Untreated ovaries were used as a control (CTR; n = 6). Both groups were analyzed to evaluate cell and DNA removal as well as ECM preservation. DECELL bioscaffolds were assessed for cytotoxicity and cell homing ability.

RESULTS

DECELL ovaries maintained shape and homogeneity without any deformation, while their color turned from red to white. Histological staining and DNA quantification confirmed a decrease of 98.11% in DNA content, compared with the native tissue (CTR). Histochemical assessments demonstrated the preservation of intact ECM microarchitecture after the decellularization process. This was also confirmed by quantitative analysis of collagen, elastin, and GAG contents. DECELL bioscaffold showed no cytotoxic effects in co-culture and, when re-seeded with homologous fibroblasts, encouraged a rapid cell adhesion and migration, with repopulating cells increasing in number and aggregating in cluster-like structures, consistent with its ability to sustain cell adherence, proliferation, and differentiation.

CONCLUSION

The protocol described allows for the generation of a 3D bioscaffold that may constitute a suitable model for ex vivo culture of ovarian cells and follicles, as well as a promising tool for the reconstruction of a bioengineered ovary.

Novel approach for the assessment of ovarian follicles infiltration in polymeric electrospun patterned scaffolds

Reproductive tissue engineering (REPROTEN) has been recently defined as the application of the tissue engineering approach targeting reproductive organs and several research works are focusing on this novel strategy. Being still an innovative field, most of the scaffold characterization techniques suitable for other tissue targets give inappropriate results, and there is the need to evaluate and investigate novel approaches. In particular the focus of this paper is the evaluation of the infiltration of ovarian follicles inside patterned electrospun scaffolds. Beyond the standard techniques, for the first time the use of magnetic resonance imaging (MRI) for this purpose is proposed and specific protocols for scaffold preparation are reported. Positive results in terms of evaluation of scaffolds incorporating follicles confirm this technique as highly effective for further applications in this field.

The periosteum-like effect of fresh human amniotic membrane on bone regeneration in a rabbit critical-sized defect model

OBJECTIVE

The purpose of this study was to investigate the effect of fresh human amniotic membrane (FHAM) as a substitute of periosteum to enhance bone regeneration in critical-sized defects.

METHODS

Tibial diaphyseal bone defects were created in forty New Zealand white rabbits and treated with FHAM or left empty. Treatment groups consisted of: FHAM implanted in the place of removed periosteum (FHAMP group); FHFAM implanted to fill the entire defect (FHAMF group) compared to negative control group; empty defect with removing the periosteum (NC group) and positive control group; and empty defect without removing the periosteum (PC group). Bone regeneration was evaluated by radiographic, micro-computed tomography (μ-CT) and histological analyses at 4 and 8weeks post-surgery.

RESULTS

Radiographic and μ-CT analysis demonstrated clearly enhanced new bone formation in positive control group (PC) and FHAMP group compared to negative control group (NC) and FHAMF group. Histological staining exhibited remaining woven bones and cartilage matrix in the FHAMP group, immature lamellar bone with medellury cavity and marrow bone formation in PC group from 4weeks post-operatively. For FHAMF group, a little new bone formation was detected only from 8weeks post-operatively, and an absence of any sign of healing in NC group at both time points.

CONCLUSION

The results provide that FHAM increases bone regeneration in critical-sized defects when it is implanted in the place of the removed periosteum, but its additive effect does not have the same effect of the natural periosteum.

Bioengineering Strategies to Treat Female Infertility

Bioengineering strategies have demonstrated enormous potential to treat female infertility as a result of chemotherapy, uterine injuries, fallopian tube occlusion, massive intrauterine adhesions, congenital uterine malformations, and hysterectomy. These strategies can be classified into two broad categories as follows: (i) Transplantation of fresh or cryopreserved organs into the host and (ii) tissue engineering approaches that utilize a combination of cells, growth factors, and biomaterials that leverages the body's inherent ability to regenerate/repair reproductive organs. While whole organ transplant has demonstrated success, the source of the organ and the immunogenic effects of allografts remain challenging. Even though tissue engineering strategies can avoid these issues, their feasibilities of creating whole organ constructs are yet to be demonstrated. In this article we summarize the recent advancements in the applications of bioengineering to treat female infertility.

Biomaterial Scaffolds for Reproductive Tissue Engineering

The reproductive system usually involves gamete producing gonads, a series of specialized ducts, accessory glands and the external genitalia. Despite there are many traditional methods such as hormonal and surgical approaches, at present no effective treatments exist to help patients suffering from serious diseases of reproductive system, including congenital and acquired abnormalities, malignant tumor, traumatic, infectious etiologies, inflammation and iatrogenic injuries. Tissue engineering holds promise for reproductive medicine through the development of biological alternative. Till now, a diverse range of biomaterials have been utilized as suitable substrates to match both the mechanical and biological context of reproductive tissues. The current review will focus mainly on the applications of biomaterial scaffolds and their major achievements in each region of reproductive systems.

Efficient biomaterials for tissue engineering of female reproductive organs

Current investigations on the bioengineering of female reproductive tissues have created new hopes for the women suffering from reproductive organ failure including congenital anomaly of the female reproductive tract or serious injuries. There are many surgically restore forms that constitute congenital anomaly, however, to date, there is no treatment except surgical treatment of transplantation for patients who are suffering from anomaly or dysfunction organs like vagina and uterus. Restoring and maintaining the normal function of ovary and uterus require the establishment of biological substitutes that can cover the roles of structural support for cells and passage of secreting molecules. As in the case of constructing other functional organs, reproductive organ manufacturing also needs biological matrices which can provide an appropriate condition for attachment, growth, proliferation and signaling of various kinds of grafted cells. Among the organs, uterus needs special features such as plasticity due to their amazing changes in volume when they are in the state of pregnancy. Although numerous natural and synthetic biomaterials are still at the experimental stage, some biomaterials have already been evaluated their efficacy for the reconstruction of female reproductive tissues. In this review, all the biomaterials cited in recent literature that have ever been used and that have a potential for the tissue engineering of female reproductive organs were reviewed, especially focused on bioengineered ovary and uterus.

Bone critical defect repair with poloxamine-cyclodextrin supramolecular gels

The aim of this study was to evaluate the osteoinductive capacity of a poloxamine (Tetronic(®) 908, T) and α-cyclodextrin (αCD) supramolecular gel (T-CD) as scaffold in a critical size defect in rat calvaria. The T-CD gel was evaluated solely and after being loaded with simvastatin (SV) and bone morphogenetic protein (BMP-2) separately and in combinations in order to reduce the doses of the active substances. Three doses of SV (7.5, 75, 750 μg) and two doses of BMP-2 (3 and 6 μg) were tested. The histology and histomorphometrical analysis showed improved bone repair with T-CD compared to T, probably due to better release control of both SV and BMP-2. In addition, as T-CD eroded more slowly than poloxamine alone, it remained longer in the defect site. Although synergism was not obtained with BMP-2 and SV, according to the observed regeneration of the defect, the dose of BMP-2 and SV can be reduced to 3 μg and 7.5 μg, respectively.

Regenerative medicine for the treatment of reproductive system disorders: current and potential options

Regenerative medicine has opened new avenues for treating patients with severe reproductive system disorders, such as congenital abnormalities, cancer, trauma, infection, inflammation and iatrogenic injuries. Over the past two decades, scientists have advanced the field of reproductive tissue engineering to restore normal sexual function and preserve fertility in both female and male patients. In this review, we summarize recent advances in the use of cell, tissue, and organ-based regenerative medicine strategies for clinical application in reproductive system disorders.

Might uterus transplantation be an option for uterine factor infertility?

Current data on uterus allotransplantation research has been reviewed and summarized. Over the past 15 years, progress in uterus transplantation research has increased dramatically. As a consequence, the first pregnancy and delivery following uterus allotransplantation in rats have been reported. The technique has been better defined. Although clinical pregnancy and delivery following uterus allotransplantation has been reported in humans, there are still many questions to be answered before clinical application. Gestational surrogacy still remains an important option for being a genetic parent in selected cases with uterine factor infertility.